Fecov based alloy sheet and manufacturing method of the same

Abstract

The FeCoV alloy-based thin plate according to the present invention comprises γ-austenite and residual α-ferrite, and is characterized in that an average size of grains is 50 to 100 µm.

Description

[Technical Field]

[0001] The present invention relates to an FeCoV alloy-based thin plate and a method for manufacturing the same, and specifically, to an FeCoV alloy-based soft magnetic thin plate and a method for manufacturing the same.[Background Art]

[0002] Generally, a magnetic material is a material having magnetic properties, and among them, a soft magnetic material is a material capable of exhibiting magnetic and non-magnetic properties, so that the magnetic properties can be selectively used in a desired direction. Typically, the soft magnetic material has been used as a motor core material and applied to various electronic products, and recently, as electric vehicles have emerged rapidly, it is receiving great attention as a material for a drive motor.

[0003] A material for a drive motor for an electric vehicle must have a high saturation magnetic flux density value in order to increase motor output. In addition, in order to increase motor efficiency related to how long it can be used with the same battery, iron loss, which means a loss generated when implementing magnetic properties, must be low.

[0004] Although the composition of the FeCoV-based alloy varies somewhat depending on target properties, it is an alloy having a high saturation magnetic flux density value and low iron loss. Although its application has been limited due to the high price of the material, it is a material that is re-emerging rapidly in recent years. In order to manufacture the FeCoV-based alloy into a thin plate, very complicated processes such as vacuum melting, slag removal, forging, and cold rolling must be performed.

[0005] In addition, since the FeCoV-based alloy has characteristics of high strength and somewhat low elongation because its microstructure forms an ordered structure, there is a problem in that rolling to a target thickness is difficult due to occurrence of rupture or cracking during a cold rolling process.

[0006] Therefore, there is a demand for development of a method for manufacturing an FeCoV alloy-based thin plate that has a simple manufacturing method, facilitates cold rolling, and can reduce process costs.[Detailed Description of the Invention][Technical Problem]

[0007] An object of the present invention is to provide a method for manufacturing an FeCoV alloy-based thin plate, which has a simple manufacturing method, facilitates cold rolling to a target thickness, and can reduce process costs.

[0008] In addition, another object of the present invention is to provide an FeCoV alloy-based thin plate having a high saturation magnetic flux density value and low iron loss.

[0009] Furthermore, another object of the present invention is to provide a drive motor having excellent driving efficiency.[Technical Solution]

[0010] The present invention provides an FeCoV alloy-based thin plate comprising γ-austenite and residual α-ferrite, wherein an average size of grains is 50 to 100 µm.

[0011] In addition, the present invention provides an FeCoV alloy-based thin plate having a first peak in a range where 2θ is 42° to 47°, a second peak in a range where 2θ is 62° to 67°, and a third peak in a range where 2θ is 80° to 85° in an X-ray diffraction chart obtained by XRD analysis.

[0012] Furthermore, the present invention provides a method for manufacturing an FeCoV alloy-based thin plate, comprising: preparing an FeCoV alloy-based plate material; heat-treating the FeCoV alloy-based plate material at 600°C to 1,200°C for 10 minutes to 240 minutes to transform at least a portion of an α-ferrite phase into a γ-austenite phase; quenching the heat-treated FeCoV alloy-based plate material; and cold-rolling the quenched FeCoV alloy-based plate material to obtain an FeCoV alloy-based thin plate.[Advantageous Effects]

[0013] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention has an advantage in that it is possible to manufacture an FeCoV alloy-based thin plate having high saturation magnetic flux density and low iron loss without going through existing complicated processes. In addition, there is an advantage of reducing process costs.

[0014] Furthermore, the FeCoV alloy-based thin plate according to the present invention has an advantage of having high saturation magnetic flux density and low iron loss.

[0015] Also, a drive motor according to the present invention has an advantage of excellent driving efficiency.[Brief Description of Drawings]

[0016] FIGS. 1A and 1B are views showing measurement results of elongation and tensile strength of an Fe 49 Co 49 V 2 thin plate manufactured according to some embodiments of the present invention. FIGS. 2A and 2B are views showing XRD analysis results of an Fe 49 Co 49 V 2 thin plate manufactured according to some embodiments of the present invention. FIGS. 3A and 3B are views showing changes in magnetic flux density values at 5000 A / m and iron loss values at 400 Hz with 1 T applied, for an Fe 49 Co 49 V 2 thin plate manufactured according to some embodiments of the present invention. FIG. 4 is a view showing an SEM image of an Fe 49 Co 49 V 2 thin plate manufactured according to some embodiments of the present invention. FIGS. 5 to 7 are views showing OM images of a side cross-sectional structure of an Fe 49 Co 49 V 2 thin plate manufactured according to some embodiments of the present invention. FIGS. 8A to 8C are views showing XRD patterns of respective specimens during a process of manufacturing an Fe 49 Co 49 V 2 thin plate according to some embodiments of the present invention. FIGS. 9A to 9C are views showing SEM images of respective specimens during a process of manufacturing an Fe 49 Co 49 V 2 thin plate according to some embodiments of the present invention. FIGS. 10A to 10D are views showing GDS surface analysis results of Fe 49 Co 49 V 2 thin plate specimens manufactured according to some embodiments of the present invention. FIGS. 11A and 11B are views showing XRD patterns of respective specimens during a process of manufacturing an Fe 49 Co 49 V 2 thin plate according to some embodiments of the present invention. FIG. 12 is a view showing hysteresis of an Fe 49 Co 49 V 2 thin plate manufactured according to some embodiments of the present invention. FIGS. 13A to 13D are views showing XRD patterns of respective specimens during a process of manufacturing an Fe 49 Co 49 V 2 thin plate according to some embodiments of the present invention. FIGS. 14A to 14E are views showing SEM images of respective specimens during a process of manufacturing an Fe 49 Co 49 V 2 thin plate according to some embodiments of the present invention. FIGS. 15A and 15B are views showing SEM images of an Fe 49 Co 49 V 2 thin plate manufactured according to some embodiments of the present invention. [Mode for Carrying Out the Invention]

[0017] Hereinafter, embodiments of the present invention will be described in detail. However, these are presented as examples, and the present invention is not limited thereto, and the present invention is only defined by the scope of the claims to be described later.

[0018] In the present invention, when a member is referred to as being positioned "on" another member, this includes not only the case where the member is directly in contact with the other member but also the case where another member is interposed between the two members.

[0019] In the present invention, when a part is referred to as "comprising" a certain component, it means that it may further include other components rather than excluding other components unless otherwise stated.

[0020] One aspect of the present invention relates to a method for manufacturing an FeCoV alloy-based thin plate, comprising: preparing an FeCoV alloy melt by vacuum melting an alloy component composed of 20 to 49 at% of cobalt, 2 to 5 at% of vanadium, and a balance of iron and other impurities; casting the alloy melt to manufacture an ingot; hot-rolling the ingot to obtain a plate material; heat-treating the plate material at 600°C to 1,200°C for 10 minutes to 240 minutes to transform at least a portion of an α-ferrite phase into a γ-austenite phase; quenching the heat-treated plate material; and cold-rolling the quenched plate material to obtain an FeCoV alloy-based thin plate.

[0021] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes the step of transforming at least a portion of the α-ferrite phase into the γ-austenite phase, whereby cold rolling can be easily performed, and there is an advantage in that an FeCoV alloy-based thin plate having excellent saturation magnetic flux density and low iron loss values can be manufactured without going through complicated processes such as conventional forging.

[0022] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes the step of preparing an FeCoV alloy melt by vacuum melting an alloy component composed of 20 to 49 at% of cobalt, 2 to 5 at% of vanadium, and a balance of iron and other impurities.

[0023] The other impurities may be one or more selected from the group consisting of carbon, oxygen, silicon, and manganese.

[0024] In one embodiment of the present invention, the FeCoV alloy melt may include an alloy component composed of 30 to 49 at% of cobalt, 2 to 3 at% of vanadium, and a balance of iron and other impurities.

[0025] In another embodiment of the present invention, the FeCoV alloy melt may include an alloy component composed of 40 to 49 at% of cobalt, 2 to 3 at% of vanadium, and a balance of iron and other impurities.

[0026] The FeCoV-based alloy is an alloy composition having soft magnetic properties, and is mainly used for motor cores of electronic products by being manufactured into a thin plate, and in particular, recently, application as a drive motor for electric vehicles is being considered.

[0027] In order to increase the output of an electric vehicle, the magnetic flux density value of the motor core material must be high. Recently, most electric vehicles have a value of 2 Tesla or more, and since the FeCoV alloy has a value of up to 2.4 Tesla level, it can be very helpful in improving motor core output. In addition, since it has a significantly lower iron loss value compared to other soft magnetic materials, it is possible to drive a longer distance due to a lower loss value compared to a battery of the same capacity as well as efficiency improvement. For the same reason, when a motor exhibiting the same performance is manufactured, miniaturization and weight reduction are possible.

[0028] Even with the same alloy composition, the defect rate of the rolling process may vary depending on the manufacturing process of such an FeCoV alloy, and mechanical and magnetic property values of the manufactured plate material may be greatly influenced.

[0029] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention has an advantage in that a thin plate having high mechanical and magnetic property values can be easily manufactured without including a conventional complicated slag removal process, forging process, process of forming into a slab shape, and the like.

[0030] Meanwhile, the saturation magnetic flux density value and coercivity value of the manufactured FeCoV alloy-based thin plate may vary somewhat depending on the composition of the FeCoV alloy component.

[0031] In the present invention, by using the FeCoV alloy component having the above composition, there is an advantage in that an FeCoV alloy-based thin plate having a high saturation magnetic flux density value and low coercivity can be obtained.

[0032] The FeCoV alloy melt may have a composition of Fe 49 Co 49 V 2 .

[0033] By vacuum melting the alloy component, a grayish ingot with little contamination can be obtained, and when solidified into an ingot shape through a casting step to be described later, it is possible to suppress a phenomenon in which an ingot having a non-uniform composition is obtained due to composition inconsistency, for example, a case where the upper and middle, or middle and lower compositions of the ingot are different, or segregation exists in the same portion, which is preferable. In addition, it is preferable because it is possible to suppress a phenomenon in which a crack is induced in a hot rolling process, a cold rolling process, or the like because an oxide layer is too thick.

[0034] The step of preparing the alloy melt may be performed under an argon, nitrogen, or carbon dioxide atmosphere. When the step of preparing the alloy melt is performed under the argon, nitrogen, or carbon dioxide atmosphere, it is preferable because a phenomenon in which the alloy component is oxidized or carbonized can be suppressed.

[0035] In the step of preparing the FeCoV alloy melt by vacuum melting the alloy component, the degree of vacuum may be 1×10 -2< to 1×10 -4< torr, preferably 1×10 -2< to 1×10 -3< torr.

[0036] When the degree of vacuum satisfies the above range, it is preferable because oxidation or carbonization can be suppressed.

[0037] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes the step of manufacturing an ingot by casting the alloy melt.

[0038] The method may further include a step of removing slag of the alloy melt liquid before casting the alloy melt, but is not limited thereto.

[0039] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention may not include the step of removing slag of the alloy melt liquid. Specifically, the method for manufacturing an FeCoV alloy-based thin plate according to the present invention has an advantage in that it is possible to manufacture an FeCoV alloy-based thin plate exhibiting excellent performance without including a slag removal process, a forging process, and a shape control slabbing process.

[0040] A method of manufacturing the ingot by casting the alloy melt is not specifically limited in the present invention.

[0041] For example, the ingot may be manufactured by injecting the alloy melt into a mold, and cooling and crystallizing it.

[0042] The injection temperature is preferably set to a temperature 100 to 2,000°C, preferably 100 to 1,000°C, and more preferably 200 to 500°C higher than the liquidus temperature of the melt. The liquidus temperature of the melt can be measured using a direct temperature measurement method with a built-in thermocouple or by measuring the surface of the melt using a non-contact laser thermometer.

[0043] In addition, the cooling temperature and rate can be controlled to prevent segregation and ensure uniformity of composition by making the cooling temperature uniform. Since the upper part of the ingot cools relatively quickly and the lower part or the inside may cool slowly, the quickly cooling part may be heated, or insulated with non-metallic ceramics or slag.

[0044] The ingot may be manufactured in, for example, a bar, polyhedron, cylinder, sphere shape, or atypical shape, but is not limited thereto.

[0045] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention may further include cutting the ingot to 4 to 30 mm.

[0046] For example, the method for manufacturing an FeCoV alloy-based thin plate may further include cutting the ingot to 10 to 30 mm. When the step of cutting the ingot within the above range is further included, it is preferable because hot rolling is smooth.

[0047] Cutting of the ingot may be performed by a method commonly performed in the art, and the present invention is not limited thereto.

[0048] In another embodiment of the present invention, the method may further include: manufacturing an ingot by casting the alloy melt; and then homogenizing heat-treating the ingot.

[0049] In another embodiment of the present invention, the homogenizing heat treatment may be performed at 1,200 to 1,300°C for 1 to 12 hours.

[0050] Preferably, the homogenizing heat treatment may be performed for 2 to 6 hours, more preferably 2 to 4 hours, but is not limited thereto.

[0051] When the step of homogenizing heat-treating is further included, it is preferable because stress generated during casting can be relieved.

[0052] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes the step of hot-rolling the ingot to obtain a plate material.

[0053] By hot-rolling the ingot, it is preferable because a plate material in which a γ-austenite phase formed by slow cooling occupies the majority or an α-ferrite phase and the γ-austenite phase are mixed can be obtained.

[0054] The hot rolling may be performed using, for example, a steel rolling mill.

[0055] The rolling start temperature, rolling speed, rolling end temperature, and the like are not particularly limited in the present invention, and may be appropriately performed according to conventional conditions performed in the art.

[0056] For example, the start temperature for the rolling may be 900°C or higher, and may not exceed 1,300°C. When the start temperature for the rolling satisfies the above range, it is preferable because there is an advantage in that the strength and formability of the manufactured plate material are excellent.

[0057] The rolling end temperature may be 1,150°C or higher. When the rolling end temperature is 1,150°C or higher, it is preferable because a phenomenon in which excessive load is applied to equipment due to high deformation resistance can be suppressed, and control of the shape is easy.

[0058] The total reduction ratio by the hot rolling may be 70 to 90%, preferably 75 to 90%, and more preferably 75 to 85%. When the total reduction ratio satisfies the above range, it is preferable because enlargement of crystal grains due to large energy can be suppressed, and the deviation thereof can be reduced.

[0059] The rolling may be performed for one pass to several passes, but is not limited thereto.

[0060] In another embodiment of the present invention, the rolling may be performed in two or more rolling passes. Specifically, the rolling may be performed in 5 or more rolling passes, but is not limited thereto.

[0061] When the temperature decreases as the hot rolling is repeated, it is preferable to perform the hot rolling after raising the temperature by reheating. The lower limit of the temperature during the rolling process is preferably controlled to 900°C or higher, preferably 900 to 1,000°C.

[0062] When the lower limit of the temperature during the rolling process satisfies the above range, it is preferable because most of the phase exists as the γ-austenite phase, so that cracks or ruptures hardly occur during hot rolling and the process becomes smooth.

[0063] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes the step of heat-treating the plate material at 600°C to 1,200°C for 10 minutes to 240 minutes to transform at least a portion of the α-ferrite phase into the γ-austenite phase.

[0064] Although not wishing to be bound by theory, generally, an FeCoV-based alloy undergoes a phase change while going through a casting process, a hot rolling process, a heat treatment process, a cold rolling process, and the like, and even the same phase changes into an ordered lattice or a disordered lattice.

[0065] For example, when an FeCoV-based alloy is melted in a vacuum and cast into an ingot, an α-ferrite phase is formed.

[0066] In the case of α-ferrite, which is a room temperature structure, it forms a Body-Centered Cubic (BCC) structure and has relatively fewer slip planes, so there is a high possibility that rolling may not be performed smoothly when cold rolling or the like is performed later to use a thin plate using the FeCoV alloy-based plate material.

[0067] In particular, due to residual stress existing inside the plate material after cold rolling, forming may be difficult, and a phenomenon in which soft magnetic properties are not properly implemented may occur.

[0068] On the other hand, a γ-austenite structure, which is a high-temperature structure, forms a Face-Centered Cubic (FCC) structure, which is a disordered structure, and has many slip planes, so rolling is easy, and plastic workability is much superior to that of α-ferrite.

[0069] Therefore, the method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes heat-treating the plate material at a temperature of 600 to 1,200°C, which is a high-temperature stable phase section, so as to have a γ-austenite structure, that is, an FCC structure, which is a high-temperature stable phase, and then quenching the plate material, thereby transforming the α-ferrite phase generated through the casting process and the hot rolling process into the γ-austenite phase, so that the structure is changed to a structure having the γ-austenite phase or a composite structure of the α-ferrite phase and the γ-austenite phase.

[0070] In another embodiment of the present invention, the heat treatment may be performed at 730 to 1,200°C. Specifically, the heat treatment may be performed at a temperature of 730°C or higher, which is a temperature at which an irregular / regular lattice structure starts to be ordered, and a temperature of 1,200°C or lower, which is a temperature at which a liquid phase is not formed and atomic structure change is expected to be most active. Specifically, the heat treatment is preferably performed within the above range, which is a temperature region where irregular / regular structure change occurs.

[0071] In another embodiment of the present invention, the heat treatment may be performed at 840 to 1,200°C.

[0072] Specifically, the heat treatment may be performed at a temperature of 840°C or higher, which is a temperature at which phase transformation occurs, and a temperature of 1,200°C or lower, which is a temperature at which solid phase control is possible without mixing of a liquid phase.

[0073] In another embodiment of the present invention, the step of transforming into the γ-austenite phase may be heat-treating at 850 to 950°C.

[0074] Since mechanical properties and / or magnetic properties may vary greatly depending on the heat treatment temperature even if the FeCoV alloy-based plate material has the same composition, in the present invention, by heat-treating at a temperature within the above range, it is possible to obtain an FeCoV alloy-based thin plate having excellent mechanical properties and excellent magnetic properties, that is, high saturation magnetic flux density and low iron loss value at the same time.

[0075] In another embodiment of the present invention, the heat treatment may be performed for 30 to 240 minutes.

[0076] Preferably, the heat treatment may be performed for 60 to 120 minutes.

[0077] When the heat treatment time satisfies the above range, it is preferable because the phase transformation time to the γ-austenite phase is sufficient while shortening the heat treatment time.

[0078] In short, the step of transforming into the γ-austenite phase may be heat-treating at a temperature of 850 to 950°C for 60 to 120 minutes.

[0079] In another embodiment of the present invention, the step of transforming into the γ-austenite phase may be performed under a vacuum or inert gas atmosphere. Since the FeCoV-based alloy is somewhat prone to oxidation, the step of transforming into the γ-austenite phase is preferably performed under a vacuum or inert gas atmosphere.

[0080] The inert gas may be, for example, high-purity argon (Ar) gas, but is not limited thereto.

[0081] In another embodiment of the present invention, the method may further include a step of removing a surface scale of the plate material before the step of heat-treating the plate material. Since an oxide scale may be formed on the surface of the plate material that has undergone the hot rolling, and the oxide scale may affect the quality of the plate material, it is preferable to further include the step of removing the surface scale of the plate material. A method of removing the surface scale of the plate material may be performed using a conventional method performed in the art. For example, the pickling treatment may be performed by introducing the plate material into a hydrochloric acid bath, or the surface scale may be removed by high-pressure spraying of a slurry mixed with high-pressure water and an abrasive onto the plate material, but is not limited thereto.

[0082] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes a step of quenching the heat-treated FeCoV alloy-based plate material. If the microstructure of the FeCoV alloy-based plate material forms an ordered structure in a cold rolling process to be described later, since it has high strength and low elongation, there is a problem in that rupture or cracking occurs during the cold rolling process, making it difficult to roll to a target thickness. Therefore, in the present invention, the FeCoV alloy-based plate material is changed to form a disordered structure by performing the step of transforming an α-ferrite phase into a γ-austenite phase by heat-treating the FeCoV alloy-based plate material at 600 to 1,200°C for 10 minutes to 240 minutes.

[0083] After that, by including the step of quenching so that the FeCoV alloy-based plate material can maintain the structure of the γ-austenite phase, elongation is improved to solve problems occurring during the cold rolling process. In another embodiment of the present invention, the step of quenching may be performed at a rate of 10 to 300°C / sec. Preferably, the quenching may be performed at a rate of 30 to 150°C / sec, and more preferably at a rate of 50 to 100°C / sec. When the quenching rate satisfies the above range, the γ-austenite phase is stably maintained, which is preferable because an FeCoV alloy-based thin plate having high saturation magnetic flux density can be manufactured. The step of quenching may be performing water cooling or oil cooling. The water cooling or oil cooling method is not particularly limited in the present invention, and a general method performed in the art may be applied. For example, it may be performed using a water-cooled or oil-cooled cooling guide and a conveyor roll, but is not limited thereto. By performing the water cooling or oil cooling, the γ-austenite phase structure, which is a high-temperature stable phase, can be stably maintained. The step of quenching may be performed by introducing the FeCoV-based alloy plate material into cooling water.

[0084] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes a step of cold-rolling the quenched FeCoV alloy-based plate material to obtain an FeCoV alloy-based thin plate. In the method for manufacturing an FeCoV alloy-based thin plate according to the present invention, cold rolling can be smoothly performed as the α-ferrite phase of a regular structure is heat-treated according to a specific temperature range and time, and is changed into a γ-austenite phase of an irregular structure by quenching it. The cold rolling may be repeatedly performed while changing a reduction ratio, but is not limited thereto. A cumulative reduction ratio may be 85% or more, specifically 90% or more, and more specifically 95% or more, but is also not limited thereto.

[0085] In another embodiment of the present invention, the method may further include: obtaining the FeCoV alloy-based thin plate; and then performing a stress relief heat treatment on the FeCoV alloy-based thin plate. By including the step of performing the stress relief heat treatment on the FeCoV alloy-based thin plate, residual stress existing inside the FeCoV alloy-based thin plate after the cold rolling can be removed, and as the irregular γ-austenite phase changes to a stable phase, regularity (ordering) is secured, and accordingly, it is preferable because an FeCoV alloy-based thin plate having a high saturation magnetic flux density value, a low iron loss value, and appropriate tensile strength and elongation can be obtained.

[0086] The soft magnetic FeCoV-based alloy undergoes a process in which the phase of the structure changes in a process of being manufactured into a thin plate, and in this process, magnetic properties such as saturation magnetic flux density, residual magnetic flux density, coercivity, core loss, etc. are affected according to a specific method of heat treatment such as heat treatment atmosphere, temperature, and time. Here, when a soft magnetic material is used as a material for a drive motor component, etc., a higher saturation magnetic flux density or a magnetic flux density value in a specific frequency region is advantageous, and a lower loss value such as iron loss indicates an advantageous characteristic. Eventually, alloy design, processing, heat treatment, etc. are proceeded to exhibit high magnetic flux density and low iron loss value, and as a result, when a value obtained by dividing magnetic flux density by iron loss is defined as a high specific efficiency value, the higher this value is, the more excellent it is as a material for a motor. In the present invention, heat treatment for microstructure control is performed between hot rolling and cold rolling so that cold rolling can be smoothly performed, and stress relief heat treatment is additionally performed to improve mechanical properties, particularly elongation and magnetic properties after cold rolling, thereby having an advantage of manufacturing an FeCoV alloy-based thin plate excellent in both mechanical properties and magnetic properties. In another embodiment of the present invention, the stress relief heat treatment may be performed at 650 to 950°C for 10 to 120 minutes. Preferably, the stress relief heat treatment may be performed at a temperature of 700 to 950°C, and more preferably 850 to 950°C, but is not limited thereto.

[0087] One aspect of the present invention relates to a method for manufacturing an FeCoV alloy-based thin plate, comprising: preparing an FeCoV alloy-based plate material; heat-treating the FeCoV alloy-based plate material at 600 to 1,200°C for 10 minutes to 240 minutes to transform at least a portion of an α-ferrite phase into a γ-austenite phase; quenching the heat-treated FeCoV alloy-based plate material; cold-rolling the quenched FeCoV alloy-based plate material to obtain an FeCoV alloy-based thin plate; and performing a stress relief heat treatment on the FeCoV alloy-based thin plate. The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes the step of transforming at least a portion of the α-ferrite phase into the γ-austenite phase, whereby cold rolling can be easily performed, and by including the step of performing the stress relief heat treatment on the FeCoV alloy-based thin plate, mechanical properties, particularly elongation and magnetic properties are improved, so that there is an advantage in that an FeCoV alloy-based thin plate having excellent saturation magnetic flux density and low iron loss values can be manufactured without going through complicated processes such as conventional forging.

[0088] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes a step of preparing an FeCoV alloy-based plate material. The step of preparing the FeCoV alloy-based plate material is not limited in the present invention. For example, a commercially available FeCoV alloy-based plate material may be purchased and used, or it may be directly manufactured and used.

[0089] In another embodiment of the present invention, the step of preparing the FeCoV alloy-based plate material may include: preparing an FeCoV alloy melt by vacuum melting an alloy component composed of 20 to 49 at% of cobalt, greater than 0 and 5 at% or less of vanadium, 0 to 15 at% of nickel, 0 to 3 wt% of chromium, 0 to 1 at% of niobium, and a balance of iron and other impurities; casting the alloy melt to manufacture an ingot; and hot-rolling the ingot to obtain an FeCoV alloy-based plate material. The other impurities may be one or more selected from the group consisting of carbon, oxygen, silicon, and manganese. Specifically, the FeCoV alloy melt may include an alloy component composed of 30 to 49 at% of cobalt, 2 to 3 at% of vanadium, and a balance of iron and other impurities. More specifically, the FeCoV alloy melt may include an alloy component composed of 40 to 49 at% of cobalt, 2 to 3 at% of vanadium, and a balance of iron and other impurities. The FeCoV-based alloy is an alloy composition having soft magnetic properties, and is mainly used for motor cores of electronic products by being manufactured into a thin plate, and in particular, recently, application as a drive motor for electric vehicles is being considered. In order to increase the output of an electric vehicle, the magnetic flux density value of the motor core material must be high. Recently, most electric vehicles have a value of 2 Tesla or more, and since the FeCoV alloy has a value of up to 2.4 Tesla level, it can be very helpful in improving motor core output. In addition, since it has a significantly lower iron loss value compared to other soft magnetic materials, it is possible to drive a longer distance due to a lower loss value compared to a battery of the same capacity as well as efficiency improvement. For the same reason, when a motor exhibiting the same performance is manufactured, miniaturization and weight reduction are possible. Even with the same alloy composition, the defect rate of the rolling process may vary depending on the manufacturing process of such an FeCoV alloy, and mechanical and magnetic property values of the manufactured plate material may be greatly influenced. The method for manufacturing an FeCoV alloy-based thin plate according to the present invention has an advantage in that a thin plate having high mechanical and magnetic property values can be easily manufactured without including a conventional complicated slag removal process, forging process, process of forming into a slab shape, and the like. Meanwhile, the saturation magnetic flux density value and coercivity value of the manufactured FeCoV alloy-based thin plate may vary somewhat depending on the composition of the FeCoV alloy component. When the FeCoV alloy component having the above composition is used, there is an advantage in that an FeCoV alloy-based thin plate having a high saturation magnetic flux density value and low coercivity can be obtained. The FeCoV alloy melt may have a composition of Fe 49 Co 49 V 2 . By vacuum melting the alloy component, a grayish ingot with little contamination can be obtained, and when solidified into an ingot shape through a casting step to be described later, it is possible to suppress a phenomenon in which an ingot having a non-uniform composition is obtained due to composition inconsistency, for example, a case where the upper and middle, or middle and lower compositions of the ingot are different, or segregation exists in the same portion, which is preferable. In addition, it is preferable because it is possible to suppress a phenomenon in which a crack is induced in a hot rolling process, a cold rolling process, or the like because an oxide layer is too thick.

[0090] The step of preparing the alloy melt may be performed under an argon, nitrogen, or carbon dioxide atmosphere. When the step of preparing the alloy melt is performed under the argon, nitrogen, or carbon dioxide atmosphere, it is preferable because a phenomenon in which the alloy component is oxidized or carbonized can be suppressed.

[0091] In the step of preparing the FeCoV alloy melt by vacuum melting the alloy component, the degree of vacuum may be 1×10 -2< to 1×10 -4< torr, preferably 1×10 -2< to 1×10 -3< torr. When the degree of vacuum satisfies the above range, it is preferable because oxidation or carbonization can be suppressed.

[0092] The method may further include a step of removing slag of the alloy melt liquid before casting the alloy melt, but is not limited thereto. Alternatively, the method may not include the step of removing slag of the alloy melt liquid before casting the alloy melt, but is not limited thereto. A method of manufacturing the ingot by casting the alloy melt is not specifically limited in the present invention. For example, the ingot may be manufactured by injecting the alloy melt into a mold, and cooling and crystallizing it. The injection temperature is preferably set to a temperature 100 to 2,000°C, preferably 100 to 1,000°C, and more preferably 200 to 500°C higher than the liquidus temperature of the melt. The liquidus temperature of the melt can be measured using a direct temperature measurement method with a built-in thermocouple or by measuring the surface of the melt using a non-contact laser thermometer. In addition, the cooling temperature and rate can be controlled to prevent segregation and ensure uniformity of composition by making the cooling temperature uniform. Since the upper part of the ingot cools relatively quickly and the lower part or the inside may cool slowly, the quickly cooling part may be heated, or insulated with non-metallic ceramics or slag.

[0093] The ingot may be manufactured in, for example, a bar, polyhedron, cylinder, sphere shape, or atypical shape, but is not limited thereto. The step of preparing the FeCoV alloy-based plate material may further include a step of cutting the ingot to 4 to 30 mm. For example, the method for manufacturing an FeCoV alloy-based thin plate may further include cutting the ingot to 10 to 30 mm. When the step of cutting the ingot within the above range is further included, it is preferable because hot rolling is smooth. Cutting of the ingot may be performed by a method commonly performed in the art, and the present invention is not limited thereto.

[0094] The method may further include: manufacturing an ingot by casting the alloy melt; and then homogenizing heat-treating the ingot. The homogenizing heat treatment may be performed at 1,200 to 1,300°C for 1 to 12 hours. Preferably, the homogenizing heat treatment may be performed for 2 to 6 hours, more preferably 2 to 4 hours, but is not limited thereto. When the step of homogenizing heat-treating is further included, it is preferable because stress generated during casting can be relieved.

[0095] The step of preparing the FeCoV alloy-based plate material may include a step of hot-rolling the ingot to obtain a plate material. By hot-rolling the ingot, it is preferable because a plate material in which a γ-austenite phase formed by slow cooling occupies the majority or an α-ferrite phase and the γ-austenite phase are mixed can be obtained.

[0096] The hot rolling may be performed using, for example, a steel rolling mill. The rolling start temperature, rolling speed, rolling end temperature, and the like are not particularly limited in the present invention, and may be appropriately performed according to conventional conditions performed in the art. For example, the start temperature for the rolling may be 900°C or higher, and may not exceed 1,300°C. When the start temperature for the rolling satisfies the above range, it is preferable because there is an advantage in that the strength and formability of the manufactured plate material are excellent. The rolling end temperature may be 1,150°C or higher. When the rolling end temperature is 1,150°C or higher, it is preferable because a phenomenon in which excessive load is applied to equipment due to high deformation resistance can be suppressed, and control of the shape is easy.

[0097] The total reduction ratio by the hot rolling may be 70 to 90%, preferably 75 to 90%, and more preferably 75 to 85%. When the total reduction ratio satisfies the above range, it is preferable because enlargement of crystal grains due to large energy can be suppressed, and the deviation thereof can be reduced.

[0098] The rolling may be performed for one pass to several passes, but is not limited thereto. In another embodiment of the present invention, the rolling may be performed in two or more rolling passes. Specifically, the rolling may be performed in 5 or more rolling passes, but is not limited thereto.

[0099] When the temperature decreases as the hot rolling is repeated, it is preferable to perform the hot rolling after raising the temperature by reheating. The lower limit of the temperature during the rolling process is preferably controlled to 900°C or higher, preferably 900 to 1,000°C. When the lower limit of the temperature during the rolling process satisfies the above range, it is preferable because most of the phase exists as the γ-austenite phase, so that cracks or ruptures hardly occur during hot rolling and the process becomes smooth.

[0100] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes the step of heat-treating the plate material at 600°C to 1,200°C for 10 minutes to 240 minutes to transform at least a portion of the α-ferrite phase into the γ-austenite phase. Although not wishing to be bound by theory, generally, an FeCoV-based alloy undergoes a phase change while going through a casting process, a hot rolling process, a heat treatment process, a cold rolling process, and the like, and even the same phase changes into an ordered lattice or a disordered lattice. For example, when an FeCoV-based alloy is melted in a vacuum and cast into an ingot, an α-ferrite phase is formed. In the case of α-ferrite, which is a room temperature structure, it forms a Body-Centered Cubic (BCC) structure and has relatively fewer slip planes, so there is a high possibility that rolling may not be performed smoothly when cold rolling or the like is performed later to use a thin plate using the FeCoV alloy-based plate material. In particular, due to residual stress existing inside the plate material after cold rolling, forming may be difficult, and a phenomenon in which soft magnetic properties are not properly implemented may occur. On the other hand, a γ-austenite structure, which is a high-temperature structure, forms a Face-Centered Cubic (FCC) structure, which is a disordered structure, and has many slip planes, so rolling is easy, and plastic workability is much superior to that of α-ferrite. Therefore, the method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes heat-treating the plate material at a temperature of 600 to 1,200°C, which is a high-temperature stable phase section, so as to have a γ-austenite structure, that is, an FCC structure, which is a high-temperature stable phase, and then quenching the plate material, thereby transforming the α-ferrite phase generated through the casting process and the hot rolling process into the γ-austenite phase, so that the structure is changed to a structure having the γ-austenite phase or a composite structure of the α-ferrite phase and the γ-austenite phase.

[0101] In another embodiment of the present invention, the heat treatment may be performed at 730 to 1,200°C. Specifically, the heat treatment may be performed at a temperature of 730°C or higher, which is a temperature at which an irregular / regular lattice structure starts to be ordered, and a temperature of 1,200°C or lower, which is a temperature at which a liquid phase is not formed and atomic structure change is expected to be most active. Specifically, the heat treatment is preferably performed within the above range, which is a temperature region where irregular / regular structure change occurs.

[0102] In another embodiment of the present invention, the heat treatment may be performed at 840 to 1,200°C. Specifically, the heat treatment may be performed at a temperature of 840°C or higher, which is a temperature at which phase transformation occurs, and a temperature of 1,200°C or lower, which is a temperature at which solid phase control is possible without mixing of a liquid phase. In another embodiment of the present invention, the step of transforming into the γ-austenite phase may be heat-treating at 850 to 950°C. Since mechanical properties and / or magnetic properties may vary greatly depending on the heat treatment temperature even if the FeCoV alloy-based plate material has the same composition, in the present invention, by heat-treating at a temperature within the above range, it is possible to obtain an FeCoV alloy-based thin plate having excellent mechanical properties and excellent magnetic properties, that is, high saturation magnetic flux density and low iron loss value at the same time.

[0103] In another embodiment of the present invention, the heat treatment may be performed for 30 to 240 minutes. Preferably, the heat treatment may be performed for 60 to 120 minutes. When the heat treatment time satisfies the above range, it is preferable because the phase transformation time to the γ-austenite phase is sufficient while shortening the heat treatment time. In short, the step of transforming into the γ-austenite phase may be heat-treating at a temperature of 850 to 950°C for 60 to 120 minutes.

[0104] In another embodiment of the present invention, the step of transforming into the γ-austenite phase may be performed under a vacuum or inert gas atmosphere. Since the FeCoV-based alloy is somewhat prone to oxidation, the step of transforming into the γ-austenite phase is preferably performed under a vacuum or inert gas atmosphere. The inert gas may be, for example, high-purity argon (Ar) gas, but is not limited thereto.

[0105] In another embodiment of the present invention, the method may further include a step of removing a surface scale of the plate material before the step of heat-treating the plate material. Since an oxide scale may be formed on the surface of the plate material that has undergone the hot rolling, and the oxide scale may affect the quality of the plate material, it is preferable to further include the step of removing the surface scale of the plate material. A method of removing the surface scale of the plate material may be performed using a conventional method performed in the art. For example, the pickling treatment may be performed by introducing the plate material into a hydrochloric acid bath, or the surface scale may be removed by high-pressure spraying of a slurry mixed with high-pressure water and an abrasive onto the plate material, but is not limited thereto.

[0106] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes a step of quenching the heat-treated FeCoV alloy-based plate material. If the microstructure of the FeCoV alloy-based plate material forms an ordered structure in a cold rolling process to be described later, since it has high strength and low elongation, there is a problem in that rupture or cracking occurs during the cold rolling process, making it difficult to roll to a target thickness. Therefore, in the present invention, the FeCoV alloy-based plate material is changed to form a disordered structure by performing the step of transforming an α-ferrite phase into a γ-austenite phase by heat-treating the FeCoV alloy-based plate material at 600 to 1,200°C for 10 minutes to 240 minutes. After that, by including the step of quenching so that the FeCoV alloy-based plate material can maintain the structure of the γ-austenite phase, elongation is improved to solve problems occurring during the cold rolling process. In another embodiment of the present invention, the step of quenching may be performed at a rate of 10 to 300°C / sec. Preferably, the quenching may be performed at a rate of 30 to 150°C / sec, and more preferably at a rate of 50 to 100°C / sec. When the quenching rate satisfies the above range, the γ-austenite phase is stably maintained, which is preferable because an FeCoV alloy-based thin plate having high saturation magnetic flux density can be manufactured. The step of quenching may be performing water cooling or oil cooling. The water cooling or oil cooling method is not particularly limited in the present invention, and a general method performed in the art may be applied. For example, it may be performed using a water-cooled or oil-cooled cooling guide and a conveyor roll, but is not limited thereto. By performing the water cooling or oil cooling, the γ-austenite phase structure, which is a high-temperature stable phase, can be stably maintained. The step of quenching may be performed by introducing the FeCoV-based alloy plate material into cooling water.

[0107] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes a step of cold-rolling the quenched FeCoV alloy-based plate material to obtain an FeCoV alloy-based thin plate. In the method for manufacturing an FeCoV alloy-based thin plate according to the present invention, cold rolling can be smoothly performed as the α-ferrite phase of a regular structure is heat-treated according to a specific temperature range and time, and is changed into a γ-austenite phase of an irregular structure by quenching it. The cold rolling may be repeatedly performed while changing a reduction ratio, but is not limited thereto. A cumulative reduction ratio may be 85% or more, specifically 90% or more, and more specifically 95% or more, but is also not limited thereto.

[0108] In another embodiment of the present invention, the method may further include: obtaining the FeCoV alloy-based thin plate; and then performing a stress relief heat treatment on the FeCoV alloy-based thin plate. By including the step of performing the stress relief heat treatment on the FeCoV alloy-based thin plate, residual stress existing inside the FeCoV alloy-based thin plate after the cold rolling can be removed, and as the irregular γ-austenite phase changes to a stable phase, regularity is secured, and accordingly, it is preferable because an FeCoV alloy-based thin plate having a high saturation magnetic flux density value, a low iron loss value, and appropriate tensile strength and elongation can be obtained.

[0109] The soft magnetic FeCoV-based alloy undergoes a process in which the phase of the structure changes in a process of being manufactured into a thin plate, and in this process, magnetic properties such as saturation magnetic flux density, residual magnetic flux density, coercivity, core loss, etc. are affected according to a specific method of heat treatment such as heat treatment atmosphere, temperature, and time. Here, when a soft magnetic material is used as a material for a drive motor component, etc., a higher saturation magnetic flux density or a magnetic flux density value in a specific frequency region is advantageous, and a lower loss value such as iron loss indicates an advantageous characteristic. Eventually, alloy design, processing, heat treatment, etc. are proceeded to exhibit high magnetic flux density and low iron loss value, and as a result, when a value obtained by dividing magnetic flux density by iron loss is defined as a high specific efficiency value, the higher this value is, the more excellent it is as a material for a motor. In the present invention, heat treatment for microstructure control is performed between hot rolling and cold rolling so that cold rolling can be smoothly performed, and stress relief heat treatment is additionally performed to improve mechanical properties, particularly elongation and magnetic properties after cold rolling, thereby having an advantage of manufacturing an FeCoV alloy-based thin plate excellent in both mechanical properties and magnetic properties. In another embodiment of the present invention, the stress relief heat treatment may be performed at 650 to 950°C for 10 to 120 minutes. Preferably, the stress relief heat treatment may be performed at a temperature of 700 to 950°C, and more preferably 850 to 950°C, but is not limited thereto.

[0110] One aspect of the present invention relates to a method for manufacturing an FeCoV alloy-based thin plate, comprising: preparing an FeCoV alloy-based plate material; heat-treating the FeCoV alloy-based plate material at 600 to 1,200°C for 10 minutes to 240 minutes to transform at least a portion of an α-ferrite phase into a γ-austenite phase; quenching the heat-treated FeCoV alloy-based plate material; cold-rolling the quenched FeCoV alloy-based plate material to obtain an FeCoV alloy-based thin plate; and performing a stress relief heat treatment on the FeCoV alloy-based thin plate. The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes the step of transforming at least a portion of the α-ferrite phase into the γ-austenite phase, whereby cold rolling can be easily performed, and by including the step of performing the stress relief heat treatment on the FeCoV alloy-based thin plate, mechanical properties, particularly elongation and magnetic properties are improved, so that there is an advantage in that an FeCoV alloy-based thin plate having excellent saturation magnetic flux density and low iron loss values can be manufactured without going through complicated processes such as conventional forging.

[0111] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes a step of preparing an FeCoV alloy-based plate material. The step of preparing the FeCoV alloy-based plate material is not limited in the present invention. For example, a commercially available FeCoV alloy-based plate material may be purchased and used, or it may be directly manufactured and used.

