Non-oriented electrical steel sheet and manufacturing method therefor

Abstract

A non-oriented electrical steel sheet according to one embodiment of the present invention comprises, by wt%, 4-7% of Si, 0.001-3% of Al, 0.003-3% of Mn, and the balance of Fe and inevitable impurities. ΔSi, which is defined as the difference ([S-MSi]-[C-MSi]) between the Si amount [C-MSi] at the plate thickness center (t / 2) and the maximum Si amount [S-MSi] in the region from the surface of the non-oriented electrical steel sheet inward to 5% of the total thickness, is 0.1 wt% or more, and the area fraction of grains having an orientation distribution within grains of 5° or less is 95% or more.

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 percent, Si: 4 to 7%, Al: 0.001 to 3%, and Mn: 0.003 to 3%, and the remainder is Fe and unavoidable impurities.

[0008] 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 ]) is 0.1 wt% or more.

[0009] The area fraction of grains with an orientation distribution within 5° can be 95% or more.

[0010] 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%.

[0011] A non-oriented electrical steel sheet according to one embodiment of the present invention may have an area fraction of grains having an angle of 15° or less between the {100} plane and the rolled plane of the steel sheet of 15° or less, an area fraction of grains having an angle of 15° or less between the {111} plane and the rolled plane of the steel sheet of 5° or less, and an area fraction of grains having an angle of 15° or less between the {110} plane and the rolled plane of the steel sheet of 0.3° or less.

[0012] The thickness of the steel plate may be 0.01 to 0.25 mm.

[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: 0.2 wt% or less, Cr: 0.5 wt% or less, 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: 0.01 wt% or less, Ca: 0.01 wt% or less, Zr: 0.01 wt% or less, Te: 0.01 wt% or less, and Mg: 0.01 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 hot-rolled sheet comprising, in weight percent, Si: 2 to 4.5%, Al: 0.001 to 3%, and Mn: 0.003 to 3%, and the remainder being Fe and unavoidable impurities; manufacturing a cold-rolled sheet by cold-rolling the hot-rolled sheet; applying a Si diffusion composition comprising a Si compound to the surface of the cold-rolled sheet; and diffusion annealing the cold-rolled sheet.

[0018] The reduction rate in the cold-rolled sheet manufacturing stage is 97% or higher.

[0019] The diffusion annealing step involves annealing the steel plate at 800 to 1200°C for 20 minutes to 12 hours.

[0020] The thickness of the hot-rolled plate can be 1 to 10 mm.

[0021] In the step of applying the Si diffusion composition, the Si diffusion composition can be applied to both sides of the steel plate.

[0022] 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.

[0023] 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.

[0024] The average particle size of the Si compound can be 1 to 1500 nm.

[0025] The average particle size of the Al compound can be 1 to 1000 nm.

[0026] The average particle size of the ceramic powder can be 8 to 2500 nm.

[0027] 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.

[0028] A non-oriented electrical steel sheet according to one embodiment of the present invention has excellent magnetic flux density and high-frequency iron loss.

[0029] 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.

[0030] FIG. 1 is a schematic diagram showing a cross-section of an electrical steel sheet according to one embodiment of the present invention.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] Also, unless otherwise specified, % means weight %, and 1 ppm is 0.0001 weight %.

[0036] 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.

[0037] 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.

[0038]

[0039] A non-oriented electrical steel sheet according to one embodiment of the present invention comprises, in weight percent, Si: 4 to 7%, Al: 0.001 to 3%, and Mn: 0.003 to 3%, and the remainder is Fe and unavoidable impurities.

[0040] First, I will explain the reason for the composition limitation of non-oriented electrical steel sheets.

[0041] Si: 4.0 to 7.0 wt%

[0042] 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.

[0043] 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.

[0044] 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%.

[0045] In one embodiment of the present invention, since 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, a concentration gradient may occur in the thickness direction of the steel plate. That is, the maximum Si content in the region from the surface of the non-oriented electrical steel plate to 5% of the total thickness in the interior direction (i.e., the surface portion (11)) may be 4.0 to 8.0 weight%. If the Si content in the surface portion (11) 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 sufficiently obtained. If the Si content is too high, it means that a large amount of Si exists only in the surface portion (11) 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 highest Si content when measuring the Si concentration of 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 portion (11) may be 4.5 to 7.5 weight%.

[0046] 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 (20). If the Si content is low in 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 obtained. If the Si content is too high in the center, a problem of reduced processability may occur. More specifically, the Si content in the center (20) may be 0.3 to 7.5 weight%, specifically 2.5 to 6.0 weight%.

