Non-oriented electrical steel sheet, manufacturing method therefor, and motor

Abstract

A non-oriented electrical steel sheet, a method for manufacturing the non-oriented electrical steel sheet, and a motor, according to one embodiment of the present invention, comprise 0.1-1.6 wt% of silicon (Si), 0.2-0.4 wt% of manganese (Mn), 0.1-0.5 wt% of aluminum (Al), 0.003 wt% or less of carbon (C), 0.003 wt% or less of sulfur (S), 0.015 wt% or less of phosphorus (P), 0.003 wt% or less of nitrogen (N), and the balance of iron (Fe) and other inevitable impurities, wherein the orientation fraction of the final texture thereof satisfies relation 1, and thus a non-oriented electrical steel sheet with excellent magnetic properties can be provided.

Description

Non-oriented electrical steel sheet, its manufacturing method, and motor

[0001] The present invention relates to a non-oriented electrical steel sheet, a method for manufacturing a non-oriented electrical steel sheet, and a motor.

[0002] Demand for motors and transformers is increasing as industrialization continues worldwide, and demand for core materials for industrial motors is also steadily increasing in line with the electrification and automation trends in various business sectors.

[0003] Non-oriented electrical steel is used as the core material for motors. This steel plays a crucial role in determining the motor's energy efficiency, requiring low core loss and high magnetic flux density. Core loss refers to the energy loss generated during the magnetization process, while magnetic flux density refers to the power that generates power.

[0004] For motors mounted in automobiles, the focus has been on technology and product development for low core loss in non-oriented electrical steel sheets, as they rotate at high speeds exceeding 200 Hz during both constant and high-speed driving. Conversely, for most industrial drive equipment, motor specifications are determined by coercive force and magnetic flux density characteristics rather than core loss characteristics, making these characteristics more important.

[0005] The magnetic flux density of non-oriented electrical steel is determined by the fraction of iron (Fe) atoms in the steel and the arrangement of the steel grains. The magnetic anisotropy of iron atoms causes the magnetic field of iron single atoms to be <100> The direction can easily be magnetized. Therefore, <100> It is necessary to create a uniform directional aggregate structure throughout the board.

[0006] Non-oriented electrical steel sheets are manufactured through a series of processes: steelmaking / casting, hot rolling, cold rolling, cold annealing, and coating. Technologies are being developed to produce electrical steel sheets with superior magnetic properties by optimizing each process condition. In particular, since general steel sheets undergo a cold rolling process without hot annealing after hot rolling, it is crucial to ensure a uniform hot-rolled steel sheet structure.

[0007] The present invention has been devised to solve the above problems, and the object of the present invention is to provide a non-oriented electrical steel sheet and a method for manufacturing a non-oriented electrical steel sheet having excellent magnetic properties by improving the aggregate structure, and to provide a motor having high energy efficiency.

[0008] The tasks of the present invention are not limited to the tasks mentioned above, and other tasks not mentioned will be clearly understood by those skilled in the art from the description below.

[0009] A non-oriented electrical steel sheet according to one embodiment of the present invention contains 0.1 to 1.6 wt% of silicon (Si), 0.2 to 0.4 wt% of manganese (Mn), 0.1 to 0.5 wt% of aluminum (Al), 0.003 wt% or less of carbon (C), 0.003 wt% or less of sulfur (S), 0.015 wt% or less of phosphorus (P), 0.003 wt% or less of nitrogen (N), and the remainder iron (Fe) and other unavoidable impurities, and the orientation fraction of the final aggregate structure satisfies the following Equation 1.

[0010] [Formula 1]

[0011] 0.1 ≤ V1 / V2 ≤ 0.7

[0012] (However, V1 is {001} <120> , {114} <481> and {113} <251> represents the sum of the set tissue fractions, and V2 is {111} <112> , {334} <483> and {223} <110> (represents the sum of the fractions of collective organization)

[0013] Additionally, the magnetic properties can satisfy the following equation 2.

[0014] [Formula 2]

[0015] 1.7 ≤ [(ΔB / ΔH)*1000] ≤ 3.0

[0016] (However, ΔB refers to the change in the number of magnetic flux lines per unit area generated from the material, and ΔH refers to the change in the strength of the magnetic field applied through an external electromagnet.)

