Non-grain-oriented electrical steel sheet and method for manufacturing same

Abstract

A non-grain-oriented electrical steel sheet according to one embodiment of the present invention comprises, in weight%, 4.0-7.0% of Si, 0.001-2.0% of Al, 0.03 to 2.0% of Mn, and the balance of Fe and inevitable impurities, and the thickness of an oxide layer present in the surface layer is 0.1 um or less.

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 and a method for manufacturing the same, which improves iron loss characteristics by diffusing Si from the surface of the steel sheet into the interior of the steel sheet to improve magnetism, while simultaneously making the surface smooth and making the thickness of the oxide layer very thin.

[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 SiCl4 gas onto the surface of cold-rolled steel sheets. 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] Accordingly, a method was proposed in which a composition containing Si powder is applied and then diffusion annealed to diffuse the Si component onto the surface of the electrical steel sheet. In this case, shot blasting or immersion in an acid solution was proposed to remove unreacted residues after diffusion annealing. However, the shot blasting method has the problem of making the surface roughness of the steel sheet very rough. While immersion in an acid solution can lower the surface roughness, the oxide layer, such as Si, generated during the diffusion annealing process remains intact, and this oxide layer has an adverse effect on magnetism.

[0007]

[0008] 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, Si is diffused from the surface of the steel sheet into the interior of the steel sheet to improve magnetism and simultaneously make the surface smooth and make the thickness of the oxide layer very thin, thereby providing a non-oriented electrical steel sheet and a method for manufacturing the same that improves iron loss characteristics.

[0009] A non-oriented electrical steel sheet according to one embodiment of the present invention comprises, in weight percent, Si: 4.0 to 7.0%, Al: 0.001 to 2.0%, and Mn: 0.03 to 2.0%, and the remainder is Fe and unavoidable impurities, and an oxide layer exists from the surface of the steel sheet toward the interior of the steel sheet, and the thickness of the oxide layer is 0.1 μm or less.

[0010] The surface roughness Ra value of the steel plate may be 0.6㎛ or less, Rz value may be 7.0㎛ or less, and Rt value may be 15.0㎛ or less.

[0011] Si content at the center of plate thickness (t / 2) [CM Si ] and maximum Si content [SM 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 The difference of ] ([SM Si ]-[ CM Si ΔSi, defined as ]), may be 0.1 wt% or more.

[0012] Al content at the center of plate thickness (t / 2) [CM Al ] and maximum Al content [SM 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 Al The difference of ] ([SM Al ]-[ CM Al ΔAl, defined as ]), may be 0.1 weight% 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 (excluding 0%), N: 0.005 wt% or less (excluding 0%), S: 0.005 wt% or less (excluding 0%), Ti: 0.005 wt% or less (excluding 0%), Nb: 0.005 wt% or less (excluding 0%), and V: 0.005 wt% or less (excluding 0%).

[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 (excluding 0%), Cu: 0.005 to 0.2 wt%, Cr: 0.01 to 0.5 wt%, Sn: 0.1 wt% or less (excluding 0%), Sb: 0.1 wt% or less (excluding 0%), Ni: 0.05 wt% or less (excluding 0%), and Zn: 0.01 wt% or less (excluding 0%).

[0015] 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 (excluding 0%), Pb: 0.200 wt% or less (excluding 0%), Ge: 0.200 wt% or less (excluding 0%), and As: 0.200 wt% or less (excluding 0%).

[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 (excluding 0%), B: 0.0050 wt% or less (excluding 0%), Ca: 0.0050 wt% or less (excluding 0%), Zr: 0.005 wt% or less (excluding 0%), Te: 0.01 wt% or less (excluding 0%), and Mg: 0.0050 wt% or less (excluding 0%).

[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 comprising, in weight percent, Si: 0.3 to 4.0%, Al: 0.001 to 2.0%, and Mn: 0.03 to 2.0%, 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 diffusion annealing step of the cold-rolled sheet and a brushing step of the diffusion annealed steel sheet.

[0018] In the brushing step, the strength of the brush bristles can be 50 to 90 MPa.

