Non-oriented electrical steel sheet and method for manufacturing same

Abstract

A non-oriented electrical steel sheet according to an embodiment of the present invention comprises, by wt%, 2.0 to 6.5% of Si, 0.001 to 1.0% of Al, and 0.03 to 1.0% of Mn, with the balance being Fe and unavoidable impurities. In a cross section taken along the thickness direction of the steel sheet, a difference (Si0% - Si12.5%) between an average Si content Si0% in a region from the steel sheet surface to 5% of the total thickness inward and a Si content Si12.5% at a position corresponding to 1 / 8 of the total thickness of the steel sheet is 0 to 0.7 wt%.

Description

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

[0001] One embodiment of the present invention relates to a non-oriented electrical steel sheet and a method for manufacturing the same. Specifically, one embodiment of the present invention relates to a non-oriented electrical steel sheet in which magnetism is enhanced by diffusing Si from the surface of the steel sheet into the interior of the steel sheet, and a method for manufacturing the same.

[0002] Non-oriented electrical steel sheets used as core materials for electronic devices require high magnetic flux density and low iron loss as devices become more efficient and smaller. Since a higher magnetic flux density requires less core material to achieve the same performance, it enables the miniaturization of electrical devices, and since lower iron loss results in less energy loss, securing these characteristics is essential for manufacturing high-efficiency motors.

[0003] Iron loss, which causes energy loss, consists of hysteresis loss and eddy current loss; in the case of high-efficiency motors with high operating frequencies of electronic devices, the impact of eddy current loss increases. Eddy current loss is heat generation caused by eddy currents generated when a magnetic field is induced in the iron core, and generally, increasing the content of resistive elements such as Si or Al within the electrical steel sheet is an effective method to reduce this. Furthermore, when the Si content is increased above a certain level, magnetostriction, which is a cause of noise, decreases to zero, and as permeability increases to its maximum, it becomes possible to manufacture electrical steel sheets with excellent high-frequency characteristics.

[0004] However, as the Si content increases, the ductility of the electrical steel sheet decreases significantly, presenting a limitation in that it is difficult to manufacture thin-film electrical steel sheets using conventional rolling processes.

[0005] To overcome the limitations of this rolling process, a technology has been proposed to manufacture electrical steel sheets with a higher Si content by diffusing Si into the surface of cold-rolled steel sheets using SiCl4 gas. However, this method utilizes SiCl4 gas, which is highly toxic and chemically unstable, and faces equipment constraints requiring production under high vacuum conditions, making it difficult to produce electrical steel sheets with a width of 500 mm or more. Furthermore, the generation of byproduct gases such as FeCl2 under high vacuum conditions is environmentally harmful and results in inferior insulation properties, necessitating a fundamental solution.

[0006] In one embodiment of the present invention, a non-oriented electrical steel sheet and a method for manufacturing the same are provided. Specifically, in one embodiment of the present invention, a non-oriented electrical steel sheet with improved magnetism by diffusing Si from the surface of the steel sheet into the interior of the steel sheet and a method for manufacturing the same are provided.

[0007] A non-oriented electrical steel sheet according to one embodiment of the present invention comprises, in weight%, Si: 2.0 to 6.5%, Al: 0.001 to 1.0%, and Mn: 0.03 to 1.0%, and the remainder is Fe and unavoidable impurities.

[0008] Average Si content in the region from the steel plate surface inward to 5% of the total thickness in the cross-section in the thickness direction of the steel plate. 0% and Si content at the 1 / 8 position of the total steel plate thickness Si 12.5% The difference (Si 0% - Si 12.5% ) is 0 to 0.7 weight%.

[0009] Si content at 1 / 8 of the total thickness of the steel plate in the thickness direction cross-section, from the steel plate surface inward. 12.5% and Si content at 1 / 4 Si 25% The difference (Si 12.5% - Si 25% ) is 0.3 to 2.0 weight%.

[0010] Si content at 1 / 4 of the total thickness of the steel plate in the thickness direction cross-section, from the surface to the interior. 25% and Si content at 3 / 8 Si 37.5% The difference (Si 25% - Si 37.5% ) is 1.0 to 2.5 weight%.

[0011] Si content at 3 / 8 of the total thickness of the steel plate in the thickness direction cross-section, from the steel plate surface inward. 37.5% and Si content in 1 / 2 Si 50% The difference (Si 37.5% - Si 50% ) is 0 to 0.2 weight%.

[0012] Si content from the surface of the steel plate inward to half of the total thickness of the steel plate Si 50% and the average Si content in the region from the surface of the above non-oriented electrical steel sheet in the inward direction up to 5% of the total thickness Si 0% The difference (Si 0% - Si 50% ΔSi, defined as ), may be 2.0 wt% or more.

[0013] A non-oriented electrical steel sheet according to one embodiment of the present invention may further include one or more of C: 0.005 wt% or less, N: 0.030 wt% or less, S: 0.005 wt% or less, Ti: 0.005 wt% or less, Nb: 0.005 wt% or less, and V: 0.005 wt% or less.

[0014] A non-oriented electrical steel sheet according to one embodiment of the present invention may further include one or more of P: 0.1 wt% or less, Cu: 0.003 to 0.2 wt%, Cr: 0.01 to 0.5 wt%, Sn: 0.1 wt% or less, Sb: 0.1 wt% or less, Ni: 0.05 wt% or less, and Zn: 0.01 wt% or less.

[0015] A non-oriented electrical steel sheet according to one embodiment of the present invention may further include one or more of Bi: 0.200 wt% or less, Pb: 0.200 wt% or less, Ge: 0.200 wt% or less, and As: 0.200 wt% or less.

[0016] A non-oriented electrical steel sheet according to one embodiment of the present invention may further include one or more of Mo: 0.03 wt% or less, B: 0.0050 wt% or less, Ca: 0.0050 wt% or less, Zr: 0.005 wt% or less, Te: 0.01 wt% or less, and Mg: 0.0050 wt% or less.

[0017] A method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention comprises the steps of: manufacturing a cold-rolled sheet satisfying Formula 1, wherein the sheet contains, in weight%, Si: 0 to 2.0%, Al: 0.001 to 0.7%, and Mn: 0.03 to 1.0%, and the remainder being Fe and unavoidable impurities; a coating step of applying a Si diffusion composition containing a Si compound to the surface of the cold-rolled sheet; a drying step of drying the Si diffusion composition; and a diffusion annealing step of the cold-rolled sheet.

