Non-oriented electrical steel sheet and method for manufacturing same

Abstract

A non-oriented electrical steel sheet according to an exemplary embodiment of the present invention comprises: 1.5-5.0% of Si; 0.1-2.0% of Al; 0.1-2.0% of Mn; and the remainder of Fe and inevitable impurities, wherein the ratio (W5 / 2000 / W10 / 400) of W5 / 2000 to W10 / 400 is 1.5 to 2.7, and the ratio (W5 / 2500 / W10 / 400) of W5 / 2500 to W10 / 400 is 2.3 to 3.7.

Description

Non-oriented electrical steel sheet and method of manufacturing the same

[0001] One embodiment of the present invention relates to a non-oriented electrical steel sheet and a method for manufacturing the same. Specifically, one embodiment of the present invention relates to a non-oriented electrical steel sheet with improved ultra-high frequency iron loss by introducing an interruption process during the cold rolling process, and a method for manufacturing the same.

[0002] Non-oriented electrical steel sheets are used as core materials in rotating equipment such as motors and generators, as well as in stationary equipment such as small transformers, and play an important role in determining the energy efficiency of electrical equipment.

[0003] The magnetic properties of non-oriented electrical steel sheets are primarily evaluated based on iron loss and magnetic flux density. Iron loss refers to the energy loss occurring in the iron core of devices such as motors, transformers, and generators at a specific magnetic flux density and frequency, while magnetic flux density refers to the degree of magnetization obtained under a specific magnetic field. It is desirable to have low iron loss and high magnetic flux density. This is because when electricity is applied to the iron core to induce a magnetic field, lower iron loss reduces energy loss as heat, allowing for the manufacture of motors with higher energy efficiency under the same conditions. Conversely, higher magnetic flux density enables the induction of a larger magnetic field with the same amount of energy, and allows for motor miniaturization or reduction of copper loss. Therefore, using non-oriented electrical steel sheets with low iron loss and high magnetic flux density enables the production of motors with excellent efficiency and torque. This extends the operating time using the same power and allows for increased motor output through higher torque.

[0004] Depending on the operating conditions of the motor, the characteristics of non-oriented electrical steel sheets that need to be considered also vary. As a general standard for evaluating the characteristics of non-oriented electrical steel sheets used in motors, W15 / 50, which is the iron loss when a 1.5T magnetic field is applied at a commercial frequency of 50Hz, is widely used.

[0005] For non-oriented electrical steel sheets with a thickness of 0.35 mm or less used in drive motors for eco-friendly vehicles, magnetic properties are often critical at low fields of 1.0 T or less and high frequencies of 400 to 800 Hz or higher. Therefore, the characteristics of these sheets are frequently evaluated using W10 / 400 and W10 / 800 iron loss. As the rotational speed of eco-friendly vehicle drive motors increases, the required frequency band rises, making iron loss in the kHz range critical. Furthermore, cordless vacuum cleaners are increasingly increasing their rotational speeds to boost suction power. Consequently, the rotational speed of cordless vacuum motors is trending toward even higher speeds. Therefore, for motors used in handheld vacuum cleaners that utilize high-speed rotation, iron loss in the frequency band of approximately 2000 Hz or higher is becoming critical. As such, for high-speed rotation motors, excellent high-frequency iron loss is particularly desirable.

[0006] One embodiment of the present invention provides a non-oriented electrical steel sheet and a method for manufacturing the same. Specifically, one embodiment of the present invention provides a non-oriented electrical steel sheet with improved ultra-high frequency iron loss and a method for manufacturing the same by introducing an interruption process during the cold rolling process.

[0007] A non-oriented electrical steel sheet according to one embodiment of the present invention comprises, in weight percent, Si: 1.5 to 5.0%, Al: 0.1 to 2.0%, Mn: 0.1 to 2.0%, the remainder being Fe and unavoidable impurities, and W 10 / 400 W about 5 / 2000 The ratio of (W 5 / 2000 / W 10 / 400 ) is 1.5 to 2.7, and W 10 / 400 W about 5 / 2500 The ratio of (W 5 / 2500 / W 10 / 400 ) is 2.3 to 3.7.

[0008] A non-oriented electrical steel sheet according to one embodiment of the present invention may have a resistivity of 50 to 70 μΩ·cm.

[0009] A non-oriented electrical steel sheet according to one embodiment of the present invention is W5 / 2000 This is 30W / kg or less, and W 5 / 2500 This is 35W / kg or less, and W 5 / 2500 The eddy current loss may be 7 W / kg or less.

[0010] A non-oriented electrical steel sheet according to one embodiment of the present invention may have a thickness of 0.05 to 0.15 mm.

[0011] A non-oriented electrical steel sheet according to one embodiment of the present invention may further include one or more of P: 0.03 wt% or less, C: 0.005 wt% or less, S: 0.005 wt% or less, Ti: 0.005 wt% or less, and N: 0.005 wt% or less.

[0012] A non-oriented electrical steel sheet according to one embodiment of the present invention may further include 0.005 to 0.200 weight% of one or more of Sn, Sb, Bi, Pb, Ge, and As, respectively or in their combined amount.

[0013] A non-oriented electrical steel sheet according to one embodiment of the present invention may further include one or more of Cu: 0.005 to 0.2 wt%, Cr: 0.01 to 0.5 wt%, Ni: 0.05 wt% or less, Zn: 0.01 wt% or less, and Co: 0.05 wt% or less.

[0014] A non-oriented electrical steel sheet according to one embodiment of the present invention may further include one or more of Mo: 0.03 wt% or less, B: 0.0050 wt% or less, V: 0.0050 wt% or less, Ca: 0.0050 wt% or less, Nb: 0.0050 wt% or less, Zr: 0.005 wt% or less, Te: 0.01 wt% or less, and Mg: 0.0050 wt% or less.

[0015] A non-oriented electrical steel sheet according to one embodiment of the present invention may have a yield strength of 330 MPa to 600 MPa.