[0019] In the brushing step, the brush bristles have a diameter (Φ) of 0.4 to 1.5 mm and 2 to 8 EA are bonded together, and the inside of the bristles may contain SiC or Al2O3 abrasive with an average particle size of 50 to 250 μm.

[0020] After the brushing step, an acid cleaning step of immersing the steel plate in an acid solution may be further included.

[0021] After the acid cleaning step, a secondary brushing step may be included.

[0022] The step of manufacturing a cold-rolled sheet comprises: a step of manufacturing a hot-rolled sheet by hot-rolling a slab containing, in weight percent, Si: 0.01 to 3.5%, Al: 0.001 to 2.0%, and Mn: 0.03 to 2.0%, and the remainder being Fe and unavoidable impurities; and a step of manufacturing a cold-rolled sheet by cold-rolling the hot-rolled sheet.

[0023] A non-oriented electrical steel sheet according to one embodiment of the present invention has excellent magnetic flux density and high-frequency iron loss.

[0024] A method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention provides an environmentally friendly manufacturing method in which no by-product gases harmful to the environment are generated during the manufacturing process.

[0025] A non-oriented electrical steel sheet according to one embodiment of the present invention has excellent surface properties, as it has no residual unreacted composition in the surface layer, low surface roughness, and a very thin oxide layer.

[0026] Figure 1 shows the results of analyzing the elemental content according to steel sheet thickness after diffusion annealing in Example 1 using a Glow Discharge Spectrometer (GDS).

[0027] Figure 2 is an electron microscope image of the steel plate surface after diffusion annealing in Example 1.

[0028] Figure 3 shows the results of analyzing the elemental content by steel plate thickness after the brushing step in Example 1 using a Glow Discharge Spectrometer (GDS).

[0029] Figure 4 is an electron microscope image of the steel plate surface after the brushing step in Example 1.

[0030] Figure 5 shows the results of analyzing the elemental content by steel plate thickness after the acid cleaning step in Example 1 using a Glow Discharge Spectrometer (GDS).

[0031] Figure 6 is an electron microscope image of the steel plate surface after the acid cleaning step in Example 1.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] Also, unless otherwise specified, % means weight %, and 1 ppm is 0.0001 weight %.

[0037] 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.

[0038] 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.

[0039]

[0040] A non-oriented electrical steel sheet according to one embodiment of the present invention comprises, in weight percent, Si: 4.0 to 7.0%, Al: 0.001 to 3.0%, and Mn: 0.03 to 3.0%, and the remainder is Fe and unavoidable impurities.

[0041] First, I will explain the reason for the limitation of the composition of non-oriented electrical steel sheets.

[0042] Si: 4.0 to 7.0 wt%

[0043] 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, when Si is included at 6.0 wt% or more, magnetostriction, which is a cause of noise, decreases to zero and permeability increases to the maximum, making it possible to manufacture electrical steel sheets with excellent high-frequency characteristics. However, when the Si content is 4 wt% or more, the ductility of the electrical steel sheet decreases significantly, and there is a limit where it is difficult to manufacture electrical steel sheets using a conventional rolling process.

[0044] 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 4.5 to 6.5 weight percent.

[0045] The maximum Si content in the region from the surface of the non-oriented electrical steel sheet in the inward direction up to 5% of the total thickness may be 4.0 to 8.0 weight%, and the Si content at the center of the sheet thickness position (t / 2) may be 0.3 to 7.5 weight%.

[0046] In one embodiment of the present invention, since a steel sheet containing a high concentration of Si is manufactured by diffusing Si from the surface of the steel sheet into the interior of the steel sheet, a concentration gradient may occur in the thickness direction of the steel sheet. That is, the maximum Si content in the region from the surface of the non-oriented electrical steel sheet to 5% of the total thickness in the interior direction (i.e., the surface portion) may be 4.0 to 8.0 weight%. If the Si content in the surface portion is low, it means that sufficient Si has not diffused, and thus 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 a large amount of Si exists only in the surface portion and has not diffused into the interior of the steel sheet, 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 highest Si content when measuring the Si concentration in the surface portion in the thickness direction. The maximum 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 maximum Si content at the surface may be 4.5 to 7.5 weight%.

