Anisotropic electrical steel sheet and its production method

Abstract

FIELD: metallurgy.SUBSTANCE: invention relates namely to a sheet of anisotropic electrical steel and a method for its manufacture, and can be used in the manufacture of a transformer core. This anisotropic electrical steel sheet includes a base steel sheet, a forsterite film optionally formed on the base steel sheet, and an insulating coating formed on the base steel sheet or the forsterite film. The base steel sheet has a plurality of grooves extending in a direction intersecting the rolling direction, the direction in which the plurality of grooves extend is defined as the longitudinal direction of the groove, the distance in the groove from an imaginary line, which is an extension of the surface of the base steel sheet, to the groove, along a straight line from this imaginary line in the thickness direction of the base steel sheet, is defined as the groove depth, the width of the groove in the rolling direction is defined as the groove width, the position where the groove depth is 0.0 mcm is defined as the end of the groove, and a 5 mm area from the end of the groove to the central portion in the longitudinal direction of the groove is defined as the end portion of the groove, the groove depths and groove widths at a plurality of positions at the end portion of the groove satisfy the predetermined ratio.EFFECT: sheets of anisotropic electrical steel can be manufactured.12 cl, 3 dwg, 3 tbl, 13 ex

Description

Field of technology

[0001] The present invention relates to an anisotropic electrical steel sheet and a method for producing the same. The benefit of Japanese Patent Application No. 2023-111726, filed on July 6, 2023, the contents of which are incorporated herein by reference, is claimed.Background of the Invention

[0002] Anisotropic electrical steel sheet is a soft magnetic material and is mainly used as a transformer core material. Therefore, anisotropic electrical steel sheet with magnetic characteristics such as high magnetic induction and low magnetic loss is desirable. Magnetic loss is the loss due to the thermal energy consumption that occurs when the core is excited by an AC magnetic field, and magnetic loss should be as low as possible for energy conservation. The level of magnetic loss is affected by magnetic susceptibility, sheet thickness, coating tension, amount of impurities, specific electrical resistance, crystal grain size, magnetic domain width, and other factors.Even today, after various methods have been developed for anisotropic electrical steel sheets, research and development to reduce magnetic losses continues to improve energy conversion efficiency. Laser irradiation of the steel sheet has been proposed as one method for reducing magnetic losses. This method introduces deformation into the surface of the steel sheet using laser irradiation, reducing the width of the magnetic domain. As a result, eddy current losses, which constitute a portion of magnetic losses, can be reduced.

[0003] For example, Patent Document 1 discloses a method for manufacturing an anisotropic electrical steel sheet in which magnetic domains are controlled by irradiation with a laser beam. The method includes the step of irradiating the surface of the anisotropic electrical steel sheet with a focused continuous laser beam while scanning the surface in a direction inclined from the rolling direction of the anisotropic electrical steel sheet, and the step of repeating a portion scanned by the continuous laser beam while shifting the portion by a predetermined interval. When the average power of the continuous laser beam is denoted as P (W), the scanning speed is denoted as Vc (mm / s), the predetermined interval is denoted as PL (mm), and the input energy Ua is defined as Ua = P / (Vc × PL) (mJ / mm 2 ), the conditions 1.0 mm ≤ PL ≤ 3.0 mm and 0.8 mJ / mm are satisfied 2 ≤ Ua ≤ 2.0 mJ / mm 2Patent Document 1 discloses that magnetic losses in both directions from the L direction and the C direction of an anisotropic electrical steel sheet can be easily reduced while ensuring high performance.

[0004] However, for example, when manufacturing a strip core, stress-relief annealing is preferable because the anisotropic electrical steel sheet is bent and formed. Accordingly, in the above-described method of introducing deformation into the surface by laser irradiation, the deformation introduced into the anisotropic electrical steel sheet is removed by stress-relief annealing. Consequently, the effect of magnetic domain refinement by laser irradiation disappears. Therefore, it was proposed that the magnetic domain width should be refined to reduce eddy current losses by forming a groove on the sheet surface, as in the case of strain introduction. In this case, since the groove remains even after stress-relief annealing, the effect of magnetic domain refinement does not disappear.Examples of the method for forming a groove in a steel sheet include an electrolytic etching method for forming a groove on the surface of an anisotropic electrical steel sheet by electrolytic etching, a gear pressing method for forming a groove on the surface of an anisotropic electrical steel sheet by mechanically pressing a gear into the surface of the sheet, and a laser irradiation method for melting and vaporizing a steel sheet by laser irradiation (a zone irradiated with a laser beam) to form a groove. For example, Patent Document 2 discloses a method for improving the magnetic loss characteristics of anisotropic electrical steel sheets that can withstand stress-relieving annealing, in which irradiation is performed by controlling a laser beam and a recess is formed in the rolling direction having a width of 0.5 mm or less and a depth of 10 μm or more.