[0016] A method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention comprises: a step of manufacturing a hot-rolled steel sheet by hot-rolling a slab comprising, in weight%, Si: 1.5 to 5.0%, Al: 0.1 to 2.0%, Mn: 0.1 to 2.0%, and the remainder being Fe and unavoidable impurities; a step of manufacturing a cold-rolled sheet by cold-rolling the hot-rolled steel sheet; and a cold-rolled sheet annealing step of annealing the cold-rolled sheet.

[0017] The step of manufacturing a cold-rolled sheet includes a plurality of rolling passes and a rolling interruption step of stopping rolling for at least 1 second between at least one of the rolling passes.

[0018] During the rolling interruption stage, the temperature of the steel plate can be 60 to 250°C.

[0019] The slab may further include one or more of P: 0.03 wt% or less, C: 0.005 wt% or less, S: 0.005 wt% or less, Ti: 0.005 wt% or less, and N: 0.005 wt% or less.

[0020] The slab may further contain 0.005 to 0.200 weight% of one or more of Sn, Sb, Bi, Pb, Ge, and As, either individually or in their combined amount.

[0021] The slab may further include one or more of Cu: 0.005 to 0.2 wt%, Cr: 0.01 to 0.5 wt%, Ni: 0.05 wt% or less, Zn: 0.01 wt% or less, and Co: 0.05 wt% or less.

[0022] The slab may further include one or more of Mo: 0.03 wt% or less, B: 0.0050 wt% or less, V: 0.0050 wt% or less, Ca: 0.0050 wt% or less, Nb: 0.0050 wt% or less, Zr: 0.005 wt% or less, Te: 0.01 wt% or less, and Mg: 0.0050 wt% or less.

[0023] After the step of manufacturing hot-rolled steel sheets, the method may further include a hot-rolled sheet annealing step in which a heat treatment is performed by holding at 980 to 1050°C for at least 0.1 seconds and then holding at 850 to 950°C for 10 to 150 seconds.

[0024] In the cold-rolled sheet annealing stage, the heating rate in the temperature range of 100 to 750℃ may be 20℃ / s or higher.

[0025] In the cold-rolled sheet annealing stage, the cooling rate may be 17℃ / s or less in the temperature range from cracking temperature to 600℃.

[0026] A non-oriented electrical steel sheet according to one embodiment of the present invention has improved ultra-high frequency iron loss and can be usefully utilized as an iron core for a motor with a high rotational speed. More specifically, it can be usefully utilized as an iron core for a cordless vacuum cleaner motor.

[0027] Terms such as first, second, and third are used to describe various parts, components, regions, layers, and / or sections, but are not limited thereto. These terms are used solely to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Accordingly, the first part, component, region, layer, or section described below may be referred to as the second part, component, region, layer, or section without departing from the scope of the present invention.

[0028] The technical terms used herein are for the reference of specific embodiments only and are not intended to limit the invention. The singular forms used herein include plural forms unless phrases clearly indicate otherwise. As used in the specification, the meaning of "comprising" specifies certain characteristics, areas, integers, steps, actions, elements, and / or components, and does not exclude the presence or addition of other characteristics, areas, integers, steps, actions, elements, and / or components.

[0029] When it is stated that one part is "above" or "on" another part, it may be directly above or on the other part, or other parts may be involved in between. In contrast, when it is stated that one part is "directly above" another part, no other parts are interposed in between.

[0030] Also, unless otherwise specified, % means weight %, and 1 ppm is 0.0001 weight %.

[0031] In one embodiment of the present invention, the meaning of including additional elements is that the remainder of iron (Fe) is replaced by an amount of the additional element.

[0032] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as generally understood by those skilled in the art to which this invention pertains. Terms defined in commonly used dictionaries are further interpreted to have meanings consistent with relevant technical literature and the present disclosure, and are not interpreted in an ideal or highly formal sense unless otherwise defined.

[0033] Hereinafter, embodiments of the present invention are described in detail so that those skilled in the art can easily implement the invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0034]

[0035] A non-oriented electrical steel sheet according to one embodiment of the present invention comprises, in weight%, Si: 1.5 to 5.0%, Al: 0.1 to 2.0%, Mn: 0.1 to 2.0%, and the remainder being Fe and unavoidable impurities.

[0036] Below, we will first explain the reason for limiting the composition of non-oriented electrical steel sheets.

[0037] Si: 1.5 to 5.0 wt%

[0038] Silicon (Si) plays a role in increasing the resistivity of the material to lower iron loss and increasing strength through solid solution strengthening. If too little Si is added, the effect of improving iron loss and strength may be insufficient. If too much Si is added, the brittleness of the material increases, causing a sharp decrease in rolling productivity and potentially forming a surface oxide layer and oxides that are harmful to magnetism. Therefore, Si may be included in an amount of 1.50 to 5.00 weight%. More specifically, it may be included in an amount of 2.25 to 3.90 weight%. Even more specifically, it may be included in an amount of 2.50 to 3.70 weight%.

[0039]

[0040] Al: 0.1 to 2.0 wt%

[0041] Aluminum (Al) plays a role in increasing the resistivity of the material to lower iron loss and increasing strength through solid solution strengthening. If too little Al is added, fine nitrides may form, making it difficult to obtain the effect of improving magnetism. If too much Al is added, excessive nitrides are formed, degrading magnetism and causing problems in all processes, such as steelmaking and continuous casting, which can significantly reduce productivity. Therefore, Al may be included in an amount of 0.10 to 2.00 weight%. More specifically, it may be included in an amount of 0.35 to 1.50 weight%. Even more specifically, it may be included in an amount of 0.40 to 1.00 weight%.

[0042]

[0043] Mn: 0.1 to 2.0 wt%

[0044] Manganese (Mn) plays a role in improving iron loss by increasing the resistivity of the material and forming sulfides. If too little Mn is added, fine sulfides are formed, causing magnetic degradation; if too much Mn is added, fine MnS is excessively precipitated, promoting the formation of a {111} texture that is unfavorable to magnetism, which causes a rapid decrease in magnetic flux density. Therefore, Mn may be included in an amount of 0.10 to 2.00 weight%. More specifically, it may be included in an amount of 0.22 to 1.30 weight%. Even more specifically, it may be included in an amount of 0.50 to 1.00 weight%.