[0018] [Equation 1]

[0019] 2 × [Mn] - [Si] / 1.5 - [Al] / 0.6 + 0.75 ≥ 0

[0020] (Where [Mn], [Si], and [Al] in Equation 1 represent the content of Mn, Si, and Al in the cold-rolled sheet, respectively)

[0021] The Si diffusion composition further comprises an Al compound, and may include 100 parts by weight of the Si compound and 1 to 50 parts by weight of the Al compound as solid content.

[0022] The Si diffusion composition may further include 10 to 1,000 parts by weight of a ceramic powder comprising an oxide, nitride, carbide, or oxynitride, comprising at least one component selected from Li, B, Ca, Sr, Mg, Al, P, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Zr, Sn, and Ba.

[0023] The average particle size of the Si compound can be 0.1 to 10 μm.

[0024] The average particle size of the Al compound can be 1 to 1000 nm.

[0025] The average particle size of the ceramic powder can be 8 to 2500 nm.

[0026] In the step of applying the Si diffusion composition, the amount of the Si diffusion composition applied is 0.1 to 300 g / m² 2 It could be.

[0027] In the diffusion annealing step, the cracking temperature may be 850 to 1050°C and the cracking time may be 2 to 10 hours.

[0028] A non-oriented electrical steel sheet according to one embodiment of the present invention can improve high magnetic flux density and ductility by concentrating Si only on the surface.

[0029] A non-oriented electrical steel sheet according to one embodiment of the present invention achieves high ductility and ensures formability.

[0030] Terms such as first, second, and third are used to describe various parts, components, regions, layers, and / or sections, but are not limited thereto. These terms are used solely to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Accordingly, the first part, component, region, layer, or section described below may be referred to as the second part, component, region, layer, or section without departing from the scope of the present invention.

[0031] The technical terms used herein are for the reference of specific embodiments only and are not intended to limit the invention. The singular forms used herein include plural forms unless phrases clearly indicate otherwise. As used in the specification, the meaning of "comprising" specifies certain characteristics, areas, integers, steps, actions, elements, and / or components, and does not exclude the presence or addition of other characteristics, areas, integers, steps, actions, elements, and / or components.

[0032] When it is stated that one part is "above" or "on" another part, it may be directly above or on the other part, or other parts may be involved in between. In contrast, when it is stated that one part is "directly above" another part, no other parts are interposed in between.

[0033] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as generally understood by those skilled in the art to which this invention pertains. Terms defined in commonly used dictionaries are further interpreted to have meanings consistent with relevant technical literature and the present disclosure, and are not interpreted in an ideal or highly formal sense unless otherwise defined.

[0034] Also, unless otherwise specified, % means weight %, and 1 ppm is 0.0001 weight %.

[0035] In one embodiment of the present invention, the meaning of including additional elements is that the remainder of iron (Fe) is replaced by an amount of the additional element.

[0036] Hereinafter, embodiments of the present invention are described in detail so that those skilled in the art can easily implement the invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0037]

[0038] A non-oriented electrical steel sheet according to one embodiment of the present invention comprises, in weight%, Si: 2.0 to 6.5%, Al: 0.001 to 1.0%, and Mn: 0.03 to 1.0%, and the remainder is Fe and unavoidable impurities.

[0039] First, I will explain the reason for the composition limitation of non-oriented electrical steel sheets.

[0040] Si: 2.0 to 6.5 wt%

[0041] Silicon (Si) plays a role in lowering iron loss by increasing the resistivity of the material, so it must be added in relatively large amounts. As the Si content increases, eddy current losses are reduced, which can lower iron loss at high frequencies. In particular, as the Si content increases, magnetostriction, which is a cause of noise, decreases to zero and permeability increases to a maximum, making it possible to manufacture electrical steel sheets with excellent high-frequency characteristics. However, as the Si content increases, the ductility of the electrical steel sheet decreases significantly, which presents a limitation in that it is difficult to manufacture electrical steel sheets using a conventional rolling process.

[0042] In one embodiment of the present invention, Si is diffused from the surface of the steel plate into the interior of the steel plate to add 4 weight percent or more of Si to the steel plate. If the amount of Si in the steel plate is too low, it is difficult to expect the aforementioned effects due to Si. If too much Si is included, there is a problem where the processability of the electrical steel plate becomes inferior when processed into products such as motors. In one embodiment of the present invention, due to the diffusion of Si from the surface to the interior, a Si concentration gradient may exist in the thickness direction of the steel plate, and unless otherwise stated, the Si content in the steel plate refers to the average content in the thickness direction. Average content refers to the content assuming that the Si in the steel plate is uniformly distributed in the thickness direction of the steel plate. More specifically, Si may be included in 2.3 to 4.5 weight percent.

[0043] In other words, the average Si content in the region from the surface to 5% of the total thickness (i.e., the outermost layer) of the non-oriented electrical steel sheet. 0% The content may be 2.50 to 7.00 weight%. If the Si content is low in the surface portion (11), it means that sufficient Si has not diffused, and the improvement in high-frequency iron loss through high-concentration Si may not be sufficiently obtained. If the Si content is too high, it means that Si exists in large quantities only in the outermost surface portion and has not diffused into the interior of the steel plate, and this also means that the improvement in high-frequency iron loss through high-concentration Si may not be sufficiently obtained. The maximum Si content refers to the Si content when the Si concentration in the outermost surface portion is measured in the thickness direction and it is assumed that the outermost surface portion has a constant Si content. The average Si content can be measured using non-destructive analysis methods such as EPMA (Electron Probe Micro-Analyzer) or Scanning Electron Microscope / Energy-dispersive X-ray Spectroscopy (SEM / EDX). More specifically, the average Si content in the outermost surface portion Si 0%The amount may be 2.70 to 6.00 weight%.

[0044] In one embodiment of the present invention, a steel plate containing a high concentration of Si is manufactured by diffusing Si from the surface of the steel plate into the interior of the steel plate, so a concentration gradient may occur in the thickness direction of the steel plate. In addition, in one embodiment of the present invention, the steel composition in the cold-rolled plate is appropriately controlled to induce an austenite phase transformation during the diffusion annealing process, and in the austenite phase, the Si diffusion rate slows down and Si is concentrated only in the surface layer, thereby not only securing high magnetic flux density but also realizing high ductility to ensure formability.

[0045] Specifically, in the cross-section in the thickness direction of the steel plate, which is the outermost surface, the average Si content in the region from the steel plate surface inward up to 5% of the total thickness. 0% and Si content at the 1 / 8 position of the total steel plate thickness Si 12.5% The difference (Si 0% - Si 12.5% ) is 0.00 to 0.70 weight%. At this position, a relatively high concentration of Si can be concentrated without a Si concentration gradient. In one embodiment of the present invention, since Si diffuses from the outside inward, the Si concentration difference (Si 0% - Si 12.5% It is difficult for ) to be less than 0 wt%. Si concentration difference (Si 0% - Si 12.5% If ) is too large, a high Si content at the surface cannot be obtained, and it may be difficult to secure the desired formability. More specifically, the difference in Si concentration (Si 0% - Si 12.5% ) may be 0.05 to 0.50 weight%.