[0047] Maximum Si content [SM in the region (i.e., surface portion (11)) from the surface (10) of the non-oriented electrical steel sheet (100) inward to 5% of the total thickness Si Si content at the center of the plate thickness position (t / 2, i.e., the center (20)) in ] [CM Si The difference excluding ] ([SM Si ]-[ CM Si ΔSi, defined as ]), may be 0.1 wt% or more. A smaller ΔSi is advantageous, but if ΔSi is too small, it does not mean that Si has diffused from the outside, and in this case, the steel sheet may fracture or defects may occur within the steel sheet during the cold rolling process. If ΔSi is too large, it means that Si has not diffused uniformly throughout the steel sheet, and sufficient magnetic improvement may not be achieved. More specifically, ΔSi may be 0.2 to 4.0 wt%. More specifically, ΔSi may be 0.3 to 3.0 wt%.

[0048] 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 4.5 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%.

[0049] Al: 0.001 to 3.000 wt%

[0050] 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%.

[0051] 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.

[0052] Al content at the center of plate thickness (t / 2) [CM Al ] and the region from the surface (10) of the above non-oriented electrical steel sheet in the inward direction up to 5% of the total thickness (i.e., the maximum Al content [UM in the surface portion (11)). Al The difference of ] ([UM Al ]-[ CM Al ΔAl, defined as ]), may be 0.1 weight% or more. When there is an appropriate difference in Al content between the center (20) and one surface (11), high-frequency iron may be further improved. More specifically, ΔAl may be 0.1 to 0.5 weight%.

[0053] The maximum Al 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 (i.e., the surface portion (11)) 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 the improvement in high-frequency iron loss through Al diffusion may not be sufficiently obtained. 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 the improvement in high-frequency iron loss through Al diffusion may not be sufficiently obtained. 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%.

[0054] The Al content in the center (20) may be 0.001 to 2.0 weight%. If the Al content in the center (20) 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 (20) 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 weight%.

[0055] 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. Alternatively, if no Al compound is present in the Si diffusion composition, the Al content of the slab and the cold-rolled sheet prior to diffusion and the steel sheet after Si diffusion may be the same. Specifically, the slab and the cold-rolled sheet prior to diffusion may contain 0.001 to 3.0 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%. More specifically, Al in the slab and the cold-rolled sheet before diffusion may be 0.01 to 1.0 weight%.

[0056] Mn: 0.003 to 3.000 wt%

[0057] 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%.

[0058] 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.

[0059] P: 0.1 wt% or less

[0060] 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%.

[0061] Cu: 0.200 wt% or less

[0062] Copper (Cu) plays a role in forming sulfides together with Mn. If more Cu is added, if too much is added, high-temperature brittleness occurs, which can lead to the formation of cracks during continuous casting or hot rolling. More specifically, Cu may be included in an amount of 0.01 to 0.100 weight%.

[0063] Cr: 0.50 wt% or less

[0064] Chromium (Cr) plays a role in improving iron loss by increasing resistivity. 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%.

[0065] Sn: 0.10 wt% or less

[0066] 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%.

[0067] Sb: 0.10 wt% or less

[0068] 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%.

[0069] Ni: 0.05 wt% or less

[0070] Nickel (Ni) can react with impurity elements to form fine sulfides, carbides, and nitrides, which can have a harmful effect on magnetism. More specifically, Ni may be included in an amount of 0.005 to 0.03 weight%.

[0071] Zn: 0.01 wt% or less

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

[0073]

[0074] 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.

[0075] 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.

[0076]

[0077] 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: 0.0100 wt% or less, Ca: 0.0100 wt% or less, Zr: 0.0100 wt% or less, Te: 0.0100 wt% or less, and Mg: 0.0100 wt% or less.

[0078] 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.

[0079]

[0080] Other impurities

[0081] 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.

[0082] N combines with Ti, Nb, and V to form nitrides and plays a role in reducing grain growth.

[0083] C reacts with N, Ti, Nb, V, etc., to form fine carbides, which hinder grain growth and domain movement.

[0084] S forms sulfides, which impair grain growth.

[0085] 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.

[0086] 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.