[0017] Additionally, the thickness may be less than 1.0 mm.

[0018] Also, iron loss (W 15 / 50 ) may be 6.0 W / kg or less, and the magnetic flux density (B1) may be 0.20 T or more.

[0019] A method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention comprises a first step of preparing a steel material containing 0.1 to 1.6 wt% of silicon (Si), 0.2 to 0.4 wt% of manganese (Mn), 0.1 to 0.5 wt% of aluminum (Al), 0.003 wt% or less of carbon (C), 0.003 wt% or less of sulfur (S), 0.015 wt% or less of phosphorus (P), 0.003 wt% or less of nitrogen (N), and the remainder iron (Fe) and other unavoidable impurities, a second step of hot-rolling the steel material to form a hot-rolled steel sheet, a third step of cold-rolling the hot-rolled steel sheet to form a cold-rolled steel sheet, and a fourth step of cold-rolling and annealing the cold-rolled steel sheet.

[0020] Additionally, the second step may further include a reheating step of heat-treating the steel material at 1000 to 1250°C for 350 to 850 minutes.

[0021] Additionally, the third step may have a final compression ratio of 70 to 85%.

[0022] Additionally, the fourth step can be performed by heat treatment at 800 to 1100°C.

[0023] A motor according to one embodiment of the present invention is manufactured by punching and laminating the non-oriented electrical steel sheet.

[0024] Additionally, the torque coefficient may be greater than 0.210 N·m / Amp.

[0025] Additionally, the spot rate can be greater than 93.8%.

[0026] According to one embodiment of the present invention, a non-oriented electrical steel sheet having excellent magnetic properties and a method for manufacturing a non-oriented electrical steel sheet can be implemented, and a motor with high energy efficiency can be implemented.

[0027] The effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the claims.

[0028] FIG. 1 is a flowchart illustrating a method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention.

[0029] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present invention. However, the present invention is not limited or restricted by the following embodiments.

[0030] Additionally, when a component (or region, layer, portion, etc.) is referred to as being "on," "connected to," or "coupled to" another component, it means that it can be directly placed / connected / coupled to the other component, or that a third component may be placed between them.

[0031] Terms such as "include" or "have" should be understood to specify the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but not to exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0032] In order to clearly explain the present invention, a detailed description of a part that is irrelevant to the description or a related known technology that may unnecessarily obscure the gist of the present invention has been omitted, and when adding reference signs to components of each drawing in this specification, the same or similar reference signs are attached to the same or similar components throughout the specification.

[0033] In addition, terms and words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0034] Unless otherwise specified, the notation 'A to B' for numerical values ​​A and B means 'A or more and B or less'. In such notation, if a unit is attached only to numerical value B, the unit shall be applied to numerical value A as well.

[0035] Also, unless otherwise stated, 1 ppm is 0.0001 wt%.

[0036] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0037]

[0038] Non-oriented electrical steel sheets and motors

[0039] A non-oriented electrical steel sheet according to one embodiment of the present invention contains 0.1 to 1.6 wt% of silicon (Si), 0.2 to 0.4 wt% of manganese (Mn), 0.1 to 0.5 wt% of aluminum (Al), 0.003 wt% or less of carbon (C), 0.003 wt% or less of sulfur (S), 0.015 wt% or less of phosphorus (P), 0.003 wt% or less of nitrogen (N), and the remainder iron (Fe) and unavoidable impurities.

[0040] Hereinafter, the role and content of alloy elements included in a non-oriented electrical steel sheet according to one embodiment of the present invention will be described in detail.

[0041]

[0042] Silicon (Si)

[0043] Silicon (Si) is a major additive element in electrical steel, which can improve magnetic properties by increasing the resistivity of the steel and reducing eddy current loss. If the silicon content is too low, the increase in resistivity may not be sufficient, and the effect of improving core loss may not be sufficient. On the other hand, if the silicon content is excessive, the material becomes more brittle, which may result in poor cold-rollability and punchability, and increased production costs. In addition, as the silicon content increases, the magnetic permeability and magnetic flux density may decrease. Therefore, the non-oriented electrical steel sheet according to one embodiment of the present invention may contain 0.1 to 1.6 wt% of silicon.