[0112] In another embodiment of the present invention, the step of preparing the FeCoV alloy-based plate material may include: preparing an FeCoV alloy melt by vacuum melting an alloy component composed of 20 to 49 at% of cobalt, greater than 0 and 5 at% or less of vanadium, 0 to 15 at% of nickel, 0 to 3 wt% of chromium, 0 to 1 at% of niobium, and a balance of iron and other impurities; casting the alloy melt to manufacture an ingot; and hot-rolling the ingot to obtain an FeCoV alloy-based plate material. The other impurities may be one or more selected from the group consisting of carbon, oxygen, silicon, and manganese. Specifically, the FeCoV alloy melt may include an alloy component composed of 30 to 49 at% of cobalt, 2 to 3 at% of vanadium, and a balance of iron and other impurities. More specifically, the FeCoV alloy melt may include an alloy component composed of 40 to 49 at% of cobalt, 2 to 3 at% of vanadium, and a balance of iron and other impurities. The FeCoV-based alloy is an alloy composition having soft magnetic properties, and is mainly used for motor cores of electronic products by being manufactured into a thin plate, and in particular, recently, application as a drive motor for electric vehicles is being considered. In order to increase the output of an electric vehicle, the magnetic flux density value of the motor core material must be high. Recently, most electric vehicles have a value of 2 Tesla or more, and since the FeCoV alloy has a value of up to 2.4 Tesla level, it can be very helpful in improving motor core output. In addition, since it has a significantly lower iron loss value compared to other soft magnetic materials, it is possible to drive a longer distance due to a lower loss value compared to a battery of the same capacity as well as efficiency improvement. For the same reason, when a motor exhibiting the same performance is manufactured, miniaturization and weight reduction are possible. Even with the same alloy composition, the defect rate of the rolling process may vary depending on the manufacturing process of such an FeCoV alloy, and mechanical and magnetic property values of the manufactured plate material may be greatly influenced. The method for manufacturing an FeCoV alloy-based thin plate according to the present invention has an advantage in that a thin plate having high mechanical and magnetic property values can be easily manufactured without including a conventional complicated slag removal process, forging process, process of forming into a slab shape, and the like. Meanwhile, the saturation magnetic flux density value and coercivity value of the manufactured FeCoV alloy-based thin plate may vary somewhat depending on the composition of the FeCoV alloy component. When the FeCoV alloy component having the above composition is used, there is an advantage in that an FeCoV alloy-based thin plate having a high saturation magnetic flux density value and low coercivity can be obtained. The FeCoV alloy melt may have a composition of Fe 49 Co 49 V 2 . By vacuum melting the alloy component, a grayish ingot with little contamination can be obtained, and when solidified into an ingot shape through a casting step to be described later, it is possible to suppress a phenomenon in which an ingot having a non-uniform composition is obtained due to composition inconsistency, for example, a case where the upper and middle, or middle and lower compositions of the ingot are different, or segregation exists in the same portion, which is preferable. In addition, it is preferable because it is possible to suppress a phenomenon in which a crack is induced in a hot rolling process, a cold rolling process, or the like because an oxide layer is too thick.

[0113] The step of preparing the alloy melt may be performed under an argon, nitrogen, or carbon dioxide atmosphere. When the step of preparing the alloy melt is performed under the argon, nitrogen, or carbon dioxide atmosphere, it is preferable because a phenomenon in which the alloy component is oxidized or carbonized can be suppressed.

[0114] In the step of preparing the FeCoV alloy melt by vacuum melting the alloy component, the degree of vacuum may be 1×10 -2< to 1×10 -4< torr, preferably 1×10 -2< to 1×10 -3< torr. When the degree of vacuum satisfies the above range, it is preferable because oxidation or carbonization can be suppressed.

[0115] The method may further include a step of removing slag of the alloy melt liquid before casting the alloy melt, but is not limited thereto. Alternatively, the method may not include the step of removing slag of the alloy melt liquid before casting the alloy melt, but is not limited thereto. A method of manufacturing the ingot by casting the alloy melt is not specifically limited in the present invention. For example, the ingot may be manufactured by injecting the alloy melt into a mold, and cooling and crystallizing it. The injection temperature is preferably set to a temperature 100 to 2,000°C, preferably 100 to 1,000°C, and more preferably 200 to 500°C higher than the liquidus temperature of the melt. The liquidus temperature of the melt can be measured using a direct temperature measurement method with a built-in thermocouple or by measuring the surface of the melt using a non-contact laser thermometer. In addition, the cooling temperature and rate can be controlled to prevent segregation and ensure uniformity of composition by making the cooling temperature uniform. Since the upper part of the ingot cools relatively quickly and the lower part or the inside may cool slowly, the quickly cooling part may be heated, or insulated with non-metallic ceramics or slag.

[0116] The ingot may be manufactured in, for example, a bar, polyhedron, cylinder, sphere shape, or atypical shape, but is not limited thereto. The step of preparing the FeCoV alloy-based plate material may further include a step of cutting the ingot to 4 to 30 mm. For example, the method for manufacturing an FeCoV alloy-based thin plate may further include cutting the ingot to 10 to 30 mm. When the step of cutting the ingot within the above range is further included, it is preferable because hot rolling is smooth. Cutting of the ingot may be performed by a method commonly performed in the art, and the present invention is not limited thereto.

[0117] The method may further include: manufacturing an ingot by casting the alloy melt; and then homogenizing heat-treating the ingot. The homogenizing heat treatment may be performed at 1,200 to 1,300°C for 1 to 12 hours. Preferably, the homogenizing heat treatment may be performed for 2 to 6 hours, more preferably 2 to 4 hours, but is not limited thereto. When the step of homogenizing heat-treating is further included, it is preferable because stress generated during casting can be relieved.

[0118] The step of preparing the FeCoV alloy-based plate material may include a step of hot-rolling the ingot to obtain a plate material. By hot-rolling the ingot, it is preferable because a plate material in which a γ-austenite phase formed by slow cooling occupies the majority or an α-ferrite phase and the γ-austenite phase are mixed can be obtained.

[0119] The hot rolling may be performed using, for example, a steel rolling mill. The rolling start temperature, rolling speed, rolling end temperature, and the like are not particularly limited in the present invention, and may be appropriately performed according to conventional conditions performed in the art. For example, the start temperature for the rolling may be 900°C or higher, and may not exceed 1,300°C. When the start temperature for the rolling satisfies the above range, it is preferable because there is an advantage in that the strength and formability of the manufactured plate material are excellent. The rolling end temperature may be 1,150°C or higher. When the rolling end temperature is 1,150°C or higher, it is preferable because a phenomenon in which excessive load is applied to equipment due to high deformation resistance can be suppressed, and control of the shape is easy.

[0120] The total reduction ratio by the hot rolling may be 70 to 90%, preferably 75 to 90%, and more preferably 75 to 85%. When the total reduction ratio satisfies the above range, it is preferable because enlargement of crystal grains due to large energy can be suppressed, and the deviation thereof can be reduced.

[0121] The rolling may be performed for one pass to several passes, but is not limited thereto. In another embodiment of the present invention, the rolling may be performed in two or more rolling passes. Specifically, the rolling may be performed in 5 or more rolling passes, but is not limited thereto.

[0122] When the temperature decreases as the hot rolling is repeated, it is preferable to perform the hot rolling after raising the temperature by reheating. The lower limit of the temperature during the rolling process is preferably controlled to 900°C or higher, preferably 900 to 1,000°C. When the lower limit of the temperature during the rolling process satisfies the above range, it is preferable because most of the phase exists as the γ-austenite phase, so that cracks or ruptures hardly occur during hot rolling and the process becomes smooth.

[0123] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes the step of heat-treating the plate material at 600 to 1,200°C for 10 minutes to 240 minutes to transform at least a portion of the α-ferrite phase into the γ-austenite phase. Although not wishing to be bound by theory, generally, an FeCoV-based alloy undergoes a phase change while going through a casting process, a hot rolling process, a heat treatment process, a cold rolling process, and the like, and even the same phase changes into an ordered lattice or a disordered lattice. For example, when an FeCoV-based alloy is melted in a vacuum and cast into an ingot, an α-ferrite phase is formed. In the case of α-ferrite, which is a room temperature structure, it forms a Body-Centered Cubic (BCC) structure and has relatively fewer slip planes, so there is a high possibility that rolling may not be performed smoothly when cold rolling or the like is performed later to use a thin plate using the FeCoV alloy-based plate material. In particular, due to residual stress existing inside the plate material after cold rolling, forming may be difficult, and a phenomenon in which soft magnetic properties are not properly implemented may occur. On the other hand, a γ-austenite structure, which is a high-temperature structure, forms a Face-Centered Cubic (FCC) structure, which is a disordered structure, and has many slip planes, so rolling is easy, and plastic workability is much superior to that of α-ferrite. Therefore, the method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes heat-treating the plate material at a temperature of 600 to 1,200°C, which is a high-temperature stable phase section, so as to have a γ-austenite structure, that is, an FCC structure, which is a high-temperature stable phase, and then quenching the plate material, thereby transforming the α-ferrite phase generated through the casting process and the hot rolling process into the γ-austenite phase, so that the structure is changed to a structure having the γ-austenite phase or a composite structure of the α-ferrite phase and the γ-austenite phase.

[0124] In another embodiment of the present invention, the heat treatment may be performed at 730 to 1,200°C. Specifically, the heat treatment may be performed at a temperature of 730°C or higher, which is a temperature at which an irregular / regular lattice structure starts to be ordered, and a temperature of 1,200°C or lower, which is a temperature at which a liquid phase is not formed and atomic structure change is expected to be most active. Specifically, the heat treatment is preferably performed within the above range, which is a temperature region where irregular / regular structure change occurs.

[0125] In another embodiment of the present invention, the heat treatment may be performed at 840 to 1,200°C. Specifically, the heat treatment may be performed at a temperature of 840°C or higher, which is a temperature at which phase transformation occurs, and a temperature of 1,200°C or lower, which is a temperature at which solid phase control is possible without mixing of a liquid phase. In another embodiment of the present invention, the step of transforming into the γ-austenite phase may be heat-treating at 850 to 950°C. Since mechanical properties and / or magnetic properties may vary greatly depending on the heat treatment temperature even if the FeCoV alloy-based plate material has the same composition, in the present invention, by heat-treating at a temperature within the above range, it is possible to obtain an FeCoV alloy-based thin plate having excellent mechanical properties and excellent magnetic properties, that is, high saturation magnetic flux density and low iron loss value at the same time.

[0126] In another embodiment of the present invention, the heat treatment may be performed for 30 to 240 minutes. Preferably, the heat treatment may be performed for 60 to 120 minutes. When the heat treatment time satisfies the above range, it is preferable because the phase transformation time to the γ-austenite phase is sufficient while shortening the heat treatment time. In short, the step of transforming into the γ-austenite phase may be heat-treating at a temperature of 850 to 950°C for 60 to 120 minutes.

[0127] In another embodiment of the present invention, the step of transforming into the γ-austenite phase may be performed under a vacuum or inert gas atmosphere. Since the FeCoV-based alloy is somewhat prone to oxidation, the step of transforming into the γ-austenite phase is preferably performed under a vacuum or inert gas atmosphere. The inert gas may be, for example, high-purity argon (Ar) gas, but is not limited thereto.

[0128] In another embodiment of the present invention, the method may further include a step of removing a surface scale of the plate material before the step of heat-treating the plate material. Since an oxide scale may be formed on the surface of the plate material that has undergone the hot rolling, and the oxide scale may affect the quality of the plate material, it is preferable to further include the step of removing the surface scale of the plate material. A method of removing the surface scale of the plate material may be performed using a conventional method performed in the art. For example, the pickling treatment may be performed by introducing the plate material into a hydrochloric acid bath, or the surface scale may be removed by high-pressure spraying of a slurry mixed with high-pressure water and an abrasive onto the plate material, but is not limited thereto.

[0129] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes a step of quenching the heat-treated FeCoV alloy-based plate material. If the microstructure of the FeCoV alloy-based plate material forms an ordered structure in a cold rolling process to be described later, since it has high strength and low elongation, there is a problem in that rupture or cracking occurs during the cold rolling process, making it difficult to roll to a target thickness. Therefore, in the present invention, the FeCoV alloy-based plate material is changed to form a disordered structure by performing the step of transforming an α-ferrite phase into a γ-austenite phase by heat-treating the FeCoV alloy-based plate material at 600 to 1,200°C for 10 minutes to 240 minutes. After that, by including the step of quenching so that the FeCoV alloy-based plate material can maintain the structure of the γ-austenite phase, elongation is improved to solve problems occurring during the cold rolling process. In another embodiment of the present invention, the step of quenching may be performed at a rate of 10 to 300°C / sec. Preferably, the quenching may be performed at a rate of 30 to 150°C / sec, and more preferably at a rate of 50 to 100°C / sec. When the quenching rate satisfies the above range, the γ-austenite phase is stably maintained, which is preferable because an FeCoV alloy-based thin plate having high saturation magnetic flux density can be manufactured. The step of quenching may be performing water cooling or oil cooling. The water cooling or oil cooling method is not particularly limited in the present invention, and a general method performed in the art may be applied. For example, it may be performed using a water-cooled or oil-cooled cooling guide and a conveyor roll, but is not limited thereto. By performing the water cooling or oil cooling, the γ-austenite phase structure, which is a high-temperature stable phase, can be stably maintained. The step of quenching may be performed by introducing the FeCoV-based alloy plate material into cooling water.

[0130] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes a step of cold-rolling the quenched FeCoV alloy-based plate material to obtain an FeCoV alloy-based thin plate. In the method for manufacturing an FeCoV alloy-based thin plate according to the present invention, cold rolling can be smoothly performed as the α-ferrite phase of a regular structure is heat-treated according to a specific temperature range and time, and is changed into a γ-austenite phase of an irregular structure by quenching it. The cold rolling may be repeatedly performed while changing a reduction ratio, but is not limited thereto. A cumulative reduction ratio may be 85% or more, specifically 90% or more, and more specifically 95% or more, but is also not limited thereto.

[0131] In another embodiment of the present invention, the method may further include: obtaining the FeCoV alloy-based thin plate; and then performing a stress relief heat treatment on the FeCoV alloy-based thin plate. By including the step of performing the stress relief heat treatment on the FeCoV alloy-based thin plate, residual stress existing inside the FeCoV alloy-based thin plate after the cold rolling can be removed, and as the irregular γ-austenite phase changes to a stable phase, regularity is secured, and accordingly, it is preferable because an FeCoV alloy-based thin plate having a high saturation magnetic flux density value, a low iron loss value, and appropriate tensile strength and elongation can be obtained.

[0132] The soft magnetic FeCoV-based alloy undergoes a process in which the phase of the structure changes in a process of being manufactured into a thin plate, and in this process, magnetic properties such as saturation magnetic flux density, residual magnetic flux density, coercivity, core loss, etc. are affected according to a specific method of heat treatment such as heat treatment atmosphere, temperature, and time. Here, when a soft magnetic material is used as a material for a drive motor component, etc., a higher saturation magnetic flux density or a magnetic flux density value in a specific frequency region is advantageous, and a lower loss value such as iron loss indicates an advantageous characteristic. Eventually, alloy design, processing, heat treatment, etc. are proceeded to exhibit high magnetic flux density and low iron loss value, and as a result, when a value obtained by dividing magnetic flux density by iron loss is defined as a high specific efficiency value, the higher this value is, the more excellent it is as a material for a motor. In the present invention, heat treatment for microstructure control is performed between hot rolling and cold rolling so that cold rolling can be smoothly performed, and stress relief heat treatment is additionally performed to improve mechanical properties, particularly elongation and magnetic properties after cold rolling, thereby having an advantage of manufacturing an FeCoV alloy-based thin plate excellent in both mechanical properties and magnetic properties. In another embodiment of the present invention, the stress relief heat treatment may be performed at 650 to 950°C for 10 to 120 minutes. Preferably, the stress relief heat treatment may be performed at a temperature of 700 to 950°C, and more preferably 850 to 950°C, but is not limited thereto.

[0133] Another aspect of the present invention relates to a method for manufacturing an FeCoV alloy-based thin plate, comprising: preparing an FeCoV alloy melt; casting the alloy melt to manufacture an ingot; hot-rolling the ingot to obtain a plate material; heat-treating the plate material at 600 to 1,200°C for 10 minutes to 240 minutes to transform at least a portion of an α-ferrite phase into a γ-austenite phase; quenching the heat-treated plate material; and cold-rolling the quenched plate material to obtain an FeCoV alloy-based thin plate, wherein the FeCoV alloy-based thin plate is characterized in that an intensity of a peak of a (100) plane among peaks of an X-ray diffraction pattern of the ingot is decreased or does not appear. The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes the step of transforming at least a portion of the α-ferrite phase into the γ-austenite phase, whereby cold rolling can be easily performed, and there is an advantage in that an FeCoV alloy-based thin plate having excellent saturation magnetic flux density and low iron loss values can be manufactured without going through complicated processes such as conventional forging.

[0134] In another embodiment of the present invention, the step of preparing the alloy melt may include a step of vacuum melting an alloy component composed of 20 to 49 at% of cobalt, 2 to 5 at% of vanadium, and a balance of iron and other impurities. The other impurities may be one or more selected from the group consisting of carbon, oxygen, silicon, and manganese. In another embodiment of the present invention, the FeCoV alloy melt may include an alloy component composed of 30 to 49 at% of cobalt, 2 to 3 at% of vanadium, and a balance of iron and other impurities. In another embodiment of the present invention, the FeCoV alloy melt may include an alloy component composed of 40 to 49 at% of cobalt, 2 to 3 at% of vanadium, and a balance of iron and other impurities. The FeCoV-based alloy is an alloy composition having soft magnetic properties, and is mainly used for motor cores of electronic products by being manufactured into a thin plate, and in particular, recently, application as a drive motor for electric vehicles is being considered. In order to increase the output of an electric vehicle, the magnetic flux density value of the motor core material must be high. Recently, most electric vehicles have a value of 2 Tesla or more, and since the FeCoV alloy has a value of up to 2.4 Tesla level, it can be very helpful in improving motor core output. In addition, since it has a significantly lower iron loss value compared to other soft magnetic materials, it is possible to drive a longer distance due to a lower loss value compared to a battery of the same capacity as well as efficiency improvement. For the same reason, when a motor exhibiting the same performance is manufactured, miniaturization and weight reduction are possible. Even with the same alloy composition, the defect rate of the rolling process may vary depending on the manufacturing process of such an FeCoV alloy, and mechanical and magnetic property values of the manufactured plate material may be greatly influenced. The method for manufacturing an FeCoV alloy-based thin plate according to the present invention has an advantage in that a thin plate having high mechanical and magnetic property values can be easily manufactured without including a conventional complicated slag removal process, forging process, process of forming into a slab shape, and the like. Meanwhile, the saturation magnetic flux density value and coercivity value of the manufactured FeCoV alloy-based thin plate may vary somewhat depending on the composition of the FeCoV alloy component. In the present invention, by using the FeCoV alloy component having the above composition, there is an advantage in that an FeCoV alloy-based thin plate having a high saturation magnetic flux density value and low coercivity can be obtained. The FeCoV alloy melt may have a composition of Fe 49 Co 49 V 2 . By vacuum melting the alloy component, a grayish ingot with little contamination can be obtained, and when solidified into an ingot shape through a casting step to be described later, it is possible to suppress a phenomenon in which an ingot having a non-uniform composition is obtained due to composition inconsistency, for example, a case where the upper and middle, or middle and lower compositions of the ingot are different, or segregation exists in the same portion, which is preferable. In addition, it is preferable because it is possible to suppress a phenomenon in which a crack is induced in a hot rolling process, a cold rolling process, or the like because an oxide layer is too thick.

[0135] The step of preparing the alloy melt may be performed under an argon, nitrogen, or carbon dioxide atmosphere. When the step of preparing the alloy melt is performed under the argon, nitrogen, or carbon dioxide atmosphere, it is preferable because a phenomenon in which the alloy component is oxidized or carbonized can be suppressed.

[0136] In the step of preparing the FeCoV alloy melt by vacuum melting the alloy component, the degree of vacuum may be 1×10 -2< to 1×10 -4< torr, preferably 1×10 -2< to 1×10 -3< torr. When the degree of vacuum satisfies the above range, it is preferable because oxidation or carbonization can be suppressed.

[0137] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes the step of manufacturing an ingot by casting the alloy melt. The method may further include a step of removing slag of the alloy melt liquid before casting the alloy melt, but is not limited thereto. The method for manufacturing an FeCoV alloy-based thin plate according to the present invention may not include the step of removing slag of the alloy melt liquid. Specifically, the method for manufacturing an FeCoV alloy-based thin plate according to the present invention has an advantage in that it is possible to manufacture an FeCoV alloy-based thin plate exhibiting excellent performance without including a slag removal process, a forging process, and a shape control slabbing process. A method of manufacturing the ingot by casting the alloy melt is not specifically limited in the present invention. For example, the ingot may be manufactured by injecting the alloy melt into a mold, and cooling and crystallizing it. The injection temperature is preferably set to a temperature 100 to 2,000°C, preferably 100 to 1,000°C, and more preferably 200 to 500°C higher than the liquidus temperature of the melt. The liquidus temperature of the melt can be measured using a direct temperature measurement method with a built-in thermocouple or by measuring the surface of the melt using a non-contact laser thermometer. In addition, the cooling temperature and rate can be controlled to prevent segregation and ensure uniformity of composition by making the cooling temperature uniform. Since the upper part of the ingot cools relatively quickly and the lower part or the inside may cool slowly, the quickly cooling part may be heated, or insulated with non-metallic ceramics or slag.

[0138] The ingot may be manufactured in, for example, a bar, polyhedron, cylinder, sphere shape, or atypical shape, but is not limited thereto. The method for manufacturing an FeCoV alloy-based thin plate according to the present invention may further include cutting the ingot to 4 to 30 mm. For example, the method for manufacturing an FeCoV alloy-based thin plate may further include cutting the ingot to 10 to 30 mm. When the step of cutting the ingot within the above range is further included, it is preferable because hot rolling is smooth. Cutting of the ingot may be performed by a method commonly performed in the art, and the present invention is not limited thereto.

[0139] In another embodiment of the present invention, the method may further include: manufacturing an ingot by casting the alloy melt; and then homogenizing heat-treating the ingot. In another embodiment of the present invention, the homogenizing heat treatment may be performed at 1,200 to 1,300°C for 1 to 12 hours. Preferably, the homogenizing heat treatment may be performed for 2 to 6 hours, more preferably 2 to 4 hours, but is not limited thereto. When the step of homogenizing heat-treating is further included, it is preferable because stress generated during casting can be relieved.

[0140] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes the step of hot-rolling the ingot to obtain a plate material. By hot-rolling the ingot, it is preferable because a plate material in which a γ-austenite phase formed by slow cooling occupies the majority or an α-ferrite phase and the γ-austenite phase are mixed can be obtained.

[0141] The hot rolling may be performed using, for example, a steel rolling mill. The rolling start temperature, rolling speed, rolling end temperature, and the like are not particularly limited in the present invention, and may be appropriately performed according to conventional conditions performed in the art. For example, the start temperature for the rolling may be 900°C or higher, and may not exceed 1,300°C. When the start temperature for the rolling satisfies the above range, it is preferable because there is an advantage in that the strength and formability of the manufactured plate material are excellent. The rolling end temperature may be 1,150°C or higher. When the rolling end temperature is 1,150°C or higher, it is preferable because a phenomenon in which excessive load is applied to equipment due to high deformation resistance can be suppressed, and control of the shape is easy.

[0142] The total reduction ratio by the hot rolling may be 70 to 90%, preferably 75 to 90%, and more preferably 75 to 85%. When the total reduction ratio satisfies the above range, it is preferable because enlargement of crystal grains due to large energy can be suppressed, and the deviation thereof can be reduced.

[0143] The rolling may be performed for one pass to several passes, but is not limited thereto. In another embodiment of the present invention, the rolling may be performed in two or more rolling passes. Specifically, the rolling may be performed in 5 or more rolling passes, but is not limited thereto.

[0144] When the temperature decreases as the hot rolling is repeated, it is preferable to perform the hot rolling after raising the temperature by reheating. The lower limit of the temperature during the rolling process is preferably controlled to 900°C or higher, preferably 900 to 1,000°C. When the lower limit of the temperature during the rolling process satisfies the above range, it is preferable because most of the phase exists as the γ-austenite phase, so that cracks or ruptures hardly occur during hot rolling and the process becomes smooth.

[0145] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes the step of heat-treating the plate material at 600 to 1,200°C for 10 minutes to 240 minutes to transform at least a portion of the α-ferrite phase into the γ-austenite phase. Although not wishing to be bound by theory, generally, an FeCoV-based alloy undergoes a phase change while going through a casting process, a hot rolling process, a heat treatment process, a cold rolling process, and the like, and even the same phase changes into an ordered lattice or a disordered lattice. For example, when an FeCoV-based alloy is melted in a vacuum and cast into an ingot, an α-ferrite phase is formed. In the case of α-ferrite, which is a room temperature structure, it forms a Body-Centered Cubic (BCC) structure and has relatively fewer slip planes, so there is a high possibility that rolling may not be performed smoothly when cold rolling or the like is performed later to use a thin plate using the FeCoV alloy-based plate material. In particular, due to residual stress existing inside the plate material after cold rolling, forming may be difficult, and a phenomenon in which soft magnetic properties are not properly implemented may occur. On the other hand, a γ-austenite structure, which is a high-temperature structure, forms a Face-Centered Cubic (FCC) structure, which is a disordered structure, and has many slip planes, so rolling is easy, and plastic workability is much superior to that of α-ferrite. Therefore, the method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes heat-treating the plate material at a temperature of 600 to 1,200°C, which is a high-temperature stable phase section, so as to have a γ-austenite structure, that is, an FCC structure, which is a high-temperature stable phase, and then quenching the plate material, thereby transforming the α-ferrite phase generated through the casting process and the hot rolling process into the γ-austenite phase, so that the structure is changed to a structure having the γ-austenite phase or a composite structure of the α-ferrite phase and the γ-austenite phase.

[0146] In another embodiment of the present invention, the heat treatment may be performed at 730 to 1,200°C. Specifically, the heat treatment may be performed at a temperature of 730°C or higher, which is a temperature at which an irregular / regular lattice structure starts to be ordered, and a temperature of 1,200°C or lower, which is a temperature at which a liquid phase is not formed and atomic structure change is expected to be most active. Specifically, the heat treatment is preferably performed within the above range, which is a temperature region where irregular / regular structure change occurs.

[0147] In another embodiment of the present invention, the heat treatment may be performed at 840 to 1,200°C. Specifically, the heat treatment may be performed at a temperature of 840°C or higher, which is a temperature at which phase transformation occurs, and a temperature of 1,200°C or lower, which is a temperature at which solid phase control is possible without mixing of a liquid phase. In another embodiment of the present invention, the step of transforming into the γ-austenite phase may be heat-treating at 850 to 950°C. Since mechanical properties and / or magnetic properties may vary greatly depending on the heat treatment temperature even if the FeCoV alloy-based plate material has the same composition, in the present invention, by heat-treating at a temperature within the above range, it is possible to obtain an FeCoV alloy-based thin plate having excellent mechanical properties and excellent magnetic properties, that is, high saturation magnetic flux density and low iron loss value at the same time.

[0148] In another embodiment of the present invention, the heat treatment may be performed for 30 to 240 minutes. Preferably, the heat treatment may be performed for 60 to 120 minutes. When the heat treatment time satisfies the above range, it is preferable because the phase transformation time to the γ-austenite phase is sufficient while shortening the heat treatment time. In short, the step of transforming into the γ-austenite phase may be heat-treating at a temperature of 850 to 950°C for 60 to 120 minutes.

[0149] In another embodiment of the present invention, the step of transforming into the γ-austenite phase may be performed under a vacuum or inert gas atmosphere. Since the FeCoV-based alloy is somewhat prone to oxidation, the step of transforming into the γ-austenite phase is preferably performed under a vacuum or inert gas atmosphere. The inert gas may be, for example, high-purity argon (Ar) gas, but is not limited thereto.

[0150] In another embodiment of the present invention, the method may further include a step of removing a surface scale of the plate material before the step of heat-treating the plate material. Since an oxide scale may be formed on the surface of the plate material that has undergone the hot rolling, and the oxide scale may affect the quality of the plate material, it is preferable to further include the step of removing the surface scale of the plate material. A method of removing the surface scale of the plate material may be performed using a conventional method performed in the art. For example, the pickling treatment may be performed by introducing the plate material into a hydrochloric acid bath, or the surface scale may be removed by high-pressure spraying of a slurry mixed with high-pressure water and an abrasive onto the plate material, but is not limited thereto.

[0151] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes a step of quenching the heat-treated FeCoV alloy-based plate material. If the microstructure of the FeCoV alloy-based plate material forms an ordered structure in a cold rolling process to be described later, since it has high strength and low elongation, there is a problem in that rupture or cracking occurs during the cold rolling process, making it difficult to roll to a target thickness. Therefore, in the present invention, the FeCoV alloy-based plate material is changed to form a disordered structure by performing the step of transforming an α-ferrite phase into a y-austenite phase by heat-treating the FeCoV alloy-based plate material at 600 to 1,200°C for 10 minutes to 240 minutes. After that, by including the step of quenching so that the FeCoV alloy-based plate material can maintain the structure of the γ-austenite phase, elongation is improved to solve problems occurring during the cold rolling process. In another embodiment of the present invention, the step of quenching may be performed at a rate of 10 to 300°C / sec. Preferably, the quenching may be performed at a rate of 30 to 150°C / sec, and more preferably at a rate of 50 to 100°C / sec. When the quenching rate satisfies the above range, the γ-austenite phase is stably maintained, which is preferable because an FeCoV alloy-based thin plate having high saturation magnetic flux density can be manufactured. The step of quenching may be performing water cooling or oil cooling. The water cooling or oil cooling method is not particularly limited in the present invention, and a general method performed in the art may be applied. For example, it may be performed using a water-cooled or oil-cooled cooling guide and a conveyor roll, but is not limited thereto. By performing the water cooling or oil cooling, the γ-austenite phase structure, which is a high-temperature stable phase, can be stably maintained. The step of quenching may be performed by introducing the FeCoV-based alloy plate material into cooling water.

[0152] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes a step of cold-rolling the quenched FeCoV alloy-based plate material to obtain an FeCoV alloy-based thin plate. In the method for manufacturing an FeCoV alloy-based thin plate according to the present invention, cold rolling can be smoothly performed as the α-ferrite phase of a regular structure is heat-treated according to a specific temperature range and time, and is changed into a γ-austenite phase of an irregular structure by quenching it. The cold rolling may be repeatedly performed while changing a reduction ratio, but is not limited thereto. A cumulative reduction ratio may be 85% or more, specifically 90% or more, and more specifically 95% or more, but is also not limited thereto.

[0153] In the FeCoV alloy-based thin plate according to the present invention, an intensity of a peak of a (100) plane among peaks of an X-ray diffraction pattern of the ingot is decreased or does not appear. In another embodiment of the present invention, in the FeCoV alloy-based thin plate, an intensity of a peak of a (211) plane among peaks of the X-ray diffraction pattern of the ingot may be increased. In the case of the ingot, since it exhibits an ordered structure due to slow cooling, the peak of the (100) plane appears highest in the X-ray diffraction pattern, and the rest show peaks of relatively very low intensity. However, when heat treatment for removing stress generated during the rolling process is finally performed after cold rolling, the intensity of the peak of the (100) plane of the ingot decreases or does not appear. On the other hand, as the disordered structure changes to an ordered structure according to the heat treatment, the intensity of the peak of the (211) plane among the peaks of the X-ray diffraction pattern of the ingot may increase.

[0154] In another embodiment of the present invention, in the FeCoV alloy-based thin plate, the intensity of the peak of the (100) plane among peaks of an X-ray diffraction pattern of the hot-rolled plate material may be decreased or may not appear. In another embodiment of the present invention, in the FeCoV alloy-based thin plate, the intensity of the peak of the (211) plane among the peaks of the hot-rolled X-ray diffraction pattern may be increased.

[0155] In the FeCoV alloy-based thin plate, a full width at half maximum (FWHM) of a maximum peak in a range where 20 is 42 to 47° in an X-ray diffraction chart obtained by XRD analysis may be different before heat-treating the plate material and after heat-treating the plate material. In the FeCoV alloy-based thin plate, a full width at half maximum (FWHM) of a maximum peak in a range where 20 is 42 to 47° in an X-ray diffraction chart obtained by XRD analysis may be different before performing the stress relief heat treatment on the FeCoV alloy-based thin plate and after performing the stress relief heat treatment on the FeCoV alloy-based thin plate.

[0156] In another embodiment of the present invention, the FeCoV alloy-based thin plate may further include crystal grains of 150 µm or less by 50% or more compared to the ingot. Since the FeCoV alloy-based thin plate retains a part of the high-temperature structure by quenching after heat treatment at the high temperature, at least a portion or all of the α-ferrite phase is changed to the γ-austenite phase through the heat treatment, and since it is manufactured through processes such as repeated cold rolling, relatively uniform crystal grains of 150 µm or less may be further included by 50% or more, specifically 60% or more, and more specifically 70% or more compared to the ingot. In another embodiment of the present invention, in the FeCoV alloy-based thin plate, a difference between an area occupied by cobalt and an area occupied by iron within a region from a surface of the FeCoV alloy-based thin plate to 35 µm on a GDS depth profile may be smaller than a difference between an area occupied by cobalt and an area occupied by iron within a region from a surface of the hot-rolled plate material to 35 µm. In another embodiment of the present invention, in the FeCoV alloy-based thin plate, a content of impurities in a region from a surface of the FeCoV alloy-based thin plate to 5 µm on a GDS depth profile may be less than a content of impurities in a region from a surface of the hot-rolled plate material to 5 µm. The impurities may refer to oxides or carbides generated due to oxygen (O 2 ), carbon (C), and the like. Specifically, in the FeCoV alloy-based thin plate according to the present invention, the content of impurities such as oxygen and carbon decreases rapidly within a region from the surface of the thin plate to 5 µm, so that oxides and carbides do not exist therein, and thus mechanical properties as well as magnetic properties may be excellent.

[0157] In another embodiment of the present invention, the method may further include: obtaining the FeCoV alloy-based thin plate; and then performing a stress relief heat treatment on the FeCoV alloy-based thin plate. By including the step of performing the stress relief heat treatment on the FeCoV alloy-based thin plate, residual stress existing inside the FeCoV alloy-based thin plate after the cold rolling can be removed, and as the irregular γ-austenite phase changes to a stable phase, regularity is secured, and accordingly, it is preferable because an FeCoV alloy-based thin plate having a high saturation magnetic flux density value, a low iron loss value, and appropriate tensile strength and elongation can be obtained.

[0158] The soft magnetic FeCoV-based alloy undergoes a process in which the phase of the structure changes in a process of being manufactured into a thin plate, and in this process, magnetic properties such as saturation magnetic flux density, residual magnetic flux density, coercivity, core loss, etc. are affected according to a specific method of heat treatment such as heat treatment atmosphere, temperature, and time. Here, when a soft magnetic material is used as a material for a drive motor component, etc., a higher saturation magnetic flux density or a magnetic flux density value in a specific frequency region is advantageous, and a lower loss value such as iron loss indicates an advantageous characteristic. Eventually, alloy design, processing, heat treatment, etc. are proceeded to exhibit high magnetic flux density and low iron loss value, and as a result, when a value obtained by dividing magnetic flux density by iron loss is defined as a high specific efficiency value, the higher this value is, the more excellent it is as a material for a motor. In the present invention, heat treatment for microstructure control is performed between hot rolling and cold rolling so that cold rolling can be smoothly performed, and stress relief heat treatment is additionally performed to improve mechanical properties, particularly elongation and magnetic properties after cold rolling, thereby having an advantage of manufacturing an FeCoV alloy-based thin plate excellent in both mechanical properties and magnetic properties. In another embodiment of the present invention, the stress relief heat treatment may be performed at 650 to 950°C for 10 to 120 minutes. Preferably, the stress relief heat treatment may be performed at a temperature of 700 to 950°C, and more preferably 850 to 950°C, but is not limited thereto.

[0159] Another aspect of the present invention relates to a method for manufacturing an FeCoV alloy-based thin plate, comprising: preparing an FeCoV alloy melt by vacuum melting an alloy component containing 49 to 66 at% (atomic percent) of iron, 20 to 49 at% of cobalt, greater than 0 and 2 at% or less of vanadium, 0 to 15 at% of nickel, 0 to 3 at% of chromium, and 0 to 1 at% of niobium; casting the alloy melt to manufacture an ingot; hot-rolling the ingot to obtain a plate material; heat-treating the plate material at 600 to 1,200°C for 10 minutes to 240 minutes to transform at least a portion of an α-ferrite phase into a γ-austenite phase; quenching the heat-treated plate material; and cold-rolling the quenched plate material to obtain an FeCoV alloy-based thin plate. The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes the step of transforming at least a portion of the α-ferrite phase into the γ-austenite phase, whereby cold rolling can be easily performed, and there is an advantage in that an FeCoV alloy-based thin plate having excellent saturation magnetic flux density and low iron loss values can be manufactured without going through complicated processes such as conventional forging.

[0160] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes preparing an FeCoV alloy melt by vacuum melting an alloy component containing 49 to 66 at% (atomic percent) of iron, 20 to 49 at% of cobalt, greater than 0 and 2 at% or less of vanadium, 0 to 15 at% of nickel, 0 to 3 at% of chromium, and 0 to 1 at% of niobium. The other impurities may be one or more selected from the group consisting of carbon, oxygen, silicon, and manganese. By preparing the FeCoV alloy melt by vacuum melting the alloy component having the above composition, there is an advantage in that mechanical properties such as strength and elongation can be secured while having a high saturation magnetic flux density value, and alloy costs can be reduced.

[0161] The FeCoV-based alloy is an alloy composition having soft magnetic properties, and is mainly used for motor cores of electronic products by being manufactured into a thin plate, and in particular, recently, application as a drive motor for electric vehicles is being considered. In order to increase the output of an electric vehicle, the magnetic flux density value of the motor core material must be high. Recently, most electric vehicles have a value of 2 Tesla or more, and since the FeCoV alloy has a value of up to 2.4 Tesla level, it can be very helpful in improving motor core output. In addition, since it has a significantly lower iron loss value compared to other soft magnetic materials, it is possible to drive a longer distance due to a lower loss value compared to a battery of the same capacity as well as efficiency improvement. For the same reason, when a motor exhibiting the same performance is manufactured, miniaturization and weight reduction are possible. Even with the same alloy composition, the defect rate of the rolling process may vary depending on the manufacturing process of such an FeCoV alloy, and mechanical and magnetic property values of the manufactured plate material may be greatly influenced. The method for manufacturing an FeCoV alloy-based thin plate according to the present invention has an advantage in that a thin plate having high mechanical and magnetic property values can be easily manufactured without including a conventional complicated slag removal process, forging process, process of forming into a slab shape, and the like. Meanwhile, the saturation magnetic flux density value and coercivity value of the manufactured FeCoV alloy-based thin plate may vary somewhat depending on the composition of the FeCoV alloy component. In the present invention, by using the FeCoV alloy component having the above composition, there is an advantage in that an FeCoV alloy-based thin plate having a high saturation magnetic flux density value and low coercivity can be obtained. By vacuum melting the alloy component, a grayish ingot with little contamination can be obtained, and when solidified into an ingot shape through a casting step to be described later, it is possible to suppress a phenomenon in which an ingot having a non-uniform composition is obtained due to composition inconsistency, for example, a case where the upper and middle, or middle and lower compositions of the ingot are different, or segregation exists in the same portion, which is preferable. In addition, it is preferable because it is possible to suppress a phenomenon in which a crack is induced in a hot rolling process, a cold rolling process, or the like because an oxide layer is too thick.

[0162] The step of preparing the alloy melt may be performed under an argon, nitrogen, or carbon dioxide atmosphere. When the step of preparing the alloy melt is performed under the argon, nitrogen, or carbon dioxide atmosphere, it is preferable because a phenomenon in which the alloy component is oxidized or carbonized can be suppressed.

[0163] In the step of preparing the FeCoV alloy melt by vacuum melting the alloy component, the degree of vacuum may be 1×10 -2< to 1×10 -4< torr, preferably 1×10 -2< to 1×10 -3< torr. When the degree of vacuum satisfies the above range, it is preferable because oxidation or carbonization can be suppressed. In the step of preparing the alloy melt, for elements having a large difference in melting point between the alloy components, high melting point metals such as Fe, Co, and V may be added and melted first, and then low melting point metals such as Al and Mg may be added later, followed by cooling described later, but the present invention is not limited thereto. However, in this case, it is preferable because a phenomenon in which fumes are generated or vaporization occurs due to exposure of the low melting point metal to high temperature for a long time can be suppressed. In addition, when it is desired to add the low melting point metal to the high melting point metal in a specific content, the target composition may be achieved by adding a slightly higher content than the target composition by predicting the content loss, but is not limited thereto.

[0164] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes the step of manufacturing an ingot by casting the alloy melt. The method may further include a step of removing slag of the alloy melt liquid before casting the alloy melt, but is not limited thereto. The method for manufacturing an FeCoV alloy-based thin plate according to the present invention may not include the step of removing slag of the alloy melt liquid. Specifically, the method for manufacturing an FeCoV alloy-based thin plate according to the present invention has an advantage in that it is possible to manufacture an FeCoV alloy-based thin plate exhibiting excellent performance without including a slag removal process, a forging process, and a shape control slabbing process.

[0165] A method of manufacturing the ingot by casting the alloy melt is not specifically limited in the present invention. For example, the ingot may be manufactured by injecting the alloy melt into a mold, and cooling and crystallizing it. The injection temperature is preferably set to a temperature 100 to 2,000°C, preferably 100 to 1,000°C, and more preferably 200 to 500°C higher than the liquidus temperature of the melt. The liquidus temperature of the melt can be measured using a direct temperature measurement method with a built-in thermocouple or by measuring the surface of the melt using a non-contact laser thermometer. In addition, the cooling temperature and rate can be controlled to prevent segregation and ensure uniformity of composition by making the cooling temperature uniform. Since the upper part of the ingot cools relatively quickly and the lower part or the inside may cool slowly, the quickly cooling part may be heated, or insulated with non-metallic ceramics or slag.

[0166] The ingot may be manufactured in, for example, a bar, polyhedron, cylinder, sphere shape, or atypical shape, but is not limited thereto. The method for manufacturing an FeCoV alloy-based thin plate according to the present invention may further include cutting the ingot to 4 to 30 mm. For example, the method for manufacturing an FeCoV alloy-based thin plate may further include cutting the ingot to 10 to 30 mm. When the step of cutting the ingot within the above range is further included, it is preferable because hot rolling is smooth. Cutting of the ingot may be performed by a method commonly performed in the art, and the present invention is not limited thereto.

[0167] In another embodiment of the present invention, the method may further include: manufacturing an ingot by casting the alloy melt; and then homogenizing heat-treating the ingot. In another embodiment of the present invention, the homogenizing heat treatment may be performed at 1,200 to 1,300°C for 1 to 12 hours. Preferably, the homogenizing heat treatment may be performed for 2 to 6 hours, more preferably 2 to 4 hours, but is not limited thereto. When the step of homogenizing heat-treating is further included, it is preferable because stress generated during casting can be relieved.

[0168] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes the step of hot-rolling the ingot to obtain a plate material. By hot-rolling the ingot, it is preferable because a plate material in which a γ-austenite phase formed by slow cooling occupies the majority or an α-ferrite phase and the γ-austenite phase are mixed can be obtained.

[0169] The hot rolling may be performed using, for example, a steel rolling mill. The rolling start temperature, rolling speed, rolling end temperature, and the like are not particularly limited in the present invention, and may be appropriately performed according to conventional conditions performed in the art. For example, the start temperature for the rolling may be 900°C or higher, and may not exceed 1,300°C. When the start temperature for the rolling satisfies the above range, it is preferable because there is an advantage in that the strength and formability of the manufactured plate material are excellent. The rolling end temperature may be 1,150°C or higher. When the rolling end temperature is 1,150°C or higher, it is preferable because a phenomenon in which excessive load is applied to equipment due to high deformation resistance can be suppressed, and control of the shape is easy.

