Non-oriented electrical steel sheet and motor core including same

Abstract

A non-oriented electrical steel sheet and a motor core including the same are provided. [Solution] The non-oriented electrical steel sheet of the present invention contains, by weight, 2.0-6.5% Si, 0.1-1.3% Al, 0.3-2.0% Mn, 0.03% or less Sn, and 0.02% or less Sb, with the remainder being Fe and other unavoidable impurities, and is characterized in that it comprises a steel sheet base material that satisfies the following formula 1 and an insulating coating located on the steel sheet base material, and satisfies the following formula 2 before stress relief annealing, and satisfies the following formula 3 after stress relief annealing. [Formula 1] 0.030≧[Sn]+[Sb]≧0.005 [Formula 2] 0.1≧[Mn coating] / [Mn50] [Formula 3] 10≧[Mn coating] / [Mn50]≧1 (In formulas 1 to 3, [Sn] and [Sb] respectively represent the Sn and Sb contents, [Mn coating] represents the average Mn content (wt%) in the insulating coating, and [Mn50] represents the Mn content (wt%) at a depth of 50 μm from the interface between the steel sheet base material and the insulating coating toward the inside of the steel sheet base material.)

Description

[Technical field]

[0001] The present invention relates to a non-oriented electrical steel sheet and a motor core including the same, and more specifically to a non-oriented electrical steel sheet in which the adhesion of an insulating coating is improved by appropriately adjusting the Sn and Sb contents and increasing the number of shot balls projected during scale removal to prevent Mn diffusion into the insulating coating during stress relief annealing, and a motor core including the same. [Background technology]

[0002] Non-oriented electrical steel sheets are mainly used in motors that convert electrical energy into mechanical energy, and excellent magnetic properties are required for non-oriented electrical steel sheets to achieve high conversion efficiency in the process. In particular, as environmentally friendly technologies have been attracting attention in recent years, it is considered very important to increase the efficiency of motors, which account for more than half of the total electrical energy consumption, and as a result, the demand for non-oriented electrical steel sheets with excellent magnetic properties is increasing. The magnetic properties of non-oriented electrical steel sheets are mainly evaluated by iron loss and magnetic flux density. Iron loss refers to the energy loss that occurs at a specific magnetic flux density and frequency, and magnetic flux density refers to the degree of magnetization obtained under a specific magnetic field. The lower the iron loss, the more energy-efficient a motor can be manufactured under the same conditions, and the higher the magnetic flux density, the more compact the motor can be and the less copper loss it can have. Therefore, it is important to create non-oriented electrical steel sheets with low iron loss and high magnetic flux density.

[0003] The characteristics of non-oriented electrical steel sheets that must be considered vary depending on the operating conditions of the motor. The most important standard for evaluating the characteristics of non-oriented electrical steel sheets used in motors is W15 / 50, which is the iron loss when the motor is applied with a commercial frequency of 50 Hz and a magnetic field of 1.5 T. However, not all motors for various applications are based on W15 / 50 iron loss, and iron loss is evaluated at different frequencies and applied magnetic fields depending on the main operating conditions. In particular, for non-oriented electrical steel sheets used in the drive motors of recent electric vehicles, magnetic properties are often important in low magnetic fields of 1.0 T or less and high frequencies of 400 Hz or more, so the characteristics of non-oriented electrical steel sheets are evaluated with iron loss such as W10 / 400.

[0004] In order to manufacture products such as motors or transformers from non-oriented electrical steel sheets, the non-oriented electrical steel sheets must be slit into a specific shape. During this process, stress is applied to the non-oriented electrical steel sheets, and stress relief annealing is performed to remove this stress. During stress relief annealing, Mn in the steel sheet diffuses into the insulating coating, which causes a decrease in adhesion between the steel sheet and the insulating coating. Attempts have been made to suppress Mn diffusion by adding Sb and Sn and adjusting the relationship between the Al and Mn contents, but these attempts have limitations. The effect of suppressing Mn diffusion by forming a surface segregation element layer and a surface oxide layer was minimal, which resulted in a decrease in the bonding strength between the insulating coating layer and the base material. Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a non-oriented electrical steel sheet and a motor core including the same, specifically, a non-oriented electrical steel sheet in which the adhesion of an insulating coating is improved by appropriately adjusting the Sn and Sb contents and the amount of shot balls projected during descaling of a hot-rolled sheet to prevent diffusion of Mn into the insulating coating during stress relief annealing, and a motor core including the same. [Means for solving the problem]

[0006] The non-oriented electrical steel sheet of the present invention contains, by weight, 2.0-6.5% Si, 0.1-1.3% Al, 0.3-2.0% Mn, 0.03% or less (excluding 0%) Sn, and 0.02% or less (excluding 0%) Sb, with the remainder being Fe and other unavoidable impurities, and is characterized in that it comprises a steel sheet base material that satisfies the following formula 1 and an insulating coating located on the steel sheet base material, and satisfies the following formula 2 before stress relief annealing, and satisfies the following formula 3 after stress relief annealing. [Formula 1] 0.030≧[Sn]+[Sb]≧0.005 [Formula 2] 0.1≧[Mn coating] / [Mn50] [Formula 3] 10≧[Mn coating] / [Mn50]≧1 (In formulas 1 to 3, [Sn] and [Sb] respectively represent the Sn and Sb contents, [Mn coating] represents the average Mn content (wt%) in the insulating coating, and [Mn50] represents the Mn content (wt%) at a depth of 50 μm from the interface between the steel sheet base material and the insulating coating toward the inside of the steel sheet base material.)

