Non-oriented electrical steel sheet, its manufacturing method and motor core including the same

Abstract

To provide a non-oriented electrical steel sheet in which the Cr content is appropriately adjusted to prevent diffusion of Mn into an insulating film during stress relief annealing and improve adhesion of the insulating film, a manufacturing method thereof, and a motor core including the same. [Solution] The non-oriented electrical steel sheet of the present invention comprises a steel sheet base material and an insulating coating located on the steel sheet base material, which contain, by weight, 2.0-6.5% Si, 0.1-1.3% Al, 0.3-2.0% Mn, 0.005-0.06% Cr, with the remainder being Fe and other unavoidable impurities, and is characterized in that before stress relief annealing, the following formula 1 is satisfied, and after stress relief annealing, the following formula 2 is satisfied. [Formula 1] 0.1≧[Mn film] / [Mn50] [Formula 2] 10≧[Mn film] / [Mn50]≧1 (In formulas 1 and 2, [Mn film] indicates the average Mn content (wt%) in the insulating film, 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 film toward the inside of the steel sheet base material.)

Description

[Technical field]

[0001] The present invention relates to a non-oriented electrical steel sheet, a manufacturing method thereof, and a motor core including the same. More specifically, the present invention relates to a non-oriented electrical steel sheet in which the Cr content is appropriately adjusted, the amount of shot balls fired during scale removal is increased, and Mn diffusion into the insulating coating during stress relief annealing is prevented, thereby improving the adhesion of the insulating coating, a manufacturing method thereof, 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 in order to achieve high efficiency in this process, the excellent magnetic properties of non-oriented electrical steel sheets are required. In particular, as environmentally friendly technologies have been attracting attention in recent years, it has become 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 also 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, while 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 be. 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. In assessing the characteristics of non-oriented electrical steel sheets used in motors, most motors place emphasis on the iron loss W15 / 50 when a 1.5T magnetic field is applied at a commercial frequency of 50Hz. However, not all motors for various applications place emphasis on the iron loss of W15 / 50, and iron loss may be evaluated at other frequencies or applied magnetic fields depending on the main operating conditions. In particular, for non-oriented electrical steel sheets used in recent electric vehicle drive motors, magnetic properties at low magnetic fields of 1.0T or less and high frequencies of 400Hz or more are often important, so the characteristics of non-oriented electrical steel sheets are evaluated at 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 the stress relief annealing process, Mn in the steel sheet diffuses into the insulating film, which causes a decrease in the adhesion between the steel sheet and the insulating film. 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 had 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 weakening of the bonding strength between the insulating coating and the base material. Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention aims to provide a non-oriented electrical steel sheet, a manufacturing method thereof, and a motor core including the same. Specifically, the present invention aims to provide a non-oriented electrical steel sheet in which the Cr content is appropriately adjusted to prevent diffusion of Mn into an insulating coating during stress relief annealing and improve adhesion of the insulating coating, a manufacturing method thereof, and a motor core including the same. [Means for solving the problem]

[0006] The non-oriented electrical steel sheet of the present invention comprises a steel sheet base material and an insulating coating located on the steel sheet base material, the steel sheet base material containing, by weight, 2.0-6.5% Si, 0.1-1.3% Al, 0.3-2.0% Mn, 0.005-0.06% Cr, with the balance being Fe and other unavoidable impurities, and satisfies the following formula 1 before stress relief annealing, and satisfies the following formula 2 after stress relief annealing. [Formula 1] 0.1≧[Mn film] / [Mn50] [Formula 2] 10≧[Mn film] / [Mn50]≧1 (In formulas 1 and 2, [Mn film] indicates the average Mn content (wt%) in the insulating film, 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 film toward the inside of the steel sheet base material.) The steel sheet base material may further contain one or more of Sn: 0.06 wt % or less and Sb: 0.06 wt % or less. 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. The stress relief annealing can be performed at a temperature of 700° C. to 850° C. for a time of 10 minutes to 300 minutes.