[0170] The total reduction ratio by the hot rolling may be 70 to 90%, preferably 75 to 90%, and more preferably 75 to 85%. When the total reduction ratio satisfies the above range, it is preferable because enlargement of crystal grains due to large energy can be suppressed, and the deviation thereof can be reduced.

[0171] The rolling may be performed for one pass to several passes, but is not limited thereto. In another embodiment of the present invention, the rolling may be performed in two or more rolling passes. Specifically, the rolling may be performed in 5 or more rolling passes, but is not limited thereto.

[0172] When the temperature decreases as the hot rolling is repeated, it is preferable to perform the hot rolling after raising the temperature by reheating. The lower limit of the temperature during the rolling process is preferably controlled to 900°C or higher, preferably 900 to 1,000°C. When the lower limit of the temperature during the rolling process satisfies the above range, it is preferable because most of the phase exists as the γ-austenite phase, so that cracks or ruptures hardly occur during hot rolling and the process becomes smooth.

[0173] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes the step of heat-treating the plate material at 600 to 1,200°C for 10 minutes to 240 minutes to transform at least a portion of the α-ferrite phase into the γ-austenite phase. Although not wishing to be bound by theory, generally, an FeCoV-based alloy undergoes a phase change while going through a casting process, a hot rolling process, a heat treatment process, a cold rolling process, and the like, and even the same phase changes into an ordered lattice or a disordered lattice. For example, when an FeCoV-based alloy is melted in a vacuum and cast into an ingot, an α-ferrite phase is formed. In the case of α-ferrite, which is a room temperature structure, it forms a Body-Centered Cubic (BCC) structure and has relatively fewer slip planes, so there is a high possibility that rolling may not be performed smoothly when cold rolling or the like is performed later to use a thin plate using the FeCoV alloy-based plate material. In particular, due to residual stress existing inside the plate material after cold rolling, forming may be difficult, and a phenomenon in which soft magnetic properties are not properly implemented may occur. On the other hand, a γ-austenite structure, which is a high-temperature structure, forms a Face-Centered Cubic (FCC) structure, which is a disordered structure, and has many slip planes, so rolling is easy, and plastic workability is much superior to that of α-ferrite. Therefore, the method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes heat-treating the plate material at a temperature of 600 to 1,200°C, which is a high-temperature stable phase section, so as to have a γ-austenite structure, that is, an FCC structure, which is a high-temperature stable phase, and then quenching the plate material, thereby transforming the α-ferrite phase generated through the casting process and the hot rolling process into the γ-austenite phase, so that the structure is changed to a structure having the γ-austenite phase or a composite structure of the α-ferrite phase and the γ-austenite phase.

[0174] In another embodiment of the present invention, the heat treatment may be performed at 730 to 1,200°C. Specifically, the heat treatment may be performed at a temperature of 730°C or higher, which is a temperature at which an irregular / regular lattice structure starts to be ordered, and a temperature of 1,200°C or lower, which is a temperature at which a liquid phase is not formed and atomic structure change is expected to be most active. Specifically, the heat treatment is preferably performed within the above range, which is a temperature region where irregular / regular structure change occurs.

[0175] In another embodiment of the present invention, the heat treatment may be performed at 840 to 1,200°C. Specifically, the heat treatment may be performed at a temperature of 840°C or higher, which is a temperature at which phase transformation occurs, and a temperature of 1,200°C or lower, which is a temperature at which solid phase control is possible without mixing of a liquid phase. In another embodiment of the present invention, the step of transforming into the γ-austenite phase may be heat-treating at 850 to 950°C. Since mechanical properties and / or magnetic properties may vary greatly depending on the heat treatment temperature even if the FeCoV alloy-based plate material has the same composition, in the present invention, by heat-treating at a temperature within the above range, it is possible to obtain an FeCoV alloy-based thin plate having excellent mechanical properties and excellent magnetic properties, that is, high saturation magnetic flux density and low iron loss value at the same time.

[0176] In another embodiment of the present invention, the heat treatment may be performed for 30 to 240 minutes. Preferably, the heat treatment may be performed for 60 to 120 minutes. When the heat treatment time satisfies the above range, it is preferable because the phase transformation time to the γ-austenite phase is sufficient while shortening the heat treatment time. In short, the step of transforming into the γ-austenite phase may be heat-treating at a temperature of 850 to 950°C for 60 to 120 minutes.

[0177] In another embodiment of the present invention, the step of transforming into the γ-austenite phase may be performed under a vacuum or inert gas atmosphere. Since the FeCoV-based alloy is somewhat prone to oxidation, the step of transforming into the γ-austenite phase is preferably performed under a vacuum or inert gas atmosphere. The inert gas may be, for example, high-purity argon (Ar) gas, but is not limited thereto.

[0178] In another embodiment of the present invention, the method may further include a step of removing a surface scale of the plate material before the step of heat-treating the plate material. Since an oxide scale may be formed on the surface of the plate material that has undergone the hot rolling, and the oxide scale may affect the quality of the plate material, it is preferable to further include the step of removing the surface scale of the plate material. A method of removing the surface scale of the plate material may be performed using a conventional method performed in the art. For example, the pickling treatment may be performed by introducing the plate material into a hydrochloric acid bath, or the surface scale may be removed by high-pressure spraying of a slurry mixed with high-pressure water and an abrasive onto the plate material, but is not limited thereto.

[0179] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes a step of quenching the heat-treated FeCoV alloy-based plate material. If the microstructure of the FeCoV alloy-based plate material forms an ordered structure in a cold rolling process to be described later, since it has high strength and low elongation, there is a problem in that rupture or cracking occurs during the cold rolling process, making it difficult to roll to a target thickness. Therefore, in the present invention, the FeCoV alloy-based plate material is changed to form a disordered structure by performing the step of transforming an α-ferrite phase into a γ-austenite phase by heat-treating the FeCoV alloy-based plate material at 600 to 1,200°C for 10 minutes to 240 minutes. After that, by including the step of quenching so that the FeCoV alloy-based plate material can maintain the structure of the γ-austenite phase, elongation is improved to solve problems occurring during the cold rolling process. In another embodiment of the present invention, the step of quenching may be performed at a rate of 10 to 300°C / sec. Preferably, the quenching may be performed at a rate of 30 to 150°C / sec, and more preferably at a rate of 50 to 100°C / sec. When the quenching rate satisfies the above range, the γ-austenite phase is stably maintained, which is preferable because an FeCoV alloy-based thin plate having high saturation magnetic flux density can be manufactured. The step of quenching may be performing water cooling or oil cooling. The water cooling or oil cooling method is not particularly limited in the present invention, and a general method performed in the art may be applied. For example, it may be performed using a water-cooled or oil-cooled cooling guide and a conveyor roll, but is not limited thereto. By performing the water cooling or oil cooling, the γ-austenite phase structure, which is a high-temperature stable phase, can be stably maintained. The step of quenching may be performed by introducing the FeCoV-based alloy plate material into cooling water.

[0180] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes a step of cold-rolling the quenched FeCoV alloy-based plate material to obtain an FeCoV alloy-based thin plate. In the method for manufacturing an FeCoV alloy-based thin plate according to the present invention, cold rolling can be smoothly performed as the α-ferrite phase of a regular structure is heat-treated according to a specific temperature range and time, and is changed into a γ-austenite phase of an irregular structure by quenching it. The cold rolling may be repeatedly performed while changing a reduction ratio, but is not limited thereto. A cumulative reduction ratio may be 85% or more, specifically 90% or more, and more specifically 95% or more, but is also not limited thereto.

[0181] In another embodiment of the present invention, the method may further include: obtaining the FeCoV alloy-based thin plate; and then performing a stress relief heat treatment on the FeCoV alloy-based thin plate. By including the step of performing the stress relief heat treatment on the FeCoV alloy-based thin plate, residual stress existing inside the FeCoV alloy-based thin plate after the cold rolling can be removed, and as the irregular γ-austenite phase changes to a stable phase, regularity is secured, and accordingly, it is preferable because an FeCoV alloy-based thin plate having a high saturation magnetic flux density value, a low iron loss value, and appropriate tensile strength and elongation can be obtained.

[0182] The soft magnetic FeCoV-based alloy undergoes a process in which the phase of the structure changes in a process of being manufactured into a thin plate, and in this process, magnetic properties such as saturation magnetic flux density, residual magnetic flux density, coercivity, core loss, etc. are affected according to a specific method of heat treatment such as heat treatment atmosphere, temperature, and time. Here, when a soft magnetic material is used as a material for a drive motor component, etc., a higher saturation magnetic flux density or a magnetic flux density value in a specific frequency region is advantageous, and a lower loss value such as iron loss indicates an advantageous characteristic. Eventually, alloy design, processing, heat treatment, etc. are proceeded to exhibit high magnetic flux density and low iron loss value, and as a result, when a value obtained by dividing magnetic flux density by iron loss is defined as a high specific efficiency value, the higher this value is, the more excellent it is as a material for a motor. In the present invention, heat treatment for microstructure control is performed between hot rolling and cold rolling so that cold rolling can be smoothly performed, and stress relief heat treatment is additionally performed to improve mechanical properties, particularly elongation and magnetic properties after cold rolling, thereby having an advantage of manufacturing an FeCoV alloy-based thin plate excellent in both mechanical properties and magnetic properties. In another embodiment of the present invention, the stress relief heat treatment may be performed at 650 to 950°C for 10 to 120 minutes. Preferably, the stress relief heat treatment may be performed at a temperature of 700 to 950°C, and more preferably 850 to 950°C, but is not limited thereto.

[0183] Another aspect of the present invention relates to an FeCoV alloy-based thin plate containing 49 to 66 at% (atomic percent) of iron, 20 to 49 at% of cobalt, greater than 0 and 2 at% or less of vanadium, 0 to 15 at% of nickel, 0 to 3 at% of chromium, and 0 to 1 at% of niobium. In another embodiment of the present invention, the FeCoV alloy-based thin plate may have a saturation magnetic flux density of 2.13 to 2.38 T. Specifically, the FeCoV alloy-based thin plate may have a saturation magnetic flux density of 2.26 to 2.38 T. The saturation magnetic flux density and a magnetic flux density in a specific range to be described later are factors related to output. Specifically, when a high instantaneous output is required, such as in an electric vehicle motor, a high saturation magnetic flux density of 2 T or more is required. Since the FeCoV alloy-based thin plate according to the present invention has a high saturation magnetic flux density, it can be usefully applied to various fields, and in particular, since it can have a saturation magnetic flux density of 2 T or more, it can be particularly usefully applied to electric vehicles. In the present invention, "saturation magnetic flux density" refers to a value measured with an applied magnetic field of 1.2×10 3< kA / m using a Vibrating Sample Magnetometer (VSM). In another embodiment of the present invention, the FeCoV alloy-based thin plate may have a coercivity of 43 Oe or less. In another embodiment of the present invention, the FeCoV alloy-based thin plate may have a coercivity of 25 Oe or less. In another embodiment of the present invention, the FeCoV alloy-based thin plate may have a coercivity of 10 Oe or less. Specifically, the FeCoV alloy-based thin plate may have a coercivity of 1 Oe or less, more specifically 0.5 Oe or less, and most specifically 0.18 to 0.5 Oe. When the coercivity of the FeCoV alloy-based thin plate satisfies the above range, it is preferable because there is an advantage of excellent workability.

[0184] Another aspect of the present invention relates to a method for manufacturing an FeCoV alloy-based thin plate, comprising: preparing an FeCoV alloy-based cast material; heat-treating the cast material at 600 to 1,200°C for 10 minutes to 240 minutes to transform at least a portion of an α-ferrite phase into a γ-austenite phase; quenching the heat-treated cast material; and cold-rolling the quenched cast material. The method for manufacturing an FeCoV alloy-based thin plate according to the present invention has an advantage in that it is possible to manufacture an FeCoV alloy-based thin plate having excellent magnetic properties while omitting processes such as conventional forging and hot rolling processes. The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes preparing an FeCoV alloy-based cast material. In another embodiment of the present invention, the step of preparing the FeCoV alloy-based cast material may include: preparing an FeCoV alloy melt; casting the alloy melt to manufacture an ingot; and cutting the ingot to a thickness of 4 to 10 mm to obtain a cast material. In another embodiment of the present invention, the step of preparing the FeCoV alloy-based cast material may be a step of forming the FeCoV alloy-based cast material by a strip casting process. In short, the FeCoV alloy-based cast material may be one obtained by cutting the ingot, or one directly manufactured in the form of a plate having a thickness of 4 to 10 mm from the alloy melt.

[0185] The step of preparing the FeCoV alloy melt may be vacuum melting an alloy component composed of the 20 to 49 at% of cobalt, 2 to 5 at% of vanadium, and a balance of iron and other impurities. The other impurities may be one or more selected from the group consisting of carbon, oxygen, silicon, and manganese. Specifically, the FeCoV alloy melt may include an alloy component composed of 30 to 49 at% of cobalt, 2 to 3 at% of vanadium, and a balance of iron and other impurities. More specifically, the FeCoV alloy melt may include an alloy component composed of 40 to 49 at% of cobalt, 2 to 3 at% of vanadium, and a balance of iron and other impurities. The FeCoV-based alloy is an alloy composition having soft magnetic properties, and is mainly used for motor cores of electronic products by being manufactured into a thin plate, and in particular, recently, application as a drive motor for electric vehicles is being considered. In order to increase the output of an electric vehicle, the magnetic flux density value of the motor core material must be high. Recently, most electric vehicles have a value of 2 Tesla or more, and since the FeCoV alloy has a value of up to 2.4 Tesla level, it can be very helpful in improving motor core output. In addition, since it has a significantly lower iron loss value compared to other soft magnetic materials, it is possible to drive a longer distance due to a lower loss value compared to a battery of the same capacity as well as efficiency improvement. For the same reason, when a motor exhibiting the same performance is manufactured, miniaturization and weight reduction are possible. Even with the same alloy composition, the defect rate of the rolling process may vary depending on the manufacturing process of such an FeCoV alloy, and mechanical and magnetic property values of the manufactured plate material may be greatly influenced. The method for manufacturing an FeCoV alloy-based thin plate according to the present invention has an advantage in that a thin plate having high mechanical and magnetic property values can be easily manufactured without including a conventional complicated slag removal process, forging process, process of forming into a slab shape, and the like. Meanwhile, the saturation magnetic flux density value and coercivity value of the manufactured FeCoV alloy-based thin plate may vary somewhat depending on the composition of the FeCoV alloy component. In the present invention, by using the FeCoV alloy component having the above composition, there is an advantage in that an FeCoV alloy-based thin plate having a high saturation magnetic flux density value and low coercivity can be obtained. The FeCoV alloy melt may have a composition of Fe 49 Co 49 V 2 . By vacuum melting the alloy component, a grayish ingot with little contamination can be obtained, and when solidified into an ingot shape through a casting step to be described later, it is possible to suppress a phenomenon in which an ingot having a non-uniform composition is obtained due to composition inconsistency, for example, a case where the upper and middle, or middle and lower compositions of the ingot are different, or segregation exists in the same portion, which is preferable. In addition, it is preferable because it is possible to suppress a phenomenon in which a crack is induced in a cold rolling process or the like because an oxide layer is too thick.

[0186] The step of preparing the alloy melt may be performed under an argon, nitrogen, or carbon dioxide atmosphere. When the step of preparing the alloy melt is performed under the argon, nitrogen, or carbon dioxide atmosphere, it is preferable because a phenomenon in which the alloy component is oxidized or carbonized can be suppressed.

[0187] In the step of preparing the FeCoV alloy melt by vacuum melting the alloy component, the degree of vacuum may be 1×10 -2< to 1×10 -4< torr, preferably 1×10 -2< to 1×10 -3< torr. When the degree of vacuum satisfies the above range, it is preferable because oxidation or carbonization can be suppressed.

[0188] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes the step of manufacturing an ingot by casting the alloy melt. The method may further include a step of removing slag of the alloy melt liquid before casting the alloy melt, but is not limited thereto. The method for manufacturing an FeCoV alloy-based thin plate according to the present invention may not include the step of removing slag of the alloy melt liquid. Specifically, the method for manufacturing an FeCoV alloy-based thin plate according to the present invention has an advantage in that it is possible to manufacture an FeCoV alloy-based thin plate exhibiting excellent performance without including a slag removal process, a forging process, and a shape control slabbing process. A method of manufacturing the ingot by casting the alloy melt is not specifically limited in the present invention. For example, the ingot may be manufactured by injecting the alloy melt into a mold, and cooling and crystallizing it. The injection temperature is preferably set to a temperature 100 to 2,000°C, preferably 100 to 1,000°C, and more preferably 200 to 500°C higher than the liquidus temperature of the melt. The liquidus temperature of the melt can be measured using a direct temperature measurement method with a built-in thermocouple or by measuring the surface of the melt using a non-contact laser thermometer. In addition, the cooling temperature and rate can be controlled to prevent segregation and ensure uniformity of composition by making the cooling temperature uniform. Since the upper part of the ingot cools relatively quickly and the lower part or the inside may cool slowly, the quickly cooling part may be heated, or insulated with non-metallic ceramics or slag.

[0189] The ingot may be manufactured in, for example, a bar, polyhedron, cylinder, sphere shape, or atypical shape, but is not limited thereto. The method for manufacturing an FeCoV alloy-based thin plate according to the present invention may further include the step of cutting the ingot to 4 to 10 mm. Specifically, when cold rolling is performed without going through the step of hot-rolling the ingot, the step of cutting the ingot to 4 to 10 mm may be further included. Cutting of the ingot may be performed by a method commonly performed in the art, and the present invention is not limited thereto.

[0190] In another embodiment of the present invention, the method may further include: manufacturing an ingot by casting the alloy melt; and then homogenizing heat-treating the ingot. In another embodiment of the present invention, the homogenizing heat treatment may be performed at 1,200 to 1,300°C for 1 to 12 hours. Preferably, the homogenizing heat treatment may be performed for 2 to 6 hours, more preferably 2 to 4 hours, but is not limited thereto. When the step of homogenizing heat-treating is further included, it is preferable because stress generated during casting can be relieved.

[0191] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention may include obtaining a cast material by cutting the ingot to a thickness of 4 to 10 mm. In another embodiment of the present invention, the step of obtaining the cast material may be cutting the ingot to a thickness of 4 to 8 mm. In another embodiment of the present invention, the step of obtaining the cast material may be cutting the ingot to a thickness of 4 to 6 mm. In short, the cast material may have a thickness of 4 to 10 mm, preferably 4 to 8 mm, and more preferably 4 to 6 mm. When the thickness of the cast material satisfies the above range, it is preferable because a cold rolling process to be described later is easy.

[0192] The cast material may be formed by a strip casting process. The strip casting process is a process technology for manufacturing a solid thin plate directly from a liquid melt, and is a technology for manufacturing a thin plate having a thickness of 4 to 10 mm, which is a process capable of improving productivity because continuous casting, reheating, and hot rolling processes can be omitted. In the present invention, the strip casting process method is not specifically limited. For example, the strip casting process may be performed by controlling cooling of the FeCoV alloy melt melted at a temperature of 1,700°C or higher to 300°C at a cooling rate of 100 to 150°C / s, but is not limited thereto.

[0193] In another embodiment of the present invention, the step of obtaining the cast material may be performed under an argon, nitrogen, or carbon dioxide atmosphere. When the step of obtaining the cast material is performed in an inert atmosphere such as argon or nitrogen, or under a carbon dioxide atmosphere, it is preferable because a phenomenon in which the cast material is oxidized or carbonized can be suppressed.

[0194] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes heat-treating the cast material at 600 to 1,200°C for 10 minutes to 240 minutes to transform at least a portion of the α-ferrite phase into the γ-austenite phase. Although not wishing to be bound by theory, generally, an FeCoV-based alloy undergoes a phase change while going through a casting process, a heat treatment process, a cold rolling process, and the like, and even the same phase changes into an ordered lattice or a disordered lattice. For example, in a cast material obtained by melting an FeCoV-based alloy in a vacuum, an α-ferrite phase is formed. In the case of α-ferrite, which is a room temperature structure, it forms a Body-Centered Cubic (BCC) structure and has relatively fewer slip planes, so there is a high possibility that rolling may not be performed smoothly when cold rolling or the like is performed later to use a thin plate using the cast material. In particular, due to residual stress existing inside the cast material after cold rolling, forming may be difficult, and a phenomenon in which soft magnetic properties are not properly implemented may occur. On the other hand, a γ-austenite structure, which is a high-temperature structure, forms a Face-Centered Cubic (FCC) structure, which is a disordered structure, and has many slip planes, so rolling is easy, and plastic workability is much superior to that of α-ferrite. Therefore, the method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes heat-treating the cast material at a temperature of 600 to 1,200°C, which is a high-temperature stable phase section, so as to have a γ-austenite structure, that is, an FCC structure, which is a high-temperature stable phase, and then quenching the cast material, thereby transforming the α-ferrite phase generated through the casting process and the hot rolling process into the γ-austenite phase, so that the structure is changed to a structure having the γ-austenite phase or a composite structure of the α-ferrite phase and the γ-austenite phase.

[0195] In another embodiment of the present invention, the heat treatment may be performed at 730 to 1,200°C. Specifically, the heat treatment may be performed at a temperature of 730°C or higher, which is a temperature at which an irregular / regular lattice structure starts to be ordered, and a temperature of 1,200°C or lower, which is a temperature at which a liquid phase is not formed and atomic structure change is expected to be most active. Specifically, the heat treatment is preferably performed within the above range, which is a temperature region where irregular / regular structure change occurs.

[0196] In another embodiment of the present invention, the heat treatment may be performed at 840 to 1,200°C. Specifically, the heat treatment may be performed at a temperature of 840°C or higher, which is a temperature at which phase transformation occurs, and a temperature of 1,200°C or lower, which is a temperature at which solid phase control is possible without mixing of a liquid phase. In another embodiment of the present invention, the step of transforming into the γ-austenite phase may be heat-treating at 850 to 950°C. Since mechanical properties and / or magnetic properties may vary greatly depending on the heat treatment temperature even if the FeCoV alloy-based thin plate has the same composition, in the present invention, by heat-treating at a temperature within the above range, it is possible to obtain an FeCoV alloy-based thin plate having excellent mechanical properties and excellent magnetic properties, that is, high saturation magnetic flux density and low iron loss value at the same time. When the heat treatment temperature satisfies the above range, the phase transformation from the α-ferrite phase to the γ-austenite phase is easy, and a phenomenon in which coarse grain boundaries of a level of 100 to 500 µm are formed is suppressed, so there is an advantage in that a cast material with high workability can be obtained. In addition, there is an advantage in that a cast material having uniform quality as a whole can be obtained because a phenomenon in which a composition ratio of the surface and the inside of the cast material, specifically a composition ratio of Fe and Co, varies can be suppressed.

[0197] In another embodiment of the present invention, the heat treatment may be performed for 30 to 240 minutes. Preferably, the heat treatment may be performed for 60 to 120 minutes. When the heat treatment time satisfies the above range, it is preferable because the phase transformation time to the γ-austenite phase is sufficient while shortening the heat treatment time. In short, the step of transforming into the γ-austenite phase may be heat-treating at a temperature of 850 to 950°C for 60 to 120 minutes.

[0198] In another embodiment of the present invention, the step of transforming into the γ-austenite phase may be performed under a vacuum or inert gas atmosphere. Since the FeCoV-based alloy is somewhat prone to oxidation, the step of transforming into the γ-austenite phase is preferably performed under a vacuum or inert gas atmosphere. The inert gas may be, for example, high-purity argon (Ar) gas, but is not limited thereto.

[0199] In another embodiment of the present invention, the method may further include a step of chemically surface-treating (chemically milling) the cast material before heat-treating the cast material. Since the cast material is rapidly cooled by directly rolling the melt due to process characteristics, surface casting defects such as solidification patterns or inverse segregation may be accompanied. In addition, since the thickness is somewhat thin at 4 to 10 mm, it is not easy to apply a conventional physical surface treatment process for removing surface defects, such as a band saw type process or a grinder type process. Therefore, surface casting defects can be removed by chemically surface-treating the cast material before heat-treating the cast material. The step of chemically surface-treating may be performed by a conventional method performed in the art, and is not particularly limited in the present invention. For example, the chemical surface treatment may be performed using a composition containing hydrochloric acid, nitric acid, hydrofluoric acid, and distilled water.

[0200] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes a step of quenching the heat-treated cast material. If the microstructure of the cast material forms an ordered structure in a cold rolling process to be described later, since it has high strength and low elongation, there is a problem in that rupture or cracking occurs during the cold rolling process, making it difficult to roll to a target thickness. Specifically, the heat-treated cast material is composed of an α phase, and the α phase has a BCC structure and has few slip planes, so it is not suitable for a shape deformation process such as cold rolling.

[0201] Therefore, in the present invention, the cast material is changed to form a disordered structure by performing the step of transforming at least a portion of an α-ferrite phase into a γ-austenite phase by heat-treating the cast material at 600 to 1,200°C for 10 minutes to 240 minutes. After that, by including the step of quenching so that the cast material can maintain the structure of the γ-austenite phase, elongation is improved to solve problems occurring during the cold rolling process. In another embodiment of the present invention, the step of quenching may be performed at a rate of 10 to 300°C / sec. Preferably, the quenching may be performed at a rate of 30 to 150°C / sec, and more preferably at a rate of 50 to 100°C / sec. When the quenching rate satisfies the above range, the γ-austenite phase is stably maintained, which is preferable because an FeCoV alloy-based thin plate having high saturation magnetic flux density can be manufactured. The step of quenching may be performing water cooling or oil cooling. The water cooling or oil cooling method is not particularly limited in the present invention, and a general method performed in the art may be applied. For example, it may be performed using a water-cooled or oil-cooled cooling guide and a conveyor roll, but is not limited thereto. By performing the water cooling or oil cooling, the γ-austenite phase structure, which is a high-temperature stable phase, can be stably maintained. The step of quenching may be performed by introducing the cast material into cooling water.

[0202] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes a step of cold-rolling the quenched cast material to obtain an FeCoV alloy-based thin plate. In the method for manufacturing an FeCoV alloy-based thin plate according to the present invention, cold rolling can be smoothly performed as the α-ferrite phase of a regular structure is heat-treated according to a specific temperature range and time, and is changed into a γ-austenite phase of an irregular structure by quenching it. The cold rolling may be repeatedly performed while changing a reduction ratio, but is not limited thereto. A cumulative reduction ratio may be 85% or more, specifically 90% or more, and more specifically 95% or more, but is also not limited thereto.

[0203] In another embodiment of the present invention, the method may further include: obtaining the FeCoV alloy-based thin plate; and then performing a stress relief heat treatment on the FeCoV alloy-based thin plate. By including the step of performing the stress relief heat treatment on the FeCoV alloy-based thin plate, residual stress existing inside the FeCoV alloy-based thin plate after the cold rolling can be removed, and as the irregular γ-austenite phase changes to a stable phase, regularity is secured, and accordingly, it is preferable because an FeCoV alloy-based thin plate having a high saturation magnetic flux density value, a low iron loss value, and appropriate tensile strength and elongation can be obtained.

[0204] The soft magnetic FeCoV-based alloy undergoes a process in which the phase of the structure changes in a process of being manufactured into a thin plate, and in this process, magnetic properties such as saturation magnetic flux density, residual magnetic flux density, coercivity, core loss, etc. are affected according to a specific method of heat treatment such as heat treatment atmosphere, temperature, and time. Here, when a soft magnetic material is used as a material for a drive motor component, etc., a higher saturation magnetic flux density or a magnetic flux density value in a specific frequency region is advantageous, and a lower loss value such as iron loss indicates an advantageous characteristic. Eventually, alloy design, processing, heat treatment, etc. are proceeded to exhibit high magnetic flux density and low iron loss value, and as a result, when a value obtained by dividing magnetic flux density by iron loss is defined as a high specific efficiency value, the higher this value is, the more excellent it is as a material for a motor. In the present invention, heat treatment for microstructure control is performed between hot rolling and cold rolling so that cold rolling can be smoothly performed, and stress relief heat treatment is additionally performed to improve mechanical properties, particularly elongation and magnetic properties after cold rolling, thereby having an advantage of manufacturing an FeCoV alloy-based thin plate excellent in both mechanical properties and magnetic properties. In another embodiment of the present invention, the stress relief heat treatment may be performed at 650 to 950°C for 10 to 120 minutes. Preferably, the stress relief heat treatment may be performed at a temperature of 700 to 950°C, and more preferably 850 to 950°C, but is not limited thereto.

[0205] Since the method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes the steps of heat treating and quenching, there is an advantage in that an FeCoV alloy-based thin plate having soft magnetic performance equivalent to a process involving conventional forging, hot rolling, and cold rolling can be manufactured only by cold rolling without going through conventional forging and hot rolling processes.

[0206] Another aspect of the present invention relates to an FeCoV alloy-based thin plate having a first peak in a range where 20 is 42 to 47°, a second peak in a range where 20 is 62 to 67°, and a third peak in a range where 20 is 80 to 85° in an X-ray diffraction chart obtained by XRD analysis. In another embodiment of the present invention, the second peak may have a maximum peak intensity. In another embodiment of the present invention, the third peak may have a maximum peak intensity. Specifically, in the FeCoV alloy-based thin plate according to the present invention, the second peak or the third peak may exhibit the maximum peak intensity according to stress relief heat treatment in the method for manufacturing the FeCoV alloy-based thin plate. More specifically, when the stress relief heat treatment is not performed during the process of manufacturing the FeCoV alloy-based thin plate, the second peak may exhibit the maximum peak intensity, and when the stress relief heat treatment is performed, the third peak may exhibit the maximum peak intensity. In another embodiment of the present invention, a full width at half maximum (FWHM) of the second peak may be in a range of 4.5 to 4.6°. Specifically, when the stress relief heat treatment is not performed during the process of manufacturing the FeCoV alloy-based thin plate, the FWHM of the second peak may be in the above range. In another embodiment of the present invention, the FWHM of the second peak may be in a range of 0.35 to 0.36°. Specifically, when the stress relief heat treatment is performed during the process of manufacturing the FeCoV alloy-based thin plate, the FWHM of the second peak may be in the above range. In another embodiment of the present invention, the magnetic permeability may be 10,000 or less. Specifically, when the stress relief heat treatment is not performed during the process of manufacturing the FeCoV alloy-based thin plate, the magnetic permeability of the FeCoV alloy-based thin plate may be 7,000 or less. In another embodiment of the present invention, the magnetic permeability may be 80,000 or more. Specifically, when the stress relief heat treatment is performed during the process of manufacturing the FeCoV alloy-based thin plate, the FeCoV alloy-based thin plate may have a magnetic permeability of 80,000 or more. Specifically, the magnetic permeability may be 80,000 to 100,000.

[0207] In another embodiment of the present invention, the FeCoV alloy-based thin plate may have a saturation magnetic flux density of 2.13 to 2.38 T. Specifically, the FeCoV alloy-based thin plate may have a saturation magnetic flux density of 2.26 to 2.38 T. The saturation magnetic flux density and a magnetic flux density in a specific range to be described later are factors related to output. Specifically, when a high instantaneous output is required, such as in an electric vehicle motor, a high saturation magnetic flux density of 2 T or more is required. Since the FeCoV alloy-based thin plate according to the present invention has a high saturation magnetic flux density, it can be usefully applied to various fields, and in particular, since it can have a saturation magnetic flux density of 2 T or more, it can be particularly usefully applied to electric vehicles. In the present invention, "saturation magnetic flux density" refers to a value measured with an applied magnetic field of 1.2×10 3< kA / m using a Vibrating Sample Magnetometer (VSM).

[0208] In another embodiment of the present invention, the FeCoV alloy-based thin plate may have a magnetic flux density of 1.5 T or more induced when a magnetic field of 5,000 A / m is applied. Specifically, the magnetic flux density may be 1.87 to 2.2207 T.

[0209] In another embodiment of the present invention, the FeCoV alloy-based thin plate may have a coercivity of 43 Oe or less. In another embodiment of the present invention, the FeCoV alloy-based thin plate may have a coercivity of 25 Oe or less. In another embodiment of the present invention, the FeCoV alloy-based thin plate may have a coercivity of 10 Oe or less. Specifically, the FeCoV alloy-based thin plate may have a coercivity of 1 Oe or less, more specifically 0.5 Oe or less, and most specifically 0.18 to 0.5 Oe. When the coercivity of the FeCoV alloy-based thin plate satisfies the above range, it is preferable because there is an advantage of excellent workability.

[0210] In another embodiment of the present invention, the FeCoV alloy-based thin plate may have an iron loss of 15 or less. In the present invention, "iron loss" may be measured under a condition where the magnitude of an applied magnetic field is 1 T and a frequency is 400 Hz. In another embodiment of the present invention, the FeCoV alloy-based thin plate may contain a γ-austenite phase. In another embodiment of the present invention, the FeCoV alloy-based thin plate may further contain an α-ferrite phase. In short, the FeCoV alloy-based thin plate may contain a γ-austenite phase, or may be in the form of a composite phase containing a γ-austenite phase and an α-ferrite phase.

[0211] Since the FeCoV alloy-based thin plate according to the present invention contains a γ-austenite phase or contains a γ-austenite phase and an α-ferrite phase, it exhibits excellent magnetic properties and excellent mechanical properties, and in particular, post-processing is easy, so it can be usefully applied to various fields.

[0212] In another embodiment of the present invention, an average band thickness of a layered structure in which the γ-austenite phase is elongated may be 1 to 10 µm in an L cross-section that is a cross-section parallel to a rolling direction. In another embodiment of the present invention, the average band thickness of the layered structure in which the γ-austenite phase is elongated may be 1 to 5 µm in the L cross-section that is the cross-section parallel to the rolling direction. Specifically, the average band thickness of the layered structure in which the γ-austenite phase is elongated may be 2 to 4 µm in the L cross-section that is the cross-section parallel to the rolling direction. When the average band thickness satisfies the above range, it means that cold rolling of the FeCoV alloy-based thin plate was smooth, and accordingly, there is an advantage of exhibiting excellent mechanical properties as well as magnetic properties. The FeCoV alloy-based thin plate may be manufactured by a method for manufacturing an FeCoV alloy-based thin plate, comprising: preparing an FeCoV alloy-based plate material; heat-treating the FeCoV alloy-based plate material at 600 to 1,200°C for 10 minutes to 240 minutes to transform at least a portion of an α-ferrite phase into a γ-austenite phase; quenching the heat-treated FeCoV alloy-based plate material; cold-rolling the quenched FeCoV alloy-based plate material to obtain an FeCoV alloy-based thin plate; and performing a stress relief heat treatment on the FeCoV alloy-based thin plate, wherein a full width at half maximum (FWHM) of a maximum peak in a range where 20 is 42 to 47° in an X-ray diffraction chart obtained by XRD analysis is different before heat-treating the FeCoV alloy-based plate material and after heat-treating the FeCoV alloy-based plate material. In another embodiment of the present invention, a full width at half maximum (FWHM) of a maximum peak in a range where 20 is 42 to 47° in an X-ray diffraction chart obtained by XRD analysis may be different before performing the stress relief heat treatment on the FeCoV alloy-based thin plate and after performing the stress relief heat treatment on the FeCoV alloy-based thin plate. The above-described contents may be applied to specific manufacturing steps of the method for manufacturing the FeCoV alloy-based thin plate.

[0213] Another aspect of the present invention relates to an FeCoV alloy-based thin plate comprising γ-austenite and residual α-ferrite, wherein an average size of grains is 50 to 100 µm. Since the FeCoV alloy-based thin plate according to the present invention includes γ-austenite and residual α-ferrite, it has an advantage of being excellent in magnetic properties and easy in post-processing, so that it can be usefully applied to various fields, particularly as a material for electric vehicles.

[0214] In another embodiment of the present invention, the average size of the grains may be 50 to 80 µm. In another embodiment of the present invention, the average size of the grains may be 50 to 60 µm. When the average size of the grains satisfies the above range, it is preferable because there is an advantage of excellent magnetic properties.

[0215] In the present invention, "average size of grains" may be based on the ASTM E112 standard. The average size of the "grains" may refer to the total average size of the γ-austenite grains and the α-ferrite grains. The average size of the γ-austenite grains may be 50 to 100 µm, preferably 50 to 80 µm, and more preferably 50 to 60 µm.

[0216] In another embodiment of the present invention, an area fraction of the γ-austenite may be larger than an area fraction of the α-ferrite. When the area fraction of the γ-austenite is larger than the area fraction of the α-ferrite, it means that cold rolling has been performed smoothly, which is preferable because the FeCoV alloy-based thin plate has an advantage of having high saturation magnetic flux density, low coercivity, and low iron loss value.

[0217] In another embodiment of the present invention, the area fraction of the γ-austenite may be 60 to 95%. In another embodiment of the present invention, the area fraction of the α-ferrite may be 5 to 50%. When the area fraction of the γ-austenite and the area fraction of the α-ferrite satisfy the above ranges, it is preferable because there is an advantage of excellent magnetic properties and easy workability.

[0218] In another embodiment of the present invention, a ratio of the number of the γ-austenite to the α-ferrite may be 80:20 to 60:40. Specifically, the number of the γ-austenite and the α-ferrite may be based on the ASTM E112 standard. Preferably, the ratio of the number of the γ-austenite to the α-ferrite may be 70:30 to 60:40. When the ratio of the number of the γ-austenite to the α-ferrite satisfies the above range, it is preferable because there is an advantage of excellent soft magnetic properties and excellent mechanical properties, particularly excellent workability.

[0219] In another embodiment of the present invention, the number of the γ-austenite grains having a size of 50 to 100 µm may be 5 to 12 based on ASTM E112. Preferably, the number of the γ-austenite grains may be 7 to 10. When the number of the γ-austenite grains satisfies the above range, it is preferable because there is an advantage of excellent post-processability.

[0220] In another embodiment of the present invention, the number of the α-ferrite grains having a size of 50 to 100 µm may be 2 to 8 based on ASTM E112. Preferably, the number of the α-ferrite grains may be 2 to 6, and more preferably 4 to 6. When the number of the α-ferrite grains satisfies the above range, it is preferable because mechanical properties are excellent.

[0221] Since the FeCoV alloy-based thin plate according to the present invention includes γ-austenite and residual α-ferrite, and the average size of grains is 50 to 100 µm, there is an advantage of excellent mechanical performance as well as magnetic properties.

[0222] The FeCoV alloy-based thin plate according to the present invention can be manufactured by the method for manufacturing an FeCoV alloy-based thin plate described above. For example, the FeCoV alloy-based thin plate may be manufactured by a method for manufacturing an FeCoV alloy-based thin plate comprising: preparing an FeCoV alloy-based plate material; heat-treating the FeCoV alloy-based plate material at 600 to 1,200°C for 10 minutes to 240 minutes to transform at least a portion of an α-ferrite phase into a γ-austenite phase; quenching the heat-treated FeCoV alloy-based plate material; and cold-rolling the quenched FeCoV alloy-based plate material to obtain an FeCoV alloy-based thin plate, but is not limited thereto. The above-described contents may be applied to specific manufacturing steps of the method for manufacturing the FeCoV alloy-based thin plate.

[0223] The average size of grains, area fractions of γ-austenite and α-ferrite, number, etc. of the FeCoV alloy-based thin plate may vary depending on the heat treatment temperature, etc. during the process of manufacturing the FeCoV alloy-based thin plate.

[0224] Another aspect of the present invention relates to a drive motor comprising: a rotor; and a stator, wherein one or more selected from the group consisting of the rotor and the stator includes a laminate in which FeCoV alloy-based thin plates are stacked, and the FeCoV alloy-based thin plate has a first peak in a range where 20 is 42 to 47°, a second peak in a range where 20 is 62 to 67°, and a third peak in a range where 20 is 80 to 85° in an X-ray diffraction chart obtained by XRD analysis.

[0225] In another embodiment of the present invention, the second peak may have a maximum peak intensity. In another embodiment of the present invention, the third peak may have a maximum peak intensity. Specifically, in the FeCoV alloy-based thin plate according to the present invention, the second peak or the third peak may exhibit the maximum peak intensity according to stress relief heat treatment in the method for manufacturing the FeCoV alloy-based thin plate. More specifically, when the stress relief heat treatment is not performed during the process of manufacturing the FeCoV alloy-based thin plate, the second peak may exhibit the maximum peak intensity, and when the stress relief heat treatment is performed, the third peak may exhibit the maximum peak intensity.

[0226] In another embodiment of the present invention, a full width at half maximum (FWHM) of the second peak may be in a range of 4.5 to 4.6°. Specifically, when the stress relief heat treatment is not performed during the process of manufacturing the FeCoV alloy-based thin plate, the FWHM of the second peak may be in the above range. In another embodiment of the present invention, the FWHM of the second peak may be in a range of 0.35 to 0.36°. Specifically, when the stress relief heat treatment is performed during the process of manufacturing the FeCoV alloy-based thin plate, the FWHM of the second peak may be in the above range.

[0227] In another embodiment of the present invention, the magnetic permeability may be 10,000 or less. Specifically, when the stress relief heat treatment is not performed during the process of manufacturing the FeCoV alloy-based thin plate, the magnetic permeability of the FeCoV alloy-based thin plate may be 7,000 or less. In another embodiment of the present invention, the magnetic permeability may be 80,000 or more. Specifically, when the stress relief heat treatment is performed during the process of manufacturing the FeCoV alloy-based thin plate, the FeCoV alloy-based thin plate may have a magnetic permeability of 80,000 or more. Specifically, the magnetic permeability may be 80,000 to 100,000.

[0228] In another embodiment of the present invention, the FeCoV alloy-based thin plate may have a saturation magnetic flux density of 2.13 to 2.38 T. Specifically, the FeCoV alloy-based thin plate may have a saturation magnetic flux density of 2.26 to 2.38 T. The saturation magnetic flux density and a magnetic flux density in a specific range to be described later are factors related to output. Specifically, when a high instantaneous output is required, such as in an electric vehicle motor, a high saturation magnetic flux density of 2 T or more is required. Since the FeCoV alloy-based thin plate according to the present invention has a high saturation magnetic flux density, it can be usefully applied to various fields, and in particular, since it can have a saturation magnetic flux density of 2 T or more, it can be particularly usefully applied to electric vehicles. In the present invention, "saturation magnetic flux density" refers to a value measured with an applied magnetic field of 1.2×10 3< kA / m using a Vibrating Sample Magnetometer (VSM).

[0229] In another embodiment of the present invention, the FeCoV alloy-based thin plate may have a magnetic flux density of 1.5 T or more induced when a magnetic field of 5,000 A / m is applied. Specifically, the magnetic flux density may be 1.87 to 2.207 T.