[0007] The steel plate base material may further contain one or more of C, N, S, Ti, Nb, and V in an amount of 0.005% by weight or less. The steel plate base material may further contain one or more of Cu: 0.01 to 0.2 wt %, P: 0.100 wt % or less, B: 0.002 wt % or less, Mo: 0.01 wt % or less, Mg: 0.005 wt % or less, and Zr: 0.005 wt % or less. It is preferable that the average crystal grain size is 60 μm or less before stress relief annealing.

[0008] It is preferable that the iron loss W10 / 800 (W / kg) after stress relief annealing satisfies the following formula 4. [Formula 4] W10 / 800≦25+60×t (In formula 4, t represents the thickness of the steel plate (mm).) The stress relief annealing is preferably performed at a temperature of 800°C to 900°C in an atmosphere containing at least one of nitrogen, hydrogen and carbon monoxide and having a dew point of 0°C or lower.

[0009] The method for producing a non-oriented electrical steel sheet of the present invention includes the steps of: hot rolling a slab containing, by weight, 2.0 to 6.5% Si, 0.1 to 1.3% Al, 0.3 to 2.0% Mn, 0.03% or less (except 0%) Sn, and 0.02% or less (except 0%) Sb, with the remainder being Fe and other unavoidable impurities, and satisfying the following formula 1 to produce a hot-rolled sheet; removing scale present on the surface of the hot-rolled sheet; cold rolling the hot-rolled sheet from which the scale has been removed to produce a cold-rolled sheet; and annealing the cold-rolled sheet, wherein the step of removing the scale comprises using shot balls at a speed of 15 to 35 kg / (min m 2 ) onto the steel plate to remove scale. [Formula 1] 0.030≧[Sn]+[Sb]≧0.005 (In formula 1, [Sn] and [Sb] represent the Sn and Sb contents (wt%), respectively.)

[0010] The average particle size of the shot balls is 0.1 to 1 mm, and they can be projected for 1 to 60 seconds. The material of the shot balls is preferably an Fe-based alloy. In the cold-rolled sheet annealing step, annealing is preferably performed at a temperature of 700° C. to 1100° C. for 10 to 1000 seconds.

[0011] The method may further include a step of annealing the hot-rolled sheet prior to the step of removing the scale. The method may further include a step of performing stress relief annealing after the step of annealing the cold rolled sheet. The stress relief annealing step is preferably carried out at a temperature of 800° C. to 900° C. in an atmosphere containing one or more of nitrogen, hydrogen and carbon monoxide and having a dew point of 0° C. or lower.

[0012] The motor core of the present invention includes a rotor formed by laminating a plurality of non-oriented electromagnetic steel sheets, and a stator formed by laminating a plurality of non-oriented electromagnetic steel sheets, The non-oriented electrical steel sheet in the rotor contains, by weight, 2.0 to 6.5% Si, 0.1 to 1.3% Al, 0.3 to 2.0% Mn, 0.03% or less (excluding 0%) Sn, and 0.02% or less (excluding 0%) Sb, with the remainder being Fe and other unavoidable impurities, and satisfies the following formulas 1 and 2: The non-oriented electrical steel sheets in the stator contain, by weight, 2.0 to 6.5% Si, 0.1 to 1.3% Al, 0.3 to 2.0% Mn, 0.03% or less (excluding 0%) Sn, and 0.02% or less (excluding 0%) Sb, with the remainder being Fe and other unavoidable impurities, and are characterized in that they satisfy the following formulas 1 and 3. [Formula 1] 0.030≧[Sn]+[Sb]≧0.005 [Formula 2] 0.1≧[Mn coating] / [Mn50] [Formula 3] 10≧[Mn coating] / [Mn50]≧1 (In formulas 1 to 3, [Sn] and [Sb] respectively represent the Sn and Sb contents, [Mn coating] represents the average Mn content (wt%) in the insulating coating, and [Mn50] represents the Mn content (wt%) at a depth of 50 μm from the interface between the steel sheet base material and the insulating coating toward the inside of the steel sheet base material.)

[0013] The non-oriented electrical steel sheets included in the stator and rotor may be non-oriented electrical steel sheets originating from the same coil. It is preferable that the difference in the Si, Al and Mn contents between the non-oriented electrical steel sheets included in the stator and the rotor is 0.20% by weight or less. Effect of the Invention

[0014] According to the present invention, the non-oriented electrical steel sheet of the present invention contains Sn and Sb within certain ranges, and by appropriately controlling the amount of shot balls projected during scaling, it is possible to prevent the Mn component contained in the steel sheet base material from diffusing into the insulating coating during stress relief annealing, and to maintain the bonding strength between the insulating coating and the steel sheet base material even after stress relief annealing. This allows the performance of environmentally friendly automobile motors, highly efficient home appliance motors, and super-premium electric motors to be additionally improved by stress relief annealing. [Brief description of the drawings]

[0015] [Figure 1] 1 is a schematic diagram of a cross section of a non-oriented electrical steel sheet according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] 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 only to distinguish one part, component, region, layer or section from another part, component, region, layer or section. Thus, the first part, component, region, layer or section described below may be read as the second part, component, region, layer or section without departing from the scope of the present invention. The terminology used herein is merely for the purpose of referring to particular embodiments and is not intended to limit the present invention. As used herein, the singular form includes the plural form unless the text clearly indicates otherwise. As used herein, the meaning of "comprising" embodies certain features, regions, integers, steps, operations, elements and / or components and does not exclude the presence or addition of other features, regions, integers, steps, operations, elements and / or components.