[0045]

[0046] A non-oriented electrical steel sheet according to one embodiment of the present invention may further include one or more of P: 0.03 wt% or less, C: 0.005 wt% or less, S: 0.005 wt% or less, Ti: 0.005 wt% or less, and N: 0.005 wt% or less.

[0047] P: 0.03 wt% or less

[0048] Phosphorus (P) can improve magnetic flux density as a grain boundary segregating element, but if added in excessive amounts, it increases the brittleness of the steel sheet, resulting in inferior weldability and cold rolling performance. More specifically, it may contain 0.0001 to 0.03 weight% of P.

[0049] C: 0.005 wt% or less

[0050] Carbon (C) can cause magnetic aging and combine with other impurity elements to form carbides, which can impede grain boundary or domain wall movement and degrade magnetic properties. More specifically, it may contain 0.0001 to 0.003 weight% of C.

[0051] S: 0.005 wt% or less

[0052] Sulfur (S) can form fine precipitates, such as MnS and CuS, which can worsen magnetic properties and hot workability. More specifically, it may contain 0.0001 to 0.0030 weight% of S.

[0053] Ti: 0.005 wt% or less

[0054] Titanium (Ti) has a very strong tendency to form precipitates in steel and can degrade iron loss by forming fine carbides, nitrides, or sulfides within the base material, thereby inhibiting grain growth and domain wall movement. More specifically, it may contain 0.0001 to 0.003 weight% of Ti.

[0055] N: 0.005 wt% or less

[0056] Nitrogen (N) not only forms fine AlN precipitates inside the base material but also combines with other impurities to form fine precipitates, thereby inhibiting grain growth and domain wall movement, which can worsen iron loss. More specifically, it may contain 0.0001 to 0.0030 weight% of N.

[0057]

[0058] A non-oriented electrical steel sheet according to one embodiment of the present invention may further include 0.005 to 0.200 weight% of one or more of Sn, Sb, Bi, Pb, Ge, and As, respectively or in their combined amount.

[0059] Sn and Sb

[0060] Tin (Sn) and antimony (Sb) play a role in suppressing the development of {111} orientations, which degrade magnetism by segregating at the grain boundaries during the initial stage of final recrystallization annealing. If too much Sn and Sb are added, it can hinder the recovery and growth of coarse elongated band structures and degrade surface quality. Therefore, one or more of Sn and Sb may be added within the aforementioned range. More specifically, it may contain 0.005 to 0.200 wt% of Sn or 0.005 to 0.200 wt% of Sb. More specifically, it may contain 0.010 to 0.150 wt% of Sn or 0.010 to 0.150 wt% of Sb.

[0061] Bi, Pb, Ge, and As

[0062] When bismuth (Bi), lead (Pb), germanium (Ge), and arsenic (As) are added, they segregate at grain boundaries, alleviating stress concentration at grain boundaries during cold rolling, which in the subsequent recrystallization annealing process <111> By suppressing the recrystallization of the / ND orientation crystal grains, the magnetic flux density is improved. If these are added appropriately, the aforementioned effects can be additionally obtained, but if they are included in too much, a large amount of segregation occurs, which suppresses crystal grain growth and may result in inferior magnetic flux density and iron loss. More specifically, one or more of Bi: 0.005 to 0.200 wt%, Pb: 0.005 to 0.200 wt%, Ge: 0.005 to 0.200 wt%, and As: 0.005 to 0.200 wt% may be further included. More specifically, one or more of Bi: 0.010 to 0.150 wt%, Pb: 0.010 to 0.150 wt%, Ge: 0.010 to 0.150 wt%, and As: 0.010 to 0.150 wt% may be further included.

[0063]

[0064] A non-oriented electrical steel sheet according to one embodiment of the present invention may further include one or more of Cu: 0.005 to 0.2 wt%, Cr: 0.01 to 0.5 wt%, Ni: 0.05 wt% or less (excluding 0%), Zn: 0.01 wt% or less (excluding 0%), and Co: 0.05 wt% or less (excluding 0%).

[0065] Cu: 0.005 to 0.200 wt%

[0066] Copper (Cu) plays a role in forming sulfides together with Mn. If more Cu is added, or if too little is added, (Cu · Mn)S may precipitate finely, which can degrade magnetism. If too much Cu is added, high-temperature brittleness occurs, which can form cracks during continuous casting or hot rolling. More specifically, it may contain 0.01 to 0.10 weight% of Cu.

[0067] Cr: 0.01 to 0.50 wt%

[0068] Chromium (Cr) plays a role in improving iron loss by increasing resistivity. If too little Cr is added, the effect of increasing resistivity may not be sufficient. If too much Cr is included, magnetic flux density may decrease. More specifically, 0.050 to 0.20 weight% of Cr may be included.

[0069] Ni: 0.05 wt% or less

[0070] Nickel (Ni) can react with impurity elements to form fine sulfides, carbides, and nitrides, which can have a harmful effect on magnetism. More specifically, it may contain 0.001 to 0.03 weight percent of Ni.

[0071] Zn: 0.01 wt% or less

[0072] If the content of zinc (Zn) is excessive, it can act as an impurity and impair magnetism. Therefore, Zn may be added within the aforementioned range. More specifically, Zn may be included in an amount of 0.001 to 0.005 weight%.

[0073] Co: 0.05 wt% or less

[0074] Cobalt (Co) does not form fine precipitates that reduce the magnetism of steel sheets, but it increases high-temperature strength, which can cause the coil shape to be defective after hot rolling.

[0075]

[0076] A non-oriented electrical steel sheet according to one embodiment of the present invention may further include one or more of Mo: 0.03 wt% or less, B: 0.0050 wt% or less, V: 0.0050 wt% or less, Ca: 0.0050 wt% or less, Nb: 0.0050 wt% or less, Zr: 0.0050 wt% or less, Te: 0.0100 wt% or less, and Mg: 0.0050 wt% or less.