[0047] The center of the plate thickness refers to the position at half the total thickness of the plate. Hereinafter, it is referred to as the center. If the Si content is low at the center, it means that sufficient Si has not diffused, and the improvement in high-frequency iron loss through high-concentration Si may not be sufficiently achieved. If the Si content is too high at the center, a problem of reduced processability may occur. More specifically, the Si content at the center may be 2.5 to 6.0 weight%.

[0048] Si content at the center of plate thickness (t / 2) [CM Si] and maximum Si content [SM 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 The difference of ] ([SM Si ]-[ CM Si ΔSi, defined as ]), may be 0.1 wt% or more. When there is an appropriate difference in Si content between the center and the surface, high-frequency iron loss and processability can be further improved. More specifically, ΔSi may be 0.5 to 3.0 wt%.

[0049] 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 2.0 to 3.5 weight% of Si. If the Si content in the slab and the cold-rolled sheet prior to diffusion is too low, the amount of Si required for diffusion increases, and the diffusion annealing process takes a long time, resulting in low efficiency; furthermore, the difference in Si content by sheet thickness becomes large, making it difficult to obtain appropriate high-frequency iron loss. If the Si content in the slab and the cold-rolled sheet prior to diffusion is too high, the steel sheet may fracture during the cold rolling process or defects may occur within the steel sheet. More specifically, the Si content in the slab may be 2.3 to 3.3 weight%.

[0050] Al: 0.001 to 3.0 wt%

[0051] 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. More specifically, Al may be included in an amount of 0.01 to 2.0 weight%. 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 0.1 to 1.5 weight%.

[0052] 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.

[0053] Al content at the center of plate thickness (t / 2) [CM Al ] and maximum Al content [SM 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 Al The difference of ] ([SM Al ]-[ CM Al ΔAl, defined as ]), may be 0.1 wt% or more. When there is an appropriate difference in Al content between the center and the surface, high-frequency iron can be further improved.

[0054] The maximum Al content in the region extending from the surface to 5% of the total thickness (i.e., the surface portion) of the non-oriented electrical steel sheet may be 0.1 to 3.0 weight%. If the Al content in the surface portion is low, it means that sufficient Al has not diffused, and thus, sufficient improvement in high-frequency iron loss through Al diffusion may not be achieved. If the Al content is too high, it means that a large amount of Al exists only in the surface portion and has not diffused into the interior of the steel sheet, and this also means that sufficient improvement in high-frequency iron loss through Al diffusion may not be achieved. The maximum Al content refers to the highest Al content when measuring the Al concentration in the surface portion in the thickness direction. The maximum Al content can be measured by GOD, FTIR, wet analysis, TEM-GDS, or SEM-GDS methods. More specifically, the maximum Al content in the surface portion may be 0.5 to 1.0 weight%.

[0055] The Al content in the center may be 0.001 to 2.0 wt%. If the Al content in the center is low, it means that sufficient Al has not diffused, and the improvement in high-frequency iron loss through Al diffusion may not be sufficiently obtained. If the Al content in the center is too high, a problem of deterioration in magnetic flux density may occur. More specifically, the Al content in the center may be 0.5 to 1.0 wt%.

[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 2.0 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, Al oxides may clump together in some locations, causing cracking during the rolling process. More specifically, the Al content in the slab and the cold-rolled sheet prior to diffusion may be 0.001 to 1.8 weight%. Even more specifically, the Al content in the slab and the cold-rolled sheet prior to diffusion may be 0.01 to 1.0 weight%.

[0057] Mn: 0.03 to 3.0 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 0.05 to 2.0 weight%.

[0059] 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: 0.005 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.

[0060] P: 0.1 wt% or less

[0061] 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%.

[0062] Cu: 0.005 to 0.200 wt%

[0063] 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%.

[0064] Cr: 0.010 to 0.50 wt%

[0065] 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%.

[0066] Sn: 0.10 wt% or less

[0067] 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%.

[0068] Sb: 0.10 wt% or less

[0069] 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%.