[0007] 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, 2.0-6.5% Si, 0.1-1.3% Al, 0.3-2.0% Mn, 0.005-0.06% Cr, with the balance being Fe as unavoidable impurities, 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 rate of 15-35 kg / (min m 2) onto the steel plate to remove scale. The average particle size of the shot balls is 0.1 to 1 mm, and they can be shot for 1 to 60 seconds. The material of the shot balls may be an Fe-based alloy. The cold-rolled sheet annealing step may involve annealing at a temperature of 700° C. to 1100° C. for 10 to 1000 seconds. The method may further include a step of hot-rolled sheet annealing prior to the step of removing the scale. After the step of annealing the cold rolled sheet, a step of stress relief annealing may be further included.

[0008] The motor core of the present invention includes a stator formed by laminating a plurality of non-oriented electrical steel sheets and a rotor formed by laminating a plurality of non-oriented electrical 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, 0.005 to 0.06% Cr, with the remainder being Fe and other unavoidable impurities, and includes a steel sheet base material and an insulating coating located on the steel sheet base material, and satisfies the following formula 1: The non-oriented electrical steel sheet in the stator includes a steel sheet base material and an insulating coating located on the steel sheet base material, which contain, by weight, 2.0 to 6.5% Si, 0.1 to 1.3% Al, 0.3 to 2.0% Mn, 0.005 to 0.06% Cr, with the remainder being Fe and other unavoidable impurities, and satisfies the following formula 2. [Formula 1] 0.1≧[Mn film] / [Mn50] [Formula 2] 10≧[Mn film] / [Mn50]≧1 (In formulas 1 and 2, [Mn coating] indicates the average Mn content (wt%) in the insulating coating, [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. The non-oriented electrical steel sheets contained within the stator and rotor may be non-oriented electrical steel sheets derived from the same coil. The difference in Si, Al and Mn content between the non-oriented electrical steel sheets included in the stator and the rotor may be 0.20% by weight or less.

[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, 2.0-6.5% Si, 0.1-1.3% Al, 0.3-2.0% Mn, 0.005-0.06% Cr, with the balance being Fe and other unavoidable impurities, to produce a hot-rolled sheet, a step of removing scale present on the hot-rolled sheet, a step of cold rolling the hot-rolled sheet to produce a cold-rolled sheet, a cold-rolled sheet annealing step of annealing the cold-rolled sheet, a step of forming an insulating coating on the cold-rolled sheet, and a stress relief annealing step, wherein the following formula 1 is satisfied before the stress relief annealing step, and the following formula 2 is satisfied after the stress relief annealing step. [Formula 1] 0.1≧[Mn film] / [Mn50] [Formula 2] 10≧[Mn film] / [Mn50]≧1 (In formulas 1 and 2, [Mn film] indicates the average Mn content (wt%) in the insulating film, 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 film toward the inside of the steel sheet base material.) The step of removing the scales may involve using shot balls at a rate of 15 kg / (m 2 min)~35kg / (m 2 The scale can be removed by projecting the powder onto the steel plate at a rate of 1000 times the normal amount (1.0 sq. min). The cold-rolled sheet annealing step may involve annealing at a temperature of 700° C. to 1100° C. for 10 to 1000 seconds. The stress relief annealing step can be carried out at a temperature of 700° C. to 850° C. for a time of 10 minutes to 300 minutes. Effect of the Invention

[0010] According to the present invention, by including Cr within a certain range, 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 makes it possible to further improve the performance of motors for environmentally friendly automobiles, motors for highly efficient home appliances, and super-premium electric motors through stress relief annealing. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram of a cross section of a non-oriented electrical steel sheet according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] 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, a first part, component, region, layer or section described below can be referred to as a 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 specific 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 "comprises" is intended to embody certain properties, regions, integers, steps, operations, elements and / or components, and does not exclude the presence or addition of other properties, regions, integers, steps, operations, elements and / or components.

[0013] When a part is described as being "on" or "above" another part, it may be exactly on or above the other part, or it may have other parts between it. In contrast, when a part is described as being "directly above" another part, there are no other parts between them. Moreover, unless otherwise specified, % means % by weight, and 1 ppm is 0.0001% by weight. In the present invention, the term "additionally containing an additional element" means that the additional amount of the additional element is substituted for the balance iron (Fe). 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 unless otherwise defined, are not interpreted in an ideal or very formal sense.