[0017] When an element is referred to as being "on" another element, it means that it is directly on top of the other element, or there may be other elements between them. In contrast, when an element is referred to as being "directly on" another element, there are no other elements between them. Moreover, unless otherwise specified, % means % by weight, and 1 ppm is 0.0001% by weight. In an embodiment of the present invention, the term "additionally containing an additional element" means that the additional amount of the additional element is substituted for the remaining iron (Fe).

[0018] Unless otherwise defined, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by a person of ordinary skill in the art to which the present invention belongs. Terms defined in commonly used dictionaries are additionally interpreted to have a meaning consistent with the relevant technical literature and the presently disclosed content, and are not interpreted in an ideal or very formal sense unless defined. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to exemplary embodiments thereof, so that those skilled in the art can easily practice the present invention. However, the present invention may be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein.

[0019] FIG. 1 shows a schematic cross section of a non-oriented electrical steel sheet according to one embodiment of the present invention. 1, a non-oriented electrical steel sheet 100 includes a steel sheet base material 10 and an insulating coating 20 located on the surface of the steel sheet base material 10. Within the steel sheet base material 10, there is a surface portion 30 formed from the surface of the base material toward the inside. The steel plate base material 10 according to one embodiment of the present invention contains, by weight, 2.0-6.5% Si, 0.1-1.3% Al, 0.3-2.0% Mn, 0.03% or less (excluding 0%) Sn, and 0.02% or less (excluding 0%) Sb, with the remainder being Fe and other unavoidable impurities. The reasons for limiting the components of the steel plate base material 10 will be explained below.

[0020] Si:2.0~6.5wt% Silicon (Si) plays a role in increasing the resistivity of the material and reducing iron loss, and if too little is added, the effect of improving high-frequency iron loss becomes insufficient. Conversely, if too much is added, the hardness of the material increases, and the cold rolling property is extremely deteriorated, which may result in a decrease in productivity and punchability. Therefore, it is preferable to add Si within the above-mentioned range. Specifically, it is preferable to include 2.0 to 5.0% by weight. More specifically, it is preferable to include 3.0 to 4.0% by weight.

[0021] Al: 0.1~1.3% by weight Aluminum (Al) plays a role in increasing the resistivity of the material and reducing iron loss. If too little Al is added, it is not effective in reducing high-frequency iron loss, and there is a risk that nitrides will be formed finely, reducing magnetic properties. Conversely, if too much is added, there is a risk that problems will arise in all processes, such as steelmaking and continuous casting, and productivity will be greatly reduced. Therefore, it is preferable to add Al within the above-mentioned range. Specifically, it is preferable to include 0.5 to 1.2% by weight. More specifically, it is preferable to include 0.7 to 1.0% by weight.

[0022] Mn:0.3~2.0wt% Manganese (Mn) is an element that increases the resistivity of a material, improves core loss, and forms sulfides. If too little Mn is added, there is a risk that fine sulfides will precipitate and reduce magnetic properties. Conversely, if too much Mn is added, there is a risk that it will promote the formation of {111} texture, which is detrimental to magnetic properties, and reduce magnetic flux density. Therefore, it is recommended to add Mn within the above-mentioned range. Specifically, it is recommended that Mn be included in an amount of 0.5 to 1.5 wt%. In one embodiment of the present invention, the resistivity may be 55 to 80 μΩ·cm.

[0023] Sn: 0.03% by weight or less, and Sb: 0.02% by weight or less Tin (Sn) and antimony (Sb) are added to improve magnetic properties by suppressing the diffusion of nitrogen through the grain boundaries as segregating elements at the grain boundaries, suppressing the {111} texture that is harmful to magnetism, and increasing the advantageous {100} texture. If Sn and Sb are added in excessive amounts, they hinder grain growth, lowering magnetism and worsening rolling properties. Therefore, it is preferable to add Sn and Sb within the above-mentioned ranges. Specifically, it is preferable to include Sn: 0.005 to 0.050 wt% and Sb: 0.005 to 0.050 wt%. More specifically, it is preferable to include Sn: 0.01 to 0.02 wt% and Sb: 0.01 to 0.02 wt%.

[0024] Sn and Sb can satisfy the following formula 1. [Formula 1] 0.030≧[Sn]+[Sb]≧0.005 (In formula 1, [Sn] and [Sb] represent the contents of Sn and Sb, respectively.) In one embodiment of the present invention, Sn or Sb concentrates in the steel sheet surface portion 30 and prevents Mn from diffusing from the steel sheet surface portion 30 to the insulating coating 20 during stress relief annealing. When the total amount of Sn and Sn is less than 0.005 wt %, a large amount of Mn diffuses into the insulating coating 20, causing a decrease in adhesion. Conversely, when an excessive amount of Sn or Sb is contained, the diffusion of Mn into the insulating coating 20 is excessively strongly prevented, resulting in a decrease in adhesion. Specifically, the value of formula 1 is preferably 0.010 to 0.025.