[0005] In this case, an insulating coating is generally formed on the surface of an anisotropic electrical steel sheet to impart electrical insulating properties, tensile strength, heat resistance, and the like to the steel sheet. As described in Patent Document 2, in the anisotropic electrical steel sheet, a groove is formed on the steel sheet approximately parallel to the width direction, so that the magnetic domain width is refined and magnetic loss is reduced. On the other hand, the width or depth of the end portions (near the front end and rear end) of the formed groove in the longitudinal direction changes compared to its central portion. Therefore, it is difficult to apply a coating solution to each corner of the end portion of the groove. As a result, there may be places in the end portion of the groove where the adhesion of the insulating coating is insufficient.The length of the region where such width or depth changes at the groove ends is a relatively small fraction of the entire groove length. Therefore, the impact on magnetic performance is considered minor, even if the adhesion of the insulating coating in this region is low. However, if the adhesion of the insulating coating at the groove end is low, the base metal on the surface is exposed, which can cause rusting. Furthermore, in this exposed base metal region, there is a possibility that significant interlayer current will flow during the lamination of anisotropic electrical steel sheets, leading to increased magnetic losses. However, Patent Document 2 does not address such base metal exposure and the occurrence of rusting.

[0006] As a method for controlling the shape of an end portion of a groove, for example, Patent Document 3 discloses a method in which etching of an end portion of a steel strip in the width direction is minimized such that the groove depth at the end portion in the width direction is set to 70% or less of the groove depth at the center portion in the width direction, in a method for manufacturing an anisotropic silicon steel sheet, in which linear or dotted grooves are formed on the surface of the steel strip.

[0007] As a method for improving the adhesion of an insulating coating and resistance to rust or the like at an end portion of a groove, for example, Patent Document 4 discloses an anisotropic electrical steel sheet in which a first angle θ formed by the surface of the sheet and a straight line at the end of the groove and an aspect ratio A obtained by dividing the average groove depth D by the average groove width W satisfy the condition θ < -21 × A + 77.

[0008] In addition, Patent Document 5 discloses an anisotropic electrical steel sheet including linear grooves formed in a direction intersecting the rolling direction on one surface or on both surfaces of the electrical steel sheet, wherein each groove includes an inclined portion (GS) and a flat portion (US) in a section including the longitudinal direction of the groove and the direction normal to the rolling surface of the steel sheet, and the length of the inclined portion and the length of the flat portion satisfy a predetermined ratio.List of ReferencesPatent Documents

[0009] Patent Document 1: Japanese Patent No. 4669565Patent Document 2: Japanese Unexamined Patent Application, First Publication No. H06-57335Patent Document 3: Japanese Patent No. 4016431Patent Document 4: Japanese Patent No. 6418322Patent Document 5: Japanese Unexamined Patent Application, First Publication No. 2022-503782Summary of the InventionTechnical Problem

[0010] However, in Patent Document 3, the reason why the etching of the end portion of the steel strip in the width direction is minimized to set the groove depth at the end portion in the width direction to 70% or less of the groove depth at the center portion in the width direction is to prevent the steel strip from being destroyed in the next step when linear grooves are introduced by electrolytic etching, and the adhesion of the insulation coating and the rust resistance at the end portion of the groove are not described. In addition, in Patent Document 4, there is no description regarding the width and depth of the groove at the end portion of the groove, and as a result of the investigations by the inventors of the present invention, it was found that the adhesion of the insulation coating and the rust resistance at the end portion of the groove cannot always be improved.Furthermore, Patent Document 5 lacks a description regarding the groove width at the groove end. Research by the present inventors has revealed that the adhesion of the insulating coating and rust resistance at the groove end cannot always be improved. Furthermore, it has been found that the reduction in magnetic induction due to groove formation cannot always be minimized.