[0044]

[0045] manganese (Mn)

[0046] Manganese (Mn), like silicon (Si), improves magnetic properties by increasing resistivity and reducing iron loss. It can also be added to enhance the grain structure, which is beneficial for magnetic properties. Insufficient manganese content reduces the resistivity-enhancing effect, potentially leading to increased high-frequency iron loss.

[0047] In addition, manganese can combine with sulfur (S) present in steel to form sulfides such as MnS. If the manganese content is too low, fine sulfides may precipitate, which may reduce magnetism. On the other hand, if the manganese content is excessive, a coarse secondary phase may be formed and a {111} texture that is unfavorable for magnetization may be formed, which may deteriorate magnetic properties. Therefore, the non-oriented electrical steel sheet according to one embodiment of the present invention may contain manganese in an amount of 0.2 to 0.4 wt%.

[0048]

[0049] Aluminum (Al)

[0050] Aluminum (Al), along with silicon (Si) and manganese (Mn), is an element that increases resistivity and reduces iron loss, thereby improving magnetic properties. It can also improve rollability and reduce magnetic anisotropy, thereby reducing magnetic deviation. When the aluminum content is less than 0.1 wt%, the increase in resistivity is insufficient, which may increase high-frequency iron loss. Conversely, when the aluminum content exceeds 0.5 wt%, excessive nitride formation may occur, reducing magnetic properties. Therefore, a non-oriented electrical steel sheet according to an embodiment of the present invention may contain 0.1 to 0.5 wt% of aluminum.

[0051]

[0052] carbon (C)

[0053] Carbon (C) can increase iron loss by combining with titanium (Ti), niobium (Nb), etc., to form carbides such as TiC and NbC. When carbon exceeds 0.003 wt%, it can cause self-aging, which can deteriorate magnetic properties. Therefore, a non-oriented electrical steel sheet according to an embodiment of the present invention can contain carbon in an amount of 0.003 wt% or less.

[0054]

[0055] Yellow (S)

[0056] Sulfur (S) is an unavoidable impurity element in steel that is present during the manufacturing process. Adding large amounts can cause brittleness. Furthermore, it can form precipitates such as manganese sulfide (MnS), increasing iron loss and inhibiting grain growth. For these reasons, sulfur addition is preferably kept as low as possible, and the present invention may include sulfur at 0.003 wt% or less.

[0057]

[0058] Person (P)

[0059] Phosphorus (P) is an element that improves grain structure through grain boundary segregation, thereby increasing resistivity and reducing iron loss. However, when phosphorus is added in large amounts exceeding 0.015 wt%, excessive grain boundary segregation may occur, resulting in grain growth inhibition, deterioration of magnetic properties, and reduced cold-rollability. Therefore, a non-oriented electrical steel sheet according to an embodiment of the present invention may contain phosphorus in an amount of 0.015 wt% or less.

[0060]

[0061] Nitrogen (N)

[0062] Nitrogen (N) is an element that contributes to the strength and corrosion resistance of steel, and it is an element that stabilizes austenite and improves the toughness of steel. However, nitrogen in steel can combine with aluminum (Al) and titanium (Ti) to form precipitates such as AlN and TiN, which can increase iron loss. Furthermore, it inhibits grain growth, so it is desirable to add as little nitrogen (N) as possible. Therefore, a non-oriented electrical steel sheet according to one embodiment of the present invention may contain nitrogen (N) at 0.003 wt% or less.

[0063]

[0064] In addition to the aforementioned steel components, the remainder may contain iron and unavoidable impurities. Unavoidable impurities are impurities introduced during the steelmaking process and the manufacturing process of non-oriented electrical steel sheets. Since these impurities are widely known in the field, a detailed description will be omitted.

[0065] In one embodiment of the present invention, the addition of elements other than the aforementioned alloy components is not excluded, and various elements may be included within a range that does not impair the technical spirit of the present invention. When additional elements are included, they may be included to replace the remaining Fe.

[0066] The non-oriented electrical steel sheet having the above-described alloy composition can have a final grain structure whose orientation fraction satisfies the following equation 1.