[0025] The steel plate base material 10 may further contain one or more of Cu: 0.01 to 0.2 wt %, P: 0.100 wt % or less, B: 0.002 wt % or less, Mo: 0.01 wt % or less, Mg: 0.005 wt % or less, and Zr: 0.005 wt % or less.

[0026] Cu:0.01~0.20wt% Copper (Cu) plays a role in forming sulfides together with Mn. When Cu is further added, if too little Cu is added, there is a risk that CuMnS will precipitate finely and reduce the magnetic property. If too much Cu is added, there is a risk that high-temperature brittleness will occur and cracks will form during continuous casting or hot rolling. Specifically, Cu can be further added in an amount of 0.05 to 0.10 wt %.

[0027] P: 0.100% by weight or less Phosphorus (P) not only plays a role in increasing the resistivity of the material, but also plays a role in improving the texture by segregating to the grain boundaries, increasing the resistivity, and reducing iron loss, so it can be added additionally. However, if the amount of P added is excessively large, it may lead to the formation of a texture unfavorable to magnetism, resulting in no effect of improving the texture, and may segregate excessively to the grain boundaries, resulting in reduced rollability and workability, making production difficult. Therefore, it is preferable to add P within the above-mentioned range. Specifically, it is preferable to include 0.001 to 0.090% by weight of P. More specifically, it is preferable to include 0.005 to 0.085% by weight of P.

[0028] B: 0.002% by weight or less, Mo: 0.01% by weight or less, Mg: 0.005% by weight or less, and Zr: 0.005% by weight or less In the case of boron (B), molybdenum (Mo), magnesium (Mg), and zirconium (Zr), they react with impurity elements to form fine sulfides, carbides, and nitrides, which have a detrimental effect on magnetic properties, so it is advisable to limit the contents of these elements as described above. The steel plate base material 10 may further contain one or more of C, N, S, Ti, Nb, and V in an amount of 0.005% by weight or less.

[0029] C: 0.005% by weight or less When a large amount of carbon (C) is added, it expands the austenite region, increases the phase transformation range, inhibits the growth of ferrite grains during annealing, and increases iron loss. It also combines with Ti and other elements to form carbides, reducing magnetism, and increases iron loss due to magnetic aging when the final product is processed into an electrical product and used. Therefore, it is recommended to add C within the above-mentioned range. More specifically, it is recommended that the C content be 0.003% by weight or less.

[0030] S: 0.005% by weight or less Sulfur (S) forms fine sulfides inside the base metal, inhibits grain growth, and deteriorates iron loss, so it is preferable to add as little as possible. If a large amount of S is included, it may combine with Mn and the like to form precipitates or induce high-temperature brittleness during hot rolling. Therefore, it is preferable to further include S at 0.005 wt% or less. Specifically, it is preferable to further include S at 0.0030 wt% or less. More specifically, it is preferable to further include S at 0.0001 to 0.0030 wt%.

[0031] N: 0.005% by weight or less Nitrogen (N) forms nitrides by strongly bonding with Al, Ti, etc., suppressing grain growth and hindering magnetic domain movement when precipitated, so it is preferable to add a small amount of N. Therefore, it is preferable to add N within the above-mentioned range. Specifically, it is preferable to include N in an amount of 0.003 wt% or less.

[0032] Ti, Nb, V: 0.005% by weight or less Titanium (Ti), niobium (Nb), vanadium (V), and the like are also strong carbonitride-forming elements, so it is preferable to avoid adding them as much as possible, and each of them should be contained in an amount of 0.01% by weight or less.

[0033] The balance includes Fe and inevitable impurities. The inevitable impurities are impurities that are mixed in during the steelmaking stage and the manufacturing process of the grain-oriented electrical steel sheet, and are widely known in the art, so a detailed description will be omitted. In one embodiment of the present invention, the addition of elements other than the above-mentioned alloy components is not excluded, and various elements may be included within a range that does not impair the technical concept of the present invention. When an additional element is further included, it is included to replace the balance Fe.

[0034] In one embodiment of the present invention, the addition of Sn and Sb to the steel sheet base material 10 can suppress the diffusion of Mn into the insulating coating 20 at the stress relief annealing stage. If the amount of Mn diffused into the insulating coating 20 increases and the Mn content of the insulating coating becomes excessively large, the insulating properties of the insulating coating may be degraded and the bonding strength between the insulating coating and the base material may be weakened.

[0035] When the Mn concentration at a depth of 50 μm from the surface of the steel sheet base material 10 toward the inside of the base material is [Mn50] and the Mn concentration in the insulating coating 20 is [Mn coating], the following formula 2 is satisfied before stress relief annealing, and the following formula 3 is satisfied after stress relief annealing. [Formula 2] 0.01≧[Mn coating] / [Mn50] [Formula 3] 10≧[Mn coating]≧1 The stress relief annealing is preferably performed at a temperature of 800° C. to 900° C. in an atmosphere containing one or more of nitrogen, hydrogen, and carbon monoxide and having a dew point of 0° C. or lower. The time is preferably 10 minutes to 300 minutes.

[0036] By adding Sn and Sb to the steel sheet base material 10, a surface portion 30 is formed in which Sn, Sb, and O are concentrated from the surface of the steel sheet base material 10 toward the inside of the base material. In other words, the surface portion 30 exists at the interface between the steel sheet base material 10 and the insulating coating 20. This surface portion 30 serves to prevent Mn from diffusing from the steel sheet base material 10 to the insulating coating 20. The surface portion 30 refers to a portion with an oxygen content of 5% by weight or more, and is formed from the surface toward the inside as oxygen in the atmosphere penetrates into the steel sheet while it is exposed to oxygen in the manufacturing process. The thickness of the surface portion 30 thus divided is preferably 10 to 50 nm.