[0011] As described above, the prior art has proposed methods for improving the adhesion of an insulating coating and rust resistance at the end portion of a groove in an anisotropic electrical steel sheet in which magnetic domain refinement is performed by forming grooves, but it cannot be said that sufficient research has been carried out. Therefore, the object of the present invention is to provide an anisotropic electrical steel sheet having high adhesion of an insulating coating and excellent rust resistance even at the end portion of a groove. Solution to the Problem

[0012] The present inventors studied methods for improving the adhesion of an insulating coating at the end portion of a groove. As a result, they found that the adhesion of the insulating coating and resistance to rusting and the like are improved by forming grooves with a shape in which the depth and width decrease (so that they become shallower and narrower) as they approach the end of the groove in the longitudinal direction (the longitudinal direction of the groove), and these depths and widths satisfy a certain ratio.

[0013] The present invention was created based on the above-described discovered facts. The essence of the present invention is as follows.

[0001] An anisotropic electrical steel sheet according to one aspect of the present invention includes: a base steel sheet; a forsterite film optionally formed on the base steel sheet; and an insulating coating formed on the base steel sheet or the forsterite film, wherein the base steel sheet has a plurality of grooves extending in a direction intersecting the rolling direction, in the case where the direction in which the plurality of grooves extend is defined as the longitudinal direction of the groove, the distance in the groove from an imaginary line that is an extension of the surface of the base steel sheet to the groove, along a straight line from this imaginary line in the thickness direction of the base steel sheet, is defined as the groove depth, the width of the groove in the rolling direction is defined as the groove width, the position where the groove depth is 0.0 μm is defined as the end of the groove, and the 5 mm region,extending from the end of the groove to the central portion in the longitudinal direction of the groove, is defined as the end portion of the groove, in the longitudinal direction of the groove for the end portion of the groove, in units of μm, the groove depth at a position of 1 mm from the end of the groove is defined as D1, and the groove width at a position of 1 mm from the end of the groove is defined as W1, the groove depth at a position of 2 mm from the end of the groove is defined as D2, and the groove width at a position of 2 mm from the end of the groove is defined as W2, the groove depth at a position of 3 mm from the end of the groove is defined as D3, and the groove width at a position of 3 mm from the end of the groove is defined as W3, the groove depth at a position of 4 mm from the end of the groove is defined as D4, and the groove width at a position of 4 mm from the end of the groove is defined as W4, and the groove depth at a position of 5 mm from the end groove is defined as D5, and the groove width at a position of 5 mm from the end of the groove is defined as W5, the average groove width at the central section in the longitudinal direction of the groove is defined as Wc,and the average groove depth at the central portion in the longitudinal direction of the groove is defined as Dc, said D1, D2, D3, D4, D5, W1, W2, W3, W4 and W5 satisfy the formulas (1) and (2), and at the end portion of the groove in the case where the groove width at the portion where the groove depth is 0.05 × Dc is defined as W0.05, and the groove width at the portion where the groove depth is 0.50 × Dc is defined as W0.50, said W0.05 and W0.50 satisfy the formulas (3) and (4): D5 ≥ D4 ≥ D3 ≥ D2 ≥ D1 … (1), W5 ≥ W4 ≥ W3 ≥ W2 ≥ W1 … (2), 0.004 ≤ W0.05 / Wc ≤ 0.210 … (3),0.180 ≤ W0.50 / Wc ≤ 0.810 … (4).,

[0002] In the anisotropic electrical steel sheet according to item [1], the mentioned W0.05 and W0.50 can satisfy the formulas (5) and (6): 0.008 ≤ W0.05 / Wc ≤ 0.160 … (5), 0.380 ≤ W0.50 / Wc ≤ 0.710 … (6).

[0003] In the anisotropic electrical steel sheet of item [1], the mentioned D1, D2, D3, D4 and D5 may satisfy the formula (1'): D5 > D4 > D3 > D2 > D1 … (1').

[0004] In the anisotropic electrical steel sheet of item [2], the mentioned D1, D2, D3, D4 and D5 may satisfy the formula (1'): D5 > D4 > D3 > D2 > D1 … (1').

[0005] In the anisotropic electrical steel sheet according to any one of items [1] to [4], said Dc may be 5.0-40.0 μm, and Wc may be 10.0-200.0 μm.

[0006] In the anisotropic electrical steel sheet according to any one of [1] to [4], the interval between the plurality of grooves in the rolling direction may be 2-10 mm, and the angle between the longitudinal direction of the groove and the rolling direction may be 60-120 degrees.

[0007] In the anisotropic electrical steel sheet according to [5], the interval between the plurality of grooves in the rolling direction may be 2-10 mm, and the angle between the longitudinal direction of the groove and the rolling direction may be 60-120 degrees.