[0067] [Formula 1]

[0068] 0.1 ≤ V1 / V2 ≤ 0.7

[0069] At this time, V1 is {001} <120> , {114} <481> and {113} <251> It means the sum of the organizational fractions of the defense. The above {001} <120> , {114} <481> and {113} <251> The organization of the defense is a set organization that is advantageous for magnetic properties, and as the V1 value including the set organization that is advantageous for magnetic properties increases, the coercive force decreases, which can improve the motor efficiency.

[0070] V2 is {111} <112> , {334} <483> and {223} <110> It means the sum of the organizational fractions of the defense. The above {111} <112> , {334} <483> and {223} <110> The organization fraction of the defense is a set of aggregates that are unfavorable for magnetic properties, and as the V2 value including this set of aggregates increases, the coercivity increases, which increases the hysteresis loss and may be unfavorable for magnetization reversal.

[0071] Therefore, if the value of V1 / V2 is less than 0.1, the magnetic properties may be inferior, and as the value increases, the magnetic properties may improve. However, in order for the value of V1 / V2 to exceed 0.7, a special heat treatment process is required, and considering the resulting increase in production cost, the value of V1 / V2 may be limited to 0.7 or less.

[0072] The fraction of the above aggregate structure can be measured using the EBSD measurement method, and the detailed measurement method will be described later.

[0073] A non-oriented electrical steel sheet according to one embodiment of the present invention can have excellent magnetic properties due to its aggregate texture characteristics, and the magnetic properties can satisfy the following equation 2.

[0074] [Formula 2]

[0075] 1.7 ≤ [(ΔB / ΔH)×1000] ≤ 3.0

[0076] Here, ΔH refers to the change in the strength of the magnetic field applied through an external electromagnet or permanent magnet, and ΔB refers to the change in the number of magnetic flux lines per unit area generated in the material. Here, the material may refer to non-oriented electrical steel sheet.

[0077] The above equation 2 will be explained in more detail. ΔH is the change in the external magnetic field from 100 A / m to 500 A / m, and the change in the magnetic flux according to the change in the external magnetic field is expressed as ΔB. At this time, the torque of the motor starting under the same power and rotation environment can be predicted through ΔB / ΔH, and the value of ΔB / ΔH and the value of the motor torque are proportional. The larger the value of ΔB / ΔH, the greater the motor torque can be applied, and the larger the motor torque value, the more efficient the operation of the device is possible.

[0078] If the value of ΔB / ΔH is less than 1.7, the predicted motor torque value is low, which may make efficient operation of the device difficult. On the other hand, if the value of ΔB / ΔH exceeds 3.0, the addition of a special processing heat treatment process is required, and there is concern about a decrease in process economics due to this, so ΔB / ΔH can be limited to 3.0 or less.

[0079] The thickness of the non-oriented electrical steel sheet according to one embodiment of the present invention may be 1.0 mm or less. If the thickness of the final product, the non-oriented electrical steel sheet, exceeds 1.0 mm, the magnetic properties may be inferior, and therefore, the thickness may be controlled to 1.0 mm or less.

[0080] A non-oriented electrical steel sheet according to one embodiment of the present invention can have excellent magnetic properties by controlling the grain structure that is advantageous to magnetic properties and the grain structure that is disadvantageous to magnetic properties. More specifically, it can have low coercivity and high magnetic flux density due to the excellent grain structure characteristics, and can have iron loss (W 15 / 50 ) may be 6.0 W / kg or less, and the magnetic flux density (B1) may be 0.20 T or more.

[0081] Here, the iron loss (W15 / 50 ) means iron loss at 50 Hz, 1.5 T, and the unit is W / kg. Magnetic flux density (B1) means the size of the magnetic flux density induced when a magnetic field of 100 A / m is applied, and the unit is Tesla.

[0082] Accordingly, the non-oriented electrical steel sheet according to one embodiment of the present invention is suitable for use as a core material for industrial motors, and can have desirable product characteristics such as low coercivity and high magnetic flux density due to excellent aggregate texture characteristics.

[0083] More specifically, a motor according to one embodiment of the present invention can be manufactured by punching and laminating the aforementioned non-oriented electrical steel sheet. Furthermore, the motor can have excellent torque coefficients and a space factor. In this case, the torque coefficient of the motor can be 0.210 N·m / Amp. or higher, and the space factor can be 93.85% or higher.

[0084] Hereinafter, a method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention will be described in detail.