[0230] In another embodiment of the present invention, the FeCoV alloy-based thin plate may have a coercivity of 43 Oe or less. In another embodiment of the present invention, the FeCoV alloy-based thin plate may have a coercivity of 25 Oe or less. In another embodiment of the present invention, the FeCoV alloy-based thin plate may have a coercivity of 10 Oe or less. Specifically, the FeCoV alloy-based thin plate may have a coercivity of 1 Oe or less, more specifically 0.5 Oe or less, and most specifically 0.18 to 0.5 Oe. When the coercivity of the FeCoV alloy-based thin plate satisfies the above range, there is an advantage that it can be usefully applied to electric vehicles.

[0231] In another embodiment of the present invention, the FeCoV alloy-based thin plate may have an iron loss of 15 or less. In the present invention, "iron loss" may be measured under a condition where the magnitude of an applied magnetic field is 1 T and a frequency is 400 Hz.

[0232] In another embodiment of the present invention, the FeCoV alloy-based thin plate may contain a γ-austenite phase. In another embodiment of the present invention, the FeCoV alloy-based thin plate may further contain an α-ferrite phase. In short, the FeCoV alloy-based thin plate may contain a γ-austenite phase, or may be in the form of a composite phase containing a γ-austenite phase and an α-ferrite phase.

[0233] Since the drive motor according to the present invention uses the FeCoV alloy-based thin plate containing the γ-austenite phase or containing the γ-austenite phase and the α-ferrite phase, it exhibits excellent magnetic properties as well as excellent mechanical properties, and thus can be particularly usefully applied as a drive motor for an electric vehicle.

[0234] In another embodiment of the present invention, an average band thickness of a layered structure in which the γ-austenite phase is elongated may be 1 to 10 µm in an L cross-section that is a cross-section parallel to a rolling direction. In another embodiment of the present invention, the average band thickness of the layered structure in which the γ-austenite phase is elongated may be 1 to 5 µm in the L cross-section that is the cross-section parallel to the rolling direction. Specifically, the average band thickness of the layered structure in which the γ-austenite phase is elongated may be 2 to 4 µm in the L cross-section that is the cross-section parallel to the rolling direction. When the average band thickness satisfies the above range, it means that cold rolling of the FeCoV alloy-based thin plate was smooth, and accordingly, there is an advantage that the drive motor including the FeCoV alloy-based thin plate exhibits excellent mechanical properties as well as magnetic properties.

[0235] In another embodiment of the present invention, efficiency may be 96% or more when a total weight is 50 kg or less and an output of the motor is 220 kW. The drive motor according to the present invention may be a drive motor for an electric vehicle suitable under a condition of rotating at 12,000 to 28,000 rpm.

[0236] The rotor may include a laminate in which the above-described FeCoV alloy-based thin plates are stacked. The stator may include a laminate in which the above-described FeCoV alloy-based thin plates are stacked. The rotor and the stator may include a laminate in which the above-described FeCoV alloy-based thin plates are stacked.

[0237] The drive motor may additionally include, but is not limited to, a battery as a main power source, an inverter for converting a DC voltage supplied from the motor and the battery, a coil wound around a rotor core, an MCU for controlling voltage supply, a current controller for supplying power of the battery to the coil, and the like.

[0238] The FeCoV alloy-based thin plate may be one manufactured by any one of the methods for manufacturing an FeCoV alloy-based thin plate described above. For example, another aspect of the present invention relates to a method for manufacturing a drive motor component, comprising: preparing an FeCoV alloy-based plate material; heat-treating the FeCoV alloy-based plate material at 600 to 1,200°C for 10 minutes to 240 minutes to transform at least a portion of an α-ferrite phase into a γ-austenite phase; quenching the heat-treated FeCoV alloy-based plate material; cold-rolling the quenched FeCoV alloy-based plate material to obtain an FeCoV alloy-based thin plate; processing the FeCoV alloy-based thin plate; and stacking the processed FeCoV alloy-based thin plates. The FeCoV alloy-based thin plate has a first peak in a range where 20 is 42 to 47°, a second peak in a range where 20 is 62 to 67°, and a third peak in a range where 20 is 80 to 85° in an X-ray diffraction chart obtained by XRD analysis. The drive motor component according to the present invention can be manufactured by performing the steps of processing the FeCoV alloy-based thin plate and stacking the processed FeCoV alloy-based thin plates in the method for manufacturing the FeCoV alloy-based thin plate described above. In short, the FeCoV alloy-based thin plate may be one manufactured by the method for manufacturing an FeCoV alloy-based thin plate described above. The specific manufacturing steps of the method for manufacturing the FeCoV alloy-based thin plate may apply the contents described above.

[0239] The step of processing may be a step of processing a plurality of the FeCoV alloy-based thin plates into a core shape. The processing process may be performed using a laser, but is not limited thereto. For example, the processing process may be performed by fusing (cutting) with a laser at a scanning speed of the laser of 10,000 mm / min or more, thereby obtaining a drive motor component suitable for high efficiency of the motor, but is not limited thereto.

[0240] The step of stacking the FeCoV alloy-based thin plates may fix the FeCoV alloy-based thin plates to each other by adhesion or the like, but is not limited thereto. For example, the stacking may be performed through a coating process of applying an adhesive to both surfaces of the processed FeCoV alloy-based thin plate, a drying process of drying the FeCoV alloy-based thin plate to which the adhesive is applied to primarily cure the applied adhesive, a bonding process of stacking the dried FeCoV alloy-based thin plates and then press-drying them to secondarily and completely cure the applied adhesive to bond the stacked and processed FeCoV alloy-based thin plates, but is not limited thereto.

[0241] Another aspect of the present invention relates to a drive motor comprising: a rotor; and a stator, wherein one or more selected from the group consisting of the rotor and the stator includes a laminate in which FeCoV alloy-based thin plates are stacked, and the FeCoV alloy-based thin plate includes γ-austenite and residual α-ferrite, and an average size of grains is 50 to 100 µm. Since the drive motor according to the present invention includes a laminate in which FeCoV alloy-based thin plates including γ-austenite and residual α-ferrite and having an average grain size of 50 to 100 µm are stacked, there is an advantage of excellent mechanical properties as well as excellent magnetic properties.

[0242] In another embodiment of the present invention, the average size of the grains may be 50 to 80 µm. In another embodiment of the present invention, the average size of the grains may be 50 to 60 µm. When the average size of the grains satisfies the above range, it is preferable because there is an advantage of excellent magnetic properties.

[0243] In the present invention, "average size of grains" may be based on the ASTM E112 standard. The average size of the "grains" may refer to the total average size of the γ-austenite grains and the α-ferrite grains. The average size of the γ-austenite grains may be 50 to 100 µm, preferably 50 to 80 µm, and more preferably 50 to 60 µm.

[0244] In another embodiment of the present invention, an area fraction of the γ-austenite may be larger than an area fraction of the α-ferrite. When the area fraction of the γ-austenite is larger than the area fraction of the α-ferrite, it means that cold rolling has been performed smoothly, and thus the FeCoV alloy-based thin plate has a high saturation magnetic flux density, low coercivity, and low iron loss value, which is preferable because the magnetic properties of the drive motor are excellent.

[0245] In another embodiment of the present invention, the area fraction of the γ-austenite may be 60 to 95%. In another embodiment of the present invention, the area fraction of the α-ferrite may be 5 to 50%. When the area fraction of the γ-austenite and the area fraction of the α-ferrite satisfy the above ranges, it is preferable because there is an advantage of excellent magnetic properties.

[0246] In another embodiment of the present invention, a ratio of the number of the γ-austenite to the α-ferrite may be 80:20 to 60:40. Specifically, the number of the γ-austenite and the α-ferrite may be based on the ASTM E112 standard. Preferably, the ratio of the number of the γ-austenite to the α-ferrite may be 70:30 to 60:40. When the ratio of the number of the γ-austenite to the α-ferrite satisfies the above range, it is preferable because there is an advantage of excellent soft magnetic properties and excellent mechanical properties.

[0247] In another embodiment of the present invention, the number of the γ-austenite grains having a size of 50 to 100 µm may be 5 to 12 based on ASTM E112. Preferably, the number of the γ-austenite grains may be 7 to 10. When the number of the γ-austenite grains satisfies the above range, it is preferable because it is easy to obtain a laminate.

[0248] In another embodiment of the present invention, the number of the α-ferrite grains having a size of 50 to 100 µm may be 2 to 8 based on ASTM E112. Preferably, the number of the α-ferrite grains may be 2 to 6, and more preferably 4 to 6. When the number of the α-ferrite grains satisfies the above range, it is preferable because mechanical properties are excellent.

[0249] Since the FeCoV alloy-based thin plate according to the present invention includes γ-austenite and residual α-ferrite, and the average size of grains is 50 to 100 µm, there is an advantage of excellent mechanical performance as well as magnetic properties.

[0250] The FeCoV alloy-based thin plate according to the present invention can be manufactured by the method for manufacturing an FeCoV alloy-based thin plate described above. For example, the FeCoV alloy-based thin plate may be manufactured by a method for manufacturing an FeCoV alloy-based thin plate comprising: preparing an FeCoV alloy-based plate material; heat-treating the FeCoV alloy-based plate material at 600 to 1,200°C for 10 minutes to 240 minutes to transform at least a portion of an α-ferrite phase into a γ-austenite phase; quenching the heat-treated FeCoV alloy-based plate material; and cold-rolling the quenched FeCoV alloy-based plate material to obtain an FeCoV alloy-based thin plate, but is not limited thereto. The FeCoV alloy-based thin plate includes γ-austenite and residual α-ferrite, and an average size of grains is 50 to 100 µm. The specific manufacturing steps of the method for manufacturing the FeCoV alloy-based thin plate may apply the contents described above. The average size of grains, area fractions of γ-austenite and α-ferrite, number, etc. of the FeCoV alloy-based thin plate may vary depending on the heat treatment temperature, etc. during the process of manufacturing the FeCoV alloy-based thin plate.

[0251] In another embodiment of the present invention, efficiency may be 96% or more when a total weight is 50 kg or less and an output of the motor is 220 kW. The drive motor according to the present invention may be a drive motor for an electric vehicle suitable under a condition of rotating at 12,000 to 28,000 rpm.

[0252] The rotor may include a laminate in which the above-described FeCoV alloy-based thin plates are stacked. The stator may include a laminate in which the above-described FeCoV alloy-based thin plates are stacked. The rotor and the stator may include a laminate in which the above-described FeCoV alloy-based thin plates are stacked.

[0253] The drive motor may additionally include, but is not limited to, a battery as a main power source, an inverter for converting a DC voltage supplied from the motor and the battery, a coil wound around a rotor core, an MCU for controlling voltage supply, a current controller for supplying power of the battery to the coil, and the like.

[0254] The FeCoV alloy-based thin plate may be one manufactured by any one of the methods for manufacturing an FeCoV alloy-based thin plate described above. For example, another aspect of the present invention relates to a method for manufacturing a drive motor component, comprising: preparing an FeCoV alloy-based plate material; heat-treating the FeCoV alloy-based plate material at 600 to 1,200°C for 10 minutes to 240 minutes to transform at least a portion of an α-ferrite phase into a γ-austenite phase; quenching the heat-treated FeCoV alloy-based plate material; cold-rolling the quenched FeCoV alloy-based plate material to obtain an FeCoV alloy-based thin plate; processing the FeCoV alloy-based thin plate; and stacking the processed FeCoV alloy-based thin plates. The drive motor component according to the present invention can be manufactured by performing the steps of processing the FeCoV alloy-based thin plate and stacking the processed FeCoV alloy-based thin plates in the method for manufacturing the FeCoV alloy-based thin plate described above. In short, the FeCoV alloy-based thin plate may be one manufactured by the method for manufacturing an FeCoV alloy-based thin plate described above. The specific manufacturing steps of the method for manufacturing the FeCoV alloy-based thin plate may apply the contents described above.

[0255] The step of processing may be a step of processing a plurality of the FeCoV alloy-based thin plates into a core shape. The processing process may be performed using a laser, but is not limited thereto. For example, the processing process may be performed by fusing (cutting) with a laser at a scanning speed of the laser of 10,000 mm / min or more, thereby obtaining a drive motor component suitable for high efficiency of the motor, but is not limited thereto.

[0256] The step of stacking the FeCoV alloy-based thin plates may fix the FeCoV alloy-based thin plates to each other by adhesion or the like, but is not limited thereto. For example, the stacking may be performed through a coating process of applying an adhesive to both surfaces of the processed FeCoV alloy-based thin plate, a drying process of drying the FeCoV alloy-based thin plate to which the adhesive is applied to primarily cure the applied adhesive, a bonding process of stacking the dried FeCoV alloy-based thin plates and then press-drying them to secondarily and completely cure the applied adhesive to bond the stacked and processed FeCoV alloy-based thin plates, but is not limited thereto.

[0257] Hereinafter, preferred examples and comparative examples of the present invention will be described. However, the following examples are only preferred embodiments of the present invention, and the present invention is not limited to the following examples.<Preparation Examples 1 and 2> Preparation Example 1

[0258] After preparing Fe 49 Co 49 V 2 (Specimens 1 to 6) and Fe 48.43 Co 51.11 Cr 0.46 (Specimen 7) plate materials, heat treatment was performed on each at a temperature and for a time according to Table 1 below. Thereafter, after quenching (at a rate of 50°C / sec) by introducing them into cooling water, cold rolling was performed with a total reduction ratio of 96.7% to manufacture Fe 49 Co 49 V 2 thin plates and Fe 48.43 Co 51.11 Cr 0.46 thin plates having a thickness of 0.2 mm. In the case of Specimen 1, cold rolling was performed after slow cooling without going through the step of quenching after the heat treatment. [Table 1]Heat Treatment ConditionSaturation Magnetic Flux Density (T)Residual Magnetic Flux Density (T)Coercivity (kA / m)Coercivity (Oe)Magnetic Flux Density at 5000 A / m (T)Iron Loss @ 400 Hz, 1 T (W / kg)Driving Efficiency (T kg / W)850°C, 1 hour (excluding quenching)Specimen 12.30800.64800.02210.27782.116021.31800.5413950°C, 1 hourSpecimen 22.16850.69560.02460.30861.986514.85100.73011,050°C, 1 hourSpecimen 32.25851.05900.01970.24702.202513.03900.8661950°C, 15 minutesSpecimen 42.28370.99530.02180.27442.220713.52630.8442950°C, 30 minutesSpecimen 52.29000.74870.01560.19612.162012.51850.9146950°C, 2 hoursSpecimen 62.27751.00360.01950.24452.220013.10200.8691950°C, 1 hour (Fe 48.43 -Co 51.11 -Cr 0. 46 )Specimen 72.29300.99850.01750.23542.186813.17200.8704 Preparation Example 2

[0259] Stress relief heat treatment was performed on the Fe 49 Co 49 V 2 thin plate manufactured by heat-treating at 950°C for 30 minutes among the Fe 49 Co 49 V 2 thin plates manufactured according to Table 1, at temperatures according to Table 2 below for 30 minutes. [Table 2]Stress Relief Heat Treatment TemperatureSpecimen TypeSaturation Magnetic Flux Density (T)Residual Magnetic Flux Density (T)Coercivity (kA / m)Coercivity (Oe)Magnetic Flux Density at 5000 A / m (T)Iron Loss @ 400 Hz, 1 T (W / kg)Driving Efficiency (T kg / W)600°CSpecimen 82.130.980.0520.7081.87180.460.059016700°CSpecimen 92.2366670.7938670.0230.2896672.11066716.810670.665252800°CSpecimen 102.260.72940.02050.26052.11714.7360.76683830°CSpecimen 112.2150.59990.016850.211352.00115.98150.692989850°CSpecimen 122.2233330.7531670.0268330.3374272.02066714.531330.765014880°CSpecimen 132.260.7450.1652.0751.87541.5770.271785900°CSpecimen 142.180.7770.0640.8091.95131.150.34992 <Experimental Example>

[0260] The saturation magnetic flux density, residual magnetic flux density, coercivity, magnetic flux density value at 5000 A / m applied, iron loss, and driving efficiency of the FeCoV alloy-based thin plates manufactured according to Tables 1 and 2 were measured, and the results are shown in Tables 1 and 2 above.(1) Iron Loss

[0261] Iron loss was measured under conditions where the magnitude of the applied magnetic field was 1 T and the frequency was 400 Hz.(2) Driving Efficiency

[0262] Driving efficiency was measured by calculating (Maximum Saturation Magnetic Flux Density) / (Iron Loss × 0.2). Specifically, in order to normalize the scale value for driving efficiency, different constant values reflecting this should be multiplied to the denominator and the numerator, respectively, which can be defined as a safety factor. Here, the values multiplied to the denominator and numerator should be less than 1, and the influence of the value and the percentage of the range should be considered. Considering that the variability of the saturation magnetic flux density value is about 5 times the variability of the iron loss value, the calculation was performed by multiplying the denominator by 0.2 and the numerator by 1.0, respectively.(3) Elongation and Tensile Strength

[0263] The elongation and tensile strength of the Fe 49 Co 49 V 2 thin plate manufactured by heat treatment at 950°C for 30 minutes and the Fe 49 Co 49 V 2 thin plate manufactured by subsequently performing stress relief heat treatment at 850°C for 30 minutes were measured, and the results are shown in FIG. 1A (without stress relief heat treatment) and FIG. 1B (with stress relief heat treatment), respectively.(4) XRD Analysis

[0264] The XRD analysis results of the Fe 49 Co 49 V 2 thin plate manufactured by heat treatment at 950°C for 30 minutes and the Fe 49 Co 49 V 2 thin plate manufactured by subsequently performing stress relief heat treatment at 850°C for 30 minutes are shown in FIG. 2A (without stress relief heat treatment) and FIG. 2B (with stress relief heat treatment), respectively.(5) Magnetic Properties

[0265] Changes in the 5000 A / m magnetic flux density value and iron loss value at 400 Hz with 1 T applied for the Fe 49 Co 49 V 2 thin plate manufactured by performing stress relief heat treatment at 850°C for 30 minutes on the Fe 49 Co 49 V 2 thin plate manufactured by heat treatment at 950°C for 30 minutes are shown in FIGS. 3A and 3B.

[0266] Referring to Table 1, it can be seen that the specimens heat-treated for a certain period of time in a specific temperature range exhibit high saturation magnetic flux density values and low iron loss values. Specifically, it can be seen that the saturation magnetic flux density value varies somewhat depending on the heat treatment temperature of the specimen, and preparing for use as a motor for an electric vehicle, it can be seen that the magnetic flux density value in a specific section (5000 A / m) also varies.

[0267] Referring to FIGS. 1A and 1B, it can be seen that mechanical properties vary somewhat before and after stress relief heat treatment. In the present invention, a condition that simultaneously satisfies mechanical properties and magnetic properties, particularly high saturation magnetic flux density values and low iron loss values, is determined as the most appropriate heat treatment condition, and it can be seen that magnetic properties and mechanical properties are most excellent under heat treatment conditions at a specific temperature when compared with magnetic property values.

[0268] Referring to FIGS. 2A and 2B, although there were differences in peak width and height of the specimen before and after stress relief heat treatment, the 2-theta positions where peaks were formed were almost identical. This means that they are composed of the same phase, and it is understood that rather than a new phase being generated through heat treatment, the regularity level changed from a disordered structure of the formed phase to an ordered structure. It is judged that cold rolling is possible due to the irregular structure formed before cold rolling, and as a stable phase at room temperature is formed in the process of removing stress after rolling to secure regularity, magnetic properties as well as mechanical properties are improved.

[0269] Referring to FIGS. 3A and 3B, it can be seen that the specimen subjected to stress relief heat treatment exhibits a high saturation magnetic flux density value (2.26 T) and a low iron loss value (14.248 W / kg), confirming that it exhibits a level similar to that of a soft magnetic thin plate (Fe 49 Co 49 V 2 ) manufactured through a conventional complicated process.<Preparation Example 3>

[0270] After preparing an Fe 49 Co 49 V 2 plate material, heat treatment was performed at 950°C for 1 hour and at 1,100°C for 1 hour, respectively. Thereafter, after quenching (at a rate of 50°C / sec) by introducing it into cooling water, cold rolling was performed with a total reduction ratio of96.7% to manufacture an Fe 49 Co 49 V 2 thin plate having a thickness of 0.2 mm.<Experimental Example>

[0271] An image measured using a scanning electron microscope (SEM: JEOL 7600F) of a cross-section of a specimen manufactured by heat-treating at 950°C for 1 hour during the manufacturing process of Preparation Example 3 is shown in FIG. 4. In addition, images of side cross-sectional structures of Fe 49 Co 49 V 2 thin plates manufactured by heat-treating at 950°C and 1,100°C for 1 hour were taken using an optical microscope (OM: Olympus DSX500) and then comparatively analyzed for each condition, and the results are shown in FIGS. 5 to 7 (FIGS. 5 and 7: 950°C heat-treated specimen, FIG. 6: 1,100°C heat-treated specimen).

[0272] Referring to FIG. 4, it can be confirmed that a composite phase is formed in which a γ-austenite phase is distributed as a whole and some residual α-ferrite phase is included. In addition, when cold rolling was performed, it was confirmed that cold rolling proceeded smoothly without cracking or bursting, and the side of the thin plate rolled to a thickness of 0.2 mm showed a uniform striped shape, proving that the cold rolling process was performed smoothly. Referring to FIGS. 4 to 7, the structure quenched under appropriate conditions mostly consists of a γ-austenite phase capable of elongation, and shows a composite structure in which some α-ferrite phase coexists. It was confirmed that it is preferable that the structure of the cross-section forms a stripe structure, and the interval thereof represents a level of approximately 1 to 3 µm.<Preparation Example 4>

[0273] An FeCoV alloy melt was prepared by melting iron alloy components at a temperature of 1,700°C using a vacuum melting method. The alloy melt was injected into a mold and cooled and crystallized at a casting speed of 75 mm / min to manufacture an ingot (Fe 49 Co 49 V 2 , Fe 47.79, Co 50.43, V 1.78 wt%: weight ratio). The manufactured ingot was cut to a thickness of 30 mm and then hot-rolled using a steel rolling mill to obtain a plate material. At this time, the rolling start temperature was 950°C, the rolling end temperature was 1,150°C, and rolling was performed with a total reduction ratio of 80% in 5 passes to have a final thickness of around 6 mm. Thereafter, the obtained plate material was heat-treated at 950°C and 1,100°C for 1 hour, respectively. Then, after quenching (at a rate of 50°C / sec) by introducing it into cooling water, cold rolling was performed with a total reduction ratio of 96.7% to manufacture an Fe 49 Co 49 V 2 thin plate having a thickness of 0.2 mm.<Experimental Example> (1) XRD Measurement

[0274] XRD patterns of the cast ingot manufactured in the process of manufacturing the Fe 49 Co 49 V 2 thin plate according to Preparation Example 4, the specimen before heat treatment (after hot rolling), and the specimen after 950°C heat treatment and quenching (after cold rolling) were compared and shown in FIGS. 8A to 8C, respectively. XRD: Using model name (DMAX2500) equipment, qualitative and quantitative analysis was performed after obtaining XRD diffraction patterns in a 2-theta value range of 10 to 100 degrees.(2) Structure Comparison

[0275] Images were measured using scanning electron microscope (SEM: model name JEOL 7600F) equipment for the cast ingot manufactured in the process of manufacturing the Fe 49 Co 49 V 2 thin plate according to Preparation Example 4, and specimens after heat treatment according to 950°C and 1,100°C and quenching (after cold rolling), and then grain size and phase analysis were performed, and the results are shown in FIGS. 9A to 9C, respectively.(3) GDS Surface Analysis

[0276] In the process of manufacturing the Fe 49 Co 49 V 2 thin plate according to Preparation Example 4, specimens of the Fe 49 Co 49 V 2 thin plate manufactured in the same manner as in Preparation Example 4 by changing the heat treatment temperature to 700°C, 850°C, and 900°C with the specimen before heat treatment (after hot rolling) were analyzed using GDS surface analysis equipment, and the results are shown in FIGS. 10A to 10D, respectively. Specifically, each specimen was prepared and surface analysis was performed while cutting the surface in the depth direction from the surface of the plate material or thin plate, and the experimental conditions are as follows.<Experimental Conditions>

[0277] Method: Zn Galv RF Lamp type: RF (Radio frequency) Analysis area: 4 mΦ Calibration factor: 0.70 Analysis conditions: 700 V, 30 mA, 21 W Depth setting: 0 to end sec, 100 points / sec Plot point: 8000, Smoothing: 3

[0278] Referring to FIGS. 8A to 8C, in the case of the cast ingot, only a single phase, that is, an Fe phase, was detected as a result of XRD analysis, whereas in the specimen before heat treatment (after hot rolling), many oxide phase peaks were detected in addition to the Fe single phase. In particular, some oxides existed even after the quenching heat treatment that changes the α-ferrite structure to the γ-austenite structure. The most important point is that the α-ferrite structure changes to the γ-austenite structure, so that the height and full width at half maximum (FWHM) of the existing α peak change on XRD, and a γ peak that was not seen previously is found. Also, even in the same Fe-α peak, in the case of the cast ingot, a (100) plane peak appears around 45 degrees, a (200) peak around 60 degrees, and a (211) peak around 85 degrees. Here, in the cast ingot, that is, a material having a complete ordered structure by slow cooling, the (100) plane peak rises highest and the rest are relatively very low, whereas in the specimen before heat treatment (after hot rolling) and the sample after heat treatment and quenching (after cold rolling), the peak of the (100) plane, which is the main peak, decreases, while the height of the (211) plane peak greatly increases. From this, it can be confirmed that even with the same structure, the ordered structure becomes a disordered structure or the disordered structure becomes ordered depending on the process or heat treatment.

[0279] Referring to FIGS. 9A to 9C, in the case of the cast ingot, grain boundaries are clear and coarse grain boundaries of a level of 100 to 500 µm are shown, whereas in the case of the specimen subjected to high-temperature heat treatment and quenching, it simultaneously contains a fine structure and a coarse structure depending on conditions, or contains fine grains of around 100 µm. Whether defects occur in the cold rolling process may depend on such differences in structure and crystal structure.

[0280] Meanwhile, surface analysis was performed using GDS analysis equipment to observe plate surface changes before heat treatment and through heat treatment for each temperature condition. Oxygen and carbon were hardly measured on the surface of the plate material not subjected to heat treatment, but as the heat treatment temperature increased, surface oxygen and carbon components were measured up to a depth of 0.1 to 0.2 µm, and phase fractions of Fe and Co were also distributed quantitatively almost identically as the heat treatment temperature increased and as they penetrated in the depth direction. Since the steel plate used in the experiment is composed of 49Fe-49Co-2V components, when the V element is solid-soluted and then a precipitation phase is generated as the heat treatment temperature increases to cause precipitation hardening, the quantitative ratio of Co and Fe elements becomes almost the same. Therefore, according to the depth profile analysis result, it is estimated that a precipitation phase of V element is formed under a heat treatment temperature condition of 880°C or higher.<Preparation Example 5>

[0281] An FeCoV alloy melt was prepared by melting iron alloy components at a temperature of 1,700°C using a vacuum melting method. The alloy melt was injected into a mold and cooled and crystallized at a casting speed of 75 mm / min to manufacture an ingot (Fe 49 Co 49 V 2 , Fe 47.79, Co 50.43, V 1.78 wt%: weight ratio). The manufactured ingot was cut to a thickness of 30 mm and then hot-rolled using a steel rolling mill to obtain a plate material. At this time, the rolling start temperature was 950°C, the rolling end temperature was 1,150°C, and rolling was performed with a total reduction ratio of 80% in 5 passes to have a final thickness of around 6 mm. Thereafter, the obtained plate material was heat-treated at 950°C for 30 minutes. Then, after quenching (at a rate of 50°C / sec) by introducing it into cooling water, cold rolling was performed with a total reduction ratio of 96.7% to manufacture an Fe 49 Co 49 V 2 thin plate having a thickness of 0.2 mm. Thereafter, annealing heat treatment was performed at a temperature of 950°C for 30 minutes.<Experimental Example> (1) XRD Measurement

[0282] XRD patterns of specimen #1 immediately after cold rolling (before annealing heat treatment) and specimen #2 after annealing heat treatment, manufactured in the process of manufacturing the Fe 49 Co 49 V 2 thin plate according to Preparation Example 5, were compared and shown in FIGS. 11A and 11B, and the intensity and FWHM are shown in Table 3 below. [Table 3]Specimen No.Position (°)Norm.IntensityFWHM(°)#121.262734.564.523444.541296.410.639464.95052480.890.630982.36621195.020.7229#244.69529.680.359765.09155904.410.081182.463536456.70.0865 (2) Magnetic Permeability Measurement

[0283] The hysteresis of Specimen #1 and Specimen #2 was measured, and the results are shown in FIG. 12.

[0284] Referring to FIGS. 11A and 11B and Table 3, in the case of Specimen #1, a typical preferred orientation form in which intensity decreases in a very wide region appears. On the other hand, in the case of Specimen #2, it appears to have multiple peaks in the rocking curve, which may occur when grains like very well-aligned single crystals are arranged in multiple directions. That is, in terms of crystallinity (or ordering), comparing Specimen #1 and Specimen #2, i.e., the specimen immediately after cold rolling and the specimen immediately after annealing heat treatment, it means that the crystallinity of Specimen #2 is very excellent when predicted in terms of the main direction plane of the peak and the full width at half maximum (FWHM). This is because the microstructure before heat treatment forms an ordered structure because it underwent slow cooling in the previous process, and constitutes an α-ferrite phase in the form of a Body-Centered Cubic (BCC) structure.

[0285] Since this structure has relatively low elongation, it may cause problems in the cold rolling process. Therefore, a heat treatment process was performed to change the phase to a γ-austenite phase, which is a Face-Centered Cubic (FCC) structure, while configuring a disordered structure or an ordered-disordered mixed structure through microstructure control heat treatment. Since the soft magnetic properties, such as magnetic properties, i.e., saturation magnetic flux density and iron loss, increase only when the structure has an ordered structure again after cold rolling, XRD changes before and after heat treatment were compared. When measuring the magnetic properties of Specimen #1 which did not undergo stress relief heat treatment after cold rolling and Specimen #2 after performing stress relief heat treatment, they appear as shown in the graph of FIG. 12. They showed a very large difference in soft magnetic properties, i.e., the slope of the hysteresis graph, the inner area, and the magnetic flux density value in the same frequency region.<Preparation Example 6>

[0286] An FeCoV alloy melt was prepared by melting iron alloy components according to Table 4 at a temperature of 1,700°C using a vacuum melting method. The alloy melt was injected into a mold and cooled and crystallized at a casting speed of 75 mm / min to manufacture an ingot. The manufactured ingot was cut to a thickness of 30 mm and then hot-rolled using a steel rolling mill to obtain a plate material. At this time, the rolling start temperature was 950°C, the rolling end temperature was 1,150°C, and rolling was performed with a total reduction ratio of 80% in 5 passes to have a final thickness of around 6 mm. Thereafter, the obtained plate material was heat-treated at 950°C for 30 minutes. Then, after quenching (at a rate of 50°C / sec) by introducing it into cooling water, cold rolling was performed with a total reduction ratio of 96.7% to manufacture an FeCoV alloy-based thin plate having a thickness of 0.2 mm, and then soft magnetic performance was measured. [Table 4]Alloy Component (at%, atomic ratio)Saturation Magnetic Flux Density (Bs) / TCoercivity (H2.04e / Oe)FeCoVNiCrNb49492---2.380.185535181-2.0433.1258252123-1.9943.436020215211.9623.2763201151-2.0126.156620210112.0442.06 <Preparation Examples 7 and 8> Preparation Example 7

[0287] An FeCoV alloy melt was prepared by melting iron alloy components at a temperature of 1,700°C using a vacuum melting method. The alloy melt was injected into a mold, and cooled and crystallized at a casting speed of 75 mm / min to manufacture an ingot (Fe 49 Co 49 V 2 , Fe 47.79, Co 50.43, V 1.78 wt%: weight ratio). The manufactured ingot was cut to a thickness of 30 mm and then hot-rolled using a steel rolling mill to obtain a plate material. At this time, the rolling start temperature was 950°C, the rolling end temperature was 1,150°C, and the rolling was performed with a total reduction ratio of 80% in 5 passes to have a final thickness of around 6 mm. Thereafter, the obtained plate material was heat-treated at 950°C and 1,100°C for 1 hour, respectively. Then, after quenching (at a rate of 50°C / sec) by introducing it into cooling water, cold rolling was performed with a total reduction ratio of 96.7% to manufacture an Fe 49 Co 49 V 2 thin plate having a thickness of 0.2 mm.Preparation Example 8

[0288] An FeCoV alloy melt was prepared by melting iron alloy components at a temperature of 1,700°C using a vacuum melting method. The alloy melt was injected into a mold, and cooled and crystallized at a casting speed of 75 mm / min to manufacture an ingot (Fe 49 Co 49 V 2 , Fe 47.79, Co 50.43, V 1.78 wt%: weight ratio). At this time, the alloy melt was melted under argon gas. The manufactured ingot was cut to a thickness of 6 mm to manufacture a cast material. Thereafter, the cast material was heat-treated at 950°C and 1,100°C for 2 hours, respectively, quenched (at a rate of 50°C / sec) by introducing it into cooling water, and then cold rolling was performed with a total reduction ratio of 96.7% to manufacture an Fe 49 Co 49 V 2 thin plate having a thickness of 0.2 mm.<Experimental Example> (1) XRD Measurement

[0289] The cast ingot (Specimen 1) manufactured in the process of manufacturing the Fe 49 Co 49 V 2 thin plate according to Preparation Example 7, the specimen immediately after hot rolling (before heat treatment) (Specimen 2), the specimen after heat treatment at 950°C and quenching (after cold rolling, Specimen 3), and the specimen after heat treatment at 950°C and quenching (Specimen 4) manufactured in the process of manufacturing the Fe 49 Co 49 V 2 thin plate according to Preparation Example 8 were subjected to qualitative and quantitative analysis after obtaining XRD diffraction patterns in a 2-theta value range of 10 to 100 degrees using XRD (model name DMAX2500) equipment, and the results are shown in FIGS. 13A to 13D, respectively.(2) Structure Comparison

[0290] Images were measured using scanning electron microscope (SEM: model name JEOL 7600F) equipment for the cast ingot (Specimen 5) manufactured in the process of manufacturing the Fe 49 Co 49 V 2 thin plate according to Preparation Example 7, specimens after heat treatment at 1,100°C and 950°C and quenching immediately after hot rolling (after cold rolling, Specimens 6 and 7, respectively), and specimens after heat treatment at 1,100°C and 950°C and quenching (Specimens 8 and 9, respectively) manufactured in the process of manufacturing the Fe 49 Co 49 V 2 thin plate according to Preparation Example 8, and the results are shown in FIGS. 14A to 14E.(3) Soft Magnetic Performance Evaluation

[0291] The soft magnetic performance of the Fe 49 Co 49 V 2 thin plates manufactured by performing heat treatment at 950°C among Preparation Examples 7 and 8 was evaluated, and the results are shown in Table 5 below. [Table 5]Saturation Magnetic Flux Density (T)Coercivity (Oe)Magnetic Flux Density at 5000 A / m (T)Core Loss @ 400 Hz, 1 T (W / kg)Preparation Example 7 (Hot Rolling + Cold Rolling)2.3180.1632.18412.565Preparation Example 8 (Cold Rolling)2.2020.2292.03117.591

[0292] Referring to FIGS. 13A to 13D, 14A to 14E, and Table 5, it can be seen that the thin plate manufactured as the FeCoV alloy-based thin plate according to the present invention has high saturation magnetic flux density and low coercivity and iron loss (core loss) values even without performing hot rolling.<Preparation Example 9>

[0293] Heat treatment was performed on FeCoV alloy-based plate materials at 950°C and 1,100°C for 1 hour, respectively. Thereafter, after quenching (at a rate of 50°C / sec) by introducing them into cooling water, cold rolling was performed with a total reduction ratio of 96.7% to manufacture Fe 49 Co 49 V 2 thin plates having a thickness of 0.2 mm.<Experimental Example> (1) Structure Comparison

[0294] Images of the Fe 49 Co 49 V 2 thin plates manufactured according to Preparation Example 9 were measured using scanning electron microscope (SEM: model name JEOL 7600F) equipment, and the results are shown in FIGS. 15A and 15B.(2) Grains and Number of Structures

[0295] The grains, γ-austenite phase, and α-ferrite phase of the Fe 49 Co 49 V 2 thin plate manufactured according to Preparation Example 9 were observed and measured according to the ASTM E112 standard, and the results are shown in Table 6 below. [Table 6]Average Size of GrainsArea Fraction of γ-AusteniteArea Fraction of α-FerriteNumber of γ-AusteniteNumber of α-FerriteRatio of Number of γ-Austenite Phase in Total StructureHeat treatment temperature 1,100°C263.427732.26.824 %Heat treatment temperature 950°C57.263.736.38.95.462 % (3) Soft Magnetic Properties

[0296] The soft magnetic properties of the Fe 49 Co 49 V 2 thin plate manufactured according to Preparation Example 9 were measured, and the results are shown in Table 7 below. [Table 7]Saturation Magnetic Flux Density (T)Coercivity (Oe)Magnetic Flux Density at 5000 A / m (T)Core Loss @ 400 Hz, 1 T (W / kg)Heat treatment temperature 1,100°C2.1150.1982.01914.479Heat treatment temperature 950°C2.3180.1632.18412.565

[0297] Referring to FIGS. 15A and 15B, it can be seen that the relatively bright portion is the γ-austenite phase and the relatively dark portion is the α-ferrite phase, indicating a composite phase containing the γ-austenite phase and the α-ferrite phase.

[0298] Referring to Table 7, it can be seen that the FeCoV alloy-based thin plate according to the present invention has a high saturation magnetic flux density and low coercivity and core loss values.

[0299] The present invention is not limited to the above-described embodiments but may be manufactured in various different forms, and those skilled in the art to which the present invention pertains will understand that the present invention may be implemented in other specific forms without departing from the technical spirit or essential features thereof. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not limiting.

Examples

preparation example 1

Preparation Example 1

[0258]After preparing Fe 49 Co 49 V 2 (Specimens 1 to 6) and Fe 48.43 Co 51.11 Cr 0.46 (Specimen 7) plate materials, heat treatment was performed on each at a temperature and for a time according to Table 1 below. Thereafter, after quenching (at a rate of 50°C / sec) by introducing them into cooling water, cold rolling was performed with a total reduction ratio of 96.7% to manufacture Fe 49 Co 49 V 2 thin plates and Fe 48.43 Co 51.11 Cr 0.46 thin plates having a thickness of 0.2 mm. In the case of Specimen 1, cold rolling was performed after slow cooling without going through the step of quenching after the heat treatment.

[Table 1]

Heat Treatment ConditionSaturation Magnetic Flux Density (T)Residual Magnetic Flux Density (T)Coercivity (kA / m)Coercivity (Oe)Magnetic Flux Density at 5000 A / m (T)Iron Loss @ 400 Hz, 1 T (W / kg)Driving Efficiency (T kg / W)

850°C, 1 hour (excluding quenching)Specimen 12.30800.64800.02210.27782.116021.31800.5413

950°C, 1 hourSpecimen 22.1...

preparation example 2

Preparation Example 2

[0259]Stress relief heat treatment was performed on the Fe 49 Co 49 V 2 thin plate manufactured by heat-treating at 950°C for 30 minutes among the Fe 49 Co 49 V 2 thin plates manufactured according to Table 1, at temperatures according to Table 2 below for 30 minutes.

[Table 2]

Stress Relief Heat Treatment TemperatureSpecimen TypeSaturation Magnetic Flux Density (T)Residual Magnetic Flux Density (T)Coercivity (kA / m)Coercivity (Oe)Magnetic Flux Density at 5000 A / m (T)Iron Loss @ 400 Hz, 1 T (W / kg)Driving Efficiency (T kg / W)

600°CSpecimen 82.130.980.0520.7081.87180.460.059016

700°CSpecimen 92.2366670.7938670.0230.2896672.11066716.810670.665252

800°CSpecimen 102.260.72940.02050.26052.11714.7360.76683

830°CSpecimen 112.2150.59990.016850.211352.00115.98150.692989

850°CSpecimen 122.2233330.7531670.0268330.3374272.02066714.531330.765014

880°CSpecimen 132.260.7450.1652.0751.87541.5770.271785

900°CSpecimen 142.180.7770.0640.8091.95131.150.34992

[0260]The saturation...

preparation example 7

Preparation Example 7

[0287]An FeCoV alloy melt was prepared by melting iron alloy components at a temperature of 1,700°C using a vacuum melting method. The alloy melt was injected into a mold, and cooled and crystallized at a casting speed of 75 mm / min to manufacture an ingot (Fe 49 Co 49 V 2 , Fe 47.79, Co 50.43, V 1.78 wt%: weight ratio). The manufactured ingot was cut to a thickness of 30 mm and then hot-rolled using a steel rolling mill to obtain a plate material. At this time, the rolling start temperature was 950°C, the rolling end temperature was 1,150°C, and the rolling was performed with a total reduction ratio of 80% in 5 passes to have a final thickness of around 6 mm. Thereafter, the obtained plate material was heat-treated at 950°C and 1,100°C for 1 hour, respectively. Then, after quenching (at a rate of 50°C / sec) by introducing it into cooling water, cold rolling was performed with a total reduction ratio of 96.7% to manufacture an Fe 49 Co 49 V 2 thin plate having a ...

[Technical Field]

[0001] The present invention relates to an FeCoV alloy-based thin plate and a method for manufacturing the same, and specifically, to an FeCoV alloy-based soft magnetic thin plate and a method for manufacturing the same.[Background Art]

[0002] Generally, a magnetic material is a material having magnetic properties, and among them, a soft magnetic material is a material capable of exhibiting magnetic and non-magnetic properties, so that the magnetic properties can be selectively used in a desired direction. Typically, the soft magnetic material has been used as a motor core material and applied to various electronic products, and recently, as electric vehicles have emerged rapidly, it is receiving great attention as a material for a drive motor.

[0003] A material for a drive motor for an electric vehicle must have a high saturation magnetic flux density value in order to increase motor output. In addition, in order to increase motor efficiency related to how long it can be used with the same battery, iron loss, which means a loss generated when implementing magnetic properties, must be low.

[0004] Although the composition of the FeCoV-based alloy varies somewhat depending on target properties, it is an alloy having a high saturation magnetic flux density value and low iron loss. Although its application has been limited due to the high price of the material, it is a material that is re-emerging rapidly in recent years. In order to manufacture the FeCoV-based alloy into a thin plate, very complicated processes such as vacuum melting, slag removal, forging, and cold rolling must be performed.

[0005] In addition, since the FeCoV-based alloy has characteristics of high strength and somewhat low elongation because its microstructure forms an ordered structure, there is a problem in that rolling to a target thickness is difficult due to occurrence of rupture or cracking during a cold rolling process.

[0006] Therefore, there is a demand for development of a method for manufacturing an FeCoV alloy-based thin plate that has a simple manufacturing method, facilitates cold rolling, and can reduce process costs.[Detailed Description of the Invention][Technical Problem]

[0007] An object of the present invention is to provide a method for manufacturing an FeCoV alloy-based thin plate, which has a simple manufacturing method, facilitates cold rolling to a target thickness, and can reduce process costs.