[0077] Mo: 0.030 wt% or less

[0078] If molybdenum (Mo) is added in excess, it may suppress the segregation of segregated elements, thereby reducing the texture improvement effect. Therefore, Mo may be included in an amount of 0.03 weight% or less. The lower limit is not specifically limited, but since it plays a role in improving the texture by segregating at the surface and grain boundaries, it may be included in an amount of 0.001 weight% or more. More specifically, Mo may be included in an amount of 0.001 to 0.010 weight%. Even more specifically, Mo may be included in an amount of 0.005 to 0.010 weight%.

[0079] B: 0.0050 wt% or less

[0080] If an excessive amount of boron (B) is added, it may cause deterioration of magnetic properties through the formation of inclusions within the steel. Therefore, B may be included in an amount of 0.005 weight% or less. The lower limit is not specifically limited, but it may be 0.0001 weight% due to steelmaking costs. More specifically, B may be included in an amount of 0.0001 to 0.0030 weight%.

[0081] V: 0.0050 wt% or less

[0082] Vanadium (V) has a very strong tendency to form precipitates in steel and degrades iron loss by forming fine carbides or nitrides inside the base material, thereby inhibiting grain growth and domain wall movement. Therefore, the V content may be 0.0050 wt% or less. The lower limit is not specifically limited, but it may be 0.0003 wt% due to steelmaking costs. That is, V may be included in 0.0003 to 0.0050 wt%. More specifically, V may be included in 0.0003 to 0.0030 wt%.

[0083] Ca: 0.0050 wt% or less

[0084] Calcium (Ca) has a very strong tendency to form precipitates within the steel and degrades iron loss by forming fine sulfides inside the base material, thereby inhibiting grain growth and domain wall movement.

[0085] Nb: 0.0050 wt% or less

[0086] Niobium (Nb) has a very strong tendency to form precipitates in steel and degrades iron loss by forming fine carbides or nitrides within the base material, thereby inhibiting grain growth and domain wall movement. Therefore, the Nb content may be 0.0050 wt% or less. The lower limit is not specifically limited, but it may be 0.0003 wt% due to steelmaking costs. That is, it may contain 0.0003 to 0.0050 wt% of Nb. More specifically, it may contain 0.0003 to 0.0030 wt% of Nb.

[0087] Zr: 0.0050 wt% or less

[0088] If an excessive amount of zirconium (Zr) is added, it may cause deterioration of magnetic properties through the formation of inclusions within the steel. Therefore, Zr may be included in an amount of 0.005 weight% or less. The lower limit is not specifically limited, but it may be set to 0.0001 weight% due to steelmaking costs. That is, Zr may be included in an amount of 0.0001 to 0.0050 weight%. More specifically, it may be included in an amount of 0.0005 to 0.0030 weight%.

[0089] Te: 0.0100 wt% or less

[0090] Tellurium (Te) can be added to prevent the oxide layer, which is fractured during rolling, from being pressed into the base material and to detach it, as it diffuses into the oxide layer on the surface of the hot-rolled coil, increases the coefficient of friction between the oxide layer and the rolling work roll, and increases hardness by concentrating beneath the oxide layer. If the amount of Te added is too small, the effect may be negligible. If too much Te is added, the oxide layer detaches easily, causing the base material to come into direct contact with the work roll, which reduces the above effect, and excessive deformation bands may be generated within the steel sheet during cold rolling, leading to the development of a {111} / ND texture that is unfavorable to magnetism. More specifically, it may contain 0.0001 to 0.007 weight% of tellurium.

[0091] Mg: 0.0050 wt% or less

[0092] Magnesium (Mg) is an element that primarily combines with S to form sulfides and can affect the surface oxide layer of the base iron. Therefore, Mg may be included in an amount of 0.0050 wt% or less. The lower limit is not specifically limited, but it may be 0.0001 wt% due to steelmaking costs. That is, Mg may be included in an amount of 0.0001 to 0.0050 wt%. More specifically, it may be included in an amount of 0.0005 to 0.0030 wt%.

[0093]

[0094] The remainder comprises Fe and unavoidable impurities. The unavoidable impurities are those introduced during the steelmaking stage and the manufacturing process of non-oriented electrical steel sheets; as this is widely known in the field, a detailed description is omitted. 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 scope that does not impair the technical spirit of the present invention. If additional elements are included, they replace the remainder, Fe.

[0095] A non-oriented electrical steel sheet according to one embodiment of the present invention may have a thickness of 0.05 to 0.15 mm. If the thickness is too thin, problems may arise in terms of the strength of the steel sheet, and if the thickness is too thick, it may have an adverse effect on ultra-high frequency iron loss. More specifically, the thickness may be 0.07 to 0.13 mm.

[0096] A non-oriented electrical steel sheet according to one embodiment of the present invention is <100> Grains whose direction is parallel to the rolling direction (ND direction) of the steel sheet at an angle of 15° or less ( <100> The fraction of / ND) is 10% or more of the area, and <110> Grains whose direction is parallel to the rolling direction (ND direction) of the steel sheet at an angle of 15° or less ( <110> / ND) The fraction is 1% to 10% of the area, and <111> Grains whose direction is parallel to the rolling direction (ND direction) of the steel sheet at an angle of 15° or less ( <111> The fraction of / ND can be 25 to 45 area%. Ultra-high frequency iron loss can be further improved through grains of appropriate orientation. <111> / ND grains are grains that are unfavorable to magnetization, so minimizing their fraction is advantageous for magnetism. <110> / ND grains and <100> / ND grains are <111> Compared to / ND grains, magnetization is easier, and securing as many of these grains as possible is advantageous for magnetism. More specifically, grains whose direction is parallel to the rolling direction of the steel sheet (ND direction) at an angle of 15° or less ( <100> The fraction of / ND) is 20 to 50 area%, and <110> Grains whose direction is parallel to the rolling direction (ND direction) of the steel sheet at an angle of 15° or less ( <110> / ND) The fraction is 1% to 5% of the area, and <111> Grains whose direction is parallel to the rolling direction (ND direction) of the steel sheet at an angle of 15° or less ( <111> / ND) The fraction may be 30 to 40 area%.