[0087] In one embodiment of the present invention, the area ratio of grains with an internal orientation distribution of 5° or less is 95.0% or more. Grains with an internal orientation distribution of 5° or less form a uniform lattice where the atoms inside the grain are not twisted in various directions. This is advantageous for magnetic domain movement and thus advantageous for improving magnetism. More specifically, the area ratio of grains with an internal orientation distribution of 5° or less may be 97.2% to 99.0%. Grains with an internal orientation distribution of 5° or less can be analyzed using EBSD. Specifically, it refers to the area ratio of grains that satisfy a tolerance angle of 5° or less relative to the average internal orientation, by measuring the orientation distribution according to the position within the grain. The area fraction can be measured in a cross-section including the thickness direction (ND direction) of the steel plate, more specifically, in a plane perpendicular to the TD direction. When measuring, the Grain Orientation Spread (GOS) method is applied to calculate the difference between the orientation of all measurement points within each grain and the average orientation of the corresponding grain, and grains with an average value of 5° or less are defined as “grains with an orientation distribution of 5° or less.” The EBSD analysis conditions can be set such that the step size is 0.5 to 5 µm, the analysis area is 3000 µm or more in the rolling direction (RD direction), and the thickness direction (ND direction) is the entire thickness of the steel plate.

[0088] The area fraction of crystal grains having an angle of 15° or less between the {100} plane and the rolled plane of the steel plate may be 15.0 to 40.0%. If the area fraction of crystal grains having an angle of 15° or less between the {100} plane and the rolled plane of the steel plate is too small, the fraction of the easy-to-magnetize axis decreases, which is unfavorable for magnetism. If the area fraction of crystal grains having an angle of 15° or less between the {100} plane and the rolled plane of the steel plate is too high, magnetic anisotropy increases, which is unfavorable for magnetism. More specifically, the area fraction of crystal grains having an angle of 15° or less between the {100} plane and the rolled plane of the steel plate may be 23.0 to 35.0%. The area fraction of crystal grains having an angle of 15° or less between the {100} plane and the rolled plane of the steel plate can be analyzed through EBSD. Specifically, the fraction of orientations with a tolerance angle of 15° or less can be measured. Area fraction refers to the ratio of the area occupied by grains of a specific orientation to the total area of ​​the steel sheet as measured by electron backscatter diffraction (EBSD). A range of within 15° means that the angle between the vertical axis of the steel sheet surface and any plane containing the corresponding orientation is within 15°.

[0089] The area fraction of crystal grains having an angle of 15° or less between the {111} plane and the rolled plane of the steel plate may be 5.0 to 20.0%. If the area fraction of crystal grains having an angle of 15° or less between the {111} plane and the rolled plane of the steel plate is too small, plastic anisotropy may decrease, leading to a problem of reduced formability. If the area fraction of crystal grains having an angle of 15° or less between the {111} plane and the rolled plane of the steel plate is too high, magnetic flux density may decrease rapidly, leading to a problem. More specifically, the area fraction of crystal grains having an angle of 15° or less between the {111} plane and the rolled plane of the steel plate may be 10.0 to 14.7%.

[0090] The area fraction of crystal grains having an angle of 15° or less between the {110} plane and the rolled plane of the steel plate may be 0.3 to 15.0%. If the area fraction of crystal grains having an angle of 15° or less between the {110} plane and the rolled plane of the steel plate is too small, the fraction of the easy magnetization axis decreases, which may cause problems unfavorable to magnetism. If the area fraction of crystal grains having an angle of 15° or less between the {110} plane and the rolled plane of the steel plate is too high, magnetic anisotropy increases, and the magnetic deviation between the RD and TD directions may increase. More specifically, the area fraction of crystal grains having an angle of 15° or less between the {110} plane and the rolled plane of the steel plate may be 3.0 to 10.0%.

[0091] When measuring, the difference between the determined orientation of each measurement point and the target orientation ({100}, {111}, {110}) is calculated, and the area where the tolerance angle is 15° or less is defined as the corresponding orientation. The EBSD analysis conditions can be set such that the step size is 0.5 to 5 µm, the analysis area is 3000 µm or more in the rolling direction (RD direction), and the thickness direction (ND direction) is the entire thickness of the steel plate.

[0092] The area fraction is calculated as the ratio of the area occupied by the grains defined by the corresponding orientation to the total measurement area.

[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 5 / 2000 ) may be 20.0 W / kg or less. In this case, iron loss is based on a thickness of 0.1 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 15.5W / 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 1,400T or more. Specifically, magnetic flux density (B 25 ) can be 1.460 to 1.500T.