[0070] Ni: 0.05 wt% or less

[0071] 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%.

[0072] Zn: 0.01 wt% or less

[0073] 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%.

[0074]

[0075] 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.

[0076] 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.

[0077]

[0078] 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.

[0079] 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.

[0080]

[0081] Other impurities

[0082] 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.

[0083] N combines with Ti, Nb, and V to form nitrides and plays a role in reducing grain growth.

[0084] C reacts with N, Ti, Nb, V, etc., to form fine carbides, which hinder grain growth and domain movement.

[0085] S forms sulfides, which impair grain growth.

[0086] In cases where additional impurity elements are included as such, one or more of C: 0.005 wt% or less (excluding 0%), N: 0.005 wt% or less (excluding 0%), S: 0.005 wt% or less (excluding 0%), Ti: 0.005 wt% or less (excluding 0%), Nb: 0.005 wt% or less (excluding 0%), and V: 0.005 wt% or less (excluding 0%) may be additionally included. More specifically, it may further include 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%.

[0087] 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.

[0088]

[0089] In one embodiment of the present invention, the thickness of the oxide layer present on the surface of the non-oriented electrical steel sheet may be 0.1 μm or less. If the oxide layer is thick, magnetic properties and iron loss properties may deteriorate. In one embodiment of the present invention, due to O diffusion from the surface to the interior, an O concentration gradient may exist in the thickness direction of the steel sheet, and the thickness of the oxide layer may be measured as the thickness from the outermost surface of the steel sheet to the interior direction where oxygen is 10 wt% or more. More specifically, the thickness of the oxide layer may be 10 nm to 800 nm. More specifically, the thickness of the oxide layer may be 100 nm to 700 nm.

[0090] The roughness Ra value of the steel plate surface may be 0.6 μm or less, the Rz value may be 7.0 μm or less, and the Rt value may be 15.0 μm or less. While a lower roughness value is advantageous for a smoother surface, some roughness may inevitably be formed when diffusing Si using a Si diffusion composition. More specifically, the roughness Ra value of the steel plate surface may be 0.1 to 0.5 μm, the Rz value may be 1.0 to 6.5 μm, and the Rt value may be 3.0 to 14.0 μm.

[0091] Surface roughness (Ra, Rz, Rt) can be measured using a surface roughness meter. More specifically, it can be measured by the methods described in ISO 4287 and ISO 4288.

[0092] 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 / 1000 ) may be 45.0 W / kg or less. In this case, iron loss is based on a thickness of 0.2 mm. Iron loss (W 10 / 1000 ) is the iron loss when a magnetic flux density of 1.0T is induced at a frequency of 1000 Hz. Iron loss can be measured using the Epstein test or the SST (single sheet test) method. More specifically, iron loss (W 10 / 1000 ) can be 25.00W / kg to 35.00W / kg.

[0093] Also, iron loss (W 5 / 2000 ) may be 16.5 W / kg or less. In this case, iron loss is based on a thickness of 0.2 mm. Iron loss (W 5 / 2000 ) is the iron loss when a magnetic flux density of 0.5T is induced at a frequency of 2000 Hz. More specifically, iron loss (W 5 / 2000 ) can be 10.0W / kg to 15.0W / kg.

[0094] 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 1.46T or greater. Specifically, magnetic flux density (B 25 ) can be 1.50 to 1.65T.

[0095] 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: 0.3 to 4.0%, Al: 0.001 to 2.0%, and Mn: 0.03 to 2.0%, 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 diffusion annealing step of the cold-rolled sheet and a brushing step of the diffusion annealed steel sheet.

[0096] Below, each step is explained in detail.

[0097] First, a cold-rolled sheet is manufactured containing, in weight percent, Si: 0.3 to 4.0%, Al: 0.001 to 2.0%, and Mn: 0.03 to 2.0%, 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.

[0098] 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 Si: 0.3 to 4.0%, Al: 0.001 to 2.0%, and Mn: 0.03 to 2.0% by weight; and the step of manufacturing a cold-rolled sheet by cold-rolling the hot-rolled sheet.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] The step of manufacturing a hot-rolled plate may include a step of finishing rolling at a temperature of 850°C or higher.