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail so as to enable those skilled in the art to easily carry out the present invention. However, the present invention may be embodied in many different forms and is not limited to the embodiments set forth herein. A cross section of a non-oriented electrical steel sheet according to the present invention is shown diagrammatically in Fig. 1. As shown in Fig. 1, the 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, a surface portion 30 formed from the base material surface toward the inside may be present.

[0015] The steel plate base material 10 of the present invention contains, by weight, 2.0-6.5% Si, 0.1-1.3% Al, 0.3-2.0% Mn, 0.005-0.06% Cr, with the balance being Fe and other unavoidable impurities. The reasons for limiting the components of the steel plate base material 10 will be explained below. Si: 2.0 to 6.5 wt. % Silicon (Si) plays a role in increasing the resistivity of the material and reducing iron loss, and if the amount added is too small, the effect of improving high-frequency iron loss may be insufficient. Conversely, if too much is added, the hardness of the material increases, the cold rolling property may be extremely deteriorated, and the productivity and punching property may be poor. Therefore, Si can be added within the above-mentioned range. More specifically, it can be contained in 2.5 to 5.0 wt %. More specifically, it can be contained in 3.0 to 4.0 wt %.

[0016] Al: 0.1~1.3% by weight Aluminum (Al) plays a role in increasing the non-resistance of the material and reducing iron loss. If the amount added is too small, it will not be effective in reducing high-frequency iron loss, and nitrates will be formed finely, which can deteriorate magnetic properties. Conversely, if the amount added is too large, problems will occur in all processes such as steelmaking and continuous casting, and productivity may be significantly reduced. Therefore, Al can be added within the above-mentioned range. More specifically, it can be contained at 0.5 to 1.2 wt %. More specifically, it can be contained at 0.7 to 1.0 wt %.

[0017] Mn:0.3~2.0wt% Manganese (Mn) is an element that plays a role in increasing the non-resistance of the material, improving core loss, and forming sulfides. If the amount of Mn added is too small, sulfides may precipitate finely, reducing magnetic properties. Conversely, if the amount of Mn added is too large, it may promote the formation of {111} texture, which is unfavorable to magnetic properties, and reduce magnetic flux density, so Mn can be added within the above-mentioned range. More specifically, Mn can be contained in an amount of 0.5 to 1.5 wt%. In the present invention, the resistivity can be 55 to 80 μΩ·cm.

[0018] Cr:0.005~0.060wt% Chromium (Cr) plays a role in increasing the resistivity of the material and reducing core loss. It also plays a role in preventing Mn in the base material from diffusing into the insulating coating during the stress relief annealing step. Therefore, Cr can be added in the above-mentioned range. More specifically, it can be contained in an amount of 0.010 to 0.050% by weight. More specifically, it can be contained in an amount of 0.050 to 0.040% by weight.

[0019] The steel plate base material 10 may further contain one or more of Sn: 0.06% by weight or less and Sb: 0.06% by weight or less. One or more of Sn: 0.06% by weight or less and Sb: 0.06% 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. When Sn and Sb are added in excess, they hinder the growth of crystal grains, lowering magnetism and worsening rolling properties. Therefore, Sn and Sb can be added within the above-mentioned ranges. More specifically, Sn: 0.005 to 0.050 wt% and Sb: 0.005 to 0.050 wt% can be included. More specifically, Sn: 0.01 to 0.02 wt% and Sb: 0.01 to 0.02 wt% can be included. As described above, when the additional element is further included, it is included in place of the remaining Fe.

[0020] 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. Cu:0.01~0.20wt% Copper (Cu) plays a role in forming sulfides together with Mn. When Cu is further added, if the amount added is too small, CuMnS may precipitate finely, which may deteriorate the magnetic property. If the amount added of Cu is too large, high-temperature brittleness may occur, which may cause cracks to form during continuous casting or hot rolling. More specifically, Cu may be further contained in an amount of 0.05 to 0.10 wt %.