[0097] The grain orientation fraction can be analyzed using EBSD. Specifically, it can be measured by observing the ND plane at 1 / 8 of the total thickness of the surface layer of the steel sheet. The fraction of orientations with a tolerance angle of deviation from the orientation within 15° can be measured. Area fraction refers to the ratio of the area occupied by grains of a specific orientation to the total area of ​​the steel sheet measured by electron backscatter diffraction (EBSD). The range of within 15° means that the angle between the vertical axis of the steel sheet surface and any plane containing the corresponding orientation is within 15°, and this can be measured using the Crystal Orientation Analysis Program (OIM) of TSL's EBSD. More specifically, the grain orientations can be analyzed by cutting the steel sheet parallel to the thickness direction and measuring the center of the cut surface using electron backscatter diffraction (EBSD).

[0098] {001} <100> The area fraction of oriented grains is 0.1 area% or more, {001} <110> The area fraction of oriented grains is 1% or more, {111} <112> The area fraction of the oriented crystal grains can be 6 to 20 area%. These crystal orientations are crystal grains that help with high-frequency iron loss, and when properly secured, high-frequency iron loss can be improved.

[0099] A non-oriented electrical steel sheet according to one embodiment of the present invention may have an average grain size of 30 to 130 μm. If the average grain size is too small, high-frequency iron loss is poor, and if the average grain size is too large, magnetic flux density is poor. More specifically, the average grain size may be 40 to 110 μm.

[0100] The average grain size can be measured by observing the ND plane at 1 / 8 of the total thickness when using EBSD. This is the average grain size based on the number used in TSL software.

[0101] A non-oriented electrical steel sheet according to one embodiment of the present invention may have a resistivity of 50.0 to 70.0 μΩ·cm. While a higher resistivity is preferable for reducing eddy current losses in high-frequency rotating machinery, if it becomes too large, the magnetic flux density may be inferior. In one embodiment of the present invention, the resistivity can be calculated from 13.25 + 11.3 × ([Si]+[Al]+[Mn] / 2+[Cu] / 2+[Cr] / 2). The elements in brackets represent the weight percent of each element, and if the corresponding element is not included, it is calculated as 0. More specifically,

[0102] As previously stated, in one embodiment of the present invention, ultra-high frequency iron loss can be improved. Specifically, W 10 / 400 W about 5 / 2000 The ratio of (W 5 / 2000 / W 10 / 400 ) is 1.50 to 2.70, and W 10 / 400 W about 5 / 2500 The ratio of (W 5 / 2500 / W 10 / 400 ) is 2.30 to 3.70. When possessing the aforementioned ultra-high frequency iron loss characteristics, it can be usefully utilized as an iron core for high-rotation speed motors. More specifically, it can be usefully utilized as an iron core for cordless vacuum cleaner motors. More specifically, W 10 / 400 W about 5 / 2000 The ratio of (W 5 / 2000 / W 10 / 400 ) is 1.70 to 2.50, and W 10 / 400 W about 5 / 2500 The ratio of (W 5 / 2500 / W 10 / 400 ) can be 2.50 to 3.30. Here

[0103] At this time, W 10 / 400 ε is the iron loss when a magnetic flux density of 1.0T is induced at a frequency of 400Hz, and W 5 / 2000 ε is the iron loss when a magnetic flux density of 0.5T is induced at a frequency of 2000Hz, and W 5 / 2500 is the iron loss when a magnetic flux density of 0.5T is induced at a frequency of 2500Hz.

[0104] More specifically, W 10 / 400 If produced by the single-roll method considering productivity, W10 / 400 can be 8.0 to 12.0 W / kg. W 5 / 2000 It may be 30 W / kg or less. More specifically, W 5 / 2000 It may be 25W / kg or less. W 5 / 2500 It may be 35 W / kg or less. More specifically, W 5 / 2500 The eddy current loss may be 30 W / kg or less. When a magnetic flux density of 0.5 T is induced at a frequency of 2500 Hz, the eddy current loss may be 7 W / kg or less.

[0105] Also, magnetic flux density (B 50 ) may be 1.56T or higher. More specifically, the magnetic flux density (B50) may be 1.58T to 1.67T. B50 refers to the magnetic flux density of the steel plate induced in a magnetic field of 5000A / m.

[0106] In one embodiment of the present invention, the yield strength may be 330 MPa to 600 MPa. In one embodiment of the present invention, it is used as an iron core for a motor with a high rotational speed, and for this purpose, it is necessary to secure an appropriate yield strength. More specifically, it may be 380 MPa to 500 MPa.

[0107]

[0108] A method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention comprises: a step of manufacturing a hot-rolled steel sheet by hot-rolling a slab; a step of manufacturing a cold-rolled sheet by cold-rolling the hot-rolled steel sheet; and a cold-rolled sheet annealing step of annealing the cold-rolled sheet.

[0109] Below, each step is explained in detail.

[0110] First, the slab is hot-rolled.

[0111] As the alloy composition of the slab has been explained in the aforementioned section on the alloy composition of non-oriented electrical steel sheets, a redundant explanation is omitted. Since the alloy composition does not substantially change during the manufacturing process of non-oriented electrical steel sheets, the alloy composition of the non-oriented electrical steel sheets and the slab is substantially the same.

[0112] Specifically, the slab contains Si: 1.5 to 5.0%, Al: 0.1 to 2.0%, Mn: 0.1 to 2.0% by weight, and the remainder is Fe and unavoidable impurities.

[0113] As other additional elements have been explained in the alloy composition of non-oriented electrical steel sheets, redundant explanations are omitted.

[0114] Slabs can be manufactured through continuous casting. Slabs manufactured through continuous casting can be maintained at 300°C or higher. When heating slabs, they can be loaded into a slab heating furnace without cooling them to a temperature below 300°C. If the slab is cooled to too low a temperature, cracks may occur in the slab.