[0046] Si content at 1 / 8 of the total thickness of the steel plate in the thickness direction cross-section, from the steel plate surface inward. 12.5% and Si content at 1 / 4 Si 25% The difference (Si 12.5% - Si 25%) is 0.30 to 2.00 wt%. From this position, a relatively steep Si concentration gradient may exist. Si concentration difference (Si 12.5% - Si 25% If ) is too small, the outermost Si 0% If the Si content is too low, or the central Si 50% This means that the Si content is too high, which may result in insufficient magnetism or, conversely, reduced ductility. Difference in Si concentration (Si 12.5% - Si 25% If ) is too large, the central Si 50% At this point, the Si concentration is too low, so the magnetism may not be sufficient. More specifically, the difference in Si concentration (Si 12.5% - Si 25% ) may be 0.50 to 1.50 weight%.

[0047] Si content at 1 / 4 of the total thickness of the steel plate in the thickness direction cross-section, from the surface to the interior. 25% and Si content at 3 / 8 Si 37.5% The difference (Si 25% - Si 37.5% ) is 1.00 to 2.50 wt%. From this position, the Si concentration gradient may be most abrupt. Si concentration difference (Si 25% - Si 37.5% If ) is too small, the outermost Si 0% If the Si content is too low, or the central Si 50% This means that the Si content is too high, which may result in insufficient magnetism or, conversely, reduced ductility. Difference in Si concentration (Si 25% - Si 37.5% If ) is too large, the central Si 50% At this point, the Si concentration is too low, so the magnetism may not be sufficient. More specifically, the difference in Si concentration (Si 25% - Si 37.5% ) may be 1.50 to 2.00 weight%.

[0048] Si content at 3 / 8 of the total thickness of the steel plate in the thickness direction cross-section, from the steel plate surface inward. 37.5% and Si content in 1 / 2 Si 50% The difference (Si 37.5% - Si 50% ) is 0.00 to 0.20 weight%. At this position, the ductility of the steel sheet can be improved by controlling the Si content of the steel sheet to a low level. In one embodiment of the present invention, since Si diffuses from the outside inward, the difference in Si concentration (Si 37.5% - Si 50% It is difficult for ) to be less than 0 wt%. Si concentration difference (Si 37.5% - Si 50% If ) is too large, the central Si 50% At this point, the Si concentration is too low, so the magnetism may not be sufficient. More specifically, the difference in Si concentration (Si 37.5% - Si 50% ) may be 0.05 to 0.20 weight%.

[0049] The center of plate thickness refers to the position halfway through the total thickness of the plate. Hereinafter, it is referred to as the center. Si content at the center Si 50% If this is low, it means that sufficient Si has not diffused, and the improvement in high-frequency iron loss through high-concentration Si may not be fully achieved. Si content in the center Si 50.0% If this is too high, a problem may occur where processability is reduced. More specifically, the Si content in the center (30) may be 0.3 to 2.0 weight%, specifically 0.5 to 1.8 weight%.

[0050] In one embodiment of the present invention, the Si content is 1 / 2 of the total thickness of the steel plate in the inward direction from the surface of the steel plate. 50% and average Si content in the region from the surface to the interior of the non-oriented electrical steel sheet up to 5% of the total thickness Si 0% The difference of (Si 0%- Si 50% ΔSi, defined as ), may be 2.0 wt% or more. If ΔSi is too small, the Si content at the outermost surface may be too low, making it difficult to secure sufficient magnetism, or the Si content at the center may be too high, making it difficult to secure ductility. More specifically, ΔSi may be 2.3 to 4.5 wt% or more.

[0051] As previously described, in one embodiment of the present invention, Si within the Si compound in the Si diffusion composition is diffused by diffusion annealing, thereby increasing the Si content, and the steel sheet prior to Si diffusion may contain less Si than previously described. Specifically, the slab and the cold-rolled sheet prior to diffusion may contain 0.00 to 2.00 weight% of Si. If there is too much Si in the slab and the cold-rolled sheet prior to diffusion, a large amount of Si is present in the center, making it difficult to secure ductility and difficult for an austenite phase transformation to occur during the diffusion annealing process. More specifically, the Si in the slab and the cold-rolled sheet prior to diffusion annealing may be 0.30 to 1.90 weight%.

[0052] Al: 0.001 to 1.00 wt%

[0053] Aluminum (Al) plays a role in lowering high-frequency iron loss by increasing the resistivity of the material. In one embodiment of the present invention, since the resistivity of the material can be sufficiently increased through the diffusion of Si, the addition of Al may be unnecessary. However, the high-frequency iron loss can be further improved by adding more Al. However, if too much Al is added, the iron loss and surface quality may deteriorate due to the formation of an aluminum silicate-based composite. In one embodiment of the present invention, due to the diffusion of Al from the surface to the interior, a concentration gradient of Al may exist in the thickness direction of the steel plate, and unless otherwise stated, the Al content in the steel plate refers to the average content in the thickness direction. More specifically, Al may be included in an amount of 0.10 to 0.70 weight%.

[0054] In one embodiment of the present invention, since Al is diffused together with Si to produce a steel plate containing a high concentration of Si, a concentration gradient of Al may occur in the thickness direction of the steel plate.

[0055] Al content at the center of plate thickness (t / 2) Al 50% and average Al content in the region from the surface to the interior of the non-oriented electrical steel sheet up to 5% of the total thickness Al 0% The difference of (Al 0% -Al 50% ΔAl, defined as ), may be 0.1 weight% or more. When there is an appropriate difference in Al content between the center and the surface, high-frequency iron loss may be further improved. More specifically, ΔAl may be 0.1 to 0.5 weight%.

[0056] As previously described, in one embodiment of the present invention, Al within the Al compound in the Si diffusion composition is diffused by diffusion annealing, thereby increasing the Al content, and the steel sheet prior to Al diffusion may contain less Al than previously described. Specifically, the slab and the cold-rolled sheet prior to diffusion may contain 0.001 to 0.70 weight% of Al. If the Al content in the slab and the cold-rolled sheet prior to diffusion is too low, the amount of Al required for diffusion increases, and the diffusion annealing process takes a long time, resulting in low efficiency; furthermore, the difference in Al content by sheet thickness becomes large, making it difficult to obtain appropriate high-frequency iron loss. If the Al content in the slab is too high, the austenite phase transformation may not occur properly during the diffusion annealing process, and Si diffusion to the center may occur rapidly. More specifically, the Al content in the slab and the cold-rolled sheet prior to diffusion may be 0.1 to 0.68 weight%.