[0021] P0.100% by weight or less Phosphorus (P) not only plays a role in increasing the non-resistance of the material, but also plays a role in improving the texture by segregating to the grain boundaries, increasing the non-resistance, and reducing iron loss, so it can be added additionally. However, if too much P is added, it will result in the formation of a texture unfavorable to magnetism, and there will be no effect in improving the texture, and it will segregate excessively to the grain boundaries, reducing rollability and workability, which may make production difficult. Therefore, P can be added within the above-mentioned range. More specifically, P can be contained in 0.001 to 0.090 wt %. More specifically, P can be contained in 0.005 to 0.085 wt %.

[0022] 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 nitrates, which have a detrimental effect on magnetic properties, so their contents can be limited 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.

[0023] 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 grain growth of ferrite during annealing, and increases iron loss. It also combines with Ti and other elements to form carbides, which reduces magnetic properties and increases iron loss due to magnetic aging during use after processing into electrical products from the final product. Therefore, C can be added within the above range. More specifically, C can be contained in an amount of 0.003 wt% or less.

[0024] S: 0.005% by weight or less Sulfur (S) forms fine sulfides inside the base material, inhibits grain growth, and weakens iron loss, so it is preferable to add it in as small an amount as possible. If a large amount of S is included, it may combine with Mn and the like to form precipitates or cause high-temperature brittleness during hot rolling. Therefore, S may be further included at 0.005 wt% or less. Specifically, S may be further included at 0.0030 wt% or less. More specifically, S may be further included at 0.0001 to 0.0030 wt%.

[0025] N: 0.005% by weight or less Nitrogen (N) strongly bonds with Al, Ti, etc. to form nitrates, which inhibit grain growth, and when precipitated, hinders magnetic domain movement, so it is preferable to add a small amount of N. Therefore, N can be added within the above-mentioned range. More specifically, N can be added in an amount of 0.003 wt % or less.

[0026] Ti, Nb, V: 0.005% by weight or less Titanium (Ti), niobium (Nb), vanadium (V), etc. are also strong carbonaceous cargo-forming elements, so it is desirable to avoid adding them as much as possible, and their content should be 0.01 wt% or less each.

[0027] The balance is composed of Fe and inevitable impurities. The inevitable impurities are impurities that are mixed in during the steelmaking step 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 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 in place of the balance Fe. In the present invention, by adding Cr to the steel sheet base material 10, it is possible to suppress the diffusion of Mn into the insulating coating 20 in the stress relief annealing step.

[0028] If the Mn content of the insulating coating is too high due to the excessive diffusion of Mn into the insulating coating 20, the insulating properties of the insulating coating may be reduced and the bonding strength between the insulating coating and the base material may be weakened. When the Mn concentration at a depth of 50 μm from the surface of the steel plate base material 10 toward the inside of the base material is [Mn50] and the Mn concentration of the insulating coating 20 is [Mn coating], the following formula 1 is satisfied before stress relief annealing, and the following formula 2 is satisfied after stress relief annealing. [Formula 1] 0.1≧[Mn film] / [Mn50] [Formula 2] 10≧[Mn film] / [Mn50]≧1

[0029] Stress relief annealing can be performed at a temperature of 700°C to 850°C for 10 to 300 minutes, more specifically at a temperature of 800°C to 850°C for 30 to 120 minutes, or more specifically at a temperature of 825°C for 60 minutes. By adding Cr to the steel plate base material 10, a surface portion 30 is formed in which Cr and O are concentrated from the surface of the steel plate base material 10 toward the inside of the base material. That is, the surface portion 30 exists at the interface between the steel plate base material 10 and the insulating coating 20. This surface portion 30 plays a role in preventing diffusion of Mn from the steel plate base material 10 to the insulating coating 20. The surface portion 30 refers to a portion having an oxygen content of 5% by weight or more, and is exposed to oxygen during the manufacturing process, and oxygen in the atmosphere penetrates into the steel plate, forming the surface portion in the direction from the surface to the inside.