[0115] The slab may be heated before hot rolling. The heating temperature of the slab is not limited, but the slab may be heated to 1200°C or lower. If the heating temperature of the slab is too high, precipitates within the slab may be re-dissolved and then finely precipitated, which may adversely affect magnetism. If the re-heating temperature is too low, hot rolling may be difficult. More specifically, it may be heated to a temperature of 1050 to 1200°C.

[0116] Next, a hot-rolled plate is manufactured by hot-rolling a slab. The thickness of the hot-rolled plate may be 1.0 to 2.0 mm. In the step of manufacturing the hot-rolled plate, the starting temperature for finishing rolling may be 920°C to 1050°C. Specifically, it may be 950°C to 1030°C. The finishing rolling end temperature may be 880°C or higher. The hot-rolled plate may be coiled at a temperature of 700°C or higher. More specifically, the thickness of the hot-rolled plate may be 1.3 to 2.0 mm.

[0117] After the step of manufacturing hot-rolled steel sheets, a hot-rolled sheet annealing step may be further included, which involves holding at 980 to 1050°C for at least 0.1 seconds and then holding at 850 to 950°C for 10 to 150 seconds. To reduce the volume of fine precipitates, it is preferable that the heating temperature is not too high, and after heating, slow cooling or cracking may be performed at a lower temperature to promote precipitate growth. More specifically, a heat treatment may be performed by holding at 1000 to 1030°C for 0.1 to 1 second and then holding at 870 to 930°C for 30 to 120 seconds.

[0118] Next, a cold-rolled sheet is manufactured by cold-rolling a hot-rolled steel sheet. At this time, the step of manufacturing the cold-rolled sheet includes a plurality of rolling passes and a rolling interruption step in which rolling is stopped for at least 10 seconds between at least one of the rolling passes.

[0119] By including a rolling interruption step, plate breakage caused by instability in widthwise rolling due to excessive deformation heat generation during cold rolling at very high reduction rates can be prevented by controlling the energy accumulated within the material. A pass refers to the number of times a steel plate passes through a rolling roll. In one embodiment of the present invention, cold rolling may include 2 to 9 passes. More specifically, it may include 5 to 8 passes. At this time, rolling interruption refers to a state in which rolling is interrupted, rather than being performed continuously to the final thickness without interruption for the entire connected steel plate coil. More specifically, the interruption time may be 10 to 500 seconds. More specifically, it may be 150 to 400 seconds.

[0120] During the rolling interruption stage, the temperature of the steel sheet may be 60 to 250°C. Stopping rolling at an appropriate temperature helps improve cold rolling performance. If the temperature is too low, brittleness increases, making rolling difficult, and if the temperature is too high, rolling in the width direction becomes unstable, which may cause problems in terms of rolling performance, such as plate breakage due to twisting. More specifically, at least one stage of the rolling interruption stage, the temperature of the steel sheet may be 60 to 230°C.

[0121] After cold rolling, the thickness may be 0.05 to 0.15 mm. If the thickness is too thin, fracture problems may occur during production, and if the thickness is too thick, it may have an adverse effect on ultra-high frequency iron loss. More specifically, the thickness may be 0.07 to 0.13 mm.

[0122] In one embodiment of the present invention, cold rolling can be performed in a single step without intermediate annealing.

[0123] Next, the cold-rolled sheet is annealed. The annealing step of the cold-rolled sheet may be 750°C to 1050°C. If the annealing temperature is too low, it is difficult to obtain appropriate magnetic properties. Conversely, if the annealing temperature is too high, surface defects may occur and high-frequency iron loss may deteriorate. More specifically, the annealing step of the cold-rolled sheet may be 800°C to 900°C.

[0124] When performing continuous annealing of cold-rolled sheets, the tension in the rolling direction (coil length direction) inside the annealing furnace is 0.35 to 0.85 kgf / mm 2 It can be done as follows. If the tension is too low, meandering or sagging may occur. On the other hand, if it becomes too high, iron loss may deteriorate. More specifically, the tension in the rolling direction is 0.50 to 0.80 kgf / mm 2 It can be done.

[0125] In the annealing stage of the cold-rolled sheet, the heating rate can be 20℃ / s or higher in the temperature range of 100 to 750℃. In one embodiment of the present invention, the thickness of the cold-rolled sheet is thin and the reduction ratio during cold rolling is high, thereby preventing the {111} orientation from elongating excessively and improving high-frequency iron loss. More specifically, the heating rate can be 30 to 100℃ / s.

[0126] During the annealing stage of the cold-rolled sheet, the cooling rate may be 17℃ / s or less in the temperature range from the cracking temperature to 600℃. If the cooling rate is too fast, iron loss may deteriorate. More specifically, the cooling rate can be controlled to 1 to 15℃ / s.

[0127] After annealing the cold-rolled sheet, an insulating film can be formed. The insulating film can be treated with organic, inorganic, or organic-inorganic composite films, and it is also possible to treat it with other insulating coating materials.

[0128]

[0129] The present invention will be explained in more detail below through examples. However, these examples are merely for illustrating the invention and the invention is not limited thereto.

[0130]

[0131] Experimental Example 1

[0132] As shown in Table 1 below, a slab was prepared containing Si, Mn, and Al, P: 0.012 wt%, C, S, N, and Ti each: 0.0025 wt%, and other impurities. The slab was maintained at 450°C or higher and charged into a reheating furnace. It was heated to 1150°C and hot-rolled through rough rolling and finish rolling. At this time, the finish rolling was performed with a starting temperature of 980°C and a finishing rolling end temperature of 901°C to produce a hot-rolled plate with a thickness of 1.8 mm. The hot-rolled plate was pickled and then cold-rolled in 8 passes to produce a cold-rolled plate with the thickness specified in Table 1 below. The process was interrupted between the first and second passes and maintained at 120°C for 10 minutes, and between the second and third passes, maintained at 70°C for 10 minutes. The cold-rolled sheet was heated to 750℃ at a rate of 25℃ / s and subjected to annealing at 900℃ for 50 seconds. During annealing, the tensile force was 0.65 kgf / mm² 2 It was controlled as follows. After cracking, it was cooled to 600℃ at a rate of 10℃ / s, and then cooled to room temperature.