[0037] If the surface portion 30 is formed too thin, it is difficult to adequately prevent the above-mentioned Mn diffusion. If the surface portion 30 is formed too thick, there is a risk of the magnetic properties being deteriorated. Therefore, it is preferable that the surface portion 30 has a thickness within the above-mentioned range. The insulating coating 20 is located on the surface of the steel sheet base material 10. The insulating coating 20 serves to provide insulation between the non-oriented electrical steel sheets when the non-oriented electrical steel sheets are laminated to manufacture a product. The insulating coating 20 may be formed by treating with an organic, inorganic or organic-inorganic composite coating agent, or by treating with other coating agents capable of insulation. For example, when the insulating coating 20 is formed using a phosphate-based insulating coating composition, the insulating coating may contain 5 to 50 weight % P and 0.01 weight % or less Mn. Thus, the insulating coating 20 before stress relief annealing contains a small amount of Mn. The balance is O. It may further contain 1 to 10 weight % Si.

[0038] The insulating coating 20 before stress relief annealing satisfies the following formula 1. [Formula 2] 0.1≧[Mn coating] / [Mn50] (In formula 2, [Mn coating] indicates the average Mn content (wt%) in the insulating coating, and [Mn50] indicates the Mn content (wt%) at a depth of 50 μm from the interface between the steel sheet base material and the insulating coating toward the inside of the steel sheet base material.) On the other hand, the insulating coating after stress relief annealing can contain 2.0 to 25.0 wt % Mn due to partial diffusion of Mn in the steel sheet base material 10. More specifically, it can contain 2.0 to 17.0 wt % Mn. The remaining components are preferably the same as those before stress relief annealing. In other words, the insulating coating 20 after stress relief annealing can satisfy the following formula 2. [Formula 3] 10≧[Mn coating] / [Mn50]≧1 (In formula 3, [Mn coating] represents the average Mn content (wt%) in the insulating coating.) Specifically, the value of formula 3 is preferably 2.0 to 9.5. More specifically, the value of formula 3 is preferably 3.0 to 9.3. That is, the insulating coating 20 after stress relief annealing can contain 5 to 50 weight % P and 2.0 to 10.0 weight % Mn. The balance is preferably O. It can further contain 1 to 10 weight % Si.

[0039] When an appropriate amount of Mn is diffused into the insulating coating 20, the inorganic ratio of the insulating coating increases, improving stability at high temperatures. In this case, stability is ensured during the stress relief annealing stage, and the bonding strength between the base material and the insulating coating 20 can be maintained thereafter. As a result, after stress relief annealing, a bonding strength of 5B or more can be maintained as a result of a crosscut test (ASTM D3559: Crosscut Test).

[0040] The average crystal grain size before stress relief annealing may be 60 μm or less. Before stress relief annealing, the average crystal grain size is small, and the mechanical strength of the steel sheet is excellent. On the other hand, after stress relief annealing, the iron loss W10 / 800 (W / kg) can satisfy the following formula 4. [Formula 4] W10 / 800≦25+60×t (In formula 4, t represents the thickness of the steel plate (mm).) After the stress relief annealing, stress relief annealing is performed to improve the core loss. More specifically, W10 / 800≦21+60×t can be satisfied.

[0041] A method for manufacturing a non-oriented electrical steel sheet according to an embodiment of the present invention includes a step of hot rolling a slab to manufacture a hot-rolled sheet, a step of cold rolling the hot-rolled sheet to manufacture a cold-rolled sheet, and a step of annealing the cold-rolled sheet. First, the slab is hot rolled. The alloy composition of the slab has been explained in the alloy composition of the non-oriented electrical steel sheet, so a duplicated explanation will be omitted. Since the alloy composition does not substantially change during the manufacturing process of the non-oriented electrical steel sheet, the alloy composition of the non-oriented electrical steel sheet and the slab are substantially the same.

[0042] Specifically, the slab contains, by weight, 2.0-6.5% Si, 0.1-1.3% Al, 0.3-2.0% Mn, 0.03% or less (except 0%) Sn, and 0.02% or less (except 0%) Sb, with the balance being Fe and other unavoidable impurities. The slab satisfies the following formula 1. [Formula 1] 0.030≧[Sn]+[Sb]≧0.005 (In formula 1, [Sn] and [Sb] represent the contents of Sn and Sb, respectively.) Other additional elements have been explained in the alloy components of the non-oriented electrical steel sheet, so duplicate explanations will be omitted.

[0043] The slab can be heated before hot rolling. The heating temperature of the slab is not limited, but the slab can be heated to 1100 to 1250 ° C. If the slab heating temperature is too high, the precipitates that impair the magnetic property may remelt and precipitate finely after hot rolling. The slab is then hot rolled to produce a hot rolled sheet, the thickness of which can be 2-3.0 mm.