[0085]

[0086] Method for manufacturing non-oriented electrical steel sheet

[0087] Hereinafter, a method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention will be described with reference to FIG. 1.

[0088] A method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention includes a first step (S1) of preparing a steel material containing 0.1 to 1.6 wt% of silicon (Si), 0.2 to 0.4 wt% of manganese (Mn), 0.1 to 0.5 wt% of aluminum (Al), 0.003 wt% or less of carbon (C), 0.003 wt% or less of sulfur (S), 0.015 wt% or less of phosphorus (P), 0.003 wt% or less of nitrogen (N), and the remainder iron (Fe) and other unavoidable impurities, a second step (S2) of hot-rolling the steel material to form a hot-rolled steel sheet, a third step (S3) of cold-rolling the hot-rolled steel sheet to form a cold-rolled steel sheet, and a fourth step (S4) of cold-rolling and annealing the cold-rolled steel sheet.

[0089] Since the alloy composition content has been described in the alloy composition of non-oriented electrical steel sheets, a duplicate description will be omitted. In addition, since the alloy composition does not substantially change during the manufacturing process described below, the composition of the above steel and the alloy composition of the non-oriented electrical steel sheets are substantially identical.

[0090] Hereinafter, each step of a method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention will be described in detail.

[0091] First, Step 1 (S1) involves preparing steel having the above-described alloy composition range. More specifically, this step may involve designing alloy components within the above-described alloy composition range to manufacture a semi-finished product. The semi-finished product may be a slab, but is not necessarily limited thereto. Furthermore, the slab may be manufactured using any process known in the relevant technical field, such as a steelmaking process or a casting process.

[0092] In a method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention, the second step (S2) may form a hot-rolled steel sheet by hot-rolling the steel material that has undergone the first step (S1).

[0093] More specifically, the second stage (S2) may include a reheating step, a hot rolling step and a coiling step.

[0094] First, the reheating step may be performed prior to the hot rolling step, and may be used to reheat the steel for subsequent processing. Specifically, this may be a step of uniformly heating the steel by loading it into a heating furnace to facilitate plastic deformation.

[0095] At this time, if the reheating temperature (SRT, Slab Reheating Temperature) is less than 1000℃, the rolling load may increase during hot rolling, which may reduce the rollability. On the other hand, if the reheating temperature exceeds 1250℃, precipitates such as carbon (C), sulfur (S), and nitrogen (N) in the semi-finished product may be re-dissolved, and fine precipitates may be formed at the grains and grain boundaries during cooling. This may be advantageous for improving strength, but it may inhibit grain growth and deteriorate iron loss, thereby reducing magnetic properties. Therefore, in the reheating step according to one embodiment of the present invention, the reheating temperature may be 1000 to 1250℃.

[0096] Additionally, if the reheating time is less than 350 minutes, the precipitate may not have enough time to dissolve, resulting in material inhomogeneity. Conversely, if the reheating time exceeds 850 minutes, the prolonged heating time can lead to increased production costs.

[0097] Next, a hot rolling step may be performed to form a hot-rolled steel sheet. The hot rolling step may include rough rolling and finishing rolling. The rough rolling step may involve forming the steel into a rolled material having an appropriate shape, thickness, and width, while the finishing rolling step may involve adjusting the steel to a specified thickness and width and rolling it at a finishing temperature appropriate for the intended use to achieve a desirable surface and shape.

[0098] At this time, the finishing temperature of the hot rolling step may be 850 to 1000°C. If the finishing rolling temperature is lower than 850°C, rolling may occur in the two-phase region, resulting in the formation of an uneven texture. On the other hand, if the finishing rolling temperature exceeds 1000°C, a problem of rapid strength reduction may occur.

[0099] The thickness of hot-rolled steel sheets after the hot rolling process can range from 1.8 to 3.5 mm. If the hot-rolled steel sheet is too thin, less than 1.8 mm, the resulting cold-rolled thickness may be insufficient, potentially resulting in shape defects during product application. Conversely, if the hot-rolled steel sheet is thicker than 3.5 mm, the cold-rolling reduction ratio increases, potentially degrading the grain structure.