[0133] Magnetic properties such as magnetic flux density and iron loss were measured for each specimen in the rolling direction and the direction perpendicular to rolling, and the average values ​​were presented.

[0134] Yield strength was measured by tensile testing at a tensile speed of 30 MPa / s.

[0135] Steel Grade Si Content (Wt%) Al Content (Wt%) Mn Content (Wt%) Type of Other Added Elements Resistivity (μΩ·cm) Final Thickness (mm) A 1 2.20 0.30 0.20 -40.9 0.10 A 2 2.25 0.40 0.26 -43.00 0.10 A 3 3.30 0.40 0.28 -54.10 0.10 A 4 3.25 0.7 20.22 -57.00 0.10 A 5 3.25 0.90 0.30 -59.6 0.10 A 6 3.50 0 .700.32-60.00.10A74.001.701.50-84.50.10A81.201.400.30-44.00.10A93.100.050.20-4 7.40.10A103.000.200.05-47.20.10B13.500.710.30Sn:0.06%60.00.10B23.500.710.30Sb: 0.03%60.00.10B33.500.710.30Bi: 0.01%60.00.10B43.500.710.30Cu: 0.06%60.00.10B53.500.710.30Cr: 0.06%60.00.10B63.500.710.30Ni: 0.04%60.00.10B73.500.710.30Mo: 0.02%60.00.10B83.500.710.30Ca: 0.004%60.00.10C13.500.881.26-68.10.20C23.500.710.28-59.90.25

[0136] Steel Grade Iron Loss W10 / 400(W / kg) Iron Loss W5 / 2000(W / kg) Iron Loss W5 / 2500(W / kg) Magnetic Flux Density B50(T) Yield Strength (Mpa) W5 / 2500 Eddy Current Loss (W / kg) (W5 / 2000) / (W10 / 400) Ratio (W5 / 2500) / (W10 / 400) Ratio Remarks A1 12.4 36.4 43.5 1.6 9280 8.1 62.9 43.51 Comparative Example A2 11.5 30.3 40.3 1.6 6310 7.2 12.6 33.50 Comparative Example A3 10.8 24.6 34.5 1.6 440 16.2 32.2 83.19 Inventive Example A4 10.4 23.3 32.2 1.6 340 55.9 42.2 43.10 Inventive Example A5 10.2 23.3 30.5 1.6 142 55.6 92.28 2.99 Invention Example A6 9.9 22.8 29.7 1.6 14 40 5.6 52.3 0 3.00 Invention Example A7 Fracture Comparative Example A8 12.6 35.2 43.3 1.6 6 32 6 7.6 32.7 9 3.4 4 Comparative Example A9 11.8 31.0 38.5 1.6 53 45 7.0 72.6 33.2 6 Comparative Example A10 11.9 31.7 39.1 1.6 43 55 7.1 12.6 6 3.2 9 Comparative Example B 19.3 21.3 28.11.634655.652.293.02 Invention Example B29.221.528.21.634555.652.343.07 Invention Example B39.621.628.41.634605.652.252.96 Invention Example B49.521.828.91.624595.652.293.04 Invention Example B59.521.728.81.624535.652.283.03 Invention Example B69.22 1.928.91.624485.652.383.14 Invention Example B79.421.728.71.624505.652.313.05 Invention Example B89.321.928.91.624415.652.353.11 Invention Example C110.332.143.21.6344519.953.124.19 Comparative Example C212.139.655.51.6642535.383.274.59 Comparative Example

[0137] As shown in Table 1, it can be confirmed that when the steel composition is properly controlled and the cold rolling thickness is appropriate, the ultra-high frequency iron loss (W5 / 2000, W5 / 2500) is excellent. On the other hand, when the composition is outside the range or the thickness is thick, it can be confirmed that the ultra-high frequency iron loss (W5 / 2000, W5 / 2500) is inferior.

[0138]

[0139] Experimental Example 2

[0140] A slab of component A6 from Table 1 was manufactured. The slab was maintained at 450°C or higher and charged into a reheating furnace. It was heated to 1150°C and hot-rolled through rough rolling and finish rolling (finish rolling). At this time, the finish rolling was performed with a starting temperature of 980°C and a finishing temperature of 903°C to produce a hot-rolled plate with a thickness of 1.8 mm. The hot-rolled plate was pickled and then cold-rolled in 8 passes to produce a cold-rolled plate with the thickness specified in Table 1 below. The process was stopped between the first and second passes at the times and temperatures specified in Table 1 below. The cold-rolled plate was heated to 750°C at a rate of 25°C / s and then annealed at 970°C for 60 seconds. During annealing, the tension was controlled as shown in Table 3. After annealing, it was cooled to 600°C at a rate of 10°C / s and then cooled to room temperature.

[0141] Magnetic properties such as magnetic flux density and iron loss were measured for each specimen in the rolling direction and the direction perpendicular to rolling, and the average values ​​were presented.

[0142] Yield strength was measured by tensile testing at a tensile speed of 30 MPa / s.