[0008] In addition, another object of the present invention is to provide an FeCoV alloy-based thin plate having a high saturation magnetic flux density value and low iron loss.

[0009] Furthermore, another object of the present invention is to provide a drive motor having excellent driving efficiency.[Technical Solution]

[0010] The present invention provides an FeCoV alloy-based thin plate comprising γ-austenite and residual α-ferrite, wherein an average size of grains is 50 to 100 µm.

[0011] In addition, the present invention provides an FeCoV alloy-based thin plate having a first peak in a range where 2θ is 42° to 47°, a second peak in a range where 2θ is 62° to 67°, and a third peak in a range where 2θ is 80° to 85° in an X-ray diffraction chart obtained by XRD analysis.

[0012] Furthermore, the present invention provides a method for manufacturing an FeCoV alloy-based thin plate, comprising: preparing an FeCoV alloy-based plate material; heat-treating the FeCoV alloy-based plate material at 600°C to 1,200°C for 10 minutes to 240 minutes to transform at least a portion of an α-ferrite phase into a γ-austenite phase; quenching the heat-treated FeCoV alloy-based plate material; and cold-rolling the quenched FeCoV alloy-based plate material to obtain an FeCoV alloy-based thin plate.[Advantageous Effects]

[0013] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention has an advantage in that it is possible to manufacture an FeCoV alloy-based thin plate having high saturation magnetic flux density and low iron loss without going through existing complicated processes. In addition, there is an advantage of reducing process costs.

[0014] Furthermore, the FeCoV alloy-based thin plate according to the present invention has an advantage of having high saturation magnetic flux density and low iron loss.

[0015] Also, a drive motor according to the present invention has an advantage of excellent driving efficiency.[Brief Description of Drawings]

[0016] FIGS. 1A and 1B are views showing measurement results of elongation and tensile strength of an Fe 49 Co 49 V 2 thin plate manufactured according to some embodiments of the present invention. FIGS. 2A and 2B are views showing XRD analysis results of an Fe 49 Co 49 V 2 thin plate manufactured according to some embodiments of the present invention. FIGS. 3A and 3B are views showing changes in magnetic flux density values at 5000 A / m and iron loss values at 400 Hz with 1 T applied, for an Fe 49 Co 49 V 2 thin plate manufactured according to some embodiments of the present invention. FIG. 4 is a view showing an SEM image of an Fe 49 Co 49 V 2 thin plate manufactured according to some embodiments of the present invention. FIGS. 5 to 7 are views showing OM images of a side cross-sectional structure of an Fe 49 Co 49 V 2 thin plate manufactured according to some embodiments of the present invention. FIGS. 8A to 8C are views showing XRD patterns of respective specimens during a process of manufacturing an Fe 49 Co 49 V 2 thin plate according to some embodiments of the present invention. FIGS. 9A to 9C are views showing SEM images of respective specimens during a process of manufacturing an Fe 49 Co 49 V 2 thin plate according to some embodiments of the present invention. FIGS. 10A to 10D are views showing GDS surface analysis results of Fe 49 Co 49 V 2 thin plate specimens manufactured according to some embodiments of the present invention. FIGS. 11A and 11B are views showing XRD patterns of respective specimens during a process of manufacturing an Fe 49 Co 49 V 2 thin plate according to some embodiments of the present invention. FIG. 12 is a view showing hysteresis of an Fe 49 Co 49 V 2 thin plate manufactured according to some embodiments of the present invention. FIGS. 13A to 13D are views showing XRD patterns of respective specimens during a process of manufacturing an Fe 49 Co 49 V 2 thin plate according to some embodiments of the present invention. FIGS. 14A to 14E are views showing SEM images of respective specimens during a process of manufacturing an Fe 49 Co 49 V 2 thin plate according to some embodiments of the present invention. FIGS. 15A and 15B are views showing SEM images of an Fe 49 Co 49 V 2 thin plate manufactured according to some embodiments of the present invention. [Mode for Carrying Out the Invention]

[0017] Hereinafter, embodiments of the present invention will be described in detail. However, these are presented as examples, and the present invention is not limited thereto, and the present invention is only defined by the scope of the claims to be described later.

[0018] In the present invention, when a member is referred to as being positioned "on" another member, this includes not only the case where the member is directly in contact with the other member but also the case where another member is interposed between the two members.

[0019] In the present invention, when a part is referred to as "comprising" a certain component, it means that it may further include other components rather than excluding other components unless otherwise stated.

[0020] One aspect of the present invention relates to a method for manufacturing an FeCoV alloy-based thin plate, comprising: preparing an FeCoV alloy melt by vacuum melting an alloy component composed of 20 to 49 at% of cobalt, 2 to 5 at% of vanadium, and a balance of iron and other impurities; casting the alloy melt to manufacture an ingot; hot-rolling the ingot to obtain a plate material; heat-treating the plate material at 600°C to 1,200°C for 10 minutes to 240 minutes to transform at least a portion of an α-ferrite phase into a γ-austenite phase; quenching the heat-treated plate material; and cold-rolling the quenched plate material to obtain an FeCoV alloy-based thin plate.

[0021] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes the step of transforming at least a portion of the α-ferrite phase into the γ-austenite phase, whereby cold rolling can be easily performed, and there is an advantage in that an FeCoV alloy-based thin plate having excellent saturation magnetic flux density and low iron loss values can be manufactured without going through complicated processes such as conventional forging.

[0022] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes the step of preparing an FeCoV alloy melt by vacuum melting an alloy component composed of 20 to 49 at% of cobalt, 2 to 5 at% of vanadium, and a balance of iron and other impurities.

[0023] The other impurities may be one or more selected from the group consisting of carbon, oxygen, silicon, and manganese.

[0024] In one embodiment of the present invention, the FeCoV alloy melt may include an alloy component composed of 30 to 49 at% of cobalt, 2 to 3 at% of vanadium, and a balance of iron and other impurities.

[0025] In another embodiment of the present invention, the FeCoV alloy melt may include an alloy component composed of 40 to 49 at% of cobalt, 2 to 3 at% of vanadium, and a balance of iron and other impurities.

[0026] The FeCoV-based alloy is an alloy composition having soft magnetic properties, and is mainly used for motor cores of electronic products by being manufactured into a thin plate, and in particular, recently, application as a drive motor for electric vehicles is being considered.

[0027] In order to increase the output of an electric vehicle, the magnetic flux density value of the motor core material must be high. Recently, most electric vehicles have a value of 2 Tesla or more, and since the FeCoV alloy has a value of up to 2.4 Tesla level, it can be very helpful in improving motor core output. In addition, since it has a significantly lower iron loss value compared to other soft magnetic materials, it is possible to drive a longer distance due to a lower loss value compared to a battery of the same capacity as well as efficiency improvement. For the same reason, when a motor exhibiting the same performance is manufactured, miniaturization and weight reduction are possible.

[0028] Even with the same alloy composition, the defect rate of the rolling process may vary depending on the manufacturing process of such an FeCoV alloy, and mechanical and magnetic property values of the manufactured plate material may be greatly influenced.

[0029] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention has an advantage in that a thin plate having high mechanical and magnetic property values can be easily manufactured without including a conventional complicated slag removal process, forging process, process of forming into a slab shape, and the like.

[0030] Meanwhile, the saturation magnetic flux density value and coercivity value of the manufactured FeCoV alloy-based thin plate may vary somewhat depending on the composition of the FeCoV alloy component.

[0031] In the present invention, by using the FeCoV alloy component having the above composition, there is an advantage in that an FeCoV alloy-based thin plate having a high saturation magnetic flux density value and low coercivity can be obtained.

[0032] The FeCoV alloy melt may have a composition of Fe 49 Co 49 V 2 .

[0033] By vacuum melting the alloy component, a grayish ingot with little contamination can be obtained, and when solidified into an ingot shape through a casting step to be described later, it is possible to suppress a phenomenon in which an ingot having a non-uniform composition is obtained due to composition inconsistency, for example, a case where the upper and middle, or middle and lower compositions of the ingot are different, or segregation exists in the same portion, which is preferable. In addition, it is preferable because it is possible to suppress a phenomenon in which a crack is induced in a hot rolling process, a cold rolling process, or the like because an oxide layer is too thick.

[0034] The step of preparing the alloy melt may be performed under an argon, nitrogen, or carbon dioxide atmosphere. When the step of preparing the alloy melt is performed under the argon, nitrogen, or carbon dioxide atmosphere, it is preferable because a phenomenon in which the alloy component is oxidized or carbonized can be suppressed.

[0035] In the step of preparing the FeCoV alloy melt by vacuum melting the alloy component, the degree of vacuum may be 1×10 -2< to 1×10 -4< torr, preferably 1×10 -2< to 1×10 -3< torr.

[0036] When the degree of vacuum satisfies the above range, it is preferable because oxidation or carbonization can be suppressed.

[0037] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes the step of manufacturing an ingot by casting the alloy melt.

[0038] The method may further include a step of removing slag of the alloy melt liquid before casting the alloy melt, but is not limited thereto.

[0039] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention may not include the step of removing slag of the alloy melt liquid. Specifically, the method for manufacturing an FeCoV alloy-based thin plate according to the present invention has an advantage in that it is possible to manufacture an FeCoV alloy-based thin plate exhibiting excellent performance without including a slag removal process, a forging process, and a shape control slabbing process.

[0040] A method of manufacturing the ingot by casting the alloy melt is not specifically limited in the present invention.

[0041] For example, the ingot may be manufactured by injecting the alloy melt into a mold, and cooling and crystallizing it.

[0042] The injection temperature is preferably set to a temperature 100 to 2,000°C, preferably 100 to 1,000°C, and more preferably 200 to 500°C higher than the liquidus temperature of the melt. The liquidus temperature of the melt can be measured using a direct temperature measurement method with a built-in thermocouple or by measuring the surface of the melt using a non-contact laser thermometer.

[0043] In addition, the cooling temperature and rate can be controlled to prevent segregation and ensure uniformity of composition by making the cooling temperature uniform. Since the upper part of the ingot cools relatively quickly and the lower part or the inside may cool slowly, the quickly cooling part may be heated, or insulated with non-metallic ceramics or slag.

[0044] The ingot may be manufactured in, for example, a bar, polyhedron, cylinder, sphere shape, or atypical shape, but is not limited thereto.

[0045] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention may further include cutting the ingot to 4 to 30 mm.

[0046] For example, the method for manufacturing an FeCoV alloy-based thin plate may further include cutting the ingot to 10 to 30 mm. When the step of cutting the ingot within the above range is further included, it is preferable because hot rolling is smooth.

[0047] Cutting of the ingot may be performed by a method commonly performed in the art, and the present invention is not limited thereto.

[0048] In another embodiment of the present invention, the method may further include: manufacturing an ingot by casting the alloy melt; and then homogenizing heat-treating the ingot.

[0049] In another embodiment of the present invention, the homogenizing heat treatment may be performed at 1,200 to 1,300°C for 1 to 12 hours.

[0050] Preferably, the homogenizing heat treatment may be performed for 2 to 6 hours, more preferably 2 to 4 hours, but is not limited thereto.

[0051] When the step of homogenizing heat-treating is further included, it is preferable because stress generated during casting can be relieved.

[0052] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes the step of hot-rolling the ingot to obtain a plate material.

[0053] By hot-rolling the ingot, it is preferable because a plate material in which a γ-austenite phase formed by slow cooling occupies the majority or an α-ferrite phase and the γ-austenite phase are mixed can be obtained.

[0054] The hot rolling may be performed using, for example, a steel rolling mill.

[0055] The rolling start temperature, rolling speed, rolling end temperature, and the like are not particularly limited in the present invention, and may be appropriately performed according to conventional conditions performed in the art.

[0056] For example, the start temperature for the rolling may be 900°C or higher, and may not exceed 1,300°C. When the start temperature for the rolling satisfies the above range, it is preferable because there is an advantage in that the strength and formability of the manufactured plate material are excellent.

[0057] The rolling end temperature may be 1,150°C or higher. When the rolling end temperature is 1,150°C or higher, it is preferable because a phenomenon in which excessive load is applied to equipment due to high deformation resistance can be suppressed, and control of the shape is easy.

[0058] The total reduction ratio by the hot rolling may be 70 to 90%, preferably 75 to 90%, and more preferably 75 to 85%. When the total reduction ratio satisfies the above range, it is preferable because enlargement of crystal grains due to large energy can be suppressed, and the deviation thereof can be reduced.

[0059] The rolling may be performed for one pass to several passes, but is not limited thereto.

[0060] In another embodiment of the present invention, the rolling may be performed in two or more rolling passes. Specifically, the rolling may be performed in 5 or more rolling passes, but is not limited thereto.

[0061] When the temperature decreases as the hot rolling is repeated, it is preferable to perform the hot rolling after raising the temperature by reheating. The lower limit of the temperature during the rolling process is preferably controlled to 900°C or higher, preferably 900 to 1,000°C.

[0062] When the lower limit of the temperature during the rolling process satisfies the above range, it is preferable because most of the phase exists as the γ-austenite phase, so that cracks or ruptures hardly occur during hot rolling and the process becomes smooth.

[0063] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes the step of heat-treating the plate material at 600°C to 1,200°C for 10 minutes to 240 minutes to transform at least a portion of the α-ferrite phase into the γ-austenite phase.

[0064] Although not wishing to be bound by theory, generally, an FeCoV-based alloy undergoes a phase change while going through a casting process, a hot rolling process, a heat treatment process, a cold rolling process, and the like, and even the same phase changes into an ordered lattice or a disordered lattice.

[0065] For example, when an FeCoV-based alloy is melted in a vacuum and cast into an ingot, an α-ferrite phase is formed.

[0066] In the case of α-ferrite, which is a room temperature structure, it forms a Body-Centered Cubic (BCC) structure and has relatively fewer slip planes, so there is a high possibility that rolling may not be performed smoothly when cold rolling or the like is performed later to use a thin plate using the FeCoV alloy-based plate material.

[0067] In particular, due to residual stress existing inside the plate material after cold rolling, forming may be difficult, and a phenomenon in which soft magnetic properties are not properly implemented may occur.

[0068] On the other hand, a γ-austenite structure, which is a high-temperature structure, forms a Face-Centered Cubic (FCC) structure, which is a disordered structure, and has many slip planes, so rolling is easy, and plastic workability is much superior to that of α-ferrite.

[0069] Therefore, the method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes heat-treating the plate material at a temperature of 600 to 1,200°C, which is a high-temperature stable phase section, so as to have a γ-austenite structure, that is, an FCC structure, which is a high-temperature stable phase, and then quenching the plate material, thereby transforming the α-ferrite phase generated through the casting process and the hot rolling process into the γ-austenite phase, so that the structure is changed to a structure having the γ-austenite phase or a composite structure of the α-ferrite phase and the γ-austenite phase.

[0070] In another embodiment of the present invention, the heat treatment may be performed at 730 to 1,200°C. Specifically, the heat treatment may be performed at a temperature of 730°C or higher, which is a temperature at which an irregular / regular lattice structure starts to be ordered, and a temperature of 1,200°C or lower, which is a temperature at which a liquid phase is not formed and atomic structure change is expected to be most active. Specifically, the heat treatment is preferably performed within the above range, which is a temperature region where irregular / regular structure change occurs.

[0071] In another embodiment of the present invention, the heat treatment may be performed at 840 to 1,200°C.

[0072] Specifically, the heat treatment may be performed at a temperature of 840°C or higher, which is a temperature at which phase transformation occurs, and a temperature of 1,200°C or lower, which is a temperature at which solid phase control is possible without mixing of a liquid phase.

[0073] In another embodiment of the present invention, the step of transforming into the γ-austenite phase may be heat-treating at 850 to 950°C.

[0074] Since mechanical properties and / or magnetic properties may vary greatly depending on the heat treatment temperature even if the FeCoV alloy-based plate material has the same composition, in the present invention, by heat-treating at a temperature within the above range, it is possible to obtain an FeCoV alloy-based thin plate having excellent mechanical properties and excellent magnetic properties, that is, high saturation magnetic flux density and low iron loss value at the same time.

[0075] In another embodiment of the present invention, the heat treatment may be performed for 30 to 240 minutes.

[0076] Preferably, the heat treatment may be performed for 60 to 120 minutes.

[0077] When the heat treatment time satisfies the above range, it is preferable because the phase transformation time to the γ-austenite phase is sufficient while shortening the heat treatment time.

[0078] In short, the step of transforming into the γ-austenite phase may be heat-treating at a temperature of 850 to 950°C for 60 to 120 minutes.

[0079] In another embodiment of the present invention, the step of transforming into the γ-austenite phase may be performed under a vacuum or inert gas atmosphere. Since the FeCoV-based alloy is somewhat prone to oxidation, the step of transforming into the γ-austenite phase is preferably performed under a vacuum or inert gas atmosphere.

[0080] The inert gas may be, for example, high-purity argon (Ar) gas, but is not limited thereto.

[0081] In another embodiment of the present invention, the method may further include a step of removing a surface scale of the plate material before the step of heat-treating the plate material. Since an oxide scale may be formed on the surface of the plate material that has undergone the hot rolling, and the oxide scale may affect the quality of the plate material, it is preferable to further include the step of removing the surface scale of the plate material. A method of removing the surface scale of the plate material may be performed using a conventional method performed in the art. For example, the pickling treatment may be performed by introducing the plate material into a hydrochloric acid bath, or the surface scale may be removed by high-pressure spraying of a slurry mixed with high-pressure water and an abrasive onto the plate material, but is not limited thereto.

[0082] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes a step of quenching the heat-treated FeCoV alloy-based plate material. If the microstructure of the FeCoV alloy-based plate material forms an ordered structure in a cold rolling process to be described later, since it has high strength and low elongation, there is a problem in that rupture or cracking occurs during the cold rolling process, making it difficult to roll to a target thickness. Therefore, in the present invention, the FeCoV alloy-based plate material is changed to form a disordered structure by performing the step of transforming an α-ferrite phase into a γ-austenite phase by heat-treating the FeCoV alloy-based plate material at 600 to 1,200°C for 10 minutes to 240 minutes.

[0083] After that, by including the step of quenching so that the FeCoV alloy-based plate material can maintain the structure of the γ-austenite phase, elongation is improved to solve problems occurring during the cold rolling process. In another embodiment of the present invention, the step of quenching may be performed at a rate of 10 to 300°C / sec. Preferably, the quenching may be performed at a rate of 30 to 150°C / sec, and more preferably at a rate of 50 to 100°C / sec. When the quenching rate satisfies the above range, the γ-austenite phase is stably maintained, which is preferable because an FeCoV alloy-based thin plate having high saturation magnetic flux density can be manufactured. The step of quenching may be performing water cooling or oil cooling. The water cooling or oil cooling method is not particularly limited in the present invention, and a general method performed in the art may be applied. For example, it may be performed using a water-cooled or oil-cooled cooling guide and a conveyor roll, but is not limited thereto. By performing the water cooling or oil cooling, the γ-austenite phase structure, which is a high-temperature stable phase, can be stably maintained. The step of quenching may be performed by introducing the FeCoV-based alloy plate material into cooling water.

[0084] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes a step of cold-rolling the quenched FeCoV alloy-based plate material to obtain an FeCoV alloy-based thin plate. In the method for manufacturing an FeCoV alloy-based thin plate according to the present invention, cold rolling can be smoothly performed as the α-ferrite phase of a regular structure is heat-treated according to a specific temperature range and time, and is changed into a γ-austenite phase of an irregular structure by quenching it. The cold rolling may be repeatedly performed while changing a reduction ratio, but is not limited thereto. A cumulative reduction ratio may be 85% or more, specifically 90% or more, and more specifically 95% or more, but is also not limited thereto.

[0085] In another embodiment of the present invention, the method may further include: obtaining the FeCoV alloy-based thin plate; and then performing a stress relief heat treatment on the FeCoV alloy-based thin plate. By including the step of performing the stress relief heat treatment on the FeCoV alloy-based thin plate, residual stress existing inside the FeCoV alloy-based thin plate after the cold rolling can be removed, and as the irregular γ-austenite phase changes to a stable phase, regularity (ordering) is secured, and accordingly, it is preferable because an FeCoV alloy-based thin plate having a high saturation magnetic flux density value, a low iron loss value, and appropriate tensile strength and elongation can be obtained.

[0086] The soft magnetic FeCoV-based alloy undergoes a process in which the phase of the structure changes in a process of being manufactured into a thin plate, and in this process, magnetic properties such as saturation magnetic flux density, residual magnetic flux density, coercivity, core loss, etc. are affected according to a specific method of heat treatment such as heat treatment atmosphere, temperature, and time. Here, when a soft magnetic material is used as a material for a drive motor component, etc., a higher saturation magnetic flux density or a magnetic flux density value in a specific frequency region is advantageous, and a lower loss value such as iron loss indicates an advantageous characteristic. Eventually, alloy design, processing, heat treatment, etc. are proceeded to exhibit high magnetic flux density and low iron loss value, and as a result, when a value obtained by dividing magnetic flux density by iron loss is defined as a high specific efficiency value, the higher this value is, the more excellent it is as a material for a motor. In the present invention, heat treatment for microstructure control is performed between hot rolling and cold rolling so that cold rolling can be smoothly performed, and stress relief heat treatment is additionally performed to improve mechanical properties, particularly elongation and magnetic properties after cold rolling, thereby having an advantage of manufacturing an FeCoV alloy-based thin plate excellent in both mechanical properties and magnetic properties. In another embodiment of the present invention, the stress relief heat treatment may be performed at 650 to 950°C for 10 to 120 minutes. Preferably, the stress relief heat treatment may be performed at a temperature of 700 to 950°C, and more preferably 850 to 950°C, but is not limited thereto.

[0087] One aspect of the present invention relates to a method for manufacturing an FeCoV alloy-based thin plate, comprising: preparing an FeCoV alloy-based plate material; heat-treating the FeCoV alloy-based plate material at 600 to 1,200°C for 10 minutes to 240 minutes to transform at least a portion of an α-ferrite phase into a γ-austenite phase; quenching the heat-treated FeCoV alloy-based plate material; cold-rolling the quenched FeCoV alloy-based plate material to obtain an FeCoV alloy-based thin plate; and performing a stress relief heat treatment on the FeCoV alloy-based thin plate. The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes the step of transforming at least a portion of the α-ferrite phase into the γ-austenite phase, whereby cold rolling can be easily performed, and by including the step of performing the stress relief heat treatment on the FeCoV alloy-based thin plate, mechanical properties, particularly elongation and magnetic properties are improved, so that there is an advantage in that an FeCoV alloy-based thin plate having excellent saturation magnetic flux density and low iron loss values can be manufactured without going through complicated processes such as conventional forging.

[0088] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes a step of preparing an FeCoV alloy-based plate material. The step of preparing the FeCoV alloy-based plate material is not limited in the present invention. For example, a commercially available FeCoV alloy-based plate material may be purchased and used, or it may be directly manufactured and used.

[0089] In another embodiment of the present invention, the step of preparing the FeCoV alloy-based plate material may include: preparing an FeCoV alloy melt by vacuum melting an alloy component composed of 20 to 49 at% of cobalt, greater than 0 and 5 at% or less of vanadium, 0 to 15 at% of nickel, 0 to 3 wt% of chromium, 0 to 1 at% of niobium, and a balance of iron and other impurities; casting the alloy melt to manufacture an ingot; and hot-rolling the ingot to obtain an FeCoV alloy-based plate material. The other impurities may be one or more selected from the group consisting of carbon, oxygen, silicon, and manganese. Specifically, the FeCoV alloy melt may include an alloy component composed of 30 to 49 at% of cobalt, 2 to 3 at% of vanadium, and a balance of iron and other impurities. More specifically, the FeCoV alloy melt may include an alloy component composed of 40 to 49 at% of cobalt, 2 to 3 at% of vanadium, and a balance of iron and other impurities. The FeCoV-based alloy is an alloy composition having soft magnetic properties, and is mainly used for motor cores of electronic products by being manufactured into a thin plate, and in particular, recently, application as a drive motor for electric vehicles is being considered. In order to increase the output of an electric vehicle, the magnetic flux density value of the motor core material must be high. Recently, most electric vehicles have a value of 2 Tesla or more, and since the FeCoV alloy has a value of up to 2.4 Tesla level, it can be very helpful in improving motor core output. In addition, since it has a significantly lower iron loss value compared to other soft magnetic materials, it is possible to drive a longer distance due to a lower loss value compared to a battery of the same capacity as well as efficiency improvement. For the same reason, when a motor exhibiting the same performance is manufactured, miniaturization and weight reduction are possible. Even with the same alloy composition, the defect rate of the rolling process may vary depending on the manufacturing process of such an FeCoV alloy, and mechanical and magnetic property values of the manufactured plate material may be greatly influenced. The method for manufacturing an FeCoV alloy-based thin plate according to the present invention has an advantage in that a thin plate having high mechanical and magnetic property values can be easily manufactured without including a conventional complicated slag removal process, forging process, process of forming into a slab shape, and the like. Meanwhile, the saturation magnetic flux density value and coercivity value of the manufactured FeCoV alloy-based thin plate may vary somewhat depending on the composition of the FeCoV alloy component. When the FeCoV alloy component having the above composition is used, there is an advantage in that an FeCoV alloy-based thin plate having a high saturation magnetic flux density value and low coercivity can be obtained. The FeCoV alloy melt may have a composition of Fe 49 Co 49 V 2 . By vacuum melting the alloy component, a grayish ingot with little contamination can be obtained, and when solidified into an ingot shape through a casting step to be described later, it is possible to suppress a phenomenon in which an ingot having a non-uniform composition is obtained due to composition inconsistency, for example, a case where the upper and middle, or middle and lower compositions of the ingot are different, or segregation exists in the same portion, which is preferable. In addition, it is preferable because it is possible to suppress a phenomenon in which a crack is induced in a hot rolling process, a cold rolling process, or the like because an oxide layer is too thick.

[0090] The step of preparing the alloy melt may be performed under an argon, nitrogen, or carbon dioxide atmosphere. When the step of preparing the alloy melt is performed under the argon, nitrogen, or carbon dioxide atmosphere, it is preferable because a phenomenon in which the alloy component is oxidized or carbonized can be suppressed.

[0091] In the step of preparing the FeCoV alloy melt by vacuum melting the alloy component, the degree of vacuum may be 1×10 -2< to 1×10 -4< torr, preferably 1×10 -2< to 1×10 -3< torr. When the degree of vacuum satisfies the above range, it is preferable because oxidation or carbonization can be suppressed.

[0092] The method may further include a step of removing slag of the alloy melt liquid before casting the alloy melt, but is not limited thereto. Alternatively, the method may not include the step of removing slag of the alloy melt liquid before casting the alloy melt, but is not limited thereto. A method of manufacturing the ingot by casting the alloy melt is not specifically limited in the present invention. For example, the ingot may be manufactured by injecting the alloy melt into a mold, and cooling and crystallizing it. The injection temperature is preferably set to a temperature 100 to 2,000°C, preferably 100 to 1,000°C, and more preferably 200 to 500°C higher than the liquidus temperature of the melt. The liquidus temperature of the melt can be measured using a direct temperature measurement method with a built-in thermocouple or by measuring the surface of the melt using a non-contact laser thermometer. In addition, the cooling temperature and rate can be controlled to prevent segregation and ensure uniformity of composition by making the cooling temperature uniform. Since the upper part of the ingot cools relatively quickly and the lower part or the inside may cool slowly, the quickly cooling part may be heated, or insulated with non-metallic ceramics or slag.

[0093] The ingot may be manufactured in, for example, a bar, polyhedron, cylinder, sphere shape, or atypical shape, but is not limited thereto. The step of preparing the FeCoV alloy-based plate material may further include a step of cutting the ingot to 4 to 30 mm. For example, the method for manufacturing an FeCoV alloy-based thin plate may further include cutting the ingot to 10 to 30 mm. When the step of cutting the ingot within the above range is further included, it is preferable because hot rolling is smooth. Cutting of the ingot may be performed by a method commonly performed in the art, and the present invention is not limited thereto.

[0094] The method may further include: manufacturing an ingot by casting the alloy melt; and then homogenizing heat-treating the ingot. The homogenizing heat treatment may be performed at 1,200 to 1,300°C for 1 to 12 hours. Preferably, the homogenizing heat treatment may be performed for 2 to 6 hours, more preferably 2 to 4 hours, but is not limited thereto. When the step of homogenizing heat-treating is further included, it is preferable because stress generated during casting can be relieved.

[0095] The step of preparing the FeCoV alloy-based plate material may include a step of hot-rolling the ingot to obtain a plate material. By hot-rolling the ingot, it is preferable because a plate material in which a γ-austenite phase formed by slow cooling occupies the majority or an α-ferrite phase and the γ-austenite phase are mixed can be obtained.

[0096] The hot rolling may be performed using, for example, a steel rolling mill. The rolling start temperature, rolling speed, rolling end temperature, and the like are not particularly limited in the present invention, and may be appropriately performed according to conventional conditions performed in the art. For example, the start temperature for the rolling may be 900°C or higher, and may not exceed 1,300°C. When the start temperature for the rolling satisfies the above range, it is preferable because there is an advantage in that the strength and formability of the manufactured plate material are excellent. The rolling end temperature may be 1,150°C or higher. When the rolling end temperature is 1,150°C or higher, it is preferable because a phenomenon in which excessive load is applied to equipment due to high deformation resistance can be suppressed, and control of the shape is easy.

[0097] The total reduction ratio by the hot rolling may be 70 to 90%, preferably 75 to 90%, and more preferably 75 to 85%. When the total reduction ratio satisfies the above range, it is preferable because enlargement of crystal grains due to large energy can be suppressed, and the deviation thereof can be reduced.

[0098] The rolling may be performed for one pass to several passes, but is not limited thereto. In another embodiment of the present invention, the rolling may be performed in two or more rolling passes. Specifically, the rolling may be performed in 5 or more rolling passes, but is not limited thereto.

[0099] When the temperature decreases as the hot rolling is repeated, it is preferable to perform the hot rolling after raising the temperature by reheating. The lower limit of the temperature during the rolling process is preferably controlled to 900°C or higher, preferably 900 to 1,000°C. When the lower limit of the temperature during the rolling process satisfies the above range, it is preferable because most of the phase exists as the γ-austenite phase, so that cracks or ruptures hardly occur during hot rolling and the process becomes smooth.

[0100] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes the step of heat-treating the plate material at 600°C to 1,200°C for 10 minutes to 240 minutes to transform at least a portion of the α-ferrite phase into the γ-austenite phase. Although not wishing to be bound by theory, generally, an FeCoV-based alloy undergoes a phase change while going through a casting process, a hot rolling process, a heat treatment process, a cold rolling process, and the like, and even the same phase changes into an ordered lattice or a disordered lattice. For example, when an FeCoV-based alloy is melted in a vacuum and cast into an ingot, an α-ferrite phase is formed. In the case of α-ferrite, which is a room temperature structure, it forms a Body-Centered Cubic (BCC) structure and has relatively fewer slip planes, so there is a high possibility that rolling may not be performed smoothly when cold rolling or the like is performed later to use a thin plate using the FeCoV alloy-based plate material. In particular, due to residual stress existing inside the plate material after cold rolling, forming may be difficult, and a phenomenon in which soft magnetic properties are not properly implemented may occur. On the other hand, a γ-austenite structure, which is a high-temperature structure, forms a Face-Centered Cubic (FCC) structure, which is a disordered structure, and has many slip planes, so rolling is easy, and plastic workability is much superior to that of α-ferrite. Therefore, the method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes heat-treating the plate material at a temperature of 600 to 1,200°C, which is a high-temperature stable phase section, so as to have a γ-austenite structure, that is, an FCC structure, which is a high-temperature stable phase, and then quenching the plate material, thereby transforming the α-ferrite phase generated through the casting process and the hot rolling process into the γ-austenite phase, so that the structure is changed to a structure having the γ-austenite phase or a composite structure of the α-ferrite phase and the γ-austenite phase.

[0101] In another embodiment of the present invention, the heat treatment may be performed at 730 to 1,200°C. Specifically, the heat treatment may be performed at a temperature of 730°C or higher, which is a temperature at which an irregular / regular lattice structure starts to be ordered, and a temperature of 1,200°C or lower, which is a temperature at which a liquid phase is not formed and atomic structure change is expected to be most active. Specifically, the heat treatment is preferably performed within the above range, which is a temperature region where irregular / regular structure change occurs.

[0102] In another embodiment of the present invention, the heat treatment may be performed at 840 to 1,200°C. Specifically, the heat treatment may be performed at a temperature of 840°C or higher, which is a temperature at which phase transformation occurs, and a temperature of 1,200°C or lower, which is a temperature at which solid phase control is possible without mixing of a liquid phase. In another embodiment of the present invention, the step of transforming into the γ-austenite phase may be heat-treating at 850 to 950°C. Since mechanical properties and / or magnetic properties may vary greatly depending on the heat treatment temperature even if the FeCoV alloy-based plate material has the same composition, in the present invention, by heat-treating at a temperature within the above range, it is possible to obtain an FeCoV alloy-based thin plate having excellent mechanical properties and excellent magnetic properties, that is, high saturation magnetic flux density and low iron loss value at the same time.

[0103] In another embodiment of the present invention, the heat treatment may be performed for 30 to 240 minutes. Preferably, the heat treatment may be performed for 60 to 120 minutes. When the heat treatment time satisfies the above range, it is preferable because the phase transformation time to the γ-austenite phase is sufficient while shortening the heat treatment time. In short, the step of transforming into the γ-austenite phase may be heat-treating at a temperature of 850 to 950°C for 60 to 120 minutes.

[0104] In another embodiment of the present invention, the step of transforming into the γ-austenite phase may be performed under a vacuum or inert gas atmosphere. Since the FeCoV-based alloy is somewhat prone to oxidation, the step of transforming into the γ-austenite phase is preferably performed under a vacuum or inert gas atmosphere. The inert gas may be, for example, high-purity argon (Ar) gas, but is not limited thereto.

[0105] In another embodiment of the present invention, the method may further include a step of removing a surface scale of the plate material before the step of heat-treating the plate material. Since an oxide scale may be formed on the surface of the plate material that has undergone the hot rolling, and the oxide scale may affect the quality of the plate material, it is preferable to further include the step of removing the surface scale of the plate material. A method of removing the surface scale of the plate material may be performed using a conventional method performed in the art. For example, the pickling treatment may be performed by introducing the plate material into a hydrochloric acid bath, or the surface scale may be removed by high-pressure spraying of a slurry mixed with high-pressure water and an abrasive onto the plate material, but is not limited thereto.

[0106] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes a step of quenching the heat-treated FeCoV alloy-based plate material. If the microstructure of the FeCoV alloy-based plate material forms an ordered structure in a cold rolling process to be described later, since it has high strength and low elongation, there is a problem in that rupture or cracking occurs during the cold rolling process, making it difficult to roll to a target thickness. Therefore, in the present invention, the FeCoV alloy-based plate material is changed to form a disordered structure by performing the step of transforming an α-ferrite phase into a γ-austenite phase by heat-treating the FeCoV alloy-based plate material at 600 to 1,200°C for 10 minutes to 240 minutes. After that, by including the step of quenching so that the FeCoV alloy-based plate material can maintain the structure of the γ-austenite phase, elongation is improved to solve problems occurring during the cold rolling process. In another embodiment of the present invention, the step of quenching may be performed at a rate of 10 to 300°C / sec. Preferably, the quenching may be performed at a rate of 30 to 150°C / sec, and more preferably at a rate of 50 to 100°C / sec. When the quenching rate satisfies the above range, the γ-austenite phase is stably maintained, which is preferable because an FeCoV alloy-based thin plate having high saturation magnetic flux density can be manufactured. The step of quenching may be performing water cooling or oil cooling. The water cooling or oil cooling method is not particularly limited in the present invention, and a general method performed in the art may be applied. For example, it may be performed using a water-cooled or oil-cooled cooling guide and a conveyor roll, but is not limited thereto. By performing the water cooling or oil cooling, the γ-austenite phase structure, which is a high-temperature stable phase, can be stably maintained. The step of quenching may be performed by introducing the FeCoV-based alloy plate material into cooling water.

[0107] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes a step of cold-rolling the quenched FeCoV alloy-based plate material to obtain an FeCoV alloy-based thin plate. In the method for manufacturing an FeCoV alloy-based thin plate according to the present invention, cold rolling can be smoothly performed as the α-ferrite phase of a regular structure is heat-treated according to a specific temperature range and time, and is changed into a γ-austenite phase of an irregular structure by quenching it. The cold rolling may be repeatedly performed while changing a reduction ratio, but is not limited thereto. A cumulative reduction ratio may be 85% or more, specifically 90% or more, and more specifically 95% or more, but is also not limited thereto.

[0108] In another embodiment of the present invention, the method may further include: obtaining the FeCoV alloy-based thin plate; and then performing a stress relief heat treatment on the FeCoV alloy-based thin plate. By including the step of performing the stress relief heat treatment on the FeCoV alloy-based thin plate, residual stress existing inside the FeCoV alloy-based thin plate after the cold rolling can be removed, and as the irregular γ-austenite phase changes to a stable phase, regularity is secured, and accordingly, it is preferable because an FeCoV alloy-based thin plate having a high saturation magnetic flux density value, a low iron loss value, and appropriate tensile strength and elongation can be obtained.

[0109] The soft magnetic FeCoV-based alloy undergoes a process in which the phase of the structure changes in a process of being manufactured into a thin plate, and in this process, magnetic properties such as saturation magnetic flux density, residual magnetic flux density, coercivity, core loss, etc. are affected according to a specific method of heat treatment such as heat treatment atmosphere, temperature, and time. Here, when a soft magnetic material is used as a material for a drive motor component, etc., a higher saturation magnetic flux density or a magnetic flux density value in a specific frequency region is advantageous, and a lower loss value such as iron loss indicates an advantageous characteristic. Eventually, alloy design, processing, heat treatment, etc. are proceeded to exhibit high magnetic flux density and low iron loss value, and as a result, when a value obtained by dividing magnetic flux density by iron loss is defined as a high specific efficiency value, the higher this value is, the more excellent it is as a material for a motor. In the present invention, heat treatment for microstructure control is performed between hot rolling and cold rolling so that cold rolling can be smoothly performed, and stress relief heat treatment is additionally performed to improve mechanical properties, particularly elongation and magnetic properties after cold rolling, thereby having an advantage of manufacturing an FeCoV alloy-based thin plate excellent in both mechanical properties and magnetic properties. In another embodiment of the present invention, the stress relief heat treatment may be performed at 650 to 950°C for 10 to 120 minutes. Preferably, the stress relief heat treatment may be performed at a temperature of 700 to 950°C, and more preferably 850 to 950°C, but is not limited thereto.

[0110] One aspect of the present invention relates to a method for manufacturing an FeCoV alloy-based thin plate, comprising: preparing an FeCoV alloy-based plate material; heat-treating the FeCoV alloy-based plate material at 600 to 1,200°C for 10 minutes to 240 minutes to transform at least a portion of an α-ferrite phase into a γ-austenite phase; quenching the heat-treated FeCoV alloy-based plate material; cold-rolling the quenched FeCoV alloy-based plate material to obtain an FeCoV alloy-based thin plate; and performing a stress relief heat treatment on the FeCoV alloy-based thin plate. The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes the step of transforming at least a portion of the α-ferrite phase into the γ-austenite phase, whereby cold rolling can be easily performed, and by including the step of performing the stress relief heat treatment on the FeCoV alloy-based thin plate, mechanical properties, particularly elongation and magnetic properties are improved, so that there is an advantage in that an FeCoV alloy-based thin plate having excellent saturation magnetic flux density and low iron loss values can be manufactured without going through complicated processes such as conventional forging.

[0111] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes a step of preparing an FeCoV alloy-based plate material. The step of preparing the FeCoV alloy-based plate material is not limited in the present invention. For example, a commercially available FeCoV alloy-based plate material may be purchased and used, or it may be directly manufactured and used.

[0112] In another embodiment of the present invention, the step of preparing the FeCoV alloy-based plate material may include: preparing an FeCoV alloy melt by vacuum melting an alloy component composed of 20 to 49 at% of cobalt, greater than 0 and 5 at% or less of vanadium, 0 to 15 at% of nickel, 0 to 3 wt% of chromium, 0 to 1 at% of niobium, and a balance of iron and other impurities; casting the alloy melt to manufacture an ingot; and hot-rolling the ingot to obtain an FeCoV alloy-based plate material. The other impurities may be one or more selected from the group consisting of carbon, oxygen, silicon, and manganese. Specifically, the FeCoV alloy melt may include an alloy component composed of 30 to 49 at% of cobalt, 2 to 3 at% of vanadium, and a balance of iron and other impurities. More specifically, the FeCoV alloy melt may include an alloy component composed of 40 to 49 at% of cobalt, 2 to 3 at% of vanadium, and a balance of iron and other impurities. The FeCoV-based alloy is an alloy composition having soft magnetic properties, and is mainly used for motor cores of electronic products by being manufactured into a thin plate, and in particular, recently, application as a drive motor for electric vehicles is being considered. In order to increase the output of an electric vehicle, the magnetic flux density value of the motor core material must be high. Recently, most electric vehicles have a value of 2 Tesla or more, and since the FeCoV alloy has a value of up to 2.4 Tesla level, it can be very helpful in improving motor core output. In addition, since it has a significantly lower iron loss value compared to other soft magnetic materials, it is possible to drive a longer distance due to a lower loss value compared to a battery of the same capacity as well as efficiency improvement. For the same reason, when a motor exhibiting the same performance is manufactured, miniaturization and weight reduction are possible. Even with the same alloy composition, the defect rate of the rolling process may vary depending on the manufacturing process of such an FeCoV alloy, and mechanical and magnetic property values of the manufactured plate material may be greatly influenced. The method for manufacturing an FeCoV alloy-based thin plate according to the present invention has an advantage in that a thin plate having high mechanical and magnetic property values can be easily manufactured without including a conventional complicated slag removal process, forging process, process of forming into a slab shape, and the like. Meanwhile, the saturation magnetic flux density value and coercivity value of the manufactured FeCoV alloy-based thin plate may vary somewhat depending on the composition of the FeCoV alloy component. When the FeCoV alloy component having the above composition is used, there is an advantage in that an FeCoV alloy-based thin plate having a high saturation magnetic flux density value and low coercivity can be obtained. The FeCoV alloy melt may have a composition of Fe 49 Co 49 V 2 . By vacuum melting the alloy component, a grayish ingot with little contamination can be obtained, and when solidified into an ingot shape through a casting step to be described later, it is possible to suppress a phenomenon in which an ingot having a non-uniform composition is obtained due to composition inconsistency, for example, a case where the upper and middle, or middle and lower compositions of the ingot are different, or segregation exists in the same portion, which is preferable. In addition, it is preferable because it is possible to suppress a phenomenon in which a crack is induced in a hot rolling process, a cold rolling process, or the like because an oxide layer is too thick.