[0100] Afterwards, a coiling step can be performed. At this time, the coiling temperature is preferably 550 to 750°C. If the coiling temperature is lower than 550°C, the grain size may become too small, preventing sufficient grain growth even after annealing. If the coiling temperature exceeds 750°C, fine precipitates may be generated, which may deteriorate magnetic properties.

[0101] A method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention omits the step of annealing a hot-rolled steel sheet. In the case of a hot-rolled steel sheet having a silicon content of 2 to 4 wt%, since the α-ferrite single phase is maintained without a solid-state phase transformation during heating from room temperature to the melting point, dynamic recrystallization (DRX) does not occur, resulting in the formation of non-recrystallized grains elongated in the longitudinal direction of the steel sheet. These non-recrystallized grains have high internal residual stress and are unstable, which may cause anisotropy enhancement and sheet fracture. At this time, heat treatment is performed to promote recrystallization of the non-recrystallized grains and to have a uniform equiaxed structure. However, in the case of the present invention, the unnecessary heat treatment, i.e., the step of annealing a hot-rolled steel sheet, is omitted, thereby reducing production costs and increasing productivity.

[0102] In addition, a shot blast and pickling treatment process can be additionally performed between the second step (S2) and the third step (S3) described below. First, the shot blast can be performed by rotating shots having a size of 2 to 1200 μm at a speed of 2000 rpm or more and at a high speed of 50 to 120 m / s. The pickling treatment can be performed by supplying 18% hydrochloric acid to the pickling tank where it reacts with the iron plate, thereby reacting with the fine residual scales that were not removed by mechanical methods.

[0103] In a non-oriented electrical steel sheet according to one embodiment of the present invention, the third step (S3) may be a process of cold rolling the hot-rolled steel sheet to form a cold-rolled steel sheet. The third step (S3) may be a process of rolling the hot-rolled steel sheet at a temperature below the recrystallization temperature to further reduce the thickness of the steel sheet. More specifically, the third step (S3) may be a process of rolling the hot-rolled steel sheet to a thickness and width that meet the final product specifications.

[0104] The third step (S3) may have a final reduction ratio of 70 to 85%. In addition, the thickness of the cold rolled steel sheet formed through the cold rolling may be 1.0 mm or less, and more preferably 0.35 to 1.0 mm.

[0105] After the third step (S3), a fourth step (S4) of cold-rolling annealing the cold-rolled steel sheet may be performed. The cold-rolling annealing may be performed to soften the cold-rolled steel sheet that has been hardened through recrystallization during cold rolling. In addition, the cold-rolling annealing step may be performed at a temperature that derives an optimal grain size in consideration of iron loss reduction and mechanical properties. If the cold-rolling annealing temperature is below the standard, the grain size may be fine, which may increase hysteresis loss. On the other hand, if the cold-rolling annealing temperature exceeds the standard, the grain size becomes coarse, and the eddy current loss increases.

[0106] Accordingly, the fourth step (S4) according to one embodiment of the present invention may be performed by heating the cold-rolled steel sheet to 800 to 1100°C, maintaining the temperature for 40 to 10,000 seconds, and then cooling the cold-rolled steel sheet. At this time, the heating rate and cooling rate may be 20°C / s or more.

[0107] Additionally, the fourth step (S4) may be performed in a mixed atmosphere of nitrogen and hydrogen to prevent oxidation and nitriding of the surface of the cold-rolled steel sheet. This can improve the surface quality of the cold-rolled steel sheet.

[0108] A method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention may further include a coating step after the fourth step (S4). The coating step may be performed to secure the insulation properties and improve the punchability of the non-oriented electrical steel sheet, and may mean forming an insulating film on the surface of the cold-rolled steel sheet on which the fourth step (S4) has been performed.

[0109]

[0110] Comparative and experimental examples

[0111] Below, the configuration and operation of the present invention will be described in more detail through preferred embodiments of the present invention. However, these are provided as preferred examples to aid understanding of the present invention and are not intended to limit the present invention.

[0112] Table 1 shows the main alloy compositions, cold rolling annealing, and cold rolling annealing times of the present embodiment, and the final thickness of the non-oriented electrical steel sheet manufactured through the same. Table 2 shows the grain structure orientation fraction, the satisfaction of Equations 1 and 2, the space factor, and the motor torque coefficient of the embodiment according to Table 1.