[0057] Mn: 0.03 to 1.00 wt%

[0058] Manganese (Mn) plays a role in improving iron loss by increasing the resistivity of the material and forming sulfides. If too little Mn is added, fine MnS precipitates, which can degrade magnetism. If too much Mn is added, it promotes the formation of a

[0111] texture, which is unfavorable to magnetism, which can cause a rapid decrease in magnetic flux density. In one embodiment of the present invention, unlike Si and Al, Mn does not diffuse from the surface to the center, but rather diffuses from the center to the surface. This is because Mn volatilizes from the surface during the Si diffusion annealing process, causing Mn to diffuse from the center to the surface. As the amount of Mn decreases and the amount of Si increases, a phase transformation occurs. As the phase transformation occurs, diffusion proceeds from the surface to the interior, and at this time, an orientation similar to the direction of diffusion <100> The environment is configured to be favorable for the formation of / ND. More specifically, Mn may be 0.10 to 0.80 weight%.

[0059] In one embodiment of the present invention, Equation 1 can be satisfied in the slab and the cold-rolled sheet before diffusion annealing.

[0060] [Equation 1]

[0061] 2 × [Mn] - [Si] / 1.5 - [Al] / 0.6 + 0.75 ≥ 0.00

[0062] (Where [Mn], [Si], and [Al] in Equation 1 represent the content of Mn, Si, and Al in the cold-rolled sheet, respectively)

[0063] If the value of the left side of Equation 1 is less than 0, it is difficult to achieve an austenite phase transformation during the diffusion annealing process, and Si diffusion in the thickness direction occurs rapidly, making it difficult to obtain the desired concentration gradient in the thickness direction, and ultimately resulting in inferior magnetism and ductility. More specifically, the value of the left side of Equation 1 may be 0.10 to 0.80.

[0064] A non-oriented electrical steel sheet according to one embodiment of the present invention may further include one or more of P: 0.1 wt% or less, Cu: 0.003 to 0.2 wt%, Cr: 0.01 to 0.5 wt%, Sn: 0.1 wt% or less, Sb: 0.1 wt% or less, Ni: 0.05 wt% or less, and Zn: 0.01 wt% or less.

[0065] P: 0.1 wt% or less

[0066] Phosphorus (P) is a grain boundary segregation element, and if added in excessive amounts, it can delay recrystallization and degrade strength uniformity in the rolling direction and the rolling perpendicular direction. More specifically, P may be 0.005 to 0.03 weight%.

[0067] Cu: 0.003 to 0.200 wt%

[0068] Copper (Cu) plays a role in forming sulfides together with Mn. If more Cu is added, or if too little is added, fine precipitation of (Cu·Mn)S may occur, which can degrade magnetism. If too much Cu is added, high-temperature brittleness may occur, which can form cracks during continuous casting or hot rolling. More specifically, Cu may be included in an amount of 0.01 to 0.100 weight%.

[0069] Cr: 0.010 to 0.50 wt%

[0070] Chromium (Cr) plays a role in improving iron loss by increasing resistivity. If too little Cr is added, the effect of increasing resistivity may not be sufficient. If too much Cr is included, magnetic flux density may decrease. More specifically, the lower limit of Cr can be 0.05 wt% or 0.30 wt%.

[0071] Sn: 0.10 wt% or less

[0072] Tin (Sn) is added to improve magnetic properties by acting as a segregating element at grain boundaries to inhibit the diffusion of nitrogen through the grain boundaries, suppressing the {111} texture harmful to magnetism, and increasing the {100} texture beneficial to magnetism. If too much Sn is added, it hinders grain growth, reduces magnetism, and results in poor rolling properties. Therefore, Sn can be added within the aforementioned range. More specifically, Sn may be included in an amount of 0.005 to 0.08 weight%.

[0073] Sb: 0.10 wt% or less

[0074] Antimony (Sb) is added to improve magnetic properties by acting as a segregating element at grain boundaries to inhibit the diffusion of nitrogen through the grain boundaries, suppressing the {111} texture harmful to magnetism, and increasing the {100} texture beneficial to magnetism. If too much Sb is added, it hinders grain growth, thereby reducing magnetism and resulting in poor rolling properties. Therefore, Sb can be added within the aforementioned range. More specifically, Sb may be included in an amount of 0.005 to 0.08 weight%.

[0075] Ni: 0.05 wt% or less

[0076] Nickel (Ni) can react with impurity elements to form fine sulfides, carbides, and nitrides, which can have a harmful effect on magnetism. More specifically, Ni may be included in an amount of 0.005 to 0.03 weight%.

[0077] Zn: 0.01 wt% or less

[0078] If the content of zinc (Zn) is excessive, it can act as an impurity and impair magnetism. Therefore, Zn may be added within the aforementioned range. More specifically, Zn may be included in an amount of 0.001 to 0.005 weight%.

[0079]

[0080] A non-oriented electrical steel sheet according to one embodiment of the present invention may further include one or more types of Bi: 0.200 wt% or less, Pb: 0.200 wt% or less, Ge: 0.200 wt% or less, and As: 0.200 wt% or less.

[0081] When the aforementioned elements are added, they segregate at the grain boundaries, alleviating stress concentration at the grain boundaries during cold rolling, and thus during the subsequent recrystallization annealing process <111> By suppressing the recrystallization of the / ND orientation grains, the magnetic flux density is improved. If these are added appropriately, the aforementioned effects can be additionally obtained, but if they are included in too much, a large amount of segregation occurs, which suppresses grain growth and may result in inferior magnetic flux density and iron loss. More specifically, one or more of Bi: 0.001 to 0.100 wt%, Pb: 0.001 to 0.100 wt%, Ge: 0.001 to 0.100 wt%, and As: 0.001 to 0.100 wt% may be further included.

[0082]

[0083] A non-oriented electrical steel sheet according to one embodiment of the present invention may further include one or more of Mo: 0.03 wt% or less, B: 0.0050 wt% or less, Ca: 0.0050 wt% or less, Zr: 0.005 wt% or less, Te: 0.01 wt% or less, and Mg: 0.0050 wt% or less.

[0084] Since these can react with inevitably included C, S, N, etc. to form fine carbides, nitrides, or sulfides that may adversely affect magnetism, an upper limit may be set as described above. More specifically, one or more of Mo: 0.001 to 0.01 wt%, B: 0.0010 to 0.0030 wt%, Ca: 0.0010 to 0.0030 wt%, Zr: 0.0010 to 0.0030 wt%, Te: 0.0010 to 0.0050 wt%, and Mg: 0.0010 to 0.0050 wt% may be further included.