[0113] The step of preparing the alloy melt may be performed under an argon, nitrogen, or carbon dioxide atmosphere. When the step of preparing the alloy melt is performed under the argon, nitrogen, or carbon dioxide atmosphere, it is preferable because a phenomenon in which the alloy component is oxidized or carbonized can be suppressed.

[0114] In the step of preparing the FeCoV alloy melt by vacuum melting the alloy component, the degree of vacuum may be 1×10 -2< to 1×10 -4< torr, preferably 1×10 -2< to 1×10 -3< torr. When the degree of vacuum satisfies the above range, it is preferable because oxidation or carbonization can be suppressed.

[0115] The method may further include a step of removing slag of the alloy melt liquid before casting the alloy melt, but is not limited thereto. Alternatively, the method may not include the step of removing slag of the alloy melt liquid before casting the alloy melt, but is not limited thereto. A method of manufacturing the ingot by casting the alloy melt is not specifically limited in the present invention. For example, the ingot may be manufactured by injecting the alloy melt into a mold, and cooling and crystallizing it. The injection temperature is preferably set to a temperature 100 to 2,000°C, preferably 100 to 1,000°C, and more preferably 200 to 500°C higher than the liquidus temperature of the melt. The liquidus temperature of the melt can be measured using a direct temperature measurement method with a built-in thermocouple or by measuring the surface of the melt using a non-contact laser thermometer. In addition, the cooling temperature and rate can be controlled to prevent segregation and ensure uniformity of composition by making the cooling temperature uniform. Since the upper part of the ingot cools relatively quickly and the lower part or the inside may cool slowly, the quickly cooling part may be heated, or insulated with non-metallic ceramics or slag.

[0116] The ingot may be manufactured in, for example, a bar, polyhedron, cylinder, sphere shape, or atypical shape, but is not limited thereto. The step of preparing the FeCoV alloy-based plate material may further include a step of cutting the ingot to 4 to 30 mm. For example, the method for manufacturing an FeCoV alloy-based thin plate may further include cutting the ingot to 10 to 30 mm. When the step of cutting the ingot within the above range is further included, it is preferable because hot rolling is smooth. Cutting of the ingot may be performed by a method commonly performed in the art, and the present invention is not limited thereto.

[0117] The method may further include: manufacturing an ingot by casting the alloy melt; and then homogenizing heat-treating the ingot. The homogenizing heat treatment may be performed at 1,200 to 1,300°C for 1 to 12 hours. Preferably, the homogenizing heat treatment may be performed for 2 to 6 hours, more preferably 2 to 4 hours, but is not limited thereto. When the step of homogenizing heat-treating is further included, it is preferable because stress generated during casting can be relieved.

[0118] The step of preparing the FeCoV alloy-based plate material may include a step of hot-rolling the ingot to obtain a plate material. By hot-rolling the ingot, it is preferable because a plate material in which a γ-austenite phase formed by slow cooling occupies the majority or an α-ferrite phase and the γ-austenite phase are mixed can be obtained.

[0119] The hot rolling may be performed using, for example, a steel rolling mill. The rolling start temperature, rolling speed, rolling end temperature, and the like are not particularly limited in the present invention, and may be appropriately performed according to conventional conditions performed in the art. For example, the start temperature for the rolling may be 900°C or higher, and may not exceed 1,300°C. When the start temperature for the rolling satisfies the above range, it is preferable because there is an advantage in that the strength and formability of the manufactured plate material are excellent. The rolling end temperature may be 1,150°C or higher. When the rolling end temperature is 1,150°C or higher, it is preferable because a phenomenon in which excessive load is applied to equipment due to high deformation resistance can be suppressed, and control of the shape is easy.

[0120] The total reduction ratio by the hot rolling may be 70 to 90%, preferably 75 to 90%, and more preferably 75 to 85%. When the total reduction ratio satisfies the above range, it is preferable because enlargement of crystal grains due to large energy can be suppressed, and the deviation thereof can be reduced.

[0121] The rolling may be performed for one pass to several passes, but is not limited thereto. In another embodiment of the present invention, the rolling may be performed in two or more rolling passes. Specifically, the rolling may be performed in 5 or more rolling passes, but is not limited thereto.

[0122] When the temperature decreases as the hot rolling is repeated, it is preferable to perform the hot rolling after raising the temperature by reheating. The lower limit of the temperature during the rolling process is preferably controlled to 900°C or higher, preferably 900 to 1,000°C. When the lower limit of the temperature during the rolling process satisfies the above range, it is preferable because most of the phase exists as the γ-austenite phase, so that cracks or ruptures hardly occur during hot rolling and the process becomes smooth.

[0123] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes the step of heat-treating the plate material at 600 to 1,200°C for 10 minutes to 240 minutes to transform at least a portion of the α-ferrite phase into the γ-austenite phase. Although not wishing to be bound by theory, generally, an FeCoV-based alloy undergoes a phase change while going through a casting process, a hot rolling process, a heat treatment process, a cold rolling process, and the like, and even the same phase changes into an ordered lattice or a disordered lattice. For example, when an FeCoV-based alloy is melted in a vacuum and cast into an ingot, an α-ferrite phase is formed. In the case of α-ferrite, which is a room temperature structure, it forms a Body-Centered Cubic (BCC) structure and has relatively fewer slip planes, so there is a high possibility that rolling may not be performed smoothly when cold rolling or the like is performed later to use a thin plate using the FeCoV alloy-based plate material. In particular, due to residual stress existing inside the plate material after cold rolling, forming may be difficult, and a phenomenon in which soft magnetic properties are not properly implemented may occur. On the other hand, a γ-austenite structure, which is a high-temperature structure, forms a Face-Centered Cubic (FCC) structure, which is a disordered structure, and has many slip planes, so rolling is easy, and plastic workability is much superior to that of α-ferrite. Therefore, the method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes heat-treating the plate material at a temperature of 600 to 1,200°C, which is a high-temperature stable phase section, so as to have a γ-austenite structure, that is, an FCC structure, which is a high-temperature stable phase, and then quenching the plate material, thereby transforming the α-ferrite phase generated through the casting process and the hot rolling process into the γ-austenite phase, so that the structure is changed to a structure having the γ-austenite phase or a composite structure of the α-ferrite phase and the γ-austenite phase.

[0124] In another embodiment of the present invention, the heat treatment may be performed at 730 to 1,200°C. Specifically, the heat treatment may be performed at a temperature of 730°C or higher, which is a temperature at which an irregular / regular lattice structure starts to be ordered, and a temperature of 1,200°C or lower, which is a temperature at which a liquid phase is not formed and atomic structure change is expected to be most active. Specifically, the heat treatment is preferably performed within the above range, which is a temperature region where irregular / regular structure change occurs.

[0125] In another embodiment of the present invention, the heat treatment may be performed at 840 to 1,200°C. Specifically, the heat treatment may be performed at a temperature of 840°C or higher, which is a temperature at which phase transformation occurs, and a temperature of 1,200°C or lower, which is a temperature at which solid phase control is possible without mixing of a liquid phase. In another embodiment of the present invention, the step of transforming into the γ-austenite phase may be heat-treating at 850 to 950°C. Since mechanical properties and / or magnetic properties may vary greatly depending on the heat treatment temperature even if the FeCoV alloy-based plate material has the same composition, in the present invention, by heat-treating at a temperature within the above range, it is possible to obtain an FeCoV alloy-based thin plate having excellent mechanical properties and excellent magnetic properties, that is, high saturation magnetic flux density and low iron loss value at the same time.

[0126] In another embodiment of the present invention, the heat treatment may be performed for 30 to 240 minutes. Preferably, the heat treatment may be performed for 60 to 120 minutes. When the heat treatment time satisfies the above range, it is preferable because the phase transformation time to the γ-austenite phase is sufficient while shortening the heat treatment time. In short, the step of transforming into the γ-austenite phase may be heat-treating at a temperature of 850 to 950°C for 60 to 120 minutes.

[0127] In another embodiment of the present invention, the step of transforming into the γ-austenite phase may be performed under a vacuum or inert gas atmosphere. Since the FeCoV-based alloy is somewhat prone to oxidation, the step of transforming into the γ-austenite phase is preferably performed under a vacuum or inert gas atmosphere. The inert gas may be, for example, high-purity argon (Ar) gas, but is not limited thereto.

[0128] In another embodiment of the present invention, the method may further include a step of removing a surface scale of the plate material before the step of heat-treating the plate material. Since an oxide scale may be formed on the surface of the plate material that has undergone the hot rolling, and the oxide scale may affect the quality of the plate material, it is preferable to further include the step of removing the surface scale of the plate material. A method of removing the surface scale of the plate material may be performed using a conventional method performed in the art. For example, the pickling treatment may be performed by introducing the plate material into a hydrochloric acid bath, or the surface scale may be removed by high-pressure spraying of a slurry mixed with high-pressure water and an abrasive onto the plate material, but is not limited thereto.

[0129] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes a step of quenching the heat-treated FeCoV alloy-based plate material. If the microstructure of the FeCoV alloy-based plate material forms an ordered structure in a cold rolling process to be described later, since it has high strength and low elongation, there is a problem in that rupture or cracking occurs during the cold rolling process, making it difficult to roll to a target thickness. Therefore, in the present invention, the FeCoV alloy-based plate material is changed to form a disordered structure by performing the step of transforming an α-ferrite phase into a γ-austenite phase by heat-treating the FeCoV alloy-based plate material at 600 to 1,200°C for 10 minutes to 240 minutes. After that, by including the step of quenching so that the FeCoV alloy-based plate material can maintain the structure of the γ-austenite phase, elongation is improved to solve problems occurring during the cold rolling process. In another embodiment of the present invention, the step of quenching may be performed at a rate of 10 to 300°C / sec. Preferably, the quenching may be performed at a rate of 30 to 150°C / sec, and more preferably at a rate of 50 to 100°C / sec. When the quenching rate satisfies the above range, the γ-austenite phase is stably maintained, which is preferable because an FeCoV alloy-based thin plate having high saturation magnetic flux density can be manufactured. The step of quenching may be performing water cooling or oil cooling. The water cooling or oil cooling method is not particularly limited in the present invention, and a general method performed in the art may be applied. For example, it may be performed using a water-cooled or oil-cooled cooling guide and a conveyor roll, but is not limited thereto. By performing the water cooling or oil cooling, the γ-austenite phase structure, which is a high-temperature stable phase, can be stably maintained. The step of quenching may be performed by introducing the FeCoV-based alloy plate material into cooling water.

[0130] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes a step of cold-rolling the quenched FeCoV alloy-based plate material to obtain an FeCoV alloy-based thin plate. In the method for manufacturing an FeCoV alloy-based thin plate according to the present invention, cold rolling can be smoothly performed as the α-ferrite phase of a regular structure is heat-treated according to a specific temperature range and time, and is changed into a γ-austenite phase of an irregular structure by quenching it. The cold rolling may be repeatedly performed while changing a reduction ratio, but is not limited thereto. A cumulative reduction ratio may be 85% or more, specifically 90% or more, and more specifically 95% or more, but is also not limited thereto.

[0131] In another embodiment of the present invention, the method may further include: obtaining the FeCoV alloy-based thin plate; and then performing a stress relief heat treatment on the FeCoV alloy-based thin plate. By including the step of performing the stress relief heat treatment on the FeCoV alloy-based thin plate, residual stress existing inside the FeCoV alloy-based thin plate after the cold rolling can be removed, and as the irregular γ-austenite phase changes to a stable phase, regularity is secured, and accordingly, it is preferable because an FeCoV alloy-based thin plate having a high saturation magnetic flux density value, a low iron loss value, and appropriate tensile strength and elongation can be obtained.

[0132] The soft magnetic FeCoV-based alloy undergoes a process in which the phase of the structure changes in a process of being manufactured into a thin plate, and in this process, magnetic properties such as saturation magnetic flux density, residual magnetic flux density, coercivity, core loss, etc. are affected according to a specific method of heat treatment such as heat treatment atmosphere, temperature, and time. Here, when a soft magnetic material is used as a material for a drive motor component, etc., a higher saturation magnetic flux density or a magnetic flux density value in a specific frequency region is advantageous, and a lower loss value such as iron loss indicates an advantageous characteristic. Eventually, alloy design, processing, heat treatment, etc. are proceeded to exhibit high magnetic flux density and low iron loss value, and as a result, when a value obtained by dividing magnetic flux density by iron loss is defined as a high specific efficiency value, the higher this value is, the more excellent it is as a material for a motor. In the present invention, heat treatment for microstructure control is performed between hot rolling and cold rolling so that cold rolling can be smoothly performed, and stress relief heat treatment is additionally performed to improve mechanical properties, particularly elongation and magnetic properties after cold rolling, thereby having an advantage of manufacturing an FeCoV alloy-based thin plate excellent in both mechanical properties and magnetic properties. In another embodiment of the present invention, the stress relief heat treatment may be performed at 650 to 950°C for 10 to 120 minutes. Preferably, the stress relief heat treatment may be performed at a temperature of 700 to 950°C, and more preferably 850 to 950°C, but is not limited thereto.

[0133] Another aspect of the present invention relates to a method for manufacturing an FeCoV alloy-based thin plate, comprising: preparing an FeCoV alloy melt; casting the alloy melt to manufacture an ingot; hot-rolling the ingot to obtain a plate material; heat-treating the plate material at 600 to 1,200°C for 10 minutes to 240 minutes to transform at least a portion of an α-ferrite phase into a γ-austenite phase; quenching the heat-treated plate material; and cold-rolling the quenched plate material to obtain an FeCoV alloy-based thin plate, wherein the FeCoV alloy-based thin plate is characterized in that an intensity of a peak of a (100) plane among peaks of an X-ray diffraction pattern of the ingot is decreased or does not appear. The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes the step of transforming at least a portion of the α-ferrite phase into the γ-austenite phase, whereby cold rolling can be easily performed, and there is an advantage in that an FeCoV alloy-based thin plate having excellent saturation magnetic flux density and low iron loss values can be manufactured without going through complicated processes such as conventional forging.

[0134] In another embodiment of the present invention, the step of preparing the alloy melt may include a step of vacuum melting an alloy component composed of 20 to 49 at% of cobalt, 2 to 5 at% of vanadium, and a balance of iron and other impurities. The other impurities may be one or more selected from the group consisting of carbon, oxygen, silicon, and manganese. In another embodiment of the present invention, the FeCoV alloy melt may include an alloy component composed of 30 to 49 at% of cobalt, 2 to 3 at% of vanadium, and a balance of iron and other impurities. In another embodiment of the present invention, the FeCoV alloy melt may include an alloy component composed of 40 to 49 at% of cobalt, 2 to 3 at% of vanadium, and a balance of iron and other impurities. The FeCoV-based alloy is an alloy composition having soft magnetic properties, and is mainly used for motor cores of electronic products by being manufactured into a thin plate, and in particular, recently, application as a drive motor for electric vehicles is being considered. In order to increase the output of an electric vehicle, the magnetic flux density value of the motor core material must be high. Recently, most electric vehicles have a value of 2 Tesla or more, and since the FeCoV alloy has a value of up to 2.4 Tesla level, it can be very helpful in improving motor core output. In addition, since it has a significantly lower iron loss value compared to other soft magnetic materials, it is possible to drive a longer distance due to a lower loss value compared to a battery of the same capacity as well as efficiency improvement. For the same reason, when a motor exhibiting the same performance is manufactured, miniaturization and weight reduction are possible. Even with the same alloy composition, the defect rate of the rolling process may vary depending on the manufacturing process of such an FeCoV alloy, and mechanical and magnetic property values of the manufactured plate material may be greatly influenced. The method for manufacturing an FeCoV alloy-based thin plate according to the present invention has an advantage in that a thin plate having high mechanical and magnetic property values can be easily manufactured without including a conventional complicated slag removal process, forging process, process of forming into a slab shape, and the like. Meanwhile, the saturation magnetic flux density value and coercivity value of the manufactured FeCoV alloy-based thin plate may vary somewhat depending on the composition of the FeCoV alloy component. In the present invention, by using the FeCoV alloy component having the above composition, there is an advantage in that an FeCoV alloy-based thin plate having a high saturation magnetic flux density value and low coercivity can be obtained. The FeCoV alloy melt may have a composition of Fe 49 Co 49 V 2 . By vacuum melting the alloy component, a grayish ingot with little contamination can be obtained, and when solidified into an ingot shape through a casting step to be described later, it is possible to suppress a phenomenon in which an ingot having a non-uniform composition is obtained due to composition inconsistency, for example, a case where the upper and middle, or middle and lower compositions of the ingot are different, or segregation exists in the same portion, which is preferable. In addition, it is preferable because it is possible to suppress a phenomenon in which a crack is induced in a hot rolling process, a cold rolling process, or the like because an oxide layer is too thick.

[0135] The step of preparing the alloy melt may be performed under an argon, nitrogen, or carbon dioxide atmosphere. When the step of preparing the alloy melt is performed under the argon, nitrogen, or carbon dioxide atmosphere, it is preferable because a phenomenon in which the alloy component is oxidized or carbonized can be suppressed.

[0136] In the step of preparing the FeCoV alloy melt by vacuum melting the alloy component, the degree of vacuum may be 1×10 -2< to 1×10 -4< torr, preferably 1×10 -2< to 1×10 -3< torr. When the degree of vacuum satisfies the above range, it is preferable because oxidation or carbonization can be suppressed.

[0137] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes the step of manufacturing an ingot by casting the alloy melt. The method may further include a step of removing slag of the alloy melt liquid before casting the alloy melt, but is not limited thereto. The method for manufacturing an FeCoV alloy-based thin plate according to the present invention may not include the step of removing slag of the alloy melt liquid. Specifically, the method for manufacturing an FeCoV alloy-based thin plate according to the present invention has an advantage in that it is possible to manufacture an FeCoV alloy-based thin plate exhibiting excellent performance without including a slag removal process, a forging process, and a shape control slabbing process. A method of manufacturing the ingot by casting the alloy melt is not specifically limited in the present invention. For example, the ingot may be manufactured by injecting the alloy melt into a mold, and cooling and crystallizing it. The injection temperature is preferably set to a temperature 100 to 2,000°C, preferably 100 to 1,000°C, and more preferably 200 to 500°C higher than the liquidus temperature of the melt. The liquidus temperature of the melt can be measured using a direct temperature measurement method with a built-in thermocouple or by measuring the surface of the melt using a non-contact laser thermometer. In addition, the cooling temperature and rate can be controlled to prevent segregation and ensure uniformity of composition by making the cooling temperature uniform. Since the upper part of the ingot cools relatively quickly and the lower part or the inside may cool slowly, the quickly cooling part may be heated, or insulated with non-metallic ceramics or slag.

[0138] The ingot may be manufactured in, for example, a bar, polyhedron, cylinder, sphere shape, or atypical shape, but is not limited thereto. The method for manufacturing an FeCoV alloy-based thin plate according to the present invention may further include cutting the ingot to 4 to 30 mm. For example, the method for manufacturing an FeCoV alloy-based thin plate may further include cutting the ingot to 10 to 30 mm. When the step of cutting the ingot within the above range is further included, it is preferable because hot rolling is smooth. Cutting of the ingot may be performed by a method commonly performed in the art, and the present invention is not limited thereto.

[0139] In another embodiment of the present invention, the method may further include: manufacturing an ingot by casting the alloy melt; and then homogenizing heat-treating the ingot. In another embodiment of the present invention, the homogenizing heat treatment may be performed at 1,200 to 1,300°C for 1 to 12 hours. Preferably, the homogenizing heat treatment may be performed for 2 to 6 hours, more preferably 2 to 4 hours, but is not limited thereto. When the step of homogenizing heat-treating is further included, it is preferable because stress generated during casting can be relieved.

[0140] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes the step of hot-rolling the ingot to obtain a plate material. By hot-rolling the ingot, it is preferable because a plate material in which a γ-austenite phase formed by slow cooling occupies the majority or an α-ferrite phase and the γ-austenite phase are mixed can be obtained.

[0141] The hot rolling may be performed using, for example, a steel rolling mill. The rolling start temperature, rolling speed, rolling end temperature, and the like are not particularly limited in the present invention, and may be appropriately performed according to conventional conditions performed in the art. For example, the start temperature for the rolling may be 900°C or higher, and may not exceed 1,300°C. When the start temperature for the rolling satisfies the above range, it is preferable because there is an advantage in that the strength and formability of the manufactured plate material are excellent. The rolling end temperature may be 1,150°C or higher. When the rolling end temperature is 1,150°C or higher, it is preferable because a phenomenon in which excessive load is applied to equipment due to high deformation resistance can be suppressed, and control of the shape is easy.

[0142] The total reduction ratio by the hot rolling may be 70 to 90%, preferably 75 to 90%, and more preferably 75 to 85%. When the total reduction ratio satisfies the above range, it is preferable because enlargement of crystal grains due to large energy can be suppressed, and the deviation thereof can be reduced.

[0143] The rolling may be performed for one pass to several passes, but is not limited thereto. In another embodiment of the present invention, the rolling may be performed in two or more rolling passes. Specifically, the rolling may be performed in 5 or more rolling passes, but is not limited thereto.

[0144] When the temperature decreases as the hot rolling is repeated, it is preferable to perform the hot rolling after raising the temperature by reheating. The lower limit of the temperature during the rolling process is preferably controlled to 900°C or higher, preferably 900 to 1,000°C. When the lower limit of the temperature during the rolling process satisfies the above range, it is preferable because most of the phase exists as the γ-austenite phase, so that cracks or ruptures hardly occur during hot rolling and the process becomes smooth.

[0145] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes the step of heat-treating the plate material at 600 to 1,200°C for 10 minutes to 240 minutes to transform at least a portion of the α-ferrite phase into the γ-austenite phase. Although not wishing to be bound by theory, generally, an FeCoV-based alloy undergoes a phase change while going through a casting process, a hot rolling process, a heat treatment process, a cold rolling process, and the like, and even the same phase changes into an ordered lattice or a disordered lattice. For example, when an FeCoV-based alloy is melted in a vacuum and cast into an ingot, an α-ferrite phase is formed. In the case of α-ferrite, which is a room temperature structure, it forms a Body-Centered Cubic (BCC) structure and has relatively fewer slip planes, so there is a high possibility that rolling may not be performed smoothly when cold rolling or the like is performed later to use a thin plate using the FeCoV alloy-based plate material. In particular, due to residual stress existing inside the plate material after cold rolling, forming may be difficult, and a phenomenon in which soft magnetic properties are not properly implemented may occur. On the other hand, a γ-austenite structure, which is a high-temperature structure, forms a Face-Centered Cubic (FCC) structure, which is a disordered structure, and has many slip planes, so rolling is easy, and plastic workability is much superior to that of α-ferrite. Therefore, the method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes heat-treating the plate material at a temperature of 600 to 1,200°C, which is a high-temperature stable phase section, so as to have a γ-austenite structure, that is, an FCC structure, which is a high-temperature stable phase, and then quenching the plate material, thereby transforming the α-ferrite phase generated through the casting process and the hot rolling process into the γ-austenite phase, so that the structure is changed to a structure having the γ-austenite phase or a composite structure of the α-ferrite phase and the γ-austenite phase.

[0146] In another embodiment of the present invention, the heat treatment may be performed at 730 to 1,200°C. Specifically, the heat treatment may be performed at a temperature of 730°C or higher, which is a temperature at which an irregular / regular lattice structure starts to be ordered, and a temperature of 1,200°C or lower, which is a temperature at which a liquid phase is not formed and atomic structure change is expected to be most active. Specifically, the heat treatment is preferably performed within the above range, which is a temperature region where irregular / regular structure change occurs.

[0147] In another embodiment of the present invention, the heat treatment may be performed at 840 to 1,200°C. Specifically, the heat treatment may be performed at a temperature of 840°C or higher, which is a temperature at which phase transformation occurs, and a temperature of 1,200°C or lower, which is a temperature at which solid phase control is possible without mixing of a liquid phase. In another embodiment of the present invention, the step of transforming into the γ-austenite phase may be heat-treating at 850 to 950°C. Since mechanical properties and / or magnetic properties may vary greatly depending on the heat treatment temperature even if the FeCoV alloy-based plate material has the same composition, in the present invention, by heat-treating at a temperature within the above range, it is possible to obtain an FeCoV alloy-based thin plate having excellent mechanical properties and excellent magnetic properties, that is, high saturation magnetic flux density and low iron loss value at the same time.

[0148] In another embodiment of the present invention, the heat treatment may be performed for 30 to 240 minutes. Preferably, the heat treatment may be performed for 60 to 120 minutes. When the heat treatment time satisfies the above range, it is preferable because the phase transformation time to the γ-austenite phase is sufficient while shortening the heat treatment time. In short, the step of transforming into the γ-austenite phase may be heat-treating at a temperature of 850 to 950°C for 60 to 120 minutes.

[0149] In another embodiment of the present invention, the step of transforming into the γ-austenite phase may be performed under a vacuum or inert gas atmosphere. Since the FeCoV-based alloy is somewhat prone to oxidation, the step of transforming into the γ-austenite phase is preferably performed under a vacuum or inert gas atmosphere. The inert gas may be, for example, high-purity argon (Ar) gas, but is not limited thereto.

[0150] In another embodiment of the present invention, the method may further include a step of removing a surface scale of the plate material before the step of heat-treating the plate material. Since an oxide scale may be formed on the surface of the plate material that has undergone the hot rolling, and the oxide scale may affect the quality of the plate material, it is preferable to further include the step of removing the surface scale of the plate material. A method of removing the surface scale of the plate material may be performed using a conventional method performed in the art. For example, the pickling treatment may be performed by introducing the plate material into a hydrochloric acid bath, or the surface scale may be removed by high-pressure spraying of a slurry mixed with high-pressure water and an abrasive onto the plate material, but is not limited thereto.

[0151] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes a step of quenching the heat-treated FeCoV alloy-based plate material. If the microstructure of the FeCoV alloy-based plate material forms an ordered structure in a cold rolling process to be described later, since it has high strength and low elongation, there is a problem in that rupture or cracking occurs during the cold rolling process, making it difficult to roll to a target thickness. Therefore, in the present invention, the FeCoV alloy-based plate material is changed to form a disordered structure by performing the step of transforming an α-ferrite phase into a y-austenite phase by heat-treating the FeCoV alloy-based plate material at 600 to 1,200°C for 10 minutes to 240 minutes. After that, by including the step of quenching so that the FeCoV alloy-based plate material can maintain the structure of the γ-austenite phase, elongation is improved to solve problems occurring during the cold rolling process. In another embodiment of the present invention, the step of quenching may be performed at a rate of 10 to 300°C / sec. Preferably, the quenching may be performed at a rate of 30 to 150°C / sec, and more preferably at a rate of 50 to 100°C / sec. When the quenching rate satisfies the above range, the γ-austenite phase is stably maintained, which is preferable because an FeCoV alloy-based thin plate having high saturation magnetic flux density can be manufactured. The step of quenching may be performing water cooling or oil cooling. The water cooling or oil cooling method is not particularly limited in the present invention, and a general method performed in the art may be applied. For example, it may be performed using a water-cooled or oil-cooled cooling guide and a conveyor roll, but is not limited thereto. By performing the water cooling or oil cooling, the γ-austenite phase structure, which is a high-temperature stable phase, can be stably maintained. The step of quenching may be performed by introducing the FeCoV-based alloy plate material into cooling water.

[0152] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes a step of cold-rolling the quenched FeCoV alloy-based plate material to obtain an FeCoV alloy-based thin plate. In the method for manufacturing an FeCoV alloy-based thin plate according to the present invention, cold rolling can be smoothly performed as the α-ferrite phase of a regular structure is heat-treated according to a specific temperature range and time, and is changed into a γ-austenite phase of an irregular structure by quenching it. The cold rolling may be repeatedly performed while changing a reduction ratio, but is not limited thereto. A cumulative reduction ratio may be 85% or more, specifically 90% or more, and more specifically 95% or more, but is also not limited thereto.

[0153] In the FeCoV alloy-based thin plate according to the present invention, an intensity of a peak of a (100) plane among peaks of an X-ray diffraction pattern of the ingot is decreased or does not appear. In another embodiment of the present invention, in the FeCoV alloy-based thin plate, an intensity of a peak of a (211) plane among peaks of the X-ray diffraction pattern of the ingot may be increased. In the case of the ingot, since it exhibits an ordered structure due to slow cooling, the peak of the (100) plane appears highest in the X-ray diffraction pattern, and the rest show peaks of relatively very low intensity. However, when heat treatment for removing stress generated during the rolling process is finally performed after cold rolling, the intensity of the peak of the (100) plane of the ingot decreases or does not appear. On the other hand, as the disordered structure changes to an ordered structure according to the heat treatment, the intensity of the peak of the (211) plane among the peaks of the X-ray diffraction pattern of the ingot may increase.

[0154] In another embodiment of the present invention, in the FeCoV alloy-based thin plate, the intensity of the peak of the (100) plane among peaks of an X-ray diffraction pattern of the hot-rolled plate material may be decreased or may not appear. In another embodiment of the present invention, in the FeCoV alloy-based thin plate, the intensity of the peak of the (211) plane among the peaks of the hot-rolled X-ray diffraction pattern may be increased.

[0155] In the FeCoV alloy-based thin plate, a full width at half maximum (FWHM) of a maximum peak in a range where 20 is 42 to 47° in an X-ray diffraction chart obtained by XRD analysis may be different before heat-treating the plate material and after heat-treating the plate material. In the FeCoV alloy-based thin plate, a full width at half maximum (FWHM) of a maximum peak in a range where 20 is 42 to 47° in an X-ray diffraction chart obtained by XRD analysis may be different before performing the stress relief heat treatment on the FeCoV alloy-based thin plate and after performing the stress relief heat treatment on the FeCoV alloy-based thin plate.

[0156] In another embodiment of the present invention, the FeCoV alloy-based thin plate may further include crystal grains of 150 µm or less by 50% or more compared to the ingot. Since the FeCoV alloy-based thin plate retains a part of the high-temperature structure by quenching after heat treatment at the high temperature, at least a portion or all of the α-ferrite phase is changed to the γ-austenite phase through the heat treatment, and since it is manufactured through processes such as repeated cold rolling, relatively uniform crystal grains of 150 µm or less may be further included by 50% or more, specifically 60% or more, and more specifically 70% or more compared to the ingot. In another embodiment of the present invention, in the FeCoV alloy-based thin plate, a difference between an area occupied by cobalt and an area occupied by iron within a region from a surface of the FeCoV alloy-based thin plate to 35 µm on a GDS depth profile may be smaller than a difference between an area occupied by cobalt and an area occupied by iron within a region from a surface of the hot-rolled plate material to 35 µm. In another embodiment of the present invention, in the FeCoV alloy-based thin plate, a content of impurities in a region from a surface of the FeCoV alloy-based thin plate to 5 µm on a GDS depth profile may be less than a content of impurities in a region from a surface of the hot-rolled plate material to 5 µm. The impurities may refer to oxides or carbides generated due to oxygen (O 2 ), carbon (C), and the like. Specifically, in the FeCoV alloy-based thin plate according to the present invention, the content of impurities such as oxygen and carbon decreases rapidly within a region from the surface of the thin plate to 5 µm, so that oxides and carbides do not exist therein, and thus mechanical properties as well as magnetic properties may be excellent.

[0157] In another embodiment of the present invention, the method may further include: obtaining the FeCoV alloy-based thin plate; and then performing a stress relief heat treatment on the FeCoV alloy-based thin plate. By including the step of performing the stress relief heat treatment on the FeCoV alloy-based thin plate, residual stress existing inside the FeCoV alloy-based thin plate after the cold rolling can be removed, and as the irregular γ-austenite phase changes to a stable phase, regularity is secured, and accordingly, it is preferable because an FeCoV alloy-based thin plate having a high saturation magnetic flux density value, a low iron loss value, and appropriate tensile strength and elongation can be obtained.

[0158] The soft magnetic FeCoV-based alloy undergoes a process in which the phase of the structure changes in a process of being manufactured into a thin plate, and in this process, magnetic properties such as saturation magnetic flux density, residual magnetic flux density, coercivity, core loss, etc. are affected according to a specific method of heat treatment such as heat treatment atmosphere, temperature, and time. Here, when a soft magnetic material is used as a material for a drive motor component, etc., a higher saturation magnetic flux density or a magnetic flux density value in a specific frequency region is advantageous, and a lower loss value such as iron loss indicates an advantageous characteristic. Eventually, alloy design, processing, heat treatment, etc. are proceeded to exhibit high magnetic flux density and low iron loss value, and as a result, when a value obtained by dividing magnetic flux density by iron loss is defined as a high specific efficiency value, the higher this value is, the more excellent it is as a material for a motor. In the present invention, heat treatment for microstructure control is performed between hot rolling and cold rolling so that cold rolling can be smoothly performed, and stress relief heat treatment is additionally performed to improve mechanical properties, particularly elongation and magnetic properties after cold rolling, thereby having an advantage of manufacturing an FeCoV alloy-based thin plate excellent in both mechanical properties and magnetic properties. In another embodiment of the present invention, the stress relief heat treatment may be performed at 650 to 950°C for 10 to 120 minutes. Preferably, the stress relief heat treatment may be performed at a temperature of 700 to 950°C, and more preferably 850 to 950°C, but is not limited thereto.

[0159] Another aspect of the present invention relates to a method for manufacturing an FeCoV alloy-based thin plate, comprising: preparing an FeCoV alloy melt by vacuum melting an alloy component containing 49 to 66 at% (atomic percent) of iron, 20 to 49 at% of cobalt, greater than 0 and 2 at% or less of vanadium, 0 to 15 at% of nickel, 0 to 3 at% of chromium, and 0 to 1 at% of niobium; casting the alloy melt to manufacture an ingot; hot-rolling the ingot to obtain a plate material; heat-treating the plate material at 600 to 1,200°C for 10 minutes to 240 minutes to transform at least a portion of an α-ferrite phase into a γ-austenite phase; quenching the heat-treated plate material; and cold-rolling the quenched plate material to obtain an FeCoV alloy-based thin plate. The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes the step of transforming at least a portion of the α-ferrite phase into the γ-austenite phase, whereby cold rolling can be easily performed, and there is an advantage in that an FeCoV alloy-based thin plate having excellent saturation magnetic flux density and low iron loss values can be manufactured without going through complicated processes such as conventional forging.

[0160] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes preparing an FeCoV alloy melt by vacuum melting an alloy component containing 49 to 66 at% (atomic percent) of iron, 20 to 49 at% of cobalt, greater than 0 and 2 at% or less of vanadium, 0 to 15 at% of nickel, 0 to 3 at% of chromium, and 0 to 1 at% of niobium. The other impurities may be one or more selected from the group consisting of carbon, oxygen, silicon, and manganese. By preparing the FeCoV alloy melt by vacuum melting the alloy component having the above composition, there is an advantage in that mechanical properties such as strength and elongation can be secured while having a high saturation magnetic flux density value, and alloy costs can be reduced.

[0161] The FeCoV-based alloy is an alloy composition having soft magnetic properties, and is mainly used for motor cores of electronic products by being manufactured into a thin plate, and in particular, recently, application as a drive motor for electric vehicles is being considered. In order to increase the output of an electric vehicle, the magnetic flux density value of the motor core material must be high. Recently, most electric vehicles have a value of 2 Tesla or more, and since the FeCoV alloy has a value of up to 2.4 Tesla level, it can be very helpful in improving motor core output. In addition, since it has a significantly lower iron loss value compared to other soft magnetic materials, it is possible to drive a longer distance due to a lower loss value compared to a battery of the same capacity as well as efficiency improvement. For the same reason, when a motor exhibiting the same performance is manufactured, miniaturization and weight reduction are possible. Even with the same alloy composition, the defect rate of the rolling process may vary depending on the manufacturing process of such an FeCoV alloy, and mechanical and magnetic property values of the manufactured plate material may be greatly influenced. The method for manufacturing an FeCoV alloy-based thin plate according to the present invention has an advantage in that a thin plate having high mechanical and magnetic property values can be easily manufactured without including a conventional complicated slag removal process, forging process, process of forming into a slab shape, and the like. Meanwhile, the saturation magnetic flux density value and coercivity value of the manufactured FeCoV alloy-based thin plate may vary somewhat depending on the composition of the FeCoV alloy component. In the present invention, by using the FeCoV alloy component having the above composition, there is an advantage in that an FeCoV alloy-based thin plate having a high saturation magnetic flux density value and low coercivity can be obtained. By vacuum melting the alloy component, a grayish ingot with little contamination can be obtained, and when solidified into an ingot shape through a casting step to be described later, it is possible to suppress a phenomenon in which an ingot having a non-uniform composition is obtained due to composition inconsistency, for example, a case where the upper and middle, or middle and lower compositions of the ingot are different, or segregation exists in the same portion, which is preferable. In addition, it is preferable because it is possible to suppress a phenomenon in which a crack is induced in a hot rolling process, a cold rolling process, or the like because an oxide layer is too thick.

[0162] The step of preparing the alloy melt may be performed under an argon, nitrogen, or carbon dioxide atmosphere. When the step of preparing the alloy melt is performed under the argon, nitrogen, or carbon dioxide atmosphere, it is preferable because a phenomenon in which the alloy component is oxidized or carbonized can be suppressed.

[0163] In the step of preparing the FeCoV alloy melt by vacuum melting the alloy component, the degree of vacuum may be 1×10 -2< to 1×10 -4< torr, preferably 1×10 -2< to 1×10 -3< torr. When the degree of vacuum satisfies the above range, it is preferable because oxidation or carbonization can be suppressed. In the step of preparing the alloy melt, for elements having a large difference in melting point between the alloy components, high melting point metals such as Fe, Co, and V may be added and melted first, and then low melting point metals such as Al and Mg may be added later, followed by cooling described later, but the present invention is not limited thereto. However, in this case, it is preferable because a phenomenon in which fumes are generated or vaporization occurs due to exposure of the low melting point metal to high temperature for a long time can be suppressed. In addition, when it is desired to add the low melting point metal to the high melting point metal in a specific content, the target composition may be achieved by adding a slightly higher content than the target composition by predicting the content loss, but is not limited thereto.

[0164] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes the step of manufacturing an ingot by casting the alloy melt. The method may further include a step of removing slag of the alloy melt liquid before casting the alloy melt, but is not limited thereto. The method for manufacturing an FeCoV alloy-based thin plate according to the present invention may not include the step of removing slag of the alloy melt liquid. Specifically, the method for manufacturing an FeCoV alloy-based thin plate according to the present invention has an advantage in that it is possible to manufacture an FeCoV alloy-based thin plate exhibiting excellent performance without including a slag removal process, a forging process, and a shape control slabbing process.

[0165] A method of manufacturing the ingot by casting the alloy melt is not specifically limited in the present invention. For example, the ingot may be manufactured by injecting the alloy melt into a mold, and cooling and crystallizing it. The injection temperature is preferably set to a temperature 100 to 2,000°C, preferably 100 to 1,000°C, and more preferably 200 to 500°C higher than the liquidus temperature of the melt. The liquidus temperature of the melt can be measured using a direct temperature measurement method with a built-in thermocouple or by measuring the surface of the melt using a non-contact laser thermometer. In addition, the cooling temperature and rate can be controlled to prevent segregation and ensure uniformity of composition by making the cooling temperature uniform. Since the upper part of the ingot cools relatively quickly and the lower part or the inside may cool slowly, the quickly cooling part may be heated, or insulated with non-metallic ceramics or slag.

[0166] The ingot may be manufactured in, for example, a bar, polyhedron, cylinder, sphere shape, or atypical shape, but is not limited thereto. The method for manufacturing an FeCoV alloy-based thin plate according to the present invention may further include cutting the ingot to 4 to 30 mm. For example, the method for manufacturing an FeCoV alloy-based thin plate may further include cutting the ingot to 10 to 30 mm. When the step of cutting the ingot within the above range is further included, it is preferable because hot rolling is smooth. Cutting of the ingot may be performed by a method commonly performed in the art, and the present invention is not limited thereto.

[0167] In another embodiment of the present invention, the method may further include: manufacturing an ingot by casting the alloy melt; and then homogenizing heat-treating the ingot. In another embodiment of the present invention, the homogenizing heat treatment may be performed at 1,200 to 1,300°C for 1 to 12 hours. Preferably, the homogenizing heat treatment may be performed for 2 to 6 hours, more preferably 2 to 4 hours, but is not limited thereto. When the step of homogenizing heat-treating is further included, it is preferable because stress generated during casting can be relieved.

[0168] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes the step of hot-rolling the ingot to obtain a plate material. By hot-rolling the ingot, it is preferable because a plate material in which a γ-austenite phase formed by slow cooling occupies the majority or an α-ferrite phase and the γ-austenite phase are mixed can be obtained.

[0169] The hot rolling may be performed using, for example, a steel rolling mill. The rolling start temperature, rolling speed, rolling end temperature, and the like are not particularly limited in the present invention, and may be appropriately performed according to conventional conditions performed in the art. For example, the start temperature for the rolling may be 900°C or higher, and may not exceed 1,300°C. When the start temperature for the rolling satisfies the above range, it is preferable because there is an advantage in that the strength and formability of the manufactured plate material are excellent. The rolling end temperature may be 1,150°C or higher. When the rolling end temperature is 1,150°C or higher, it is preferable because a phenomenon in which excessive load is applied to equipment due to high deformation resistance can be suppressed, and control of the shape is easy.

[0170] The total reduction ratio by the hot rolling may be 70 to 90%, preferably 75 to 90%, and more preferably 75 to 85%. When the total reduction ratio satisfies the above range, it is preferable because enlargement of crystal grains due to large energy can be suppressed, and the deviation thereof can be reduced.

[0171] The rolling may be performed for one pass to several passes, but is not limited thereto. In another embodiment of the present invention, the rolling may be performed in two or more rolling passes. Specifically, the rolling may be performed in 5 or more rolling passes, but is not limited thereto.

[0172] When the temperature decreases as the hot rolling is repeated, it is preferable to perform the hot rolling after raising the temperature by reheating. The lower limit of the temperature during the rolling process is preferably controlled to 900°C or higher, preferably 900 to 1,000°C. When the lower limit of the temperature during the rolling process satisfies the above range, it is preferable because most of the phase exists as the γ-austenite phase, so that cracks or ruptures hardly occur during hot rolling and the process becomes smooth.