[0103] 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℃.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] Hot-rolled plates can be pickled as needed.

[0109] 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.

[0110] Next, in the coating step, a Si diffusion composition containing a Si compound is applied to the cold-rolled plate.

[0111] 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.

[0112] More specifically, it may include pure Si, Si alloys, and Fe3Si.

[0113] The average particle size of the Si compound may be 1 to 850 nm. 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 a uniform coating to the surface of the steel plate, which may hinder the 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 a laser diffraction method. More specifically, the average particle size of the Si compound may be 10 nm to 500 nm. Even more specifically, it may be 20 nm to 100 nm.

[0114] The Si diffusion composition further comprises an Al compound and may include 100 parts by weight of the Si compound and 10 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 heating each compound at 180°C for 20 minutes or more to remove all volatile matter.

[0115] 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.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] 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.

[0120] 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.

[0121] 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.

[0122] 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. In the first application step, the application amount of the Si diffusion composition is 0.1 to 300 g / m² 2 It could be.

[0123] In this case, the coating amount is based on solid content. If the coating amount is too small, sufficient Si diffusion does not occur, making it difficult to fully achieve the effects of Si diffusion. If the coating amount is too large, a problem may arise where processability deteriorates.

[0124] Application methods include using a roll coater, brush, and dipping. From a productivity standpoint, application can be performed using a roll coater.

[0125] In terms of the coating direction, the coating can be applied by forming an angle of -10 to 10° with respect to the rolling direction or an angle of 80 to 100° with respect to the rolling direction. More specifically, in terms of the coating direction, the coating can be applied by forming an angle of -5 to 5° with respect to the rolling direction or an angle of 85 to 95° with respect to the rolling direction. From the perspective of productivity, the coating can be applied by forming an angle of -10 to 10° with respect to the rolling direction.

[0126] After the coating step, the method may further include a step of drying the Si diffusion composition to form a Si diffusion coating layer. 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.

[0127] Next, the cold-rolled sheet is diffusion annealed. During this process, Si and Al diffuse into the interior of the steel sheet from the Si diffusion composition applied to the surface of the cold-rolled sheet.

[0128] Prior to the diffusion annealing step, the temperature can be increased in a range of 20 to 700°C at a rate of 5 to 50°C / hr. In this way, uniform quality can be obtained by increasing the temperature at a relatively slow rate. If the rate of increase is too slow, the process time becomes unnecessarily long and productivity decreases. If the rate of increase is too fast, the aforementioned effects cannot be properly obtained. More specifically, the temperature can be increased at a rate of 10 to 30°C / hr.

[0129] The diffusion annealing temperature may be 850°C to 1250°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 be degraded. More specifically, it may be 900°C to 1150°C.

[0130] The time may be 30 minutes to 600 minutes. If the time is too short, the diffusion of Si and Ti may not occur sufficiently, and the desired effect may not be obtained. If the time is too long, it is difficult to control the amount of diffusion, and processability may be inferior. More specifically, it may be 60 to 300 minutes.

[0131] 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.

[0132] 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.

[0133] Next, the diffusion-annealed steel sheet is brushed. During this process, unreacted components remaining on the surface of the cold-rolled sheet are removed, and the oxide layer is also partially removed.

[0134] In the brushing stage, the strength of the brush bristles may be 50 to 90 MPa. If the strength of the brush bristles is too low, the removal of unreacted composition and oxide layer may not be properly performed. If the strength of the brush bristles is too high, the surface roughness (Ra, Rz, Rt) of the steel plate surface increases significantly, and surface properties may be significantly degraded. More specifically, when polyethylene is used for the brush bristles, the strength may be 50 to 80 MPa, and when nylon is used for the brush bristles, the strength may be 70 to 90 MPa.