[0030] The thickness of the surface portion 30 thus divided may be 10 to 100 nm. 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, the magnetic properties may be deteriorated. Therefore, the surface portion 30 may have a thickness in the above-mentioned range. More specifically, the thickness of the surface portion may be 15 to 80 nm. The surface portion 30 may contain 0.5 to 5 wt % Cr and 5 to 50 wt % O. As described above, the Cr and O contents in the surface portion 30 have a concentration gradient in the thickness direction, and the above ranges refer to the average contents in the thickness direction of the surface portion 30. The remaining components may be the same as those of the steel plate base material 10.

[0031] The insulating coating 20 is located on the surface of the steel sheet base material 10. The insulating coating 20 serves to insulate the non-oriented electrical steel sheets from each other when the non-oriented electrical steel sheets are laminated to manufacture a product. The insulating coating 20 may be an organic, inorganic, or organic-inorganic composite coating, or may be formed 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 % of P and 0.01 weight % or less of Mn. Thus, the insulating coating 20 before stress relief annealing contains a small amount of Mn. The balance may be O. It may further contain 1 to 10 weight % of Si. The insulating coating 20 before stress relief annealing can satisfy the following formula 1. [Formula 1] 0.1≧[Mn film] / [Mn50] (In formula 1, [Mn film] indicates the average Mn content (wt%) in the insulating film, 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 film toward the inside of the steel sheet base material.)

[0032] On the other hand, the insulating coating after stress relief annealing may contain 2.0 to 10.0 wt % Mn due to partial diffusion of Mn in the steel sheet base material 10. The remaining components may be the same as those before stress relief annealing. That is, the insulating coating 20 after stress relief annealing can satisfy the following formula 2. [Formula 2] 10≧[Mn film] / [Mn50]≧1 (In formula 2, [Mn coating] indicates the average Mn content (wt%) in the insulating coating.) More specifically, the value of formula 2 may be 1.10 to 5.0. That is, the insulating coating 20 after stress relief annealing can contain 5 to 50% by weight of P and 2.0 to 10.0% by weight of Mn. The balance may be O. It can further contain 1 to 10% by weight of Si.

[0033] When an appropriate amount of Mn is diffused into the insulating coating 20, the inorganic matter ratio of the insulating coating increases, improving stability at high temperatures. In this case, stability is ensured in the stress relief annealing step, and the bonding strength between the base material and the insulating coating 20 can be maintained even after the stress relief annealing. As a result, the bonding strength of 5B or more can be maintained after the stress relief annealing in the bond strength test ASTM D3559 cross-cut test.

[0034] The method for producing a non-oriented electrical steel sheet of the present invention includes a step of hot rolling a slab to produce a hot-rolled sheet, a step of cold rolling the hot-rolled sheet to produce 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 above in connection with the alloy composition of the non-oriented electrical steel sheet, and therefore a duplicate 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. Specifically, the slab contains, by weight, 2.0-6.5% Si, 0.1-1.3% Al, 0.3-2.0% Mn, 0.005-0.06% Cr, with the remainder being Fe and other unavoidable impurities. Other additional elements have been explained in the alloy components of the non-oriented electrical steel sheet, so duplicate explanations will be omitted.

[0035] The slab can be heated before hot rolling. The heating temperature of the slab is not limited, but the slab can be heated at 1100 to 1250°C. If the slab heating temperature is too high, the precipitates that impair the magnetic property may be remelted and precipitate finely after hot rolling. The slab is then hot-rolled to produce a hot-rolled sheet. The thickness of the hot-rolled sheet can be 2 to 3.0 mm. The method may further include a step of 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 without phase transformation, and is effective in improving the texture of the final annealed sheet and increasing the magnetic flux density.

[0036] At this time, the step of annealing the hot-rolled sheet can be annealed at a temperature of 850 to 1200 ° C. If the annealing temperature of the hot-rolled sheet is too low, the structure does not grow or grows finely, and the effect of increasing the magnetic flux density cannot be expected. 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. The annealing of the hot-rolled sheet is performed to increase the orientation favorable to magnetism as necessary, and can be omitted. Next, scale present on the surface of the hot-rolled or annealed hot-rolled sheet is removed. In the present invention, the shot ball projection amount is increased to contribute to the formation of a Cr oxide layer on the surface of the base material in the final product, thereby adjusting the Mn diffusion into the insulating coating in the stress relief annealing step.