[0173] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes the step of heat-treating the plate material at 600 to 1,200°C for 10 minutes to 240 minutes to transform at least a portion of the α-ferrite phase into the γ-austenite phase. Although not wishing to be bound by theory, generally, an FeCoV-based alloy undergoes a phase change while going through a casting process, a hot rolling process, a heat treatment process, a cold rolling process, and the like, and even the same phase changes into an ordered lattice or a disordered lattice. For example, when an FeCoV-based alloy is melted in a vacuum and cast into an ingot, an α-ferrite phase is formed. In the case of α-ferrite, which is a room temperature structure, it forms a Body-Centered Cubic (BCC) structure and has relatively fewer slip planes, so there is a high possibility that rolling may not be performed smoothly when cold rolling or the like is performed later to use a thin plate using the FeCoV alloy-based plate material. In particular, due to residual stress existing inside the plate material after cold rolling, forming may be difficult, and a phenomenon in which soft magnetic properties are not properly implemented may occur. On the other hand, a γ-austenite structure, which is a high-temperature structure, forms a Face-Centered Cubic (FCC) structure, which is a disordered structure, and has many slip planes, so rolling is easy, and plastic workability is much superior to that of α-ferrite. Therefore, the method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes heat-treating the plate material at a temperature of 600 to 1,200°C, which is a high-temperature stable phase section, so as to have a γ-austenite structure, that is, an FCC structure, which is a high-temperature stable phase, and then quenching the plate material, thereby transforming the α-ferrite phase generated through the casting process and the hot rolling process into the γ-austenite phase, so that the structure is changed to a structure having the γ-austenite phase or a composite structure of the α-ferrite phase and the γ-austenite phase.

[0174] In another embodiment of the present invention, the heat treatment may be performed at 730 to 1,200°C. Specifically, the heat treatment may be performed at a temperature of 730°C or higher, which is a temperature at which an irregular / regular lattice structure starts to be ordered, and a temperature of 1,200°C or lower, which is a temperature at which a liquid phase is not formed and atomic structure change is expected to be most active. Specifically, the heat treatment is preferably performed within the above range, which is a temperature region where irregular / regular structure change occurs.

[0175] In another embodiment of the present invention, the heat treatment may be performed at 840 to 1,200°C. Specifically, the heat treatment may be performed at a temperature of 840°C or higher, which is a temperature at which phase transformation occurs, and a temperature of 1,200°C or lower, which is a temperature at which solid phase control is possible without mixing of a liquid phase. In another embodiment of the present invention, the step of transforming into the γ-austenite phase may be heat-treating at 850 to 950°C. Since mechanical properties and / or magnetic properties may vary greatly depending on the heat treatment temperature even if the FeCoV alloy-based plate material has the same composition, in the present invention, by heat-treating at a temperature within the above range, it is possible to obtain an FeCoV alloy-based thin plate having excellent mechanical properties and excellent magnetic properties, that is, high saturation magnetic flux density and low iron loss value at the same time.

[0176] In another embodiment of the present invention, the heat treatment may be performed for 30 to 240 minutes. Preferably, the heat treatment may be performed for 60 to 120 minutes. When the heat treatment time satisfies the above range, it is preferable because the phase transformation time to the γ-austenite phase is sufficient while shortening the heat treatment time. In short, the step of transforming into the γ-austenite phase may be heat-treating at a temperature of 850 to 950°C for 60 to 120 minutes.

[0177] In another embodiment of the present invention, the step of transforming into the γ-austenite phase may be performed under a vacuum or inert gas atmosphere. Since the FeCoV-based alloy is somewhat prone to oxidation, the step of transforming into the γ-austenite phase is preferably performed under a vacuum or inert gas atmosphere. The inert gas may be, for example, high-purity argon (Ar) gas, but is not limited thereto.

[0178] In another embodiment of the present invention, the method may further include a step of removing a surface scale of the plate material before the step of heat-treating the plate material. Since an oxide scale may be formed on the surface of the plate material that has undergone the hot rolling, and the oxide scale may affect the quality of the plate material, it is preferable to further include the step of removing the surface scale of the plate material. A method of removing the surface scale of the plate material may be performed using a conventional method performed in the art. For example, the pickling treatment may be performed by introducing the plate material into a hydrochloric acid bath, or the surface scale may be removed by high-pressure spraying of a slurry mixed with high-pressure water and an abrasive onto the plate material, but is not limited thereto.

[0179] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes a step of quenching the heat-treated FeCoV alloy-based plate material. If the microstructure of the FeCoV alloy-based plate material forms an ordered structure in a cold rolling process to be described later, since it has high strength and low elongation, there is a problem in that rupture or cracking occurs during the cold rolling process, making it difficult to roll to a target thickness. Therefore, in the present invention, the FeCoV alloy-based plate material is changed to form a disordered structure by performing the step of transforming an α-ferrite phase into a γ-austenite phase by heat-treating the FeCoV alloy-based plate material at 600 to 1,200°C for 10 minutes to 240 minutes. After that, by including the step of quenching so that the FeCoV alloy-based plate material can maintain the structure of the γ-austenite phase, elongation is improved to solve problems occurring during the cold rolling process. In another embodiment of the present invention, the step of quenching may be performed at a rate of 10 to 300°C / sec. Preferably, the quenching may be performed at a rate of 30 to 150°C / sec, and more preferably at a rate of 50 to 100°C / sec. When the quenching rate satisfies the above range, the γ-austenite phase is stably maintained, which is preferable because an FeCoV alloy-based thin plate having high saturation magnetic flux density can be manufactured. The step of quenching may be performing water cooling or oil cooling. The water cooling or oil cooling method is not particularly limited in the present invention, and a general method performed in the art may be applied. For example, it may be performed using a water-cooled or oil-cooled cooling guide and a conveyor roll, but is not limited thereto. By performing the water cooling or oil cooling, the γ-austenite phase structure, which is a high-temperature stable phase, can be stably maintained. The step of quenching may be performed by introducing the FeCoV-based alloy plate material into cooling water.

[0180] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes a step of cold-rolling the quenched FeCoV alloy-based plate material to obtain an FeCoV alloy-based thin plate. In the method for manufacturing an FeCoV alloy-based thin plate according to the present invention, cold rolling can be smoothly performed as the α-ferrite phase of a regular structure is heat-treated according to a specific temperature range and time, and is changed into a γ-austenite phase of an irregular structure by quenching it. The cold rolling may be repeatedly performed while changing a reduction ratio, but is not limited thereto. A cumulative reduction ratio may be 85% or more, specifically 90% or more, and more specifically 95% or more, but is also not limited thereto.

[0181] In another embodiment of the present invention, the method may further include: obtaining the FeCoV alloy-based thin plate; and then performing a stress relief heat treatment on the FeCoV alloy-based thin plate. By including the step of performing the stress relief heat treatment on the FeCoV alloy-based thin plate, residual stress existing inside the FeCoV alloy-based thin plate after the cold rolling can be removed, and as the irregular γ-austenite phase changes to a stable phase, regularity is secured, and accordingly, it is preferable because an FeCoV alloy-based thin plate having a high saturation magnetic flux density value, a low iron loss value, and appropriate tensile strength and elongation can be obtained.

[0182] The soft magnetic FeCoV-based alloy undergoes a process in which the phase of the structure changes in a process of being manufactured into a thin plate, and in this process, magnetic properties such as saturation magnetic flux density, residual magnetic flux density, coercivity, core loss, etc. are affected according to a specific method of heat treatment such as heat treatment atmosphere, temperature, and time. Here, when a soft magnetic material is used as a material for a drive motor component, etc., a higher saturation magnetic flux density or a magnetic flux density value in a specific frequency region is advantageous, and a lower loss value such as iron loss indicates an advantageous characteristic. Eventually, alloy design, processing, heat treatment, etc. are proceeded to exhibit high magnetic flux density and low iron loss value, and as a result, when a value obtained by dividing magnetic flux density by iron loss is defined as a high specific efficiency value, the higher this value is, the more excellent it is as a material for a motor. In the present invention, heat treatment for microstructure control is performed between hot rolling and cold rolling so that cold rolling can be smoothly performed, and stress relief heat treatment is additionally performed to improve mechanical properties, particularly elongation and magnetic properties after cold rolling, thereby having an advantage of manufacturing an FeCoV alloy-based thin plate excellent in both mechanical properties and magnetic properties. In another embodiment of the present invention, the stress relief heat treatment may be performed at 650 to 950°C for 10 to 120 minutes. Preferably, the stress relief heat treatment may be performed at a temperature of 700 to 950°C, and more preferably 850 to 950°C, but is not limited thereto.

[0183] Another aspect of the present invention relates to an FeCoV alloy-based thin plate containing 49 to 66 at% (atomic percent) of iron, 20 to 49 at% of cobalt, greater than 0 and 2 at% or less of vanadium, 0 to 15 at% of nickel, 0 to 3 at% of chromium, and 0 to 1 at% of niobium. In another embodiment of the present invention, the FeCoV alloy-based thin plate may have a saturation magnetic flux density of 2.13 to 2.38 T. Specifically, the FeCoV alloy-based thin plate may have a saturation magnetic flux density of 2.26 to 2.38 T. The saturation magnetic flux density and a magnetic flux density in a specific range to be described later are factors related to output. Specifically, when a high instantaneous output is required, such as in an electric vehicle motor, a high saturation magnetic flux density of 2 T or more is required. Since the FeCoV alloy-based thin plate according to the present invention has a high saturation magnetic flux density, it can be usefully applied to various fields, and in particular, since it can have a saturation magnetic flux density of 2 T or more, it can be particularly usefully applied to electric vehicles. In the present invention, "saturation magnetic flux density" refers to a value measured with an applied magnetic field of 1.2×10 3< kA / m using a Vibrating Sample Magnetometer (VSM). In another embodiment of the present invention, the FeCoV alloy-based thin plate may have a coercivity of 43 Oe or less. In another embodiment of the present invention, the FeCoV alloy-based thin plate may have a coercivity of 25 Oe or less. In another embodiment of the present invention, the FeCoV alloy-based thin plate may have a coercivity of 10 Oe or less. Specifically, the FeCoV alloy-based thin plate may have a coercivity of 1 Oe or less, more specifically 0.5 Oe or less, and most specifically 0.18 to 0.5 Oe. When the coercivity of the FeCoV alloy-based thin plate satisfies the above range, it is preferable because there is an advantage of excellent workability.

[0184] Another aspect of the present invention relates to a method for manufacturing an FeCoV alloy-based thin plate, comprising: preparing an FeCoV alloy-based cast material; heat-treating the cast material at 600 to 1,200°C for 10 minutes to 240 minutes to transform at least a portion of an α-ferrite phase into a γ-austenite phase; quenching the heat-treated cast material; and cold-rolling the quenched cast material. The method for manufacturing an FeCoV alloy-based thin plate according to the present invention has an advantage in that it is possible to manufacture an FeCoV alloy-based thin plate having excellent magnetic properties while omitting processes such as conventional forging and hot rolling processes. The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes preparing an FeCoV alloy-based cast material. In another embodiment of the present invention, the step of preparing the FeCoV alloy-based cast material may include: preparing an FeCoV alloy melt; casting the alloy melt to manufacture an ingot; and cutting the ingot to a thickness of 4 to 10 mm to obtain a cast material. In another embodiment of the present invention, the step of preparing the FeCoV alloy-based cast material may be a step of forming the FeCoV alloy-based cast material by a strip casting process. In short, the FeCoV alloy-based cast material may be one obtained by cutting the ingot, or one directly manufactured in the form of a plate having a thickness of 4 to 10 mm from the alloy melt.

[0185] The step of preparing the FeCoV alloy melt may be vacuum melting an alloy component composed of the 20 to 49 at% of cobalt, 2 to 5 at% of vanadium, and a balance of iron and other impurities. The other impurities may be one or more selected from the group consisting of carbon, oxygen, silicon, and manganese. Specifically, the FeCoV alloy melt may include an alloy component composed of 30 to 49 at% of cobalt, 2 to 3 at% of vanadium, and a balance of iron and other impurities. More specifically, the FeCoV alloy melt may include an alloy component composed of 40 to 49 at% of cobalt, 2 to 3 at% of vanadium, and a balance of iron and other impurities. The FeCoV-based alloy is an alloy composition having soft magnetic properties, and is mainly used for motor cores of electronic products by being manufactured into a thin plate, and in particular, recently, application as a drive motor for electric vehicles is being considered. In order to increase the output of an electric vehicle, the magnetic flux density value of the motor core material must be high. Recently, most electric vehicles have a value of 2 Tesla or more, and since the FeCoV alloy has a value of up to 2.4 Tesla level, it can be very helpful in improving motor core output. In addition, since it has a significantly lower iron loss value compared to other soft magnetic materials, it is possible to drive a longer distance due to a lower loss value compared to a battery of the same capacity as well as efficiency improvement. For the same reason, when a motor exhibiting the same performance is manufactured, miniaturization and weight reduction are possible. Even with the same alloy composition, the defect rate of the rolling process may vary depending on the manufacturing process of such an FeCoV alloy, and mechanical and magnetic property values of the manufactured plate material may be greatly influenced. The method for manufacturing an FeCoV alloy-based thin plate according to the present invention has an advantage in that a thin plate having high mechanical and magnetic property values can be easily manufactured without including a conventional complicated slag removal process, forging process, process of forming into a slab shape, and the like. Meanwhile, the saturation magnetic flux density value and coercivity value of the manufactured FeCoV alloy-based thin plate may vary somewhat depending on the composition of the FeCoV alloy component. In the present invention, by using the FeCoV alloy component having the above composition, there is an advantage in that an FeCoV alloy-based thin plate having a high saturation magnetic flux density value and low coercivity can be obtained. The FeCoV alloy melt may have a composition of Fe 49 Co 49 V 2 . By vacuum melting the alloy component, a grayish ingot with little contamination can be obtained, and when solidified into an ingot shape through a casting step to be described later, it is possible to suppress a phenomenon in which an ingot having a non-uniform composition is obtained due to composition inconsistency, for example, a case where the upper and middle, or middle and lower compositions of the ingot are different, or segregation exists in the same portion, which is preferable. In addition, it is preferable because it is possible to suppress a phenomenon in which a crack is induced in a cold rolling process or the like because an oxide layer is too thick.

[0186] The step of preparing the alloy melt may be performed under an argon, nitrogen, or carbon dioxide atmosphere. When the step of preparing the alloy melt is performed under the argon, nitrogen, or carbon dioxide atmosphere, it is preferable because a phenomenon in which the alloy component is oxidized or carbonized can be suppressed.

[0187] In the step of preparing the FeCoV alloy melt by vacuum melting the alloy component, the degree of vacuum may be 1×10 -2< to 1×10 -4< torr, preferably 1×10 -2< to 1×10 -3< torr. When the degree of vacuum satisfies the above range, it is preferable because oxidation or carbonization can be suppressed.

[0188] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes the step of manufacturing an ingot by casting the alloy melt. The method may further include a step of removing slag of the alloy melt liquid before casting the alloy melt, but is not limited thereto. The method for manufacturing an FeCoV alloy-based thin plate according to the present invention may not include the step of removing slag of the alloy melt liquid. Specifically, the method for manufacturing an FeCoV alloy-based thin plate according to the present invention has an advantage in that it is possible to manufacture an FeCoV alloy-based thin plate exhibiting excellent performance without including a slag removal process, a forging process, and a shape control slabbing process. A method of manufacturing the ingot by casting the alloy melt is not specifically limited in the present invention. For example, the ingot may be manufactured by injecting the alloy melt into a mold, and cooling and crystallizing it. The injection temperature is preferably set to a temperature 100 to 2,000°C, preferably 100 to 1,000°C, and more preferably 200 to 500°C higher than the liquidus temperature of the melt. The liquidus temperature of the melt can be measured using a direct temperature measurement method with a built-in thermocouple or by measuring the surface of the melt using a non-contact laser thermometer. In addition, the cooling temperature and rate can be controlled to prevent segregation and ensure uniformity of composition by making the cooling temperature uniform. Since the upper part of the ingot cools relatively quickly and the lower part or the inside may cool slowly, the quickly cooling part may be heated, or insulated with non-metallic ceramics or slag.

[0189] The ingot may be manufactured in, for example, a bar, polyhedron, cylinder, sphere shape, or atypical shape, but is not limited thereto. The method for manufacturing an FeCoV alloy-based thin plate according to the present invention may further include the step of cutting the ingot to 4 to 10 mm. Specifically, when cold rolling is performed without going through the step of hot-rolling the ingot, the step of cutting the ingot to 4 to 10 mm may be further included. Cutting of the ingot may be performed by a method commonly performed in the art, and the present invention is not limited thereto.

[0190] In another embodiment of the present invention, the method may further include: manufacturing an ingot by casting the alloy melt; and then homogenizing heat-treating the ingot. In another embodiment of the present invention, the homogenizing heat treatment may be performed at 1,200 to 1,300°C for 1 to 12 hours. Preferably, the homogenizing heat treatment may be performed for 2 to 6 hours, more preferably 2 to 4 hours, but is not limited thereto. When the step of homogenizing heat-treating is further included, it is preferable because stress generated during casting can be relieved.

[0191] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention may include obtaining a cast material by cutting the ingot to a thickness of 4 to 10 mm. In another embodiment of the present invention, the step of obtaining the cast material may be cutting the ingot to a thickness of 4 to 8 mm. In another embodiment of the present invention, the step of obtaining the cast material may be cutting the ingot to a thickness of 4 to 6 mm. In short, the cast material may have a thickness of 4 to 10 mm, preferably 4 to 8 mm, and more preferably 4 to 6 mm. When the thickness of the cast material satisfies the above range, it is preferable because a cold rolling process to be described later is easy.

[0192] The cast material may be formed by a strip casting process. The strip casting process is a process technology for manufacturing a solid thin plate directly from a liquid melt, and is a technology for manufacturing a thin plate having a thickness of 4 to 10 mm, which is a process capable of improving productivity because continuous casting, reheating, and hot rolling processes can be omitted. In the present invention, the strip casting process method is not specifically limited. For example, the strip casting process may be performed by controlling cooling of the FeCoV alloy melt melted at a temperature of 1,700°C or higher to 300°C at a cooling rate of 100 to 150°C / s, but is not limited thereto.

[0193] In another embodiment of the present invention, the step of obtaining the cast material may be performed under an argon, nitrogen, or carbon dioxide atmosphere. When the step of obtaining the cast material is performed in an inert atmosphere such as argon or nitrogen, or under a carbon dioxide atmosphere, it is preferable because a phenomenon in which the cast material is oxidized or carbonized can be suppressed.

[0194] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes heat-treating the cast material at 600 to 1,200°C for 10 minutes to 240 minutes to transform at least a portion of the α-ferrite phase into the γ-austenite phase. Although not wishing to be bound by theory, generally, an FeCoV-based alloy undergoes a phase change while going through a casting process, a heat treatment process, a cold rolling process, and the like, and even the same phase changes into an ordered lattice or a disordered lattice. For example, in a cast material obtained by melting an FeCoV-based alloy in a vacuum, an α-ferrite phase is formed. In the case of α-ferrite, which is a room temperature structure, it forms a Body-Centered Cubic (BCC) structure and has relatively fewer slip planes, so there is a high possibility that rolling may not be performed smoothly when cold rolling or the like is performed later to use a thin plate using the cast material. In particular, due to residual stress existing inside the cast material after cold rolling, forming may be difficult, and a phenomenon in which soft magnetic properties are not properly implemented may occur. On the other hand, a γ-austenite structure, which is a high-temperature structure, forms a Face-Centered Cubic (FCC) structure, which is a disordered structure, and has many slip planes, so rolling is easy, and plastic workability is much superior to that of α-ferrite. Therefore, the method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes heat-treating the cast material at a temperature of 600 to 1,200°C, which is a high-temperature stable phase section, so as to have a γ-austenite structure, that is, an FCC structure, which is a high-temperature stable phase, and then quenching the cast material, thereby transforming the α-ferrite phase generated through the casting process and the hot rolling process into the γ-austenite phase, so that the structure is changed to a structure having the γ-austenite phase or a composite structure of the α-ferrite phase and the γ-austenite phase.

[0195] In another embodiment of the present invention, the heat treatment may be performed at 730 to 1,200°C. Specifically, the heat treatment may be performed at a temperature of 730°C or higher, which is a temperature at which an irregular / regular lattice structure starts to be ordered, and a temperature of 1,200°C or lower, which is a temperature at which a liquid phase is not formed and atomic structure change is expected to be most active. Specifically, the heat treatment is preferably performed within the above range, which is a temperature region where irregular / regular structure change occurs.

[0196] In another embodiment of the present invention, the heat treatment may be performed at 840 to 1,200°C. Specifically, the heat treatment may be performed at a temperature of 840°C or higher, which is a temperature at which phase transformation occurs, and a temperature of 1,200°C or lower, which is a temperature at which solid phase control is possible without mixing of a liquid phase. In another embodiment of the present invention, the step of transforming into the γ-austenite phase may be heat-treating at 850 to 950°C. Since mechanical properties and / or magnetic properties may vary greatly depending on the heat treatment temperature even if the FeCoV alloy-based thin plate has the same composition, in the present invention, by heat-treating at a temperature within the above range, it is possible to obtain an FeCoV alloy-based thin plate having excellent mechanical properties and excellent magnetic properties, that is, high saturation magnetic flux density and low iron loss value at the same time. When the heat treatment temperature satisfies the above range, the phase transformation from the α-ferrite phase to the γ-austenite phase is easy, and a phenomenon in which coarse grain boundaries of a level of 100 to 500 µm are formed is suppressed, so there is an advantage in that a cast material with high workability can be obtained. In addition, there is an advantage in that a cast material having uniform quality as a whole can be obtained because a phenomenon in which a composition ratio of the surface and the inside of the cast material, specifically a composition ratio of Fe and Co, varies can be suppressed.

[0197] In another embodiment of the present invention, the heat treatment may be performed for 30 to 240 minutes. Preferably, the heat treatment may be performed for 60 to 120 minutes. When the heat treatment time satisfies the above range, it is preferable because the phase transformation time to the γ-austenite phase is sufficient while shortening the heat treatment time. In short, the step of transforming into the γ-austenite phase may be heat-treating at a temperature of 850 to 950°C for 60 to 120 minutes.

[0198] In another embodiment of the present invention, the step of transforming into the γ-austenite phase may be performed under a vacuum or inert gas atmosphere. Since the FeCoV-based alloy is somewhat prone to oxidation, the step of transforming into the γ-austenite phase is preferably performed under a vacuum or inert gas atmosphere. The inert gas may be, for example, high-purity argon (Ar) gas, but is not limited thereto.

[0199] In another embodiment of the present invention, the method may further include a step of chemically surface-treating (chemically milling) the cast material before heat-treating the cast material. Since the cast material is rapidly cooled by directly rolling the melt due to process characteristics, surface casting defects such as solidification patterns or inverse segregation may be accompanied. In addition, since the thickness is somewhat thin at 4 to 10 mm, it is not easy to apply a conventional physical surface treatment process for removing surface defects, such as a band saw type process or a grinder type process. Therefore, surface casting defects can be removed by chemically surface-treating the cast material before heat-treating the cast material. The step of chemically surface-treating may be performed by a conventional method performed in the art, and is not particularly limited in the present invention. For example, the chemical surface treatment may be performed using a composition containing hydrochloric acid, nitric acid, hydrofluoric acid, and distilled water.

[0200] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes a step of quenching the heat-treated cast material. If the microstructure of the cast material forms an ordered structure in a cold rolling process to be described later, since it has high strength and low elongation, there is a problem in that rupture or cracking occurs during the cold rolling process, making it difficult to roll to a target thickness. Specifically, the heat-treated cast material is composed of an α phase, and the α phase has a BCC structure and has few slip planes, so it is not suitable for a shape deformation process such as cold rolling.

[0201] Therefore, in the present invention, the cast material is changed to form a disordered structure by performing the step of transforming at least a portion of an α-ferrite phase into a γ-austenite phase by heat-treating the cast material at 600 to 1,200°C for 10 minutes to 240 minutes. After that, by including the step of quenching so that the cast material can maintain the structure of the γ-austenite phase, elongation is improved to solve problems occurring during the cold rolling process. In another embodiment of the present invention, the step of quenching may be performed at a rate of 10 to 300°C / sec. Preferably, the quenching may be performed at a rate of 30 to 150°C / sec, and more preferably at a rate of 50 to 100°C / sec. When the quenching rate satisfies the above range, the γ-austenite phase is stably maintained, which is preferable because an FeCoV alloy-based thin plate having high saturation magnetic flux density can be manufactured. The step of quenching may be performing water cooling or oil cooling. The water cooling or oil cooling method is not particularly limited in the present invention, and a general method performed in the art may be applied. For example, it may be performed using a water-cooled or oil-cooled cooling guide and a conveyor roll, but is not limited thereto. By performing the water cooling or oil cooling, the γ-austenite phase structure, which is a high-temperature stable phase, can be stably maintained. The step of quenching may be performed by introducing the cast material into cooling water.

[0202] The method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes a step of cold-rolling the quenched cast material to obtain an FeCoV alloy-based thin plate. In the method for manufacturing an FeCoV alloy-based thin plate according to the present invention, cold rolling can be smoothly performed as the α-ferrite phase of a regular structure is heat-treated according to a specific temperature range and time, and is changed into a γ-austenite phase of an irregular structure by quenching it. The cold rolling may be repeatedly performed while changing a reduction ratio, but is not limited thereto. A cumulative reduction ratio may be 85% or more, specifically 90% or more, and more specifically 95% or more, but is also not limited thereto.

[0203] In another embodiment of the present invention, the method may further include: obtaining the FeCoV alloy-based thin plate; and then performing a stress relief heat treatment on the FeCoV alloy-based thin plate. By including the step of performing the stress relief heat treatment on the FeCoV alloy-based thin plate, residual stress existing inside the FeCoV alloy-based thin plate after the cold rolling can be removed, and as the irregular γ-austenite phase changes to a stable phase, regularity is secured, and accordingly, it is preferable because an FeCoV alloy-based thin plate having a high saturation magnetic flux density value, a low iron loss value, and appropriate tensile strength and elongation can be obtained.

[0204] The soft magnetic FeCoV-based alloy undergoes a process in which the phase of the structure changes in a process of being manufactured into a thin plate, and in this process, magnetic properties such as saturation magnetic flux density, residual magnetic flux density, coercivity, core loss, etc. are affected according to a specific method of heat treatment such as heat treatment atmosphere, temperature, and time. Here, when a soft magnetic material is used as a material for a drive motor component, etc., a higher saturation magnetic flux density or a magnetic flux density value in a specific frequency region is advantageous, and a lower loss value such as iron loss indicates an advantageous characteristic. Eventually, alloy design, processing, heat treatment, etc. are proceeded to exhibit high magnetic flux density and low iron loss value, and as a result, when a value obtained by dividing magnetic flux density by iron loss is defined as a high specific efficiency value, the higher this value is, the more excellent it is as a material for a motor. In the present invention, heat treatment for microstructure control is performed between hot rolling and cold rolling so that cold rolling can be smoothly performed, and stress relief heat treatment is additionally performed to improve mechanical properties, particularly elongation and magnetic properties after cold rolling, thereby having an advantage of manufacturing an FeCoV alloy-based thin plate excellent in both mechanical properties and magnetic properties. In another embodiment of the present invention, the stress relief heat treatment may be performed at 650 to 950°C for 10 to 120 minutes. Preferably, the stress relief heat treatment may be performed at a temperature of 700 to 950°C, and more preferably 850 to 950°C, but is not limited thereto.

[0205] Since the method for manufacturing an FeCoV alloy-based thin plate according to the present invention includes the steps of heat treating and quenching, there is an advantage in that an FeCoV alloy-based thin plate having soft magnetic performance equivalent to a process involving conventional forging, hot rolling, and cold rolling can be manufactured only by cold rolling without going through conventional forging and hot rolling processes.

[0206] Another aspect of the present invention relates to an FeCoV alloy-based thin plate having a first peak in a range where 20 is 42 to 47°, a second peak in a range where 20 is 62 to 67°, and a third peak in a range where 20 is 80 to 85° in an X-ray diffraction chart obtained by XRD analysis. In another embodiment of the present invention, the second peak may have a maximum peak intensity. In another embodiment of the present invention, the third peak may have a maximum peak intensity. Specifically, in the FeCoV alloy-based thin plate according to the present invention, the second peak or the third peak may exhibit the maximum peak intensity according to stress relief heat treatment in the method for manufacturing the FeCoV alloy-based thin plate. More specifically, when the stress relief heat treatment is not performed during the process of manufacturing the FeCoV alloy-based thin plate, the second peak may exhibit the maximum peak intensity, and when the stress relief heat treatment is performed, the third peak may exhibit the maximum peak intensity. In another embodiment of the present invention, a full width at half maximum (FWHM) of the second peak may be in a range of 4.5 to 4.6°. Specifically, when the stress relief heat treatment is not performed during the process of manufacturing the FeCoV alloy-based thin plate, the FWHM of the second peak may be in the above range. In another embodiment of the present invention, the FWHM of the second peak may be in a range of 0.35 to 0.36°. Specifically, when the stress relief heat treatment is performed during the process of manufacturing the FeCoV alloy-based thin plate, the FWHM of the second peak may be in the above range. In another embodiment of the present invention, the magnetic permeability may be 10,000 or less. Specifically, when the stress relief heat treatment is not performed during the process of manufacturing the FeCoV alloy-based thin plate, the magnetic permeability of the FeCoV alloy-based thin plate may be 7,000 or less. In another embodiment of the present invention, the magnetic permeability may be 80,000 or more. Specifically, when the stress relief heat treatment is performed during the process of manufacturing the FeCoV alloy-based thin plate, the FeCoV alloy-based thin plate may have a magnetic permeability of 80,000 or more. Specifically, the magnetic permeability may be 80,000 to 100,000.

[0207] In another embodiment of the present invention, the FeCoV alloy-based thin plate may have a saturation magnetic flux density of 2.13 to 2.38 T. Specifically, the FeCoV alloy-based thin plate may have a saturation magnetic flux density of 2.26 to 2.38 T. The saturation magnetic flux density and a magnetic flux density in a specific range to be described later are factors related to output. Specifically, when a high instantaneous output is required, such as in an electric vehicle motor, a high saturation magnetic flux density of 2 T or more is required. Since the FeCoV alloy-based thin plate according to the present invention has a high saturation magnetic flux density, it can be usefully applied to various fields, and in particular, since it can have a saturation magnetic flux density of 2 T or more, it can be particularly usefully applied to electric vehicles. In the present invention, "saturation magnetic flux density" refers to a value measured with an applied magnetic field of 1.2×10 3< kA / m using a Vibrating Sample Magnetometer (VSM).

[0208] In another embodiment of the present invention, the FeCoV alloy-based thin plate may have a magnetic flux density of 1.5 T or more induced when a magnetic field of 5,000 A / m is applied. Specifically, the magnetic flux density may be 1.87 to 2.2207 T.

[0209] In another embodiment of the present invention, the FeCoV alloy-based thin plate may have a coercivity of 43 Oe or less. In another embodiment of the present invention, the FeCoV alloy-based thin plate may have a coercivity of 25 Oe or less. In another embodiment of the present invention, the FeCoV alloy-based thin plate may have a coercivity of 10 Oe or less. Specifically, the FeCoV alloy-based thin plate may have a coercivity of 1 Oe or less, more specifically 0.5 Oe or less, and most specifically 0.18 to 0.5 Oe. When the coercivity of the FeCoV alloy-based thin plate satisfies the above range, it is preferable because there is an advantage of excellent workability.

[0210] In another embodiment of the present invention, the FeCoV alloy-based thin plate may have an iron loss of 15 or less. In the present invention, "iron loss" may be measured under a condition where the magnitude of an applied magnetic field is 1 T and a frequency is 400 Hz. In another embodiment of the present invention, the FeCoV alloy-based thin plate may contain a γ-austenite phase. In another embodiment of the present invention, the FeCoV alloy-based thin plate may further contain an α-ferrite phase. In short, the FeCoV alloy-based thin plate may contain a γ-austenite phase, or may be in the form of a composite phase containing a γ-austenite phase and an α-ferrite phase.

[0211] Since the FeCoV alloy-based thin plate according to the present invention contains a γ-austenite phase or contains a γ-austenite phase and an α-ferrite phase, it exhibits excellent magnetic properties and excellent mechanical properties, and in particular, post-processing is easy, so it can be usefully applied to various fields.

[0212] In another embodiment of the present invention, an average band thickness of a layered structure in which the γ-austenite phase is elongated may be 1 to 10 µm in an L cross-section that is a cross-section parallel to a rolling direction. In another embodiment of the present invention, the average band thickness of the layered structure in which the γ-austenite phase is elongated may be 1 to 5 µm in the L cross-section that is the cross-section parallel to the rolling direction. Specifically, the average band thickness of the layered structure in which the γ-austenite phase is elongated may be 2 to 4 µm in the L cross-section that is the cross-section parallel to the rolling direction. When the average band thickness satisfies the above range, it means that cold rolling of the FeCoV alloy-based thin plate was smooth, and accordingly, there is an advantage of exhibiting excellent mechanical properties as well as magnetic properties. The FeCoV alloy-based thin plate may be manufactured by a method for manufacturing an FeCoV alloy-based thin plate, comprising: preparing an FeCoV alloy-based plate material; heat-treating the FeCoV alloy-based plate material at 600 to 1,200°C for 10 minutes to 240 minutes to transform at least a portion of an α-ferrite phase into a γ-austenite phase; quenching the heat-treated FeCoV alloy-based plate material; cold-rolling the quenched FeCoV alloy-based plate material to obtain an FeCoV alloy-based thin plate; and performing a stress relief heat treatment on the FeCoV alloy-based thin plate, wherein a full width at half maximum (FWHM) of a maximum peak in a range where 20 is 42 to 47° in an X-ray diffraction chart obtained by XRD analysis is different before heat-treating the FeCoV alloy-based plate material and after heat-treating the FeCoV alloy-based plate material. In another embodiment of the present invention, a full width at half maximum (FWHM) of a maximum peak in a range where 20 is 42 to 47° in an X-ray diffraction chart obtained by XRD analysis may be different before performing the stress relief heat treatment on the FeCoV alloy-based thin plate and after performing the stress relief heat treatment on the FeCoV alloy-based thin plate. The above-described contents may be applied to specific manufacturing steps of the method for manufacturing the FeCoV alloy-based thin plate.

[0213] Another aspect of the present invention relates to an FeCoV alloy-based thin plate comprising γ-austenite and residual α-ferrite, wherein an average size of grains is 50 to 100 µm. Since the FeCoV alloy-based thin plate according to the present invention includes γ-austenite and residual α-ferrite, it has an advantage of being excellent in magnetic properties and easy in post-processing, so that it can be usefully applied to various fields, particularly as a material for electric vehicles.

[0214] In another embodiment of the present invention, the average size of the grains may be 50 to 80 µm. In another embodiment of the present invention, the average size of the grains may be 50 to 60 µm. When the average size of the grains satisfies the above range, it is preferable because there is an advantage of excellent magnetic properties.

[0215] In the present invention, "average size of grains" may be based on the ASTM E112 standard. The average size of the "grains" may refer to the total average size of the γ-austenite grains and the α-ferrite grains. The average size of the γ-austenite grains may be 50 to 100 µm, preferably 50 to 80 µm, and more preferably 50 to 60 µm.

[0216] In another embodiment of the present invention, an area fraction of the γ-austenite may be larger than an area fraction of the α-ferrite. When the area fraction of the γ-austenite is larger than the area fraction of the α-ferrite, it means that cold rolling has been performed smoothly, which is preferable because the FeCoV alloy-based thin plate has an advantage of having high saturation magnetic flux density, low coercivity, and low iron loss value.

[0217] In another embodiment of the present invention, the area fraction of the γ-austenite may be 60 to 95%. In another embodiment of the present invention, the area fraction of the α-ferrite may be 5 to 50%. When the area fraction of the γ-austenite and the area fraction of the α-ferrite satisfy the above ranges, it is preferable because there is an advantage of excellent magnetic properties and easy workability.

[0218] In another embodiment of the present invention, a ratio of the number of the γ-austenite to the α-ferrite may be 80:20 to 60:40. Specifically, the number of the γ-austenite and the α-ferrite may be based on the ASTM E112 standard. Preferably, the ratio of the number of the γ-austenite to the α-ferrite may be 70:30 to 60:40. When the ratio of the number of the γ-austenite to the α-ferrite satisfies the above range, it is preferable because there is an advantage of excellent soft magnetic properties and excellent mechanical properties, particularly excellent workability.

[0219] In another embodiment of the present invention, the number of the γ-austenite grains having a size of 50 to 100 µm may be 5 to 12 based on ASTM E112. Preferably, the number of the γ-austenite grains may be 7 to 10. When the number of the γ-austenite grains satisfies the above range, it is preferable because there is an advantage of excellent post-processability.

[0220] In another embodiment of the present invention, the number of the α-ferrite grains having a size of 50 to 100 µm may be 2 to 8 based on ASTM E112. Preferably, the number of the α-ferrite grains may be 2 to 6, and more preferably 4 to 6. When the number of the α-ferrite grains satisfies the above range, it is preferable because mechanical properties are excellent.

[0221] Since the FeCoV alloy-based thin plate according to the present invention includes γ-austenite and residual α-ferrite, and the average size of grains is 50 to 100 µm, there is an advantage of excellent mechanical performance as well as magnetic properties.

[0222] The FeCoV alloy-based thin plate according to the present invention can be manufactured by the method for manufacturing an FeCoV alloy-based thin plate described above. For example, the FeCoV alloy-based thin plate may be manufactured by a method for manufacturing an FeCoV alloy-based thin plate comprising: preparing an FeCoV alloy-based plate material; heat-treating the FeCoV alloy-based plate material at 600 to 1,200°C for 10 minutes to 240 minutes to transform at least a portion of an α-ferrite phase into a γ-austenite phase; quenching the heat-treated FeCoV alloy-based plate material; and cold-rolling the quenched FeCoV alloy-based plate material to obtain an FeCoV alloy-based thin plate, but is not limited thereto. The above-described contents may be applied to specific manufacturing steps of the method for manufacturing the FeCoV alloy-based thin plate.

[0223] The average size of grains, area fractions of γ-austenite and α-ferrite, number, etc. of the FeCoV alloy-based thin plate may vary depending on the heat treatment temperature, etc. during the process of manufacturing the FeCoV alloy-based thin plate.

[0224] Another aspect of the present invention relates to a drive motor comprising: a rotor; and a stator, wherein one or more selected from the group consisting of the rotor and the stator includes a laminate in which FeCoV alloy-based thin plates are stacked, and the FeCoV alloy-based thin plate has a first peak in a range where 20 is 42 to 47°, a second peak in a range where 20 is 62 to 67°, and a third peak in a range where 20 is 80 to 85° in an X-ray diffraction chart obtained by XRD analysis.

[0225] In another embodiment of the present invention, the second peak may have a maximum peak intensity. In another embodiment of the present invention, the third peak may have a maximum peak intensity. Specifically, in the FeCoV alloy-based thin plate according to the present invention, the second peak or the third peak may exhibit the maximum peak intensity according to stress relief heat treatment in the method for manufacturing the FeCoV alloy-based thin plate. More specifically, when the stress relief heat treatment is not performed during the process of manufacturing the FeCoV alloy-based thin plate, the second peak may exhibit the maximum peak intensity, and when the stress relief heat treatment is performed, the third peak may exhibit the maximum peak intensity.

[0226] In another embodiment of the present invention, a full width at half maximum (FWHM) of the second peak may be in a range of 4.5 to 4.6°. Specifically, when the stress relief heat treatment is not performed during the process of manufacturing the FeCoV alloy-based thin plate, the FWHM of the second peak may be in the above range. In another embodiment of the present invention, the FWHM of the second peak may be in a range of 0.35 to 0.36°. Specifically, when the stress relief heat treatment is performed during the process of manufacturing the FeCoV alloy-based thin plate, the FWHM of the second peak may be in the above range.

[0227] In another embodiment of the present invention, the magnetic permeability may be 10,000 or less. Specifically, when the stress relief heat treatment is not performed during the process of manufacturing the FeCoV alloy-based thin plate, the magnetic permeability of the FeCoV alloy-based thin plate may be 7,000 or less. In another embodiment of the present invention, the magnetic permeability may be 80,000 or more. Specifically, when the stress relief heat treatment is performed during the process of manufacturing the FeCoV alloy-based thin plate, the FeCoV alloy-based thin plate may have a magnetic permeability of 80,000 or more. Specifically, the magnetic permeability may be 80,000 to 100,000.

[0228] In another embodiment of the present invention, the FeCoV alloy-based thin plate may have a saturation magnetic flux density of 2.13 to 2.38 T. Specifically, the FeCoV alloy-based thin plate may have a saturation magnetic flux density of 2.26 to 2.38 T. The saturation magnetic flux density and a magnetic flux density in a specific range to be described later are factors related to output. Specifically, when a high instantaneous output is required, such as in an electric vehicle motor, a high saturation magnetic flux density of 2 T or more is required. Since the FeCoV alloy-based thin plate according to the present invention has a high saturation magnetic flux density, it can be usefully applied to various fields, and in particular, since it can have a saturation magnetic flux density of 2 T or more, it can be particularly usefully applied to electric vehicles. In the present invention, "saturation magnetic flux density" refers to a value measured with an applied magnetic field of 1.2×10 3< kA / m using a Vibrating Sample Magnetometer (VSM).

[0229] In another embodiment of the present invention, the FeCoV alloy-based thin plate may have a magnetic flux density of 1.5 T or more induced when a magnetic field of 5,000 A / m is applied. Specifically, the magnetic flux density may be 1.87 to 2.207 T.

[0230] In another embodiment of the present invention, the FeCoV alloy-based thin plate may have a coercivity of 43 Oe or less. In another embodiment of the present invention, the FeCoV alloy-based thin plate may have a coercivity of 25 Oe or less. In another embodiment of the present invention, the FeCoV alloy-based thin plate may have a coercivity of 10 Oe or less. Specifically, the FeCoV alloy-based thin plate may have a coercivity of 1 Oe or less, more specifically 0.5 Oe or less, and most specifically 0.18 to 0.5 Oe. When the coercivity of the FeCoV alloy-based thin plate satisfies the above range, there is an advantage that it can be usefully applied to electric vehicles.

[0231] In another embodiment of the present invention, the FeCoV alloy-based thin plate may have an iron loss of 15 or less. In the present invention, "iron loss" may be measured under a condition where the magnitude of an applied magnetic field is 1 T and a frequency is 400 Hz.

[0232] In another embodiment of the present invention, the FeCoV alloy-based thin plate may contain a γ-austenite phase. In another embodiment of the present invention, the FeCoV alloy-based thin plate may further contain an α-ferrite phase. In short, the FeCoV alloy-based thin plate may contain a γ-austenite phase, or may be in the form of a composite phase containing a γ-austenite phase and an α-ferrite phase.

[0233] Since the drive motor according to the present invention uses the FeCoV alloy-based thin plate containing the γ-austenite phase or containing the γ-austenite phase and the α-ferrite phase, it exhibits excellent magnetic properties as well as excellent mechanical properties, and thus can be particularly usefully applied as a drive motor for an electric vehicle.

[0234] In another embodiment of the present invention, an average band thickness of a layered structure in which the γ-austenite phase is elongated may be 1 to 10 µm in an L cross-section that is a cross-section parallel to a rolling direction. In another embodiment of the present invention, the average band thickness of the layered structure in which the γ-austenite phase is elongated may be 1 to 5 µm in the L cross-section that is the cross-section parallel to the rolling direction. Specifically, the average band thickness of the layered structure in which the γ-austenite phase is elongated may be 2 to 4 µm in the L cross-section that is the cross-section parallel to the rolling direction. When the average band thickness satisfies the above range, it means that cold rolling of the FeCoV alloy-based thin plate was smooth, and accordingly, there is an advantage that the drive motor including the FeCoV alloy-based thin plate exhibits excellent mechanical properties as well as magnetic properties.