[0135] The strength of the brush bristles can be appropriately adjusted by changing the amount of abrasive material added to the brush bristles. In this case, the types of abrasive materials may include one or more of SiC and Al2O3. In this case, the average particle size of the abrasive material may be 50 to 250 μm. If the average particle size of the abrasive material is too small, the brush polishing characteristics become inferior, and the possibility of residual slurry and oxides remaining on the surface after polishing increases. Furthermore, if the average particle size of the abrasive material is too large, polishing characteristics increase, but a problem may arise where the surface roughness becomes rough after polishing. More specifically, the average particle size of the abrasive material may be 50 to 230 μm.

[0136]

[0137] In addition to the abrasive material, the brush body may be composed of multiple strands of general polymer fibers combined into a spiral shape. The polymer fibers may include one or more of polyethylene and nylon. The diameter of the polymer fibers may be 0.4 to 1.5 mm. The brush body may be formed by twisting 2 to 8 strands of polymer fibers together.

[0138] The oxide layer present on the surface of the steel plate can be partially polished through a brushing step. Specifically, the thickness of the oxide layer after the brushing step can be 0.1㎛ or less.

[0139] After the brushing step, an acid cleaning step in which the steel plate is immersed in an acid solution may be further included. Although the oxide layer can be partially polished through the aforementioned brushing step, the surface roughness (Ra, Rz, Rt) needs to be further reduced. By adding the acid cleaning step, the surface roughness (Ra, Rz, Rt) can be further reduced.

[0140] The acid solution may include one or more of hydrochloric acid, hydrofluoric acid, sulfuric acid, and nitric acid. Specifically, it may include hydrochloric acid. The concentration of the acid solution may be 50 to 150 g / L, and the temperature of the acid solution may be 50 to 90°C.

[0141] After the acid cleaning step, a washing step may be additionally included to remove residual acid components on the surface. In the washing step, water may be sprayed onto the surface of the steel plate to clean it. At this time, to prevent yellow discoloration caused by corrosion products remaining on the surface, 1 to 10 g of hydrogen peroxide (H2O2) may be added per 1 L of water to prevent yellow discoloration of the surface.

[0142] After the acid cleaning step, a second brushing step may be included. Unlike the first brushing step prior to the aforementioned acid cleaning step, the second brushing step is intended to remove moisture from the surface, etc., rather than to remove the oxide layer or adjust the roughness, so the strength of the brush bristles does not need to be high.

[0143] After the acid washing step, a drying step may be further included. At this time, the temperature of the drying air may be 200 to 350°C. If the air temperature is too low, it takes a long time for moisture to evaporate from the surface of the steel plate, and stains may occur on the surface. If the temperature is too high, there is a high possibility of oxidative discoloration occurring on the surface of the steel plate.

[0144] 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.

[0145] In the case where an insulating film is formed, the aforementioned oxide layer thickness and surface roughness of the steel plate can be measured after removing the insulating film.

[0146]

[0147] 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.

[0148]

[0149] Experimental Example

[0150] A slab was prepared containing 2.0 wt% silicon (Si), 0.002 wt% aluminum (Al), 0.10 wt% manganese (Mn), 0.04 wt% tin (Sn), 0.04 wt% antimony (Sb), and 0.013 wt% phosphorus (P), with the remainder being Fe and other unavoidable impurities.

[0151] A hot-rolled plate was manufactured by heating a slab to 1100℃ and then hot-rolling it to a thickness of 1.8mm.

[0152] 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.

[0153] 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, 10 parts by weight of a ceramic powder mixture (3:1 SrTiO3, MgAl2O4), and 50 parts by weight of water.

[0154] The prepared Si diffusion composition was applied to a cold-rolled plate. The composition was applied to both surfaces of the cold-rolled plate, with a coating amount of 20 g / m² per surface. 2 It was applied uniformly.

[0155] A cold-rolled sheet coated with a Si diffusion composition was diffusion annealed in a 100v% H2 atmosphere at 1000℃ for 1 hour.

[0156] The surface of the steel sheet after diffusion annealing was analyzed and is shown in Figures 1 and 2. In addition, surface roughness (Ra, Rz, Rt) was measured using the 2D contact method and ISO 4287 and ISO 4288 methods. Ra was 2.06 μm, Rz was 11.01 μm, and Rt was 22.51 μm.