[0113] In this example, a slab having an alloy composition as described in Table 1 below was heated to 1150°C, hot-rolled to produce a hot-rolled steel sheet having a thickness of 2.7 mm, cold-rolled to the final thickness as described in Table 1 below, and then continuously heat-treated for 3 minutes in a nitrogen atmosphere at the cold-rolling annealing temperature as described in Table 1 below, and coated to produce a final product, a non-oriented electrical steel sheet. In addition, the non-oriented electrical steel sheet was punched and laminated to produce a motor.

[0114] Other alloy components not listed in Table 1 were controlled as control variables and were controlled under the same conditions within the alloy composition range listed in the non-oriented electrical steel sheet according to one embodiment of the present invention described above.

[0115] The texture of this example was measured at a point 1 / 2t of the sheet thickness using the following method. The area ratio for the major crystal orientations was calculated as a percentage by interpreting the results measured by EBSD (Electron Back Scattered Diffraction). More specifically, the cross-section in the vertical direction of the rolling including the entire thickness layer of the specimen was measured by EBSD with an area of ​​10,000 ㎛ × 25,000 ㎛ and a step size of 5 ㎛. The Kikuchi pattern was measured using a Hikari Super EBSD detector manufactured by AMETEK Inc. so that each step did not overlap with each other. The measured results were interpreted and merged using TSL-OIM software, and the area ratio for the major crystal orientations within a margin of error of 15 degrees was calculated as a percentage.

[0116] In addition, the characteristics of the motor were measured as follows. The space factor of this example was measured according to the IEC 60404-13 international standard and was measured using an Epstein steel strip. The motor torque coefficient was measured under the following test conditions. The rated output was 300 W, the applied voltage was 48 V DC, the driving voltage was a 120° square wave, the stator size was 178 mm in outer diameter, 75 mm in inner diameter, and 25 mm in height, the rotor size was 74 mm in outer diameter, 25 mm in height, the number of poles was 8, the number of slots was 10, the carrier frequency was 1.6 kHz, and the winding method was a three-phase star connection with 4 coils per phase.

[0117] In the table below, V1 is {001} <120> , {114} <481> and {113} <251> It means the sum of the organizational fractions of the defense, and V2 is {111} <112> , {334} <483> and {223} <110> It refers to the sum of the organizational fractions of the defense.

[0118] Classification Si [wt%] Mn [wt%] Al [wt%] Final thickness [mm] Cold rolling annealing temperature [℃] Experimental example 10.10.20.30.5800 Experimental example 2950 Experimental example 31100 Comparative example 10.060.15-1.18001 Experimental example 40.80.30.40.5800 Experimental example 5950 Experimental example 61100 Comparative example 2750 Experimental example 71.50.250.350.5800 Experimental example 8950 Experimental example 91100 Comparative example 320.30.451.1800

[0119] Satisfaction of the segmented set structure (ΔB / ΔH) × 1000 [Formula 2] Point space factor [%] Motor torque coefficient [N m / Amp.] V1 [%] V2 [%] V1 / V2 [Formula 1] Satisfaction Experimental example 18.146.70.17O2.475O94.10.241 Experimental example 28.543.30.21O2.7O94.60.261 Experimental example 38.645.20.19O2.575O93.80.247 Comparative example 11.678.40.02X1.675X85.30.189 Experimental example 412.134.60.34O2.4O95.90.24 Experimental example 511.8330.36O2.175O96.10.225Experimental example 610.435.50.29O2.25O94.70.238Comparative example 25.660.80.09X1.7O93.50.206Experimental example 713.333.20.4O2.275O96.30.233Experimental example 815.130.70.49O2.075O95.20.219Experimental example 914.531.20.46O2.15O96.60.223Comparative example 33.256.10.05X1.725X84.40.175

[0120] As shown in Tables 1 and 2 above, Experimental Examples 1 to 9 according to an embodiment of the present invention satisfy Equation 1 above, and the magnetic properties satisfy Equation 2 above. In addition, Experimental Examples 1 to 9 have a higher value of V1, which is the sum of the aggregate textures favorable to the magnetic properties, and a lower value of V2, which is the sum of the aggregate textures unfavorable to the magnetic properties, compared to the comparative example. Accordingly, excellent magnetic properties due to the improved aggregate texture can be expected.