[0037] The scale removal step 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 is too small, the residual oxide layer on the surface will prevent the formation of a Cr oxide layer in the final annealing step, making it difficult to adjust the diffusion of Mn in the stress relief annealing step. Conversely, if the amount of shot balls is too large, the steel sheet surface will be significantly damaged, so the upper limit can be appropriately adjusted. More specifically, the amount of shot balls should be 17 to 30 kg / (min m 2 Even if the same amount is projected per area, the formation of the Cr oxide layer and the Mn diffusion will differ depending on the length of time for which the projection is performed. Therefore, in one embodiment of the present invention, the projection amount is defined according to the time and area.

[0038] The average particle size of the shot balls is 0.1 to 1 mm, and the shot balls 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 the shot balls can be projected for 5 to 30 seconds. The average particle size of the shot balls and the shot ball projection time can also affect the diffusion of Mn into the insulating coating. The material of the shot balls is not particularly limited, but an Fe-based alloy can be used. Next, the hot-rolled sheet is cold-rolled to produce a cold-rolled sheet. The cold rolling is final rolling to a thickness of 0.15 mm to 0.65 mm. If necessary, a second cold rolling can be performed after the first cold rolling and intermediate annealing, and the final rolling reduction can be in the range of 50 to 95%.

[0039] Next, the cold-rolled sheet is annealed. The cold-rolled sheet is annealed at a temperature in the range of 700 to 1100°C for 10 to 1000 seconds so that the grain size in the cross section of the steel sheet is 50 to 150 μm. If the final annealing temperature is too low, the grains become small, and the iron loss may deteriorate. If the temperature is too high, the grains become coarse, the abnormal eddy current loss increases, and the total iron loss increases. More specifically, the cold-rolled sheet can be annealed at a temperature in the range of 900 to 1050°C. After annealing the cold-rolled sheet, the steel sheet can completely (99% or more) recrystallize the structure processed by the cold rolling. The heating rate up to the crack temperature during annealing of the cold-rolled sheet is 30 to 150° C. / sec. By appropriately adjusting the heating rate, the surface portion is formed thin and dense, and the diffusion of Mn can be prevented.

[0040] In the step of annealing the cold-rolled sheet, the cold-rolled sheet can be annealed in an atmosphere containing 40 volume % or less of hydrogen (H2) and 60 volume % or more of nitrogen, with a dew point of 0 to -40°C. Specifically, the cold-rolled sheet can be annealed in an atmosphere containing 0 to 10 volume % of hydrogen and 90 to 100 volume % of nitrogen. By appropriately adjusting the annealing atmosphere, the surface portion can be formed thin and dense, and the diffusion of Mn can be prevented. Next, after annealing the cold-rolled sheet, an insulating film can be formed. The insulating film can be treated with an organic, inorganic, or organic-inorganic composite film, and can also be treated with other insulating film agents. For example, it can be formed by applying an insulating film-forming composition containing 40 to 70% by weight of metal phosphate and 0.5 to 10% by weight of silica. The insulating film contains a large amount of P in the metal phosphate of 5% by weight or more, and is distinguished from the steel sheet base material containing P less than 5% by weight. Next, a stress relief annealing step is performed at a temperature of 700° C. to 850° C. for a time period of 10 minutes to 300 minutes.

[0041] The motor core of the present invention includes a stator formed by laminating a plurality of non-oriented electrical steel sheets and a rotor formed by laminating a plurality of non-oriented electrical steel sheets, The non-oriented electrical steel sheet in the rotor includes a steel sheet base material and an insulating coating located on the steel sheet base material, which contain, by weight, 2.0 to 6.5% Si, 0.1 to 1.3% Al, 0.3 to 2.0% Mn, 0.005 to 0.06% Cr, with the remainder being Fe and other unavoidable impurities, and satisfies the following formula 1. The non-oriented electrical steel sheet in the stator includes a steel sheet base material and an insulating coating located on the steel sheet base material, which contain, by weight, 2.0 to 6.5% Si, 0.1 to 1.3% Al, 0.3 to 2.0% Mn, 0.005 to 0.06% Cr, with the remainder being Fe and other unavoidable impurities, and satisfies the following formula 2. [Formula 1] 0.1≧[Mn film] / [Mn50] [Formula 2] 10≧[Mn film] / [Mn50]≧1 (In Equation 1 and Equation 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.)