[0096] A method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention comprises the steps of: manufacturing a hot-rolled sheet comprising, in weight percent, Si: 2 to 4.5%, Al: 0.001 to 3%, and Mn: 0.003 to 3%, and the remainder being Fe and unavoidable impurities; manufacturing a cold-rolled sheet by cold-rolling the hot-rolled sheet; applying a Si diffusion composition comprising a Si compound to the surface of the cold-rolled sheet; and diffusion annealing the cold-rolled sheet.

[0097] Below, each step is explained in detail.

[0098] First, a hot-rolled sheet is manufactured containing, in weight percent, Si: 2 to 4.5%, Al: 0.001 to 3%, and Mn: 0.003 to 3%, with the remainder being Fe and unavoidable impurities. Since the alloy composition of the hot-rolled sheet is the same as that described above, a redundant description is omitted.

[0099] The method for manufacturing a hot-rolled plate is not particularly limited and includes the step of manufacturing a hot-rolled plate by hot-rolling a slab containing, in weight percent, Si: 2 to 4.5%, Al: 0.001 to 3%, and Mn: 0.003 to 3%, and the remainder being Fe and unavoidable impurities.

[0100] 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 or 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.

[0101] 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.

[0102] The heated slab is hot-rolled to a thickness of 1.0 to 10.0 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 6.0 mm.

[0103] The step of manufacturing a hot-rolled plate may include a step of finishing rolling at a temperature of 850°C or higher.

[0104] 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℃.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] 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.

[0109] Hot-rolled plates can be pickled as needed.

[0110] Next, the hot-rolled plate is pickled and cold-rolled to a predetermined plate thickness. In one embodiment of the present invention, a high reduction ratio can be applied to improve grain characteristics and further enhance magnetism. Specifically, a reduction ratio of 97% or more can be applied. If the reduction ratio is too low, appropriate grains may not be formed. More specifically, in the step of manufacturing the cold-rolled plate, the total reduction ratio may be 97 to 99%. In one embodiment of the present invention, cold rolling may be performed in a single step without intermediate annealing.

[0111] After cold rolling, the thickness may be 0.01 to 0.25 mm. If the thickness is too thin, problems may arise in terms of the strength of the steel sheet, and if the thickness is too thick, the reduction ratio is low, making it difficult to form an appropriate texture. More specifically, the thickness may be 0.02 to 0.10 mm. More specifically, the thickness may be 0.06 to 0.10 mm.

[0112] Next, in the coating step, a Si diffusion composition containing a Si compound is applied to the cold-rolled plate.

[0113] 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.

[0114] More specifically, it may include pure Si, Si alloys, and Fe3Si.

[0115] The average particle size of the Si compound may be 1 to 1500 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 it uniformly to the surface of the steel plate, which may hinder smooth Si diffusion 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 10 nm to 1500 nm. Even more specifically, it may be 20 nm to 1000 nm.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] 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.

[0120] 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.

[0121] 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.

[0122] 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.

[0123] 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.

[0124] 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.

[0125] 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.

[0126] 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.

[0127] Application methods include using a roll coater, brush, and dipping. From a productivity standpoint, application can be performed using a roll coater.

[0128] In one embodiment of the present invention, a Si diffusion composition can be applied to both sides of a steel plate. When applied to both sides, Si diffusion occurs on both sides, thereby further improving diffusion efficiency.

[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] The diffusion annealing step includes a heating step of heating the steel plate to a cracking temperature and a cracking step of cracking at the cracking temperature.

[0132] In the diffusion annealing step, the cracking temperature of the cracking step may be 800 to 1200°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 1150°C.

[0133] The time can be from 20 minutes to 12 hours. If the time is too short, the diffusion of Si may not occur sufficiently, and the desired effect may not be achieved. If the time is increased further, productivity will decrease. More specifically, it can be from 30 minutes to 10 hours.

[0134] 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.

[0135] After diffusion annealing, the final thickness of the steel sheet may be 0.01 to 0.25 mm, and due to the application and diffusion of the Si diffusion composition, the thickness may increase slightly compared to the cold-rolled sheet.

[0136] 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.

[0137] 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.

[0138]

[0139] 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.

[0140]

[0141] Examples

[0142] A slab was prepared containing 3.5 wt% silicon (Si), 0.8 wt% aluminum (Al), 0.30 wt% manganese (Mn), 0.04 wt% tin (Sn), and 0.013 wt% phosphorus (P), with the remainder being Fe and other unavoidable impurities.

[0143] A hot-rolled plate was manufactured by heating a slab to 1100℃ and then hot-rolling it to the thickness shown in Table 1 below.