[0085]

[0086] Other impurities

[0087] In addition to the aforementioned elements, inevitably incorporated impurities such as carbon (C), sulfur (S), nitrogen (N), titanium (Ti), niobium (Nb), and vanadium (V) may be included.

[0088] N combines with Ti, Nb, and V to form nitrides and plays a role in reducing grain growth.

[0089] C reacts with N, Ti, Nb, V, etc., to form fine carbides, which hinder grain growth and domain movement.

[0090] S forms sulfides, which impair grain growth.

[0091] In cases where impurity elements are further included as described above, one or more of C: 0.005 wt% or less, N: 0.030 wt% or less, S: 0.005 wt% or less, Ti: 0.005 wt% or less, Nb: 0.005 wt% or less, and V: 0.005 wt% or less may be further included. More specifically, one or more of C: 0.001 to 0.003 wt%, N: 0.001 to 0.005 wt%, S: 0.001 to 0.005 wt%, Ti: 0.001 to 0.005 wt%, Nb: 0.001 to 0.005 wt%, and V: 0.001 to 0.005 wt% may be further included.

[0092] In addition, unavoidable impurities may be included. These unavoidable impurities are those introduced during the steelmaking stage and the manufacturing process of non-oriented electrical steel sheets; since this is widely known in the field, a detailed explanation is omitted. In one embodiment of the present invention, the addition of elements other than the aforementioned alloy components is not excluded, and various elements may be included within a scope that does not impair the technical spirit of the present invention. If additional elements are included, they are included to replace the remainder, Fe.

[0093]

[0094] A non-oriented electrical steel sheet according to one embodiment of the present invention exhibits excellent high-frequency iron loss due to the diffusion of Si. Specifically, iron loss (W 10 / 400 ) may be 12.0 W / kg or less. In this case, iron loss is based on a steel plate with a thickness of 0.2 mm. Iron loss (W 10 / 400 ) is the iron loss when a magnetic flux density of 1.0T is induced at a frequency of 400 Hz. Iron loss can be measured using the Epstein test or the SST (single sheet test) method. More specifically, iron loss (W 10 / 400 ) can be 9.0W / kg to 11.5W / kg.

[0095] In one embodiment of the present invention, not only iron loss but also magnetic flux density is excellent simultaneously. Specifically, magnetic flux density (B 25 ) can be 1.60T or more. Specifically, magnetic flux density (B 25 ) can be 1.61 to 1.80T.

[0096] The non-oriented electrical steel sheet according to one embodiment of the present invention also has excellent ductility. Specifically, the non-oriented electrical steel sheet according to one embodiment of the present invention may have an elongation of 4.5% or more. More specifically, it may be 5.0 to 13.0%. The elongation can be measured in accordance with ISO 6892-1.

[0097]

[0098] A method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention comprises the steps of: manufacturing a cold-rolled sheet comprising, in weight percent, Si: 0.0 to 2.0%, Al: 0.001 to 0.7%, and Mn: 0.03 to 1.0%, and the remainder being Fe and unavoidable impurities; a coating step of applying a Si diffusion composition comprising a Si compound to the surface of the cold-rolled sheet; a drying step of drying the Si diffusion composition; and a diffusion annealing step of the cold-rolled sheet.

[0099] Below, each step is explained in detail.

[0100] First, a cold-rolled sheet is manufactured containing, in weight percent, Si: 0.0 to 2.0%, Al: 0.001 to 0.7%, and Mn: 0.03 to 1.0%, with the remainder being Fe and unavoidable impurities. Since the alloy composition of the cold-rolled sheet is the same as that described above, a redundant description is omitted.

[0101] The method for manufacturing a cold-rolled sheet is not particularly limited and may include the step of manufacturing a hot-rolled sheet by hot-rolling a slab containing, in weight percent, Si: 0.0 to 2.0%, Al: 0.001 to 0.7%, and Mn: 0.03 to 1.0%, and the remainder being Fe and unavoidable impurities; and the step of manufacturing a cold-rolled sheet by cold-rolling the hot-rolled sheet.

[0102] First, a slab is manufactured. The reason for limiting the addition ratio of each component within the slab is the same as the reason for limiting the composition of the non-oriented electrical steel sheet described above, so a repeated explanation is omitted. Since the composition of the slab does not substantially change during the manufacturing processes described later, such as hot rolling, hot-rolled sheet annealing, and cold rolling, the composition of the slab and the composition of the cold-rolled sheet are substantially the same. Furthermore, in the diffusion annealing process, only Si and Al diffuse, and the alloy composition of the non-oriented electrical steel sheet may be the same as the remaining components excluding Si and Al.

[0103] Prior to the step of manufacturing a hot-rolled plate, the slab may be heated to 1100°C or higher. Specifically, the slab is loaded into a heating furnace and heated to 1100 to 1250°C. When heated at a temperature exceeding 1250°C, precipitates may be redissolved and finely precipitated after hot rolling. More specifically, the slab heating temperature may be 1100°C to 1200°C.

[0104] The heated slab is hot-rolled to a thickness of 1.5 to 4.0 mm to produce a hot-rolled plate. In one embodiment of the present invention, a step of pre-cold rolling before cold rolling is also included, so that a non-oriented electrical steel plate of appropriate thickness can be produced even if the thickness of the hot-rolled plate is relatively thick. More specifically, the thickness of the hot-rolled plate may be 1.5 mm to 3.5 mm.

[0105] The step of manufacturing a hot-rolled plate may include a step of finishing rolling at a temperature of 850°C or higher.

[0106] If the finishing rolling temperature of hot rolling is too low, the rolling load increases, leading to reduced hot rolling workability. Furthermore, a significant amount of deformation remains in the hot-rolled steel sheet, which causes an increase in the rolling load during the subsequent pre-cold rolling process. In addition, from the deformation during intermediate annealing <111> / ND Recrystallization of the grains is promoted, resulting in lower magnetic flux density. Therefore, the hot rolling finish rolling temperature should be as high as possible, and more specifically, the finish rolling temperature can be 850 to 1000℃.

[0107] The step of manufacturing a hot-rolled plate may include a coiling step at a temperature of 600 to 800°C. It may also include a rough rolling step before the finish rolling step.