[0042] In the case of a stator, magnetic properties are more important than mechanical properties, and magnetic properties can be improved through SRA after punching and lamination. Therefore, the properties of non-oriented electrical steel sheet appear in the stator after SRA. The steel components of non-oriented electrical steel sheet, Mn diffusion, and Mn content in the insulation coating have been described in relation to the non-oriented electrical steel sheet above, so a duplicated description will be omitted.

[0043] In the case of rotors, mechanical properties are more important than magnetic properties. Therefore, the SRA process, which may deteriorate mechanical properties, can be omitted. This allows the properties of the non-oriented electrical steel sheet before SRA to be obtained. The steel components of the non-oriented electrical steel sheet, the diffusion of Mn, and the Mn content in the insulation coating have been described in relation to the non-oriented electrical steel sheet described above, so a duplicated description will be omitted. Meanwhile, the stator and rotor are punched out into roughly a doughnut or disk shape. If the stator and rotor are manufactured by punching out the stator and rotor from separate coils of non-oriented electrical steel, the remaining punched parts are scrapped, which increases the process cost and leads to waste of resources and energy. If the stator and rotor are manufactured by punching out the same coil, the parts that are scrapped can be minimized.

[0044] Therefore, in the present invention, the non-oriented electrical steel sheets contained in the stator and rotor may be non-oriented electrical steel sheets derived from the same coil. In the present invention, the term "derived from the same coil" means that the steel components such as Si, Al, and Mn in the non-oriented steels contained in the stator and rotor are substantially the same. Specifically, it means that the difference in the Si, Al, and Mn content between the stator and rotor is 0.20% by weight or less. More specifically, it means that the difference in the Si, Al, and Mn content between the stator and 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 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 rotor is 0.01% by weight or less. In the case of Cr, the difference in the content between the stator and rotor may be 0.01% by weight or less. More specifically, it may be 0.005% by weight or less. The components of the insulating coating may also be substantially the same between the stator and rotor.

[0045] The present invention will be described in more detail below with reference to examples. However, these examples are merely for the purpose of illustrating the present invention, and the present invention is not limited thereto. Example 1 Slabs were manufactured according to the following Tables 1 and 2, with the balance being Fe and other unavoidably added impurities. The slabs were 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 sheets were annealed at 1100°C for 4 minutes, and then blasted with the shot ball projection amount shown in Table 3 below to remove scale. The sheets were then cold-rolled to a thickness of 0.27 mm, and then heated at a rate of 100°C / sec, and final 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. Then, the specimen was annealed at 825℃ for 1 hour to remove stress. As a result, a non-oriented electrical steel sheet with no stress was finally manufactured. The composition in the depth direction was measured three times using a glow discharge spectrometer, and the average values ​​of Mn film and Mn50 are shown in Table 3 below according to the experimental conditions. The adhesion was measured by the Crosscut Test (ASTM D3359).

[0046] [Table 1]

[0047] [Table 2]

[0048] [Table 3]

[0049] As shown in Tables 1 to 3, in the examples in which the appropriate amount of Cr is included to prevent Mn diffusion, it can be confirmed that the Mn component is appropriately distributed in the insulating film after stress relief annealing is performed. On the other hand, in No. 8 to No. 15 in which the alloy components are not appropriately adjusted, it can be confirmed that Mn does not diffuse sufficiently in the insulating film. On the other hand, even if the alloy composition is appropriately adjusted, if the shot ball projection amount is not appropriately adjusted, a thick oxide layer is formed on the surface, and Mn cannot be sufficiently diffused into the insulating coating.