[0044] The method may further include annealing the hot-rolled sheet after the step of producing the hot-rolled sheet. The hot-rolled sheet annealing is preferably performed when producing a high-grade electrical steel sheet that does not undergo phase transformation, and is effective in improving the texture of the final annealed sheet and increasing the magnetic flux density. At this time, the step of annealing the hot-rolled sheet is preferably performed at a temperature of 850 to 1200°C. If the annealing temperature of the hot-rolled sheet is too low, less than 850°C, the structure does not grow or grows finely, making it difficult to expect an increase in magnetic flux density. If the annealing temperature of the hot-rolled sheet is too high, the magnetic properties may deteriorate and the rolling workability may deteriorate due to deformation of the sheet shape. The annealing of the hot-rolled sheet is performed as necessary to increase the orientation favorable to magnetism, and may be omitted.

[0045] Next, scale present on the surface of the hot-rolled or annealed hot-rolled sheet is removed. In one embodiment of the present invention, the shot ball projection amount is increased to contribute to the formation of a Sn / Sb-enriched layer on the surface of the base material, thereby controlling Mn diffusion into the insulation coating. The scale removal stage involves using shot balls at 15 to 35 kg / (min m 2 ) onto the steel sheet to remove scale. If the amount of shot balls projected is too small, the remaining oxide layer on the surface will prevent the formation of a Sn / Sb concentrated layer, making it difficult to control the diffusion of Mn. Conversely, if the amount of shot balls projected is too large, the surface of the steel sheet will be significantly damaged, so the upper limit can be appropriately adjusted. More specifically, the amount of shot balls projected is 17~30kg / (min·m 2 ) can be projected onto the steel plate.

[0046] The average particle size of the shot balls is 0.1 to 1 mm, and they can be projected for 1 to 60 seconds. More specifically, the average particle size of the shot balls is 0.3 to 0.8 mm, and they can be projected for 5 to 30 seconds. The average particle size of the shot balls and the shot ball projection time also affect the diffusion of Mn into the insulating coating. The material of the shot balls is not particularly limited, but it is preferable to use an Fe-based alloy.

[0047] Next, the hot rolled sheet is cold rolled to produce a cold rolled sheet. The cold rolling is final rolled to a thickness of 0.15mm to 0.65mm. If necessary, a second cold rolling can be performed after the first cold rolling and intermediate annealing, and the final reduction ratio can be in the range of 50 to 95%. Next, the cold-rolled sheet is annealed. The cold-rolled sheet is annealed for 10 to 1000 seconds in the range of 700 to 1100°C so that the grain size in the cross section of the steel sheet is 20 to 150 μm. If the cold-rolled sheet annealing temperature is too low, the grains may be small and the iron loss may deteriorate. If the temperature is too high, the grains are coarsened, the abnormal eddy current loss increases, and the total iron loss increases. More specifically, it is preferable to anneal in the range of 900 to 1050°C.

[0048] After cold-rolling annealing, the steel sheet can completely recrystallize (99% or more) the structure processed by cold rolling. During annealing of the cold-rolled sheet, the heating rate to the soaking temperature may be 30 to 150° C. / sec. Only when the heating rate is appropriately controlled can the oxide layer be formed thin and dense to prevent the diffusion of Mn. In the step of annealing the cold-rolled sheet, the cold-rolled sheet is preferably annealed in an atmosphere containing 40 vol% or less of hydrogen (H2) and 60 vol% or more of nitrogen, with a dew point of 0 to -40°C. Specifically, the cold-rolled sheet is preferably annealed in an atmosphere containing 0 to 10 vol% of hydrogen and 90 to 100 vol% of nitrogen. Only when the annealing atmosphere is appropriately controlled can a thin and dense oxide layer be formed to prevent the diffusion of Mn.

[0049] Next, after annealing the cold-rolled sheet, an insulating coating can be formed. The insulating coating can be treated with an organic, inorganic, or organic-inorganic composite coating agent, or can be treated with other coating agents capable of insulation. For example, it can be formed by applying an insulating coating forming composition containing 40 to 70% by weight of metal phosphate and 0.5 to 10% by weight of silica. The insulating coating contains 5% by weight or more of P, and the steel sheet base material is classified as containing less than 5% by weight of P. Next, a stress relief annealing step is performed at a temperature of 700° C. to 850° C. for a time of 10 minutes to 300 minutes.

[0050] A motor core according to one embodiment of the present invention includes a rotor formed by laminating a plurality of non-oriented electromagnetic steel sheets, and a stator formed by laminating a plurality of non-oriented electromagnetic steel sheets. The non-oriented electrical steel sheets in the rotor contain, by weight, 2.0 to 6.5% Si, 0.1 to 1.3% Al, 0.3 to 2.0% Mn, 0.03% or less (excluding 0%) Sn, and 0.02% or less (excluding 0%) Sb, with the remainder being Fe and other unavoidable impurities, and satisfying the following formulas 1 and 2. The non-oriented electrical steel sheets in the stator contain, by weight, 2.0 to 6.5% Si, 0.1 to 1.3% Al, 0.3 to 2.0% Mn, 0.03% or less (excluding 0%) Sn, and 0.02% or less (excluding 0%) Sb, with the remainder being Fe and other unavoidable impurities, and satisfying the following formulas 1 and 3. [Formula 1] 0.030≧[Sn]+[Sb]≧0.005 [Formula 2] 0.1≧[Mn coating] / [Mn50] [Formula 3] 10≧[Mn coating] / [Mn50]≧1 (In formulas 1 to 3, [Sn] and [Sb] respectively represent the Sn and Sb contents, [Mn coating] represents the average Mn content (wt%) in the insulating coating, and [Mn50] represents the Mn content (wt%) at a depth of 50 μm from the interface between the steel sheet base material and the insulating coating toward the inside of the steel sheet base material.)