[0008] A method for producing an anisotropic electrical steel sheet according to another aspect of the present invention includes: a groove forming step of irradiating a steel sheet with a laser beam while scanning the steel sheet in a direction intersecting the rolling direction to form a groove extending in the rolling direction; a decarburization annealing step of performing decarburization annealing on the steel sheet after the groove forming step; a finish annealing step of performing finish annealing on the steel sheet after the decarburization annealing step; and an insulating coating forming step of forming an insulating coating on a steel sheet that serves as a base steel sheet and is obtained after the finish annealing step, to obtain an anisotropic electrical steel sheet having a base steel sheet, a forsterite film optionally formed on the base steel sheet, and an insulating coating,formed on the base steel sheet or on the forsterite film, wherein, in the step of forming grooves, in the case where the direction along which the groove extends is defined as the longitudinal direction of the groove, the distance in the groove from an imaginary line, which is an extension of the surface of the base steel sheet, to the groove, along a straight line from this imaginary line in the thickness direction of the base steel sheet, is defined as the groove depth, the width of the groove in the rolling direction is defined as the groove width, the position where the groove depth is 0.0 μm is defined as the groove end, and a 5 mm area extending from the groove end to the central portion in the longitudinal direction of the groove is defined as the groove end portion, in the longitudinal direction of the groove for the groove end portion, in units of μm, the groove depth at a position 1 mm from the groove end is defined as D1, and the groove width at a position 1 mm from the end of the groove is defined as W1,the groove depth at a position of 2 mm from the end of the groove is defined as D2, and the groove width at a position of 2 mm from the end of the groove is defined as W2, the groove depth at a position of 3 mm from the end of the groove is defined as D3, and the groove width at a position of 3 mm from the end of the groove is defined as W3, the groove depth at a position of 4 mm from the end of the groove is defined as D4, and the groove width at a position of 4 mm from the end of the groove is defined as W4, and the groove depth at a position of 5 mm from the end of the groove is defined as D5, and the groove width at a position of 5 mm from the end of the groove is defined as W5, the average groove width at the central portion in the longitudinal direction of the groove is defined as Wc, and the average groove depth at the central portion in the longitudinal direction of the groove is defined as Dc, the groove is formed by irradiation with a laser beam in such a way that the mentioned D1, D2, D3, D4, D5, W1, W2, W3, W4 and W5 satisfy formulas (1) and (2), and at the end section of the groove in the case when the width of the groove in the section,where the groove depth is 0.05 × Dc is defined as W0.05, and the groove width at the portion where the groove depth is 0.50 × Dc is defined as W0.50, said W0.05 and W0.50 satisfy the formulas (3) and (4), by changing the distance between the focal point of the laser beam and the surface of the base steel sheet in accordance with the distance from the end of the groove at the end portion of the groove: D5 ≥ D4 ≥ D3 ≥ D2 ≥ D1 … (1), W5 ≥ W4 ≥ W3 ≥ W2 ≥ W1 … (2), 0.004 ≤ W0.05 / Wc ≤ 0.210 … (3), 0.180 ≤ W0.50 / Wc ≤ 0.810 … (4).,

[0009] In the method for manufacturing anisotropic electrical steel sheet according to item [8], at the groove formation step, the groove may be formed in such a way that the mentioned W0.05 and W0.50 satisfy formulas (5) and (6): 0.008 ≤ W0.05 / Wc ≤ 0.160 … (5), 0.380 ≤ W0.50 / Wc ≤ 0.710 … (6).

[0010] In the method for producing an anisotropic electrical steel sheet according to item [8] or [9], in the groove forming step, a groove in which Dc is 5.0-40.0 μm and Wc is 10.0-200.0 μm may be formed under laser beam irradiation conditions such that the power of the laser beam is set to 200-3000 W, the diameter of the focused spot of the laser, defined as the diameter in the rolling direction that contains 86% of the power, is set to 10-1000 μm, the diameter of the focused spot of the laser beam in the width direction of the sheet is 10-1000 μm, and the scanning speed is set to 2-50 m / s.

[0011] In the method for producing an anisotropic electrical steel sheet according to [8] or [9], in the groove forming step, the groove may be formed in such a manner that the interval between a plurality of grooves, each of which is identical to the groove, in the rolling direction is 2-10 mm, and the angle between the longitudinal direction of the groove and the rolling direction is 60-120 degrees.