[0121] In addition, Experimental Examples 1 to 9 have excellent aggregate structure and magnetic properties, and thus it can be confirmed that the space factor and motor torque coefficient of the motor manufactured as the experimental examples are superior to those of the comparative examples.

[0122] On the other hand, Comparative Examples 1 to 3 do not satisfy Equations 1 and 2. In addition, compared to the experimental examples, the value of V1, which is the sum of aggregate structures favorable to magnetic properties, is lower, and the value of V2, which is the sum of aggregate structures unfavorable to magnetic properties, is higher.

[0123] In addition, it can be confirmed that the space factor and motor torque coefficient of the motors manufactured in Comparative Examples 1 to 3 are lower than those of the experimental examples.

[0124] As described above, preferred embodiments of the present invention have been described. It will be apparent to those skilled in the art that the present invention may be embodied in other specific forms, in addition to the embodiments described above, without departing from the spirit or scope thereof. Therefore, the above-described embodiments should be considered illustrative rather than restrictive, and accordingly, the present invention is not limited to the above description, but may be modified within the scope of the appended claims and their equivalents.

Claims

1. Contains 0.1 to 1.6 wt% of silicon (Si), 0.2 to 0.4 wt% of manganese (Mn), 0.1 to 0.5 wt% of aluminum (Al), 0.003 wt% or less of carbon (C), 0.003 wt% or less of sulfur (S), 0.015 wt% or less of phosphorus (P), 0.003 wt% or less of nitrogen (N), and the remainder of iron (Fe) and other unavoidable impurities. A non-oriented electrical steel sheet having a final grain structure having a directional fraction satisfying the following equation 1. [Formula 1] 0.1 ≤ V1 / V2 ≤ 0.7 (However, V1 is {001} <120> , {114} <481> and {113} <251> It represents the sum of the fractions of the set of tissues, and V2 is {111} <112> , {334} <483> and {223} <110> (represents the sum of the fractions of the collective organization) 2. In paragraph 1, A non-oriented electrical steel sheet having magnetic properties satisfying the following equation 2. [Formula 2] 1.7 ≤ [(ΔB / ΔH)*1000] ≤ 3.0 (Where, ΔB refers to the change in the number of magnetic flux lines per unit area generated from the material, and ΔH refers to the change in the strength of the magnetic field applied through an external electromagnet.) 3. In paragraph 1, Non-oriented electrical steel sheet with a thickness of 1.0 mm or less.

4. In paragraph 1, Iron Hand(W 15 / 50 ) Non-oriented electrical steel sheet with a strength of 6.0 W / kg or less and a magnetic flux density (B1) of 0.20 T or more.

5. A first step of preparing a steel material containing 0.1 to 1.6 wt% of silicon (Si), 0.2 to 0.4 wt% of manganese (Mn), 0.1 to 0.5 wt% of aluminum (Al), 0.003 wt% or less of carbon (C), 0.003 wt% or less of sulfur (S), 0.015 wt% or less of phosphorus (P), 0.003 wt% or less of nitrogen (N), and the remainder iron (Fe) and other unavoidable impurities; A second step of hot rolling the above steel to form a hot rolled steel plate; A third step of cold rolling the hot rolled steel sheet to form a cold rolled steel sheet, and A method for manufacturing a non-oriented electrical steel sheet, comprising a fourth step of cold-rolling and annealing the cold-rolled steel sheet.

6. In paragraph 5, The second step above is, A method for manufacturing a non-oriented electrical steel sheet further comprising a reheating step of heat-treating the above steel at 1000 to 1250°C for 350 to 850 minutes.

7. In paragraph 5, The third step above is, A method for manufacturing non-oriented electrical steel sheets having a final reduction ratio of 70 to 85%.

8. In paragraph 5, The fourth step above is, A method for manufacturing non-oriented electrical steel sheets by performing heat treatment at 800 to 1100°C.

9. A motor manufactured by stamping and laminating the non-oriented electrical steel plate of claim 1.

10. In paragraph 8, A motor with a torque coefficient of 0.210 N·m / Amp. or higher.

11. In paragraph 8, Motor with a loading rate of 93.8% or higher.

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