[0051] In the case of rotors, mechanical properties are more important than magnetic properties, so the SRA process, which can degrade mechanical properties, can be omitted. For this reason, the properties of the non-oriented electrical steel sheet before SRA are derived. The steel components of the non-oriented electrical steel sheet, Mn diffusion, and Mn in the insulation coating have been explained in relation to the non-oriented electrical steel sheet described above, so duplicate explanations will be omitted. In the case of a stator, magnetic properties are more important than mechanical properties, and after punching and lamination, SRA can be used to improve magnetic properties. Therefore, the properties of non-oriented electrical steel appear in the stator after SRA. The steel components of non-oriented electrical steel, the diffusion of Mn, and Mn in the insulation coating have been explained in relation to the non-oriented electrical steel mentioned above, so a duplicate explanation will be omitted.

[0052] On the other hand, the stator and rotor are stamped into a rough doughnut or disk shape. When the stator and rotor are manufactured by punching out the stator and rotor from separate coils of non-oriented electrical steel, the remaining parts are scrapped, which increases the process cost and wastes resources and energy. When the stator and rotor are manufactured by punching out the stator and rotor from the same coil, the parts that are scrapped can be minimized.

[0053] Therefore, in one embodiment of the present invention, the non-oriented electrical steel sheets contained in the stator and the rotor may be non-oriented electrical steel sheets derived from the same coil. In one embodiment of the present invention, the meaning of originating from the same coil means that the steel components such as Si, Al, and Mn in the non-oriented steel sheets contained in the stator and the rotor are substantially the same. Specifically, it means that the difference in the Si, Al, and Mn content between the stator and the rotor is 0.20% by weight or less. Specifically, it means that the difference in the Si, Al, and Mn content between the stator and the rotor is 0.10% by weight or less. More specifically, it means that the difference in the Si, Al, and Mn content between the stator and the rotor is 0.05% by weight or less. More specifically, it means that the difference in the Si, Al, and Mn content between the stator and the rotor is 0.01% by weight or less. In the case of Sn and Sb, the difference in the content is preferably 0.01% by weight or less. Specifically, it is preferably 0.005% by weight or less. More specifically, it is preferably 0.001% by weight or less. The composition of the insulation coating may also be substantially the same between the stator and rotor.

[0054] The present invention will be described in more detail with reference to the following examples, which are merely for illustrative purposes and are not intended to limit the scope of the present invention. Example 1 A slab was manufactured, which is composed of the following Tables 1 and 2, the balance being Fe and other unavoidably mixed impurities. The slab was heated to 1150°C, and hot-rolled to a thickness of 2.3 mm by finish rolling at 850°C. The hot-rolled hot-rolled sheet was annealed at 1100°C for 4 minutes, and then blasted with the shot ball projection amount summarized in Table 3 below to remove scale. Then, the sheet was cold-rolled to a thickness of 0.27 mm, and then heated at a rate of 100°C / s, and finally annealed at 970°C for 5 minutes in a nitrogen atmosphere. An insulating coating was formed to a thickness of 0.5 μm using an insulating coating composition containing 50 wt% Al phosphate and 5 wt% silica.

[0055] Then, the specimen was annealed at 825℃ for 1 hour to relieve stress. As a result, a non-oriented electrical steel sheet with stress relief was finally manufactured. The composition in the depth direction was measured three times using a glow discharge spectrometer, and the average values ​​of Mn coating and Mn50 are shown in Table 3 below according to the experimental conditions. The adhesion was measured by the crosscut test (ASTM D3359).

[0056] [Table 1]

[0057] [Table 2]

[0058] [Table 3]

[0059] [Table 4]

[0060] As shown in Tables 1 to 4, in the examples in which the appropriate amounts of Sn and Sb are contained and the amount of shot balls is adjusted upward to prevent diffusion of Mn, it can be confirmed that the Mn component of the insulation coating and the Mn content at a depth of 50 μm toward the inside of the steel sheet base material are appropriately adjusted after stress relief annealing is performed. In contrast, in the cases of Nos. 15 to 20, which have small amounts of Sn and Sb, the diffusion of Mn cannot be effectively prevented and a large amount of Mn is present in the insulation coating, and in the cases of Nos. 11 to 14 and 21 to 22, which have large amounts of Sn and Sb, it can be confirmed that a small amount of Mn is present in the insulation coating. On the other hand, in Nos. 23 to 26, which do not satisfy the projection amount condition even though they contain appropriate amounts of Sn and Sb, it can be confirmed that the insulation coating contains either an excessive amount or an insufficient amount of Mn.