[0235] In another embodiment of the present invention, efficiency may be 96% or more when a total weight is 50 kg or less and an output of the motor is 220 kW. The drive motor according to the present invention may be a drive motor for an electric vehicle suitable under a condition of rotating at 12,000 to 28,000 rpm.

[0236] The rotor may include a laminate in which the above-described FeCoV alloy-based thin plates are stacked. The stator may include a laminate in which the above-described FeCoV alloy-based thin plates are stacked. The rotor and the stator may include a laminate in which the above-described FeCoV alloy-based thin plates are stacked.

[0237] The drive motor may additionally include, but is not limited to, a battery as a main power source, an inverter for converting a DC voltage supplied from the motor and the battery, a coil wound around a rotor core, an MCU for controlling voltage supply, a current controller for supplying power of the battery to the coil, and the like.

[0238] The FeCoV alloy-based thin plate may be one manufactured by any one of the methods for manufacturing an FeCoV alloy-based thin plate described above. For example, another aspect of the present invention relates to a method for manufacturing a drive motor component, comprising: preparing an FeCoV alloy-based plate material; heat-treating the FeCoV alloy-based plate material at 600 to 1,200°C for 10 minutes to 240 minutes to transform at least a portion of an α-ferrite phase into a γ-austenite phase; quenching the heat-treated FeCoV alloy-based plate material; cold-rolling the quenched FeCoV alloy-based plate material to obtain an FeCoV alloy-based thin plate; processing the FeCoV alloy-based thin plate; and stacking the processed FeCoV alloy-based thin plates. The FeCoV alloy-based thin plate has a first peak in a range where 20 is 42 to 47°, a second peak in a range where 20 is 62 to 67°, and a third peak in a range where 20 is 80 to 85° in an X-ray diffraction chart obtained by XRD analysis. The drive motor component according to the present invention can be manufactured by performing the steps of processing the FeCoV alloy-based thin plate and stacking the processed FeCoV alloy-based thin plates in the method for manufacturing the FeCoV alloy-based thin plate described above. In short, the FeCoV alloy-based thin plate may be one manufactured by the method for manufacturing an FeCoV alloy-based thin plate described above. The specific manufacturing steps of the method for manufacturing the FeCoV alloy-based thin plate may apply the contents described above.

[0239] The step of processing may be a step of processing a plurality of the FeCoV alloy-based thin plates into a core shape. The processing process may be performed using a laser, but is not limited thereto. For example, the processing process may be performed by fusing (cutting) with a laser at a scanning speed of the laser of 10,000 mm / min or more, thereby obtaining a drive motor component suitable for high efficiency of the motor, but is not limited thereto.

[0240] The step of stacking the FeCoV alloy-based thin plates may fix the FeCoV alloy-based thin plates to each other by adhesion or the like, but is not limited thereto. For example, the stacking may be performed through a coating process of applying an adhesive to both surfaces of the processed FeCoV alloy-based thin plate, a drying process of drying the FeCoV alloy-based thin plate to which the adhesive is applied to primarily cure the applied adhesive, a bonding process of stacking the dried FeCoV alloy-based thin plates and then press-drying them to secondarily and completely cure the applied adhesive to bond the stacked and processed FeCoV alloy-based thin plates, but is not limited thereto.

[0241] Another aspect of the present invention relates to a drive motor comprising: a rotor; and a stator, wherein one or more selected from the group consisting of the rotor and the stator includes a laminate in which FeCoV alloy-based thin plates are stacked, and the FeCoV alloy-based thin plate includes γ-austenite and residual α-ferrite, and an average size of grains is 50 to 100 µm. Since the drive motor according to the present invention includes a laminate in which FeCoV alloy-based thin plates including γ-austenite and residual α-ferrite and having an average grain size of 50 to 100 µm are stacked, there is an advantage of excellent mechanical properties as well as excellent magnetic properties.

[0242] In another embodiment of the present invention, the average size of the grains may be 50 to 80 µm. In another embodiment of the present invention, the average size of the grains may be 50 to 60 µm. When the average size of the grains satisfies the above range, it is preferable because there is an advantage of excellent magnetic properties.

[0243] In the present invention, "average size of grains" may be based on the ASTM E112 standard. The average size of the "grains" may refer to the total average size of the γ-austenite grains and the α-ferrite grains. The average size of the γ-austenite grains may be 50 to 100 µm, preferably 50 to 80 µm, and more preferably 50 to 60 µm.

[0244] In another embodiment of the present invention, an area fraction of the γ-austenite may be larger than an area fraction of the α-ferrite. When the area fraction of the γ-austenite is larger than the area fraction of the α-ferrite, it means that cold rolling has been performed smoothly, and thus the FeCoV alloy-based thin plate has a high saturation magnetic flux density, low coercivity, and low iron loss value, which is preferable because the magnetic properties of the drive motor are excellent.

[0245] In another embodiment of the present invention, the area fraction of the γ-austenite may be 60 to 95%. In another embodiment of the present invention, the area fraction of the α-ferrite may be 5 to 50%. When the area fraction of the γ-austenite and the area fraction of the α-ferrite satisfy the above ranges, it is preferable because there is an advantage of excellent magnetic properties.

[0246] In another embodiment of the present invention, a ratio of the number of the γ-austenite to the α-ferrite may be 80:20 to 60:40. Specifically, the number of the γ-austenite and the α-ferrite may be based on the ASTM E112 standard. Preferably, the ratio of the number of the γ-austenite to the α-ferrite may be 70:30 to 60:40. When the ratio of the number of the γ-austenite to the α-ferrite satisfies the above range, it is preferable because there is an advantage of excellent soft magnetic properties and excellent mechanical properties.

[0247] In another embodiment of the present invention, the number of the γ-austenite grains having a size of 50 to 100 µm may be 5 to 12 based on ASTM E112. Preferably, the number of the γ-austenite grains may be 7 to 10. When the number of the γ-austenite grains satisfies the above range, it is preferable because it is easy to obtain a laminate.

[0248] In another embodiment of the present invention, the number of the α-ferrite grains having a size of 50 to 100 µm may be 2 to 8 based on ASTM E112. Preferably, the number of the α-ferrite grains may be 2 to 6, and more preferably 4 to 6. When the number of the α-ferrite grains satisfies the above range, it is preferable because mechanical properties are excellent.

[0249] Since the FeCoV alloy-based thin plate according to the present invention includes γ-austenite and residual α-ferrite, and the average size of grains is 50 to 100 µm, there is an advantage of excellent mechanical performance as well as magnetic properties.

[0250] The FeCoV alloy-based thin plate according to the present invention can be manufactured by the method for manufacturing an FeCoV alloy-based thin plate described above. For example, the FeCoV alloy-based thin plate may be manufactured by a method for manufacturing an FeCoV alloy-based thin plate comprising: preparing an FeCoV alloy-based plate material; heat-treating the FeCoV alloy-based plate material at 600 to 1,200°C for 10 minutes to 240 minutes to transform at least a portion of an α-ferrite phase into a γ-austenite phase; quenching the heat-treated FeCoV alloy-based plate material; and cold-rolling the quenched FeCoV alloy-based plate material to obtain an FeCoV alloy-based thin plate, but is not limited thereto. The FeCoV alloy-based thin plate includes γ-austenite and residual α-ferrite, and an average size of grains is 50 to 100 µm. The specific manufacturing steps of the method for manufacturing the FeCoV alloy-based thin plate may apply the contents described above. The average size of grains, area fractions of γ-austenite and α-ferrite, number, etc. of the FeCoV alloy-based thin plate may vary depending on the heat treatment temperature, etc. during the process of manufacturing the FeCoV alloy-based thin plate.

[0251] In another embodiment of the present invention, efficiency may be 96% or more when a total weight is 50 kg or less and an output of the motor is 220 kW. The drive motor according to the present invention may be a drive motor for an electric vehicle suitable under a condition of rotating at 12,000 to 28,000 rpm.

[0252] The rotor may include a laminate in which the above-described FeCoV alloy-based thin plates are stacked. The stator may include a laminate in which the above-described FeCoV alloy-based thin plates are stacked. The rotor and the stator may include a laminate in which the above-described FeCoV alloy-based thin plates are stacked.

[0253] The drive motor may additionally include, but is not limited to, a battery as a main power source, an inverter for converting a DC voltage supplied from the motor and the battery, a coil wound around a rotor core, an MCU for controlling voltage supply, a current controller for supplying power of the battery to the coil, and the like.

[0254] The FeCoV alloy-based thin plate may be one manufactured by any one of the methods for manufacturing an FeCoV alloy-based thin plate described above. For example, another aspect of the present invention relates to a method for manufacturing a drive motor component, comprising: preparing an FeCoV alloy-based plate material; heat-treating the FeCoV alloy-based plate material at 600 to 1,200°C for 10 minutes to 240 minutes to transform at least a portion of an α-ferrite phase into a γ-austenite phase; quenching the heat-treated FeCoV alloy-based plate material; cold-rolling the quenched FeCoV alloy-based plate material to obtain an FeCoV alloy-based thin plate; processing the FeCoV alloy-based thin plate; and stacking the processed FeCoV alloy-based thin plates. The drive motor component according to the present invention can be manufactured by performing the steps of processing the FeCoV alloy-based thin plate and stacking the processed FeCoV alloy-based thin plates in the method for manufacturing the FeCoV alloy-based thin plate described above. In short, the FeCoV alloy-based thin plate may be one manufactured by the method for manufacturing an FeCoV alloy-based thin plate described above. The specific manufacturing steps of the method for manufacturing the FeCoV alloy-based thin plate may apply the contents described above.

[0255] The step of processing may be a step of processing a plurality of the FeCoV alloy-based thin plates into a core shape. The processing process may be performed using a laser, but is not limited thereto. For example, the processing process may be performed by fusing (cutting) with a laser at a scanning speed of the laser of 10,000 mm / min or more, thereby obtaining a drive motor component suitable for high efficiency of the motor, but is not limited thereto.

[0256] The step of stacking the FeCoV alloy-based thin plates may fix the FeCoV alloy-based thin plates to each other by adhesion or the like, but is not limited thereto. For example, the stacking may be performed through a coating process of applying an adhesive to both surfaces of the processed FeCoV alloy-based thin plate, a drying process of drying the FeCoV alloy-based thin plate to which the adhesive is applied to primarily cure the applied adhesive, a bonding process of stacking the dried FeCoV alloy-based thin plates and then press-drying them to secondarily and completely cure the applied adhesive to bond the stacked and processed FeCoV alloy-based thin plates, but is not limited thereto.

[0257] Hereinafter, preferred examples and comparative examples of the present invention will be described. However, the following examples are only preferred embodiments of the present invention, and the present invention is not limited to the following examples.<Preparation Examples 1 and 2> Preparation Example 1

[0258] After preparing Fe 49 Co 49 V 2 (Specimens 1 to 6) and Fe 48.43 Co 51.11 Cr 0.46 (Specimen 7) plate materials, heat treatment was performed on each at a temperature and for a time according to Table 1 below. Thereafter, after quenching (at a rate of 50°C / sec) by introducing them into cooling water, cold rolling was performed with a total reduction ratio of 96.7% to manufacture Fe 49 Co 49 V 2 thin plates and Fe 48.43 Co 51.11 Cr 0.46 thin plates having a thickness of 0.2 mm. In the case of Specimen 1, cold rolling was performed after slow cooling without going through the step of quenching after the heat treatment. [Table 1]Heat Treatment ConditionSaturation Magnetic Flux Density (T)Residual Magnetic Flux Density (T)Coercivity (kA / m)Coercivity (Oe)Magnetic Flux Density at 5000 A / m (T)Iron Loss @ 400 Hz, 1 T (W / kg)Driving Efficiency (T kg / W)850°C, 1 hour (excluding quenching)Specimen 12.30800.64800.02210.27782.116021.31800.5413950°C, 1 hourSpecimen 22.16850.69560.02460.30861.986514.85100.73011,050°C, 1 hourSpecimen 32.25851.05900.01970.24702.202513.03900.8661950°C, 15 minutesSpecimen 42.28370.99530.02180.27442.220713.52630.8442950°C, 30 minutesSpecimen 52.29000.74870.01560.19612.162012.51850.9146950°C, 2 hoursSpecimen 62.27751.00360.01950.24452.220013.10200.8691950°C, 1 hour (Fe 48.43 -Co 51.11 -Cr 0. 46 )Specimen 72.29300.99850.01750.23542.186813.17200.8704 Preparation Example 2

[0259] Stress relief heat treatment was performed on the Fe 49 Co 49 V 2 thin plate manufactured by heat-treating at 950°C for 30 minutes among the Fe 49 Co 49 V 2 thin plates manufactured according to Table 1, at temperatures according to Table 2 below for 30 minutes. [Table 2]Stress Relief Heat Treatment TemperatureSpecimen TypeSaturation Magnetic Flux Density (T)Residual Magnetic Flux Density (T)Coercivity (kA / m)Coercivity (Oe)Magnetic Flux Density at 5000 A / m (T)Iron Loss @ 400 Hz, 1 T (W / kg)Driving Efficiency (T kg / W)600°CSpecimen 82.130.980.0520.7081.87180.460.059016700°CSpecimen 92.2366670.7938670.0230.2896672.11066716.810670.665252800°CSpecimen 102.260.72940.02050.26052.11714.7360.76683830°CSpecimen 112.2150.59990.016850.211352.00115.98150.692989850°CSpecimen 122.2233330.7531670.0268330.3374272.02066714.531330.765014880°CSpecimen 132.260.7450.1652.0751.87541.5770.271785900°CSpecimen 142.180.7770.0640.8091.95131.150.34992 <Experimental Example>

[0260] The saturation magnetic flux density, residual magnetic flux density, coercivity, magnetic flux density value at 5000 A / m applied, iron loss, and driving efficiency of the FeCoV alloy-based thin plates manufactured according to Tables 1 and 2 were measured, and the results are shown in Tables 1 and 2 above.(1) Iron Loss

[0261] Iron loss was measured under conditions where the magnitude of the applied magnetic field was 1 T and the frequency was 400 Hz.(2) Driving Efficiency

[0262] Driving efficiency was measured by calculating (Maximum Saturation Magnetic Flux Density) / (Iron Loss × 0.2). Specifically, in order to normalize the scale value for driving efficiency, different constant values reflecting this should be multiplied to the denominator and the numerator, respectively, which can be defined as a safety factor. Here, the values multiplied to the denominator and numerator should be less than 1, and the influence of the value and the percentage of the range should be considered. Considering that the variability of the saturation magnetic flux density value is about 5 times the variability of the iron loss value, the calculation was performed by multiplying the denominator by 0.2 and the numerator by 1.0, respectively.(3) Elongation and Tensile Strength

[0263] The elongation and tensile strength of the Fe 49 Co 49 V 2 thin plate manufactured by heat treatment at 950°C for 30 minutes and the Fe 49 Co 49 V 2 thin plate manufactured by subsequently performing stress relief heat treatment at 850°C for 30 minutes were measured, and the results are shown in FIG. 1A (without stress relief heat treatment) and FIG. 1B (with stress relief heat treatment), respectively.(4) XRD Analysis

[0264] The XRD analysis results of the Fe 49 Co 49 V 2 thin plate manufactured by heat treatment at 950°C for 30 minutes and the Fe 49 Co 49 V 2 thin plate manufactured by subsequently performing stress relief heat treatment at 850°C for 30 minutes are shown in FIG. 2A (without stress relief heat treatment) and FIG. 2B (with stress relief heat treatment), respectively.(5) Magnetic Properties

[0265] Changes in the 5000 A / m magnetic flux density value and iron loss value at 400 Hz with 1 T applied for the Fe 49 Co 49 V 2 thin plate manufactured by performing stress relief heat treatment at 850°C for 30 minutes on the Fe 49 Co 49 V 2 thin plate manufactured by heat treatment at 950°C for 30 minutes are shown in FIGS. 3A and 3B.

[0266] Referring to Table 1, it can be seen that the specimens heat-treated for a certain period of time in a specific temperature range exhibit high saturation magnetic flux density values and low iron loss values. Specifically, it can be seen that the saturation magnetic flux density value varies somewhat depending on the heat treatment temperature of the specimen, and preparing for use as a motor for an electric vehicle, it can be seen that the magnetic flux density value in a specific section (5000 A / m) also varies.

[0267] Referring to FIGS. 1A and 1B, it can be seen that mechanical properties vary somewhat before and after stress relief heat treatment. In the present invention, a condition that simultaneously satisfies mechanical properties and magnetic properties, particularly high saturation magnetic flux density values and low iron loss values, is determined as the most appropriate heat treatment condition, and it can be seen that magnetic properties and mechanical properties are most excellent under heat treatment conditions at a specific temperature when compared with magnetic property values.

[0268] Referring to FIGS. 2A and 2B, although there were differences in peak width and height of the specimen before and after stress relief heat treatment, the 2-theta positions where peaks were formed were almost identical. This means that they are composed of the same phase, and it is understood that rather than a new phase being generated through heat treatment, the regularity level changed from a disordered structure of the formed phase to an ordered structure. It is judged that cold rolling is possible due to the irregular structure formed before cold rolling, and as a stable phase at room temperature is formed in the process of removing stress after rolling to secure regularity, magnetic properties as well as mechanical properties are improved.

[0269] Referring to FIGS. 3A and 3B, it can be seen that the specimen subjected to stress relief heat treatment exhibits a high saturation magnetic flux density value (2.26 T) and a low iron loss value (14.248 W / kg), confirming that it exhibits a level similar to that of a soft magnetic thin plate (Fe 49 Co 49 V 2 ) manufactured through a conventional complicated process.<Preparation Example 3>

[0270] After preparing an Fe 49 Co 49 V 2 plate material, heat treatment was performed at 950°C for 1 hour and at 1,100°C for 1 hour, respectively. Thereafter, after quenching (at a rate of 50°C / sec) by introducing it into cooling water, cold rolling was performed with a total reduction ratio of96.7% to manufacture an Fe 49 Co 49 V 2 thin plate having a thickness of 0.2 mm.<Experimental Example>

[0271] An image measured using a scanning electron microscope (SEM: JEOL 7600F) of a cross-section of a specimen manufactured by heat-treating at 950°C for 1 hour during the manufacturing process of Preparation Example 3 is shown in FIG. 4. In addition, images of side cross-sectional structures of Fe 49 Co 49 V 2 thin plates manufactured by heat-treating at 950°C and 1,100°C for 1 hour were taken using an optical microscope (OM: Olympus DSX500) and then comparatively analyzed for each condition, and the results are shown in FIGS. 5 to 7 (FIGS. 5 and 7: 950°C heat-treated specimen, FIG. 6: 1,100°C heat-treated specimen).

[0272] Referring to FIG. 4, it can be confirmed that a composite phase is formed in which a γ-austenite phase is distributed as a whole and some residual α-ferrite phase is included. In addition, when cold rolling was performed, it was confirmed that cold rolling proceeded smoothly without cracking or bursting, and the side of the thin plate rolled to a thickness of 0.2 mm showed a uniform striped shape, proving that the cold rolling process was performed smoothly. Referring to FIGS. 4 to 7, the structure quenched under appropriate conditions mostly consists of a γ-austenite phase capable of elongation, and shows a composite structure in which some α-ferrite phase coexists. It was confirmed that it is preferable that the structure of the cross-section forms a stripe structure, and the interval thereof represents a level of approximately 1 to 3 µm.<Preparation Example 4>

[0273] An FeCoV alloy melt was prepared by melting iron alloy components at a temperature of 1,700°C using a vacuum melting method. The alloy melt was injected into a mold and cooled and crystallized at a casting speed of 75 mm / min to manufacture an ingot (Fe 49 Co 49 V 2 , Fe 47.79, Co 50.43, V 1.78 wt%: weight ratio). The manufactured ingot was cut to a thickness of 30 mm and then hot-rolled using a steel rolling mill to obtain a plate material. At this time, the rolling start temperature was 950°C, the rolling end temperature was 1,150°C, and rolling was performed with a total reduction ratio of 80% in 5 passes to have a final thickness of around 6 mm. Thereafter, the obtained plate material was heat-treated at 950°C and 1,100°C for 1 hour, respectively. Then, after quenching (at a rate of 50°C / sec) by introducing it into cooling water, cold rolling was performed with a total reduction ratio of 96.7% to manufacture an Fe 49 Co 49 V 2 thin plate having a thickness of 0.2 mm.<Experimental Example> (1) XRD Measurement

[0274] XRD patterns of the cast ingot manufactured in the process of manufacturing the Fe 49 Co 49 V 2 thin plate according to Preparation Example 4, the specimen before heat treatment (after hot rolling), and the specimen after 950°C heat treatment and quenching (after cold rolling) were compared and shown in FIGS. 8A to 8C, respectively. XRD: Using model name (DMAX2500) equipment, qualitative and quantitative analysis was performed after obtaining XRD diffraction patterns in a 2-theta value range of 10 to 100 degrees.(2) Structure Comparison

[0275] Images were measured using scanning electron microscope (SEM: model name JEOL 7600F) equipment for the cast ingot manufactured in the process of manufacturing the Fe 49 Co 49 V 2 thin plate according to Preparation Example 4, and specimens after heat treatment according to 950°C and 1,100°C and quenching (after cold rolling), and then grain size and phase analysis were performed, and the results are shown in FIGS. 9A to 9C, respectively.(3) GDS Surface Analysis

[0276] In the process of manufacturing the Fe 49 Co 49 V 2 thin plate according to Preparation Example 4, specimens of the Fe 49 Co 49 V 2 thin plate manufactured in the same manner as in Preparation Example 4 by changing the heat treatment temperature to 700°C, 850°C, and 900°C with the specimen before heat treatment (after hot rolling) were analyzed using GDS surface analysis equipment, and the results are shown in FIGS. 10A to 10D, respectively. Specifically, each specimen was prepared and surface analysis was performed while cutting the surface in the depth direction from the surface of the plate material or thin plate, and the experimental conditions are as follows.<Experimental Conditions>

[0277] Method: Zn Galv RF Lamp type: RF (Radio frequency) Analysis area: 4 mΦ Calibration factor: 0.70 Analysis conditions: 700 V, 30 mA, 21 W Depth setting: 0 to end sec, 100 points / sec Plot point: 8000, Smoothing: 3

[0278] Referring to FIGS. 8A to 8C, in the case of the cast ingot, only a single phase, that is, an Fe phase, was detected as a result of XRD analysis, whereas in the specimen before heat treatment (after hot rolling), many oxide phase peaks were detected in addition to the Fe single phase. In particular, some oxides existed even after the quenching heat treatment that changes the α-ferrite structure to the γ-austenite structure. The most important point is that the α-ferrite structure changes to the γ-austenite structure, so that the height and full width at half maximum (FWHM) of the existing α peak change on XRD, and a γ peak that was not seen previously is found. Also, even in the same Fe-α peak, in the case of the cast ingot, a (100) plane peak appears around 45 degrees, a (200) peak around 60 degrees, and a (211) peak around 85 degrees. Here, in the cast ingot, that is, a material having a complete ordered structure by slow cooling, the (100) plane peak rises highest and the rest are relatively very low, whereas in the specimen before heat treatment (after hot rolling) and the sample after heat treatment and quenching (after cold rolling), the peak of the (100) plane, which is the main peak, decreases, while the height of the (211) plane peak greatly increases. From this, it can be confirmed that even with the same structure, the ordered structure becomes a disordered structure or the disordered structure becomes ordered depending on the process or heat treatment.

[0279] Referring to FIGS. 9A to 9C, in the case of the cast ingot, grain boundaries are clear and coarse grain boundaries of a level of 100 to 500 µm are shown, whereas in the case of the specimen subjected to high-temperature heat treatment and quenching, it simultaneously contains a fine structure and a coarse structure depending on conditions, or contains fine grains of around 100 µm. Whether defects occur in the cold rolling process may depend on such differences in structure and crystal structure.

[0280] Meanwhile, surface analysis was performed using GDS analysis equipment to observe plate surface changes before heat treatment and through heat treatment for each temperature condition. Oxygen and carbon were hardly measured on the surface of the plate material not subjected to heat treatment, but as the heat treatment temperature increased, surface oxygen and carbon components were measured up to a depth of 0.1 to 0.2 µm, and phase fractions of Fe and Co were also distributed quantitatively almost identically as the heat treatment temperature increased and as they penetrated in the depth direction. Since the steel plate used in the experiment is composed of 49Fe-49Co-2V components, when the V element is solid-soluted and then a precipitation phase is generated as the heat treatment temperature increases to cause precipitation hardening, the quantitative ratio of Co and Fe elements becomes almost the same. Therefore, according to the depth profile analysis result, it is estimated that a precipitation phase of V element is formed under a heat treatment temperature condition of 880°C or higher.<Preparation Example 5>

[0281] An FeCoV alloy melt was prepared by melting iron alloy components at a temperature of 1,700°C using a vacuum melting method. The alloy melt was injected into a mold and cooled and crystallized at a casting speed of 75 mm / min to manufacture an ingot (Fe 49 Co 49 V 2 , Fe 47.79, Co 50.43, V 1.78 wt%: weight ratio). The manufactured ingot was cut to a thickness of 30 mm and then hot-rolled using a steel rolling mill to obtain a plate material. At this time, the rolling start temperature was 950°C, the rolling end temperature was 1,150°C, and rolling was performed with a total reduction ratio of 80% in 5 passes to have a final thickness of around 6 mm. Thereafter, the obtained plate material was heat-treated at 950°C for 30 minutes. Then, after quenching (at a rate of 50°C / sec) by introducing it into cooling water, cold rolling was performed with a total reduction ratio of 96.7% to manufacture an Fe 49 Co 49 V 2 thin plate having a thickness of 0.2 mm. Thereafter, annealing heat treatment was performed at a temperature of 950°C for 30 minutes.<Experimental Example> (1) XRD Measurement

[0282] XRD patterns of specimen #1 immediately after cold rolling (before annealing heat treatment) and specimen #2 after annealing heat treatment, manufactured in the process of manufacturing the Fe 49 Co 49 V 2 thin plate according to Preparation Example 5, were compared and shown in FIGS. 11A and 11B, and the intensity and FWHM are shown in Table 3 below. [Table 3]Specimen No.Position (°)Norm.IntensityFWHM(°)#121.262734.564.523444.541296.410.639464.95052480.890.630982.36621195.020.7229#244.69529.680.359765.09155904.410.081182.463536456.70.0865 (2) Magnetic Permeability Measurement

[0283] The hysteresis of Specimen #1 and Specimen #2 was measured, and the results are shown in FIG. 12.

[0284] Referring to FIGS. 11A and 11B and Table 3, in the case of Specimen #1, a typical preferred orientation form in which intensity decreases in a very wide region appears. On the other hand, in the case of Specimen #2, it appears to have multiple peaks in the rocking curve, which may occur when grains like very well-aligned single crystals are arranged in multiple directions. That is, in terms of crystallinity (or ordering), comparing Specimen #1 and Specimen #2, i.e., the specimen immediately after cold rolling and the specimen immediately after annealing heat treatment, it means that the crystallinity of Specimen #2 is very excellent when predicted in terms of the main direction plane of the peak and the full width at half maximum (FWHM). This is because the microstructure before heat treatment forms an ordered structure because it underwent slow cooling in the previous process, and constitutes an α-ferrite phase in the form of a Body-Centered Cubic (BCC) structure.

[0285] Since this structure has relatively low elongation, it may cause problems in the cold rolling process. Therefore, a heat treatment process was performed to change the phase to a γ-austenite phase, which is a Face-Centered Cubic (FCC) structure, while configuring a disordered structure or an ordered-disordered mixed structure through microstructure control heat treatment. Since the soft magnetic properties, such as magnetic properties, i.e., saturation magnetic flux density and iron loss, increase only when the structure has an ordered structure again after cold rolling, XRD changes before and after heat treatment were compared. When measuring the magnetic properties of Specimen #1 which did not undergo stress relief heat treatment after cold rolling and Specimen #2 after performing stress relief heat treatment, they appear as shown in the graph of FIG. 12. They showed a very large difference in soft magnetic properties, i.e., the slope of the hysteresis graph, the inner area, and the magnetic flux density value in the same frequency region.<Preparation Example 6>

[0286] An FeCoV alloy melt was prepared by melting iron alloy components according to Table 4 at a temperature of 1,700°C using a vacuum melting method. The alloy melt was injected into a mold and cooled and crystallized at a casting speed of 75 mm / min to manufacture an ingot. The manufactured ingot was cut to a thickness of 30 mm and then hot-rolled using a steel rolling mill to obtain a plate material. At this time, the rolling start temperature was 950°C, the rolling end temperature was 1,150°C, and rolling was performed with a total reduction ratio of 80% in 5 passes to have a final thickness of around 6 mm. Thereafter, the obtained plate material was heat-treated at 950°C for 30 minutes. Then, after quenching (at a rate of 50°C / sec) by introducing it into cooling water, cold rolling was performed with a total reduction ratio of 96.7% to manufacture an FeCoV alloy-based thin plate having a thickness of 0.2 mm, and then soft magnetic performance was measured. [Table 4]Alloy Component (at%, atomic ratio)Saturation Magnetic Flux Density (Bs) / TCoercivity (H2.04e / Oe)FeCoVNiCrNb49492---2.380.185535181-2.0433.1258252123-1.9943.436020215211.9623.2763201151-2.0126.156620210112.0442.06 <Preparation Examples 7 and 8> Preparation Example 7

[0287] An FeCoV alloy melt was prepared by melting iron alloy components at a temperature of 1,700°C using a vacuum melting method. The alloy melt was injected into a mold, and cooled and crystallized at a casting speed of 75 mm / min to manufacture an ingot (Fe 49 Co 49 V 2 , Fe 47.79, Co 50.43, V 1.78 wt%: weight ratio). The manufactured ingot was cut to a thickness of 30 mm and then hot-rolled using a steel rolling mill to obtain a plate material. At this time, the rolling start temperature was 950°C, the rolling end temperature was 1,150°C, and the rolling was performed with a total reduction ratio of 80% in 5 passes to have a final thickness of around 6 mm. Thereafter, the obtained plate material was heat-treated at 950°C and 1,100°C for 1 hour, respectively. Then, after quenching (at a rate of 50°C / sec) by introducing it into cooling water, cold rolling was performed with a total reduction ratio of 96.7% to manufacture an Fe 49 Co 49 V 2 thin plate having a thickness of 0.2 mm.Preparation Example 8

[0288] An FeCoV alloy melt was prepared by melting iron alloy components at a temperature of 1,700°C using a vacuum melting method. The alloy melt was injected into a mold, and cooled and crystallized at a casting speed of 75 mm / min to manufacture an ingot (Fe 49 Co 49 V 2 , Fe 47.79, Co 50.43, V 1.78 wt%: weight ratio). At this time, the alloy melt was melted under argon gas. The manufactured ingot was cut to a thickness of 6 mm to manufacture a cast material. Thereafter, the cast material was heat-treated at 950°C and 1,100°C for 2 hours, respectively, quenched (at a rate of 50°C / sec) by introducing it into cooling water, and then cold rolling was performed with a total reduction ratio of 96.7% to manufacture an Fe 49 Co 49 V 2 thin plate having a thickness of 0.2 mm.<Experimental Example> (1) XRD Measurement

[0289] The cast ingot (Specimen 1) manufactured in the process of manufacturing the Fe 49 Co 49 V 2 thin plate according to Preparation Example 7, the specimen immediately after hot rolling (before heat treatment) (Specimen 2), the specimen after heat treatment at 950°C and quenching (after cold rolling, Specimen 3), and the specimen after heat treatment at 950°C and quenching (Specimen 4) manufactured in the process of manufacturing the Fe 49 Co 49 V 2 thin plate according to Preparation Example 8 were subjected to qualitative and quantitative analysis after obtaining XRD diffraction patterns in a 2-theta value range of 10 to 100 degrees using XRD (model name DMAX2500) equipment, and the results are shown in FIGS. 13A to 13D, respectively.(2) Structure Comparison

[0290] Images were measured using scanning electron microscope (SEM: model name JEOL 7600F) equipment for the cast ingot (Specimen 5) manufactured in the process of manufacturing the Fe 49 Co 49 V 2 thin plate according to Preparation Example 7, specimens after heat treatment at 1,100°C and 950°C and quenching immediately after hot rolling (after cold rolling, Specimens 6 and 7, respectively), and specimens after heat treatment at 1,100°C and 950°C and quenching (Specimens 8 and 9, respectively) manufactured in the process of manufacturing the Fe 49 Co 49 V 2 thin plate according to Preparation Example 8, and the results are shown in FIGS. 14A to 14E.(3) Soft Magnetic Performance Evaluation

[0291] The soft magnetic performance of the Fe 49 Co 49 V 2 thin plates manufactured by performing heat treatment at 950°C among Preparation Examples 7 and 8 was evaluated, and the results are shown in Table 5 below. [Table 5]Saturation Magnetic Flux Density (T)Coercivity (Oe)Magnetic Flux Density at 5000 A / m (T)Core Loss @ 400 Hz, 1 T (W / kg)Preparation Example 7 (Hot Rolling + Cold Rolling)2.3180.1632.18412.565Preparation Example 8 (Cold Rolling)2.2020.2292.03117.591

[0292] Referring to FIGS. 13A to 13D, 14A to 14E, and Table 5, it can be seen that the thin plate manufactured as the FeCoV alloy-based thin plate according to the present invention has high saturation magnetic flux density and low coercivity and iron loss (core loss) values even without performing hot rolling.<Preparation Example 9>

[0293] Heat treatment was performed on FeCoV alloy-based plate materials at 950°C and 1,100°C for 1 hour, respectively. Thereafter, after quenching (at a rate of 50°C / sec) by introducing them into cooling water, cold rolling was performed with a total reduction ratio of 96.7% to manufacture Fe 49 Co 49 V 2 thin plates having a thickness of 0.2 mm.<Experimental Example> (1) Structure Comparison

[0294] Images of the Fe 49 Co 49 V 2 thin plates manufactured according to Preparation Example 9 were measured using scanning electron microscope (SEM: model name JEOL 7600F) equipment, and the results are shown in FIGS. 15A and 15B.(2) Grains and Number of Structures

[0295] The grains, γ-austenite phase, and α-ferrite phase of the Fe 49 Co 49 V 2 thin plate manufactured according to Preparation Example 9 were observed and measured according to the ASTM E112 standard, and the results are shown in Table 6 below. [Table 6]Average Size of GrainsArea Fraction of γ-AusteniteArea Fraction of α-FerriteNumber of γ-AusteniteNumber of α-FerriteRatio of Number of γ-Austenite Phase in Total StructureHeat treatment temperature 1,100°C263.427732.26.824 %Heat treatment temperature 950°C57.263.736.38.95.462 % (3) Soft Magnetic Properties

[0296] The soft magnetic properties of the Fe 49 Co 49 V 2 thin plate manufactured according to Preparation Example 9 were measured, and the results are shown in Table 7 below. [Table 7]Saturation Magnetic Flux Density (T)Coercivity (Oe)Magnetic Flux Density at 5000 A / m (T)Core Loss @ 400 Hz, 1 T (W / kg)Heat treatment temperature 1,100°C2.1150.1982.01914.479Heat treatment temperature 950°C2.3180.1632.18412.565

[0297] Referring to FIGS. 15A and 15B, it can be seen that the relatively bright portion is the γ-austenite phase and the relatively dark portion is the α-ferrite phase, indicating a composite phase containing the γ-austenite phase and the α-ferrite phase.

[0298] Referring to Table 7, it can be seen that the FeCoV alloy-based thin plate according to the present invention has a high saturation magnetic flux density and low coercivity and core loss values.

[0299] The present invention is not limited to the above-described embodiments but may be manufactured in various different forms, and those skilled in the art to which the present invention pertains will understand that the present invention may be implemented in other specific forms without departing from the technical spirit or essential features thereof. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not limiting.

Examples

preparation example 1

Preparation Example 1

[0258]After preparing Fe 49 Co 49 V 2 (Specimens 1 to 6) and Fe 48.43 Co 51.11 Cr 0.46 (Specimen 7) plate materials, heat treatment was performed on each at a temperature and for a time according to Table 1 below. Thereafter, after quenching (at a rate of 50°C / sec) by introducing them into cooling water, cold rolling was performed with a total reduction ratio of 96.7% to manufacture Fe 49 Co 49 V 2 thin plates and Fe 48.43 Co 51.11 Cr 0.46 thin plates having a thickness of 0.2 mm. In the case of Specimen 1, cold rolling was performed after slow cooling without going through the step of quenching after the heat treatment.

[Table 1]

Heat Treatment ConditionSaturation Magnetic Flux Density (T)Residual Magnetic Flux Density (T)Coercivity (kA / m)Coercivity (Oe)Magnetic Flux Density at 5000 A / m (T)Iron Loss @ 400 Hz, 1 T (W / kg)Driving Efficiency (T kg / W)

850°C, 1 hour (excluding quenching)Specimen 12.30800.64800.02210.27782.116021.31800.5413

950°C, 1 hourSpecimen 22.1...

preparation example 2

Preparation Example 2

[0259]Stress relief heat treatment was performed on the Fe 49 Co 49 V 2 thin plate manufactured by heat-treating at 950°C for 30 minutes among the Fe 49 Co 49 V 2 thin plates manufactured according to Table 1, at temperatures according to Table 2 below for 30 minutes.

[Table 2]

Stress Relief Heat Treatment TemperatureSpecimen TypeSaturation Magnetic Flux Density (T)Residual Magnetic Flux Density (T)Coercivity (kA / m)Coercivity (Oe)Magnetic Flux Density at 5000 A / m (T)Iron Loss @ 400 Hz, 1 T (W / kg)Driving Efficiency (T kg / W)

600°CSpecimen 82.130.980.0520.7081.87180.460.059016

700°CSpecimen 92.2366670.7938670.0230.2896672.11066716.810670.665252

800°CSpecimen 102.260.72940.02050.26052.11714.7360.76683

830°CSpecimen 112.2150.59990.016850.211352.00115.98150.692989

850°CSpecimen 122.2233330.7531670.0268330.3374272.02066714.531330.765014

880°CSpecimen 132.260.7450.1652.0751.87541.5770.271785

900°CSpecimen 142.180.7770.0640.8091.95131.150.34992

[0260]The saturation...

preparation example 7

Preparation Example 7

[0287]An FeCoV alloy melt was prepared by melting iron alloy components at a temperature of 1,700°C using a vacuum melting method. The alloy melt was injected into a mold, and cooled and crystallized at a casting speed of 75 mm / min to manufacture an ingot (Fe 49 Co 49 V 2 , Fe 47.79, Co 50.43, V 1.78 wt%: weight ratio). The manufactured ingot was cut to a thickness of 30 mm and then hot-rolled using a steel rolling mill to obtain a plate material. At this time, the rolling start temperature was 950°C, the rolling end temperature was 1,150°C, and the rolling was performed with a total reduction ratio of 80% in 5 passes to have a final thickness of around 6 mm. Thereafter, the obtained plate material was heat-treated at 950°C and 1,100°C for 1 hour, respectively. Then, after quenching (at a rate of 50°C / sec) by introducing it into cooling water, cold rolling was performed with a total reduction ratio of 96.7% to manufacture an Fe 49 Co 49 V 2 thin plate having a ...

Claims

1. An FeCoV alloy-based thin plate, comprising: γ-austenite; and residual α-ferrite, wherein an average size of grains is 50 to 100 µm.

2. The FeCoV alloy-based thin plate of claim 1, wherein: an area fraction of the γ-austenite is larger than an area fraction of the α-ferrite.

3. The FeCoV alloy-based thin plate of claim 2, wherein: the area fraction of the γ-austenite is 60% to 95%.

4. The FeCoV alloy-based thin plate of claim 2, wherein: the area fraction of the α-ferrite is 5% to 50%.

5. The FeCoV alloy-based thin plate of claim 1, wherein: a ratio of the number of the γ-austenite to the α-ferrite is 80:20 to 60:40.

6. The FeCoV alloy-based thin plate of claim 1, wherein: the number of the γ-austenite grains having a size of 50 to 100 µm is 5 to 12 based on ASTM E112.

7. The FeCoV alloy-based thin plate of claim 1, wherein: the number of the α-ferrite grains having a size of 50 to 100 µm is 2 to 8 based on ASTM E112.

8. An FeCoV alloy-based thin plate, having: a first peak in a range where 20 is 42° to 47°; a second peak in a range where 20 is 62° to 67°; and a third peak in a range where 20 is 80° to 85°, in an X-ray diffraction chart obtained by XRD analysis.

9. The FeCoV alloy-based thin plate of claim 8, wherein: the second peak has a maximum peak intensity.

10. The FeCoV alloy-based thin plate of claim 8, wherein: the third peak has a maximum peak intensity.

11. The FeCoV alloy-based thin plate of claim 8, wherein: a full width at half maximum (FWHM) of the second peak is in a range of 4.5° to 4.6°.

12. The FeCoV alloy-based thin plate of claim 8, wherein: a full width at half maximum (FWHM) of the second peak is in a range of 0.35° to 0.36°.

13. The FeCoV alloy-based thin plate of claim 8, wherein: an average band thickness of a layered structure in which the γ-austenite phase is elongated is 1 to 10 µm in an L cross-section that is a cross-section parallel to a rolling direction.

14. The FeCoV alloy-based thin plate of claim 13, wherein: the average band thickness of the layered structure in which the γ-austenite phase is elongated is 1 to 5 µm in the L cross-section that is the cross-section parallel to the rolling direction.

15. A method for manufacturing an FeCoV alloy-based thin plate, comprising: preparing an FeCoV alloy-based plate material; heat-treating the FeCoV alloy-based plate material at 600°C to 1,200°C for 10 minutes to 240 minutes to transform at least a portion of an α-ferrite phase into a γ-austenite phase; quenching the heat-treated FeCoV alloy-based plate material; and cold-rolling the quenched FeCoV alloy-based plate material to obtain an FeCoV alloy-based thin plate.

16. The method for manufacturing an FeCoV alloy-based thin plate of claim 15, wherein: the heat-treating is performed at 730°C to 1,200°C.

17. The method for manufacturing an FeCoV alloy-based thin plate of claim 15, wherein: the heat-treating is performed for 30 minutes to 240 minutes.

18. The method for manufacturing an FeCoV alloy-based thin plate of claim 15, further comprising: performing a stress relief heat treatment on the FeCoV alloy-based thin plate after the step of obtaining the FeCoV alloy-based thin plate.

19. The method for manufacturing an FeCoV alloy-based thin plate of claim 18, wherein: the stress relief heat treatment is performed at 650°C to 950°C for 10 minutes to 120 minutes.

20. The method for manufacturing an FeCoV alloy-based thin plate of claim 15, wherein: the quenching is performed at a cooling rate of 10°C / sec to 300°C / sec.

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