[0050] The present invention is not limited to the examples, and can be manufactured in various different forms, and a person having ordinary skill in the art to which the present invention belongs can understand that the present invention can be embodied in other specific forms without changing the technical idea or essential characteristics of the present invention. Therefore, it should be understood that the above-described examples are illustrative in all respects and are not limiting. [Explanation of symbols]

[0051] 10 Steel plate base material 20 Insulating Film 30 Surface area 100 Non-oriented electrical steel sheet

Claims

1. A steel plate base material containing, by weight, 2.0 to 6.5% Si, 0.1 to 1.3% Al, 0.3 to 2.0% Mn, 0.005 to 0.06% Cr, with the balance being Fe and other unavoidable impurities; An insulating coating is provided on the steel plate base material, A non-oriented electrical steel sheet, characterized in that it satisfies the following formula 1 before stress relief annealing, and satisfies the following formula 2 after stress relief annealing. [Formula 1] 0.1 ≧ [Mn film] / [Mn50] [Formula 2] 10≧[Mn film] / [Mn50]≧1 (In formulas 1 and 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.)

2. The non-oriented electrical steel sheet according to claim 1 , wherein the steel sheet base material further contains at least one of Sn: 0.06 wt % or less and Sb: 0.06 wt % or less.

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

4. 2. The non-oriented electrical steel sheet according to claim 1, wherein the steel sheet base material further comprises 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.

5. The non-oriented electrical steel sheet according to claim 1, wherein the stress relief annealing is performed at a temperature of 700° C. to 850° C. for a time period of 10 minutes to 300 minutes.

6. A step of producing a hot-rolled sheet by hot rolling a slab containing, in weight percent, 2.0 to 6.5% Si, 0.1 to 1.3% Al, 0.3 to 2.0% Mn, 0.005 to 0.06% Cr, with the balance being Fe and unavoidable impurities; removing scale present on the surface of the hot-rolled sheet; cold rolling the descaled hot-rolled sheet to produce a cold-rolled sheet; and The cold-rolled sheet is annealed, The step of removing the scales involves subjecting the shot balls to a pressure of 15 to 35 kg / (min.m ２ ) onto the steel sheet to remove scale.

7. The method for producing a non-oriented electrical steel sheet according to claim 6, 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.

8. The method for producing a non-oriented electrical steel sheet according to claim 6, characterized in that the material of the shot balls is an Fe-based alloy.

9. The method for producing a non-oriented electrical steel sheet according to claim 6, wherein the cold-rolled sheet annealing step comprises annealing the sheet at a temperature of 700 to 1100° C. for 10 to 1000 seconds.

10. The method for producing a non-oriented electrical steel sheet according to claim 6, further comprising the step of annealing the hot-rolled sheet prior to the step of removing the scale.

11. The method for producing a non-oriented electrical steel sheet according to claim 6, further comprising the step of performing stress relief annealing after the step of annealing the cold rolled sheet.

12. The rotor includes a stator formed by laminating a plurality of non-oriented electrical steel sheets, and a rotor formed by laminating a plurality of non-oriented electrical steel sheets. The non-oriented electrical steel sheet in the rotor includes a steel sheet base material and an insulating coating located on the steel sheet base material, each of which contains, by weight percent, 2.0 to 6.5% Si, 0.1 to 1.3% Al, 0.3 to 2.0% Mn, 0.005 to 0.06% Cr, with the balance being Fe and other unavoidable impurities, and satisfies the following formula 1: The non-oriented electrical steel sheet in the stator includes, by weight, 2.0 to 6.5% Si, 0.1 to 1.3% Al, 0.3 to 2.0% Mn, 0.005 to 0.06% Cr, with the remainder being Fe and other unavoidable impurities. The motor core includes a steel sheet base material and an insulating coating located on the steel sheet base material, and satisfies the following formula 2. [Formula 1] 0.1 ≧ [Mn film] / [Mn50] [Formula 2] 10≧[Mn film] / [Mn50]≧1 (In formulas 1 and 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.)

13. 13. The motor core of claim 12, wherein the non-oriented electrical steel sheets included in the stator and rotor come from the same coil.

14. 13. The motor core according to claim 12, wherein the 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.

Images