[0108] If the temperature during the coiling stage is managed too low, the recovery and recrystallization of the hot-rolled deformed structure do not occur effectively. Additionally, the cooling load increases to rapidly cool the steel sheet to a low temperature, which may cause difficulties in coiling the supercooled coil. Conversely, if the temperature is too high, recovery and recrystallization may be promoted, but additional oxidation by atmospheric oxygen may occur during coiling, leading to the formation of a thicker scale and problems with intergranular oxidation. Intergranular oxidation of the hot-rolled sheet promotes intergranular corrosion during the subsequent pickling process, increasing the likelihood of surface streak defects and causing severe wear on the rolling rolls. More specifically, the coiling temperature may be 650 to 750°C.

[0109] After the step of manufacturing a hot-rolled plate, the process may further include a step of annealing the hot-rolled plate at a temperature range of 600 to 1100°C. If the annealing temperature of the hot-rolled plate is too low, a recrystallization structure is not formed or grows finely, resulting in a small increase in magnetic flux density; if the annealing temperature is too high, magnetic properties may actually deteriorate, and rolling workability may be poor due to deformation of the plate shape. More specifically, the annealing temperature of the hot-rolled plate may be 750 to 1000°C.

[0110] Annealing of hot-rolled plates is performed as needed to increase the magnetic orientation, and it may be omitted. The form of annealing is not particularly limited and can be performed in batch or continuous motion.

[0111] Hot-rolled plates can be pickled as needed.

[0112] Next, the hot-rolled sheet is pickled and cold-rolled to a predetermined thickness. Depending on the thickness of the hot-rolled sheet, a reduction rate of 70 to 95% may be applied to cold-roll the sheet so that the final thickness is 0.10 to 0.65 mm. To achieve the reduction rate, one cold-rolling step or two or more cold-rolling steps with intermediate annealing in between may be performed. More specifically, the reduction rate may be 75 to 90%. The thickness of the cold-rolled sheet may be 0.15 to 0.35 mm.

[0113] Next, in the coating step, a Si diffusion composition containing a Si compound is applied to the cold-rolled plate.

[0114] As for the Si compound, any material capable of diffusing Si into the interior of the steel sheet through long-term annealing may be used without limitation. Specifically, it may include one or more of pure Si, Si alloys, Si oxides, nitrides or carbides, and silane compounds. In addition, it may include one or more of FeSi, Fe3Si, Fe3Al, and FeAl.

[0115] More specifically, it may include pure Si, Si alloys, and Fe3Si.

[0116] The average particle size of the Si compound may be 0.1 to 10 µm. If the particle size of the Si compound is too small, problems may arise where they aggregate during slurry mixing, causing surface defects. If the particle size of the Si compound is too large, it may be difficult to apply it uniformly to the surface of the steel plate, which may hinder smooth diffusion of Si into the interior of the steel plate. The average particle size of the Si compound is the average particle size relative to the number of compound particles and can be measured using a particle size analyzer (PSA) utilizing laser diffraction. More specifically, the average particle size of the Si compound may be 0.5 to 5 µm.

[0117] The Si diffusion composition further comprises an Al compound and may include 100 parts by weight of the Si compound and 1 to 50 parts by weight of the Al compound as solid content. In one embodiment of the present invention, solid content refers to the weight after all volatile components have been removed by heating each compound at 180°C for at least 20 minutes.

[0118] Al compounds improve insulation, increase bonding with Si compounds, and also play a role in promoting the formation of intermetallic compounds. If too little Al compound is included, it may be difficult to obtain the aforementioned effects adequately. If too much Al compound is included, a problem may arise where numerous Al inclusions are formed, resulting in reduced magnetism. More specifically, the Al compound may be included in an amount of 15 to 30 parts by weight.

[0119] As for Al compounds, any material capable of diffusing Al into the steel sheet can be used without restriction. For example, pure Al and aluminum alkoxides may be used.

[0120] The average particle size of the Al compound may be 1 to 1000 nm. If the particle size of the Al compound is too small, a problem of aggregation between Al compounds may occur. If the particle size of the Al compound is too large, Al diffusion into the steel sheet may not occur smoothly. More specifically, the lower limit of the average particle size of the Al compound may be 5 nm. The upper limit of the average particle size of the Al compound may be 750 nm.

[0121] The Si diffusion composition may further include ceramic powder comprising oxides, nitrides, carbides, or oxynitrides, comprising at least one component selected from Li, B, Ca, Sr, Mg, Al, P, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Zr, Sn, and Ba. The ceramic powder serves to control the amount of slurry applied and to determine the Si content of the final steel sheet.

[0122] The ceramic powder may be included in an amount of 10 to 1,000 parts by weight as a solid content. If too little ceramic powder is included, problems may arise in terms of securing the coating amount. If too much ceramic powder is included, the slurry viscosity increases, which may cause problems in terms of surface defects. More specifically, the ceramic powder may be included in an amount of 20 to 500 parts by weight.

[0123] The ceramic powder may be one or more of Al2O3, TiO2, MgO·Al2O3, MgO·TiO2, 3Al2O3·2SiO2, ZrO2·SiO2, TiN, CrN, SrTiO3, MgAl2O4, Y2O3, FeTiO3, and Li2O·Al2O3·SiO2.

[0124] The average particle size of the ceramic powder may be 8 to 2500 nm. If the particle size of the ceramic powder is too small, there may be a problem in securing a sufficient coating amount. If the particle size of the ceramic powder is too large, the viscosity increases, the surface quality deteriorates, and Si diffusion into the steel plate may not proceed smoothly. More specifically, the average particle size of the ceramic powder may be 10 nm to 1500 nm.

[0125] The Si diffusion composition may further include a solvent in addition to the aforementioned components. The solvent enables the uniform application of the Si diffusion composition. If the amount of solvent is too small, the application of the Si diffusion composition may not be easy. If the amount of solvent is too large, the viscosity of the Si diffusion composition may be too low, making it difficult to apply a sufficient amount of the composition onto the steel plate. The solvent may be included in an amount of 10 to 1,500 parts by weight per 100 parts by weight of the Si compound. More specifically, the solvent may be included in an amount of 50 to 1,000 parts by weight. The solvent may include one or more of water and alcohol.

[0126] In addition to the aforementioned components, the Si diffusion composition may further include additional components, and this is not excluded in one embodiment of the present invention. Examples of additional components may include phosphoric acid, sodium silicate, fluoride ion solution, etc.

[0127] In the coating step, the coating amount of the Si diffusion composition is 0.1 to 300 g / m² 2 It may be. In this case, the coating amount is based on the solid content. If the coating amount is too small, sufficient Si diffusion does not occur, making it difficult to fully achieve the effect of Si diffusion. If the coating amount is too large, a problem of inferior processability may occur. In one embodiment of the present invention, the Si diffusion composition may be applied to one or both sides of a steel plate, and when applied to both sides, the coating amount for each side is 0.1 to 300 g / m² 2 It could be.