[0143] Specimen No. Temperature after interruption during cold rolling (°C) Time after interruption during cold rolling (sec) Final thickness (mm) Annealing temperature (°C) Annealing time (sec) Annealing furnace tension (kgf / mm 2 )Grain size (ND plane measurement, EBSD (Based on Number)(㎛)11403000.1750450.6529.821403000.1870450.6550.331403000.1900450.6558.841403000.1925450.6567.551403000.1950450.6579.261403000.1975450.6588.371403000.11000450.65104.982550.1870450.6548.291403000.1950450.3579.2101403000.1950450.7579.2

[0144] Specimen No. Yield Strength (Mpa) Iron Loss W10 / 400(W / kg) Iron Loss W5 / 2000(W / kg) Iron Loss W5 / 2500(W / kg) Magnetic Flux Density B50(T)(W5 / 2000) / (W10 / 400)(W5 / 2500) / (W10 / 400)166019.15941.6354.511.622.172.85249611.69926.6634.501.622.282.95345010.98524.1433.641.612.203.0644309.86523.2532 .131.612.363.2654209.51823.1131.701.612.433.3364109.05722.4030.731.602.473.3973809.49823.4032.561.612.463.43844012.50030.5037.501.592.443.0094258.81821.1129.701.622.393.371042210.52023.9032.801.612.273.12

[0145] As shown in Tables 3 and 4, it can be confirmed that when the steel composition is appropriately controlled and the cold rolling process is properly stopped at an appropriate time and temperature, the ultra-high frequency iron loss (W5 / 2000, W5 / 2500) is superior. The present invention is not limited to the embodiments described above but can be manufactured in various different forms, and those skilled in the art will understand that the present invention can be implemented in other specific forms without changing the technical concept or essential features of the invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

Claims

1. In weight%, it comprises Si: 1.5 to 5.0%, Al: 0.1 to 2.0%, Mn: 0.1 to 2.0%, and the remainder being Fe and unavoidable impurities, and W 10 / 400 W about 5 / 2000 The ratio of (W 5 / 2000 / W 10 / 400 ) is 1.5 to 2.7 and, W 10 / 400 W about 5 / 2500 The ratio of (W 5 / 2500 / W 10 / 400 Non-oriented electrical steel sheet having a ) of 2.3 to 3.

7.

2. In Paragraph 1, Non-oriented electrical steel sheet with a resistivity of 50 to 70 μΩ·cm.

3. In Paragraph 1, W 5 / 2000 This is 30W / kg or less, and W 5 / 2500 This is 35W / kg or less, and W 5 / 2500 Non-oriented electrical steel sheet with an eddy current loss of 7 W / kg or less.

4. In Paragraph 1, Non-oriented electrical steel sheet with a thickness of 0.05 to 0.15 mm.

5. In Paragraph 1, A non-oriented electrical steel sheet further comprising one or more of P: 0.03 wt% or less, C: 0.005 wt% or less, S: 0.005 wt% or less, Ti: 0.005 wt% or less, and N: 0.005 wt% or less.

6. In Paragraph 1, A non-oriented electrical steel sheet further comprising 0.005 to 0.200 weight% of one or more of Sn, Sb, Bi, Pb, Ge, and As, either individually or in their combined amount.

7. In Paragraph 1, A non-oriented electrical steel sheet further comprising one or more of Cu: 0.005 to 0.2 wt%, Cr: 0.01 to 0.5 wt%, Ni: 0.05 wt% or less, Zn: 0.01 wt% or less, and Co: 0.05 wt% or less.

8. In Paragraph 1, A non-oriented electrical steel sheet further comprising one or more of Mo: 0.03 wt% or less, B: 0.0050 wt% or less, V: 0.0050 wt% or less, Ca: 0.0050 wt% or less, Nb: 0.0050 wt% or less, Zr: 0.005 wt% or less, Te: 0.01 wt% or less, and Mg: 0.0050 wt% or less.

9. In Paragraph 1, Non-oriented electrical steel sheet with a yield strength of 330 MPa to 600 MPa.

10. A step of manufacturing a hot-rolled steel sheet by hot-rolling a slab containing Si: 1.5 to 5.0%, Al: 0.1 to 2.0%, Mn: 0.1 to 2.0% by weight, and the remainder being Fe and unavoidable impurities; A step of manufacturing a cold-rolled plate by cold-rolling the above hot-rolled steel plate and Cold-rolled plate annealing step for annealing the above-mentioned cold-rolled plate; Includes, The step of manufacturing the above cold-rolled plate includes a plurality of rolling passes, and A method for manufacturing a non-oriented electrical steel sheet comprising a rolling interruption step of stopping rolling for at least 1 second between at least one rolling pass.

11. In Paragraph 10, A method for manufacturing a non-oriented electrical steel sheet in which the temperature of the steel sheet is 60 to 250℃ during the above rolling interruption step.

12. In Paragraph 10, A method for manufacturing a non-oriented electrical steel sheet, wherein the above slab further comprises one or more of P: 0.03 wt% or less, C: 0.005 wt% or less, S: 0.005 wt% or less, Ti: 0.005 wt% or less, and N: 0.005 wt% or less.

13. In Paragraph 10, A method for manufacturing a non-oriented electrical steel sheet, wherein the above slab further comprises 0.005 to 0.200 weight% of one or more of Sn, Sb, Bi, Pb, Ge, and As, respectively or in their combined amount.

14. In Paragraph 10, A method for manufacturing a non-oriented electrical steel sheet, wherein the above slab further comprises one or more of Cu: 0.005 to 0.2 wt%, Cr: 0.01 to 0.5 wt%, Ni: 0.05 wt% or less, Zn: 0.01 wt% or less, and Co: 0.05 wt% or less.

15. In Paragraph 10, A method for manufacturing a non-oriented electrical steel sheet, wherein the above slab further comprises one or more of Mo: 0.03 wt% or less, B: 0.0050 wt% or less, V: 0.0050 wt% or less, Ca: 0.0050 wt% or less, Nb: 0.0050 wt% or less, Zr: 0.005 wt% or less, Te: 0.01 wt% or less, and Mg: 0.0050 wt% or less.

16. In Paragraph 10, A method for manufacturing a non-oriented electrical steel sheet, further comprising a hot-rolled sheet annealing step after the step of manufacturing the hot-rolled steel sheet, wherein the hot-rolled sheet is maintained at 980 to 1050°C for at least 0.1 seconds and then maintained at 850 to 950°C for 10 to 150 seconds.

17. In Paragraph 10, A method for manufacturing a non-oriented electrical steel sheet in which the heating rate in the temperature range of 100 to 750℃ during the annealing step of the cold-rolled sheet is 20℃ / s or higher.

18. In Paragraph 10, A method for manufacturing a non-oriented electrical steel sheet in which the cooling rate in the cracking temperature to 600℃ temperature range during the annealing step of the cold-rolled sheet is 17℃ / s or less.