[0157] A steel plate that had undergone diffusion annealing was brushed using the brush base material listed in Table 1 below. The evaluation was conducted by fixing the brush rotation speed at 1000 RPM, the steel plate feed speed at 100 MPM, and the gap between the steel plate and the brush at 2 mm. In Comparative Example 1, shot blasting was used instead of a brush.

[0158] After brushing, the surface of the steel plate was analyzed and is shown in Figures 3 and 4. In addition, surface roughness (Ra, Rz, Rt) was measured using the 2D contact method and ISO 4287 and ISO 4288 methods, and the oxide layer thickness was measured using GDS and summarized in Tables 1 and 2.

[0159] Next, a non-oriented electrical steel sheet was manufactured by immersing it in a hydrochloric acid solution with a concentration of 100 g / L at 80°C for 30 seconds, washing it again with water, and finally drying it. At this time, 0.03 g of inhibitor was added per 100 g of hydrochloric acid concentration.

[0160] The surface of the final manufactured steel plate was analyzed and is shown in Figures 5 and 6. In addition, surface roughness (Ra, Rz, Rt) was measured using the 2D contact method and ISO 4287 and ISO 4288 methods, and the oxide layer thickness was measured using GDS and summarized in Tables 1 and 2.

[0161] Remarks Brush bristle strength (Mpa) Type of brush base material Surface roughness after brushing (㎛) Oxide layer thickness after brushing (㎛) RaRzRt Example 15 55 1.4mm, 7 strands, SiC particle size 180∼212㎛ 0.5 3 6 48 13 28 0.056 Example 26 0.0mm, 3 strands, SiC particle size 125∼150㎛ 0.4 9 5 65 11 06 0.064 Example 37 50.8mm, 3 strands, SiC particle size 53∼75㎛ 0.4 4 4 4 8 48 0.075 Example 47 50.8mm, 7 strands, SiC particle size 53∼75㎛ 0.4 3 4 5 36 74 0.075 Comparative Example 19 50.8mm, 1 strand 2.03 10.45 20.68 2.66 Comparative Example 2 Shot blast 4.30 18.32 35.01 1.56 Comparative Example 3 Brush omitted (after diffusion heat treatment) 2.06 11.01 22.5 13.50

[0162] Surface roughness after acid pickling (㎛) Oxide layer thickness after pickling (㎛) Magnetic properties (B25, Tesla) RaRzRt Example 1 0.35 2.75 6.46 0.045 1.536 Example 20.31 2.45 5.65 0.039 1.536 Example 30.24 2.06 4.12 0.059 1.538 Example 40.20 1.95 3.45 0.056 1.541 Comparative Example 11.56 5.65 10.75 1.25 0 1.524 Comparative Example 23.45 10.53 25.65 0.045 1.501 Comparative Example 31.76 6.45 13.25 1.62 51.520

[0163] As shown in Tables 1 and 2 and Figures 1 to 6, it can be confirmed that the oxide layer on the surface of the steel plate can be properly polished and removed using a brush. On the other hand, when shot blasting is used as in Comparative Example 2, the oxide layer is removed, but the surface roughness of the steel plate is significantly inferior, resulting in inferior magnetic properties. Furthermore, in the case of Comparative Example 1, abrasive stones are not mixed in the brush bristles, so the removal of residues and oxides is insufficient, resulting in a rough surface roughness and inferior magnetic properties. Additionally, when only acid cleaning is performed without a brush as in Comparative Example 3, it is impossible to remove residues and the oxide layer, resulting in a rough surface roughness. For these reasons, the magnetic properties are inferior. As described above, in the case of the comparative example, the magnetic property (B25) shows a low value of 1.525 T or less, but in the case of the example, the removal of residuals and oxides remaining on the surface is good and the surface roughness changes well, so the magnetic property (B25) shows a high value of 1.535 T or more.

[0164]

[0165] The present invention is not limited to the above embodiments but 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: 4.0 to 7.0%, Al: 0.001 to 2.0%, and Mn: 0.03 to 2.0%, and the remainder comprises Fe and unavoidable impurities, Non-oriented electrical steel sheet having an oxide layer thickness of 0.1㎛ or less on the surface.