[0061] The present invention is not limited to the embodiments, and can be manufactured in various different forms, and a person skilled in the art to which the present invention pertains will understand that the present invention can be embodied in other specific forms without changing the technical idea or essential features of the present invention. Therefore, it should be understood that the embodiments described above are illustrative in all respects and are not limiting. [Explanation of symbols]

[0062] 100: non-oriented electrical steel sheet, 10: steel sheet base material, 20: insulating coating, 30: oxide layer

Claims

1. The present invention comprises a steel plate base material containing, by weight percent, 2.0 to 6.5% Si, 0.1 to 1.3% Al, 0.3 to 2.0% Mn, 0.03% or less (excluding 0%) Sn, and 0.02% or less (excluding 0%) Sb, with the balance being Fe and other unavoidable impurities, and satisfying the following formula 1, and an insulating coating located on the steel plate base material, A non-oriented electrical steel sheet, characterized in that it satisfies the following formula 2 before stress relief annealing, and satisfies the following formula 3 after stress relief annealing. [Formula 1] 0.030≧[Sn]+[Sb]≧0.005 [Formula 2] 0.1≧[Mn coating] / [Mn50] [Formula 3] 10≧[Mn coating] / [Mn50]≧1 (In Formulas 1 to 3, [Sn] and [Sb] respectively represent the Sn and Sb contents (wt%), [Mn coating] represents the average Mn content (wt%) in the insulating coating, and [Mn50] represents the Mn content (wt%) at a depth of 50 μm from the interface between the steel sheet base material and the insulating coating toward the inside of the steel sheet base material.)

2. 2. The non-oriented electrical steel sheet according to claim 1, wherein the steel sheet base material further contains one or more of C, N, S, Ti, Nb, and V in an amount of 0.005% by weight or less.

3. 2. The non-oriented electrical steel sheet according to claim 1, wherein the steel sheet base material further contains one or more of Cu: 0.01 to 0.2 wt %, P: 0.100 wt % or less, B: 0.002 wt % or less, Mo: 0.01 wt % or less, Mg: 0.005 wt % or less, and Zr: 0.005 wt % or less.

4. 2. The non-oriented electrical steel sheet according to claim 1, wherein the average crystal grain size before the stress relief annealing is 60 μm or less.

5. 2. The non-oriented electrical steel sheet according to claim 1, wherein the iron loss W10 / 800 (W / kg) after the stress relief annealing satisfies the following formula 4: [Formula 4] W10 / 800≦25+60×t (In formula 4, t represents the thickness of the steel plate (mm).)

6. The non-oriented electrical steel sheet according to claim 1, characterized in that the stress relief annealing is performed at a temperature of 800°C to 900°C in an atmosphere containing one or more of nitrogen, hydrogen and carbon monoxide and having a dew point of 0°C or lower.

7. A step of producing a hot-rolled sheet by hot-rolling a slab containing, by weight, 2.0 to 6.5% Si, 0.1 to 1.3% Al, 0.3 to 2.0% Mn, 0.03% or less (excluding 0%) Sn, and 0.02% or less (excluding 0%) Sb, with the balance being Fe and other inevitable impurities, and satisfying the following formula 1; removing scale present on the surface of the hot-rolled strip; cold rolling the descaled hot-rolled sheet to produce a cold-rolled sheet; and annealing the cold-rolled sheet. The scale removing step is performed by subjecting the shot balls to a pressure of 15 to 35 kg / (min.m ２ ) onto the steel sheet to remove scale. [Formula 1] 0.030≧[Sn]+[Sb]≧0.005 (In formula 1, [Sn] and [Sb] represent the contents (wt%) of Sn and Sb, respectively.)

8. The method for producing a non-oriented electrical steel sheet according to claim 7, wherein the average particle size of the shot balls is 0.1 to 1 mm, and the shot balls are projected for 1 to 60 seconds.

9. The method for producing a non-oriented electrical steel sheet according to claim 7, characterized in that the material of the shot balls is an Fe-based alloy.

10. 8. The method of claim 7, wherein the cold-rolled sheet is annealed at a temperature of 700 to 1100° C. for 10 to 1000 seconds.

11. The method of claim 7, further comprising the step of annealing the hot-rolled sheet before the step of removing the scale.

12. The method of claim 7, further comprising the step of performing stress relief annealing after the step of annealing the cold rolled sheet.

13. The rotor is made of a plurality of non-oriented electromagnetic steel sheets laminated together, and the stator is made of a plurality of non-oriented electromagnetic steel sheets laminated together, The non-oriented electrical steel sheet in the rotor contains, by weight, 2.0 to 6.5% Si, 0.1 to 1.3% Al, 0.3 to 2.0% Mn, 0.03% or less (excluding 0%) Sn, and 0.02% or less (excluding 0%) Sb, with the remainder being Fe and other unavoidable impurities, and satisfies the following formulas 1 and 2: A motor core characterized in that the non-oriented electrical steel sheets in the stator contain, by weight, 2.0 to 6.5% Si, 0.1 to 1.3% Al, 0.3 to 2.0% Mn, 0.03% or less (excluding 0%) Sn, and 0.02% or less (excluding 0%) Sb, with the remainder being Fe and other unavoidable impurities, and which satisfies the following formulas 1 and 3. [Formula 1] 0.030≧[Sn]+[Sb]≧0.005 [Formula 2] 0.1≧[Mn coating] / [Mn50] [Formula 3] 10≧[Mn coating] / [Mn50]≧1 (In Formulas 1 to 3, [Sn] and [Sb] respectively represent the Sn and Sb contents, [Mn coating] represents the average Mn content (wt%) in the insulating coating, and [Mn50] represents the Mn content (wt%) at a depth of 50 μm from the interface between the steel sheet base material and the insulating coating toward the inside of the steel sheet base material.)

14. 14. The motor core of claim 13, wherein the non-oriented electrical steel sheets included in the stator and the rotor originate from the same coil.

15. 14. The motor core according to claim 13, wherein a difference in Si, Al and Mn content between the non-oriented electrical steel sheets included in the stator and the rotor is 0.20 wt % or less.

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