[0144] A hot-rolled plate was coiled at 700°C, cooled in air, and then annealed at 1030°C for 2 minutes. After that, it was rapidly cooled in water and pickled, and then cold-rolled to the thickness shown in Table 1 below to produce a cold-rolled plate.

[0145] 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 ammonium fluoride (NHF4), and 50 parts by weight of water.

[0146] The prepared Si diffusion composition was applied to a cold-rolled plate. The composition was applied to both sides of the cold-rolled plate, with a coating amount of 20 g / m². 2 It was applied uniformly.

[0147] The cracking temperature and time were controlled as shown in Table 1 below. Diffusion annealing was performed in a 100v% H2 atmosphere.

[0148] After the surface of the steel plate that had undergone diffusion annealing was washed with water and dried at room temperature, it was 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. As a result of analysis using a scanning electron microscope / energy-dispersive X-ray spectroscopy, it was confirmed that the average steel composition in the thickness direction of the steel plate was Mn: 0.30 wt%, Sn: 0.04 wt%, and P: 0.013 wt%.

[0149] The area ratio of grains in which the distribution of internal orientation within the grain is within 5° with respect to the plane perpendicular to the TD direction of the manufactured steel plate was measured using EBSD, and the area fraction of grains in which the {100} plane and the rolling plane of the steel plate have an angle of within 15°, the area fraction of grains in which the {111} plane and the rolling plane of the steel plate have an angle of within 15°, and the area fraction of grains in which the {110} plane and the rolling plane of the steel plate have an angle of within 15° were measured using EBSD.

[0150] When measuring, the Grain Orientation Spread (GOS) method is applied to calculate the difference between the orientation of all measurement points within each grain and the average orientation of the grain, and grains with an average value of 5° or less are defined as “grains with an orientation distribution of 5° or less.”

[0151] In addition, the difference between the determination orientation of each measurement point and the target orientation ({100}, {111}, {110}) is calculated, and the area where the tolerance angle is 15° or less is defined as the corresponding orientation, and the area fraction is calculated as the ratio of the area occupied by the grains defined as the corresponding orientation to the total measurement area.

[0152] The EBSD analysis conditions were set such that the step size was 0.5 to 5 µm, the analysis area was 3000 µm or more in the rolling direction (RD direction), and the thickness direction (ND direction) was the entire thickness of the steel plate.

[0153] Magnetic flux density and iron loss were measured in the rolling direction and the rolling perpendicular direction, and the averages are shown in Table 3.

[0154] Classification Hot Rolled Plate Thickness (mm) Cold Rolling Reduction Ratio (%) Cold Rolled Plate Thickness (mm) Diffusion Annealing Temperature (°C) Diffusion Annealing Time (min) 16.00 99.00.06 1150 120 26.00 99.00.06 1050 600 33.00 98.00.06 1100 300 43.00 98.00.06 1050 600 52.40 97.50.06 1100 300 65.00 98.00.10 1150 120 75.00 98.00.10 1100 300 85.00 98.00.10 1050 480 94.00 97.50.10 1100 300 1 04.0097.50.101050480112.0097.00.061100300123.3497.00.101050480132.0095.00.101050480141.0090.00.101050480154.0097.50.10950720164.0097.50.101050120174.0097.50.10110020184.0097.50.101100720

[0155] Classification Average Si(%)[SM Si ][CM Si ]ΔSi16.046.495.650.8426.086.265.910.3536.076.255.910.3446.076.265.900.3656.066. 245.920.3265.655.925.410.5175.645.935.410.5285.636.195.131.0695.655.945.400.5410 5.636.185.141.04116.076.235.920.31125.626.215.131.08135.636.205.131.07145.626.185.141.04155.547.443.843.60165.547.533.813.72175.567.194.083.11185.675.755.600.15

[0156] Area fraction (%) of grains with an intra-grain orientation distribution within 5° {100} plane fraction (%) {111} plane fraction (%) {110} plane fraction (%) B25(T)W5 / 2k(W / kg) 198.432.310.17.81.46912.2 Example 2 98.132.510.88.11.46712.1 Example 3 97.724.813.36.31.46112.5 Example 4 97.825.113.26.51.46212.4 Example 5 97.323.714.65.1 1.460 12.5 Example 697.9 29.7 11.3 7.5 1.475 15.0 Example 798.3 29.6 11.8 7.6 1.474 15.2 Example 897.2 30.6 11.7 6.6 1.475 15.1 Example 997.3 23.3 14.3 4.31 468 14.9 Example 1097 .224.114.44.41.46915.2 Example 1197.120.614.81.11.42212.9 Example 1297.021.114.81.21.45316.2 Example 1391.410.339.80.21.38721.5 Comparative Example 1490.311.037.40. 11.39221.1 Comparative Example 1597.624.313.15.31.45015.6 Example 1697.724.112.95.41.45115.6 Example 1797.522.812.95.31.45015.6 Example 1897.626.612.65.11.44915.7 Example