2. In Paragraph 1, A non-oriented electrical steel sheet having a surface roughness Ra value of 0.6㎛ or less, an Rz value of 7.0㎛ or less, and a Rt value of 15.0㎛ or less.

3. In Paragraph 1, Si content at the center of plate thickness (t / 2) [CM Si ] and maximum Si content [SM 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 The difference of ] ([SM Si ]-[ CM Si Non-oriented electrical steel sheet having ΔSi defined as ]) of 0.1 wt% or more.

4. In Paragraph 1, Al content at the center of plate thickness (t / 2) [CM Al ] and maximum Al content [SM 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 Al The difference of ] ([SM Al ]-[ CM Al Non-oriented electrical steel sheet having ΔAl defined as ]) 0.1 wt% or more.

5. In Paragraph 1, A non-oriented electrical steel sheet further comprising one or more of C: 0.005 wt% or less (excluding 0%), N: 0.005 wt% or less (excluding 0%), S: 0.005 wt% or less (excluding 0%), Ti: 0.005 wt% or less (excluding 0%), Nb: 0.005 wt% or less (excluding 0%), and V: 0.005 wt% or less (excluding 0%).

6. In Paragraph 1, A non-oriented electrical steel sheet further comprising one or more of P: 0.1 wt% or less (excluding 0%), Cu: 0.005 to 0.2 wt%, Cr: 0.01 to 0.5 wt%, Sn: 0.1 wt% or less (excluding 0%), Sb: 0.1 wt% or less (excluding 0%), Ni: 0.05 wt% or less (excluding 0%), and Zn: 0.01 wt% or less (excluding 0%).

7. In Paragraph 1, A non-oriented electrical steel sheet further comprising one or more of Bi: 0.200 wt% or less (excluding 0%), Pb: 0.200 wt% or less (excluding 0%), Ge: 0.200 wt% or less (excluding 0%), and As: 0.200 wt% or less (excluding 0%).

8. In Paragraph 1, A non-oriented electrical steel sheet further comprising one or more of Mo: 0.03 wt% or less (excluding 0%), B: 0.0050 wt% or less (excluding 0%), Ca: 0.0050 wt% or less (excluding 0%), Zr: 0.005 wt% or less (excluding 0%), Te: 0.01 wt% or less (excluding 0%), and Mg: 0.0050 wt% or less (excluding 0%).

9. A step of manufacturing a cold-rolled sheet comprising, by weight, Si: 0.3 to 4.0%, Al: 0.001 to 2.0%, and Mn: 0.03 to 2.0%, 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 above cold-rolled plate; The step of diffusion annealing the above cold-rolled plate and A method for manufacturing a non-oriented electrical steel sheet comprising the step of brushing a diffusion-annealed steel sheet.

10. In Paragraph 9, A method for manufacturing a non-oriented electrical steel sheet in which the strength of the brush bristles in the brushing step is 50 MPa to 90 MPa.

11. In Paragraph 9, A method for manufacturing a non-oriented electrical steel sheet comprising, in the brushing step, a SiC or Al2O3 abrasive having a diameter of 0.4 mm to 1.5 mm and an average particle size of 50 to 250 μm inside the brush bristles.

12. In Paragraph 9, A method for manufacturing a non-oriented electrical steel sheet, comprising, after the brushing step, an acid cleaning step of immersing the steel sheet in an acid solution.

13. In Paragraph 12, A method for manufacturing a non-oriented electrical steel sheet, further comprising a secondary brushing step after the above acid cleaning step.

14. In Paragraph 9, The step of manufacturing the above cold-rolled plate is, A step of manufacturing a hot-rolled plate by hot-rolling a slab comprising, in weight%, Si: 0.01 to 3.5%, Al: 0.001 to 2.0%, and Mn: 0.03 to 2.0%, and the remainder being Fe and unavoidable impurities; and A method for manufacturing a non-oriented electrical steel sheet comprising the step of cold-rolling the above hot-rolled sheet to produce a cold-rolled sheet.

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