[0128] Application methods include using a roll coater, brush, and dipping. From a productivity standpoint, application can be performed using a roll coater.

[0129] After the coating step, the method may further include a step of forming a Si diffusion coating layer by drying the Si diffusion composition through drying. The drying temperature is sufficient if it is a temperature capable of removing the solvent within the Si diffusion composition, and specifically, it may be 300 to 850°C. The time may be 10 seconds to 180 seconds. More specifically, the temperature may be 500 to 800°C. The time may be 15 seconds to 150 seconds. After drying at the drying temperature, cooling may be performed at a cooling rate of 20°C / second or higher. By rapidly cooling in this manner, the automatic detachment of the unreacted residual composition can be induced by utilizing the difference in thermal shrinkage between the steel plate and the unreacted composition layer. The cooling range may be from the drying temperature to 100°C.

[0130] Next, the cold-rolled sheet is diffusion annealed. During this process, Si and / or Al diffuse into the interior of the steel sheet from the Si diffusion composition applied to the surface of the cold-rolled sheet.

[0131] In the diffusion annealing step, the cracking temperature of the cracking step may be 850 to 1050°C. If the diffusion annealing temperature is too low, the diffusion of Si may not occur sufficiently, and the desired effect may not be obtained. If the diffusion annealing temperature is too high, pores may form, and the magnetic properties may deteriorate. More specifically, it may be 900 to 1000°C.

[0132] The time may be 0.5 to 10 hours. If the time is too short, the diffusion of Si may not occur sufficiently, and the desired effect may not be obtained. If the time is too long, Si may diffuse sufficiently into the interior of the steel sheet, making it difficult to secure the desired ductility. More specifically, it may be 0.5 to 5 hours.

[0133] During diffusion annealing, the atmosphere may be an atmosphere containing one or more of hydrogen, nitrogen, or argon. The oxidizing power of the atmosphere (PH2O / PH2) may be 6.4 or less. If the oxidizing power is too high, an oxide may form inside Al2O3, which may degrade the magnetic properties. Specifically, the oxidizing power of the atmosphere (PH2O / PH2) may be 3.0 or less. Specifically, the oxidizing power of the atmosphere (PH2O / PH2) may be 1.0 or less.

[0134] After diffusion annealing, the final thickness of the steel sheet may be 0.10 to 0.65 mm, and due to the application and diffusion of the Al diffusion composition, the thickness may increase slightly compared to the cold-rolled sheet.

[0135] Next, the method may further include a step of brushing the diffusion-annealed steel sheet to remove unreacted composition remaining on the surface of the cold-rolled sheet and also to partially remove the oxide layer.

[0136] Subsequently, a step of forming an insulating film may be further included. Since insulating films are widely known, a detailed description is omitted. Specifically, an insulating coating layer can be formed by applying an insulating coating layer forming composition comprising metal phosphate and silica as main components and heat treating.

[0137]

[0138] Preferred embodiments and comparative examples of the present invention are described below. However, the following examples are merely preferred embodiments of the present invention, and the present invention is not limited to the following examples.

[0139]

[0140] Examples

[0141] A slab was prepared containing the steel composition summarized in Table 1 below, with the remainder consisting of Fe and other unavoidable impurities.

[0142] A hot-rolled plate was manufactured by heating a slab to 1100℃ and then hot-rolling it to a thickness of 1.8mm.

[0143] A hot-rolled plate was coiled at 700°C, cooled in air, annealed at 1030°C for 2 minutes, then rapidly cooled in water and pickled, and then cold-rolled to a thickness of 0.20 mm to produce a cold-rolled plate.

[0144] A Si diffusion composition was prepared by stirring 30 parts by weight of silicon powder (Si: 99.99 wt% or more) with an average particle size of 1 μm, water, and 60 parts by weight of a catalyst.

[0145] The prepared Si diffusion composition was applied to both sides of a cold-rolled plate. The coating amount was 20 g / m². 2 It was applied uniformly.

[0146] After coating, the steel plate was diffusion annealed at a temperature of 1000°C for 1 hour. The diffusion annealing was performed in a 100v% H2 atmosphere.

[0147] After the diffusion annealing was completed, the surface of the steel sheet was washed with water and dried at room temperature, then immersed in a nitric acid solution containing 0.5% hydrofluoric acid at 65°C for 12 seconds to remove unreacted material, washed again with water, and finally dried to produce a non-oriented electrical steel sheet.

[0148] The Si content by thickness was measured by EDS (Energy Dispersion Spectroscopy) and summarized in Table 2.

[0149] Magnetic flux density and iron loss were measured in the rolling direction and perpendicular to the rolling direction, and their averages are shown in Table 3. In addition, elongation was measured using the ISO 6892-1 method and summarized in Table 3.

[0150] Steel Grade (Wt%) SiAlMnC Other Additives Formula 1 Value 10.82 0.48 0.67 0.002Ti: 0.004, Nb: 0.003 0.742 1.75 0.25 0.54 0.002V: 0.002, Cu: 0.003 0.25 30.91 0.35 0.33 0.001Ca: 0.003, Sn: 0.003 0.22 40.35 0.68 0.54 0.004Sb: 0.003, Ni: 0.01, Zr 0.003 20.465 1.80 0.03 0.33 0.004Zn: 0.005, Bi: 0.003, Mg:0.0040.1660.540.620.550.002Pb:0.002, Ge:0.003, B:0.00230.4671.120.380.510.002As:0.02, Mo:0.01, Ca:0.0030.3982.310.190.650.001-0.1992.810.170.710.001-0.01100.850.141.320.004-2.59110.870. 340.720.020-1.04120.720.930.730.001-0.18131.880.530.180.004--1.03140.770.650.150.001--0.55

[0151] Average Si content of the entire steel grade (wg%) Si content at the outermost surface (Si 0%, wt%) Si 0% - Si 12.5% (Wet%)Si 12.5%- Si 25% (Wet%)Si 25% - Si 37.5% (Wet%)Si 37.5% - Si 50% (Wt%)ΔSi(Wt%)12.35 3.50 0.13 0.69 1.87 0.10 2.79 22.9 14.55 0.09 1.09 1.52 0.16 2.86 33.43 4.97 0.40 1.48 1.96 0.15 3.99 42.9 14.35 0.48 1.41 1.98 0.19 4.06 53.26 4.23 0.18 0.89 1.56 0.10 2.73 62.36 2.95 0.17 0.62 1.52 0.11 2.42 73.43 4.29 0.17 1.16 1.84 0.13 3.3083.353.600.120.870.300.051.3494.285.710.820.811.870.233.73103.774.890.110.893.050.244.29113.403.730.111.181.570.082.94123.284.550.220.892.720.194.02134.265.531.270.721.560.113.66142.462.831.200.180.620.072.07