[0157] As shown in Tables 1 to 3, when the reduction rate is appropriately controlled during cold rolling, a large number of grains with an orientation distribution within 5° are produced, and it can be confirmed that the magnetism is excellent.

[0158] On the other hand, it can be confirmed that steel grades 13 and 14 have inferior magnetic properties because the reduction rate is not properly controlled and grains with an orientation distribution within 5° are not sufficiently formed.

[0159] In addition, it can be confirmed that the magnetism is even better when the thickness of the hot-rolled and cold-rolled plates, as well as the temperature and time during Si diffusion annealing, are appropriately controlled.

[0160]

[0161] 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.

[0162] [Explanation of the symbol]

[0163] 100: Non-oriented electrical steel sheet, 10: Surface,

[0164] 11: Surface, 20: Center

Claims

1. In weight%, it comprises Si: 4 to 7%, Al: 0.001 to 3%, and Mn: 0.003 to 3%, and the remainder comprises Fe and unavoidable impurities, and Si content at the center of plate thickness (t / 2) [CM Si ] and maximum 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 [SM Si The difference of ] ([SM Si ]-[ CM Si ΔSi defined as ]) is 0.1 wt% or more, and Non-oriented electrical steel sheet having an area fraction of grains with an intra-grain orientation distribution of 5° or less of 95% or more.

2. In Paragraph 1, A non-oriented electrical steel sheet having a maximum Si content of 4.0 to 8.0 weight% in the region from the surface to 5% of the total thickness in the inward direction of the above non-oriented electrical steel sheet, and a Si content of 0.3 to 7.5 weight% at the center of the sheet thickness position (t / 2).

3. In Paragraph 1, A non-oriented electrical steel sheet having an area fraction of grains having an angle of 15° or less between the {100} plane and the rolled plane of the steel sheet of 15° or less, an area fraction of grains having an angle of 15° or less between the {111} plane and the rolled plane of the steel sheet of 5° or less, and an area fraction of grains having an angle of 15° or less between the {110} plane and the rolled plane of the steel sheet of 0.3° or less.

4. In Paragraph 1, Non-oriented electrical steel sheet with a thickness of 0.01 to 0.25 mm.

5. 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.

6. In Paragraph 1, A non-oriented electrical steel sheet further comprising one or more of P: 0.1 wt% or less, Cu: 0.2 wt% or less, Cr: 0.5 wt% or less, 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.

7. 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.

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

9. A step of manufacturing a hot-rolled plate comprising, in weight%, Si: 2 to 4.5%, Al: 0.001 to 3%, and Mn: 0.003 to 3%, and the remainder being Fe and unavoidable impurities; A step of manufacturing a cold-rolled plate by cold-rolling the above hot-rolled plate; A step of applying a Si diffusion composition containing a Si compound to the surface of the above cold-rolled plate; and The above cold-rolled plate includes the step of diffusion annealing, and The step of manufacturing the above cold-rolled sheet has a reduction rate of 97% or more, and The above diffusion annealing step is a method for manufacturing a non-oriented electrical steel sheet by annealing the steel sheet at 800 to 1200°C for 20 minutes to 12 hours.

10. In Paragraph 9, A method for manufacturing a non-oriented electrical steel sheet having a thickness of 1 to 10 mm of the hot-rolled sheet.

11. In Paragraph 9, A method for manufacturing a non-oriented electrical steel sheet by applying the Si diffusion composition to both sides of the steel sheet in the step of applying the Si diffusion composition.

12. In Paragraph 9, 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.

13. In Paragraph 9, 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.

14. In Paragraph 9, A method for manufacturing a non-oriented electrical steel sheet in which the average particle size of the above Si compound is 1 to 1500 nm.

15. In Paragraph 12, 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.

16. In Paragraph 13, 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.

17. In Paragraph 9, In the step of applying the above Si diffusion composition, the amount of the Si diffusion composition applied is 0.1 to 300 g / m² 2 Method for manufacturing non-oriented electrical steel sheets.

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