[0152] Iron loss (W10 / 400, W / Kg) Magnetic flux density (B50, Tesla) Elongation (%) Type 1 1.2 1.6 1.8 2 Example 2 1 0.6 1.6 5 7.3 Example 3 1 0.1 1.6 9 7.9 Example 4 1 0.6 1.7 3 1.2 Example 5 1 0.2 1.7 7 5.5 Example 6 1 1.1 1.6 7 1 0.2 Example 7 1 0.1 1.7 3 8.8 Example 8 1 5.4 1.5 6 3.2 Comparative Example 9 1 3.2 1.6 7 2.8 Comparative Example 10 1 3.4 1.6 6 3.8 Comparative Example 11 1 6.2 1.6 8 3.6 Comparative Example 12 1 5.3 1.5 6 2.3 Comparative Example 13 1 4.2 1.5 2 3.4 Comparative Example 14 1 3.8 1.5 7 4.2 Comparative Example

[0153] As shown in Tables 1 to 3, by appropriately controlling the steel composition of the cold-rolled sheet before diffusion annealing, the Si diffusion annealing rate can be controlled, and it can be confirmed that the Si concentration gradient according to thickness is appropriately achieved. Ultimately, it can be confirmed that the magnetic and ductile properties are excellent simultaneously.

[0154] On the other hand, for steel grades 8 to 14, the steel composition of the cold-rolled sheet before diffusion annealing was not properly controlled, and it can be confirmed that the magnetic or ductile properties are inferior.

[0155]

[0156] The present invention is not limited to the above embodiments and can be manufactured in various different forms, and those skilled in the art will understand that the invention can be implemented in other specific forms without changing the technical concept or essential features of the invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

Claims

1. In weight%, it comprises Si: 2.0 to 6.5%, Al: 0.001 to 1.0%, and Mn: 0.03 to 1.0%, and the remainder comprises Fe and unavoidable impurities, and Average Si content in the region from the steel plate surface inward to 5% of the total thickness in the cross-section in the thickness direction of the steel plate. 0% and Si content at the 1 / 8 position of the total steel plate thickness Si 12.5% The difference (Si 0% - Si 12.5% ) is 0 to 0.7 weight%, and Si content at 1 / 8 of the total thickness of the steel plate in the thickness direction cross-section, from the steel plate surface inward. 12.5% and Si content at 1 / 4 Si 25% The difference (Si 12.5% - Si 25% ) is 0.3 to 2.0 weight%, and Si content at 1 / 4 of the total thickness of the steel plate in the thickness direction cross-section, from the surface to the interior. 25% and Si content at 3 / 8 Si 37.5% The difference (Si 25% - Si 37.5% ) is 1.0 to 2.5 weight%, and Si content at 3 / 8 of the total thickness of the steel plate in the thickness direction cross-section, from the steel plate surface inward. 37.5% and Si content in 1 / 2 Si 50% The difference (Si 37.5% - Si 50% Non-oriented electrical steel sheet having ) 0 to 0.2 weight%.

2. In Paragraph 1, Si content from the surface of the steel plate inward to half of the total thickness of the steel plate Si 50% and the average Si content in the region from the surface of the above non-oriented electrical steel sheet in the inward direction up to 5% of the total thickness Si 0% The difference of (Si 0% - Si 50% Non-oriented electrical steel sheet having ΔSi defined as ) 2.0 wt% or more.

3. In Paragraph 1, A non-oriented electrical steel sheet further comprising one or more of C: 0.005 wt% or less, N: 0.030 wt% or less, S: 0.005 wt% or less, Ti: 0.005 wt% or less, Nb: 0.005 wt% or less, and V: 0.005 wt% or less.

4. In Paragraph 1, A non-oriented electrical steel sheet further comprising one or more of P: 0.1 wt% or less, Cu: 0.003 to 0.2 wt%, Cr: 0.01 to 0.5 wt%, Sn: 0.1 wt% or less, Sb: 0.1 wt% or less, Ni: 0.05 wt% or less, and Zn: 0.01 wt% or less.

5. In Paragraph 1, A non-oriented electrical steel sheet further comprising one or more of Bi: 0.200 wt% or less, Pb: 0.200 wt% or less, Ge: 0.200 wt% or less, and As: 0.200 wt% or less.

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

7. A step of manufacturing a cold-rolled sheet comprising, in weight%, Si: 0.0 to 2.0%, Al: 0.001 to 0.7%, and Mn: 0.03 to 1.0%, and the remainder being Fe and unavoidable impurities, satisfying Formula 1 below; A coating step of applying a Si diffusion composition containing a Si compound to the surface of the above cold-rolled plate; A drying step for drying the above Si diffusion composition; and A method for manufacturing a non-oriented electrical steel sheet comprising the step of diffusion annealing the above cold-rolled sheet. [Equation 1] 2 × [Mn] - [Si] / 1.5 - [Al] / 0.6 + 0.75 ≥ 0 (Where [Mn], [Si], and [Al] in Equation 1 represent the content of Mn, Si, and Al in the cold-rolled sheet, respectively) 8. In Paragraph 7, A method for manufacturing a non-oriented electrical steel sheet, wherein the above Si diffusion composition further comprises an Al compound, and the solid content comprises 100 parts by weight of Si compound and 1 to 50 parts by weight of Al compound.

9. In Paragraph 7, A method for manufacturing a non-oriented electrical steel sheet, comprising 10 to 1,000 parts by weight of a ceramic powder comprising an oxide, nitride, carbide, or oxynitride, wherein the above Si diffusion composition comprises at least one component selected from Li, B, Ca, Sr, Mg, Al, P, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Zr, Sn, and Ba.

10. In Paragraph 7, A method for manufacturing a non-oriented electrical steel sheet in which the average particle size of the above Si compound is 0.1 to 10 μm.

11. In Paragraph 8, A method for manufacturing a non-oriented electrical steel sheet in which the average particle size of the above Al compound is 1 to 1000 nm.

12. In Paragraph 9, A method for manufacturing a non-oriented electrical steel sheet in which the average particle size of the ceramic powder is 8 to 2500 nm.

13. In Paragraph 7, In the above coating step, the application amount of the Si diffusion composition for each step is 0.1 to 300 g / m² 2 Method for manufacturing non-oriented electrical steel sheets.

14. In Paragraph 7, A method for manufacturing a non-oriented electrical steel sheet in which, in the above diffusion annealing step, the cracking temperature is 850 to 1050℃ and the cracking time is 2 to 10 hours.