[0012] In the method for producing anisotropic electrical steel sheet according to

[10] , in the groove forming step, the groove can be formed in such a way that the interval between a plurality of grooves in the rolling direction is 2-10 mm, and the angle between the longitudinal direction of the groove and the rolling direction is 60-120 degrees. Advantageous effects of the invention

[0014] According to the above aspects of the present invention, it is possible to obtain an anisotropic electrical steel sheet having high adhesion of an insulating coating and excellent rust resistance even at the end portion of a groove.Brief Description of the Drawings

[0015] Fig. 1 is a view illustrating an example of forming grooves on an anisotropic electrical steel sheet according to an embodiment of the present invention. Fig. 2A is a schematic sectional view including a groove and parallel to the rolling direction and the thickness direction of the anisotropic electrical steel sheet according to an embodiment of the present invention. Fig. 2B is a schematic sectional view of the anisotropic electrical steel sheet according to an embodiment of the present invention, wherein the section is parallel to the sheet thickness direction and the groove passing direction and is taken along the center of the groove width. Fig. 3A is a schematic sectional view including a groove and parallel to the rolling direction and the thickness direction of the anisotropic electrical steel sheet according to an embodiment of the present invention after the insulation coating is removed to measure the width and depth of the groove. Fig.3B is a schematic cross-sectional view of an anisotropic electrical steel sheet according to an embodiment of the present invention after the insulation coating is removed to measure the width and depth of the groove, wherein the cross-section is parallel to the sheet thickness direction and the groove running direction and taken along the center of the groove width. Description of embodiments.

[0016] Hereinafter, an anisotropic electrical steel sheet according to an embodiment of the present invention (anisotropic electrical steel sheet according to the present embodiment) and a manufacturing method thereof will be described.

[0017] As illustrated in Fig. 1, 2A and 2B, the anisotropic electrical steel sheet 1 according to the present embodiment includes a base steel sheet 2 and an insulating coating 3 formed on the base steel sheet 2. Alternatively, although not illustrated, a forsterite film may be provided between the base steel sheet 2 and the insulating coating 3. That is, the base steel sheet 2, the forsterite film formed on the base steel sheet 2, and the insulating coating 3 formed on the forsterite film may be provided. In the anisotropic electrical steel sheet 1 according to the present embodiment, the base steel sheet 2 has a plurality of grooves extending in a direction intersecting the rolling direction.Each groove has a predetermined shape at the groove end, which is a 5-millimeter region extending from the groove end E to the center section in the groove's longitudinal direction. Details will be described below.

[0018] In the present embodiment, the direction in which the groove extends is defined as the longitudinal direction of the groove. In addition, the distance in the groove from an imaginary line that is an extension of the surface of the base steel sheet to the groove (groove bottom), along a straight line from this imaginary line in the thickness direction of the base steel sheet, is defined as the groove depth, and the groove width in the rolling direction is defined as the groove width. In addition, the position where the groove depth is 0.0 μm is defined as the end of the groove, and a 5 mm region extending from the end of the groove to the center portion in the longitudinal direction of the groove is defined as the end portion of the groove.In addition, in the longitudinal direction of the groove for the end portion of the groove, in units of μm, the groove depth at a position of 1 mm from the end of the groove is defined as D1, and the groove width at a position of 1 mm from the end of the groove is defined as W1, the groove depth at a position of 2 mm from the end of the groove is defined as D2, and the groove width at a position of 2 mm from the end of the groove is defined as W2, the groove depth at a position of 3 mm from the end of the groove is defined as D3, and the groove width at a position of 3 mm from the end of the groove is defined as W3, the groove depth at a position of 4 mm from the end of the groove is defined as D4, and the groove width at a position of 4 mm from the end of the groove is defined as W4, and the groove depth at a position of 5 mm from the end of the groove is defined as D5, and the groove width at a position of 5 mm from the end of the groove is defined as W5.In addition, the average groove width at the central portion in the longitudinal direction of the groove is defined as Wc, and the average groove depth at the central portion in the longitudinal direction of the groove is defined as Dc.<Anisotropic Electrical Steel Sheet>[Base Steel Sheet](Groove).

[0019] In an anisotropic electrical steel sheet, grooves are formed substantially parallel to the width direction of the steel sheet to reduce magnetic loss. However, the prior art foresaw a case where the width or depth of the end sections (near the front end and rear end) in the longitudinal direction of the groove varied compared to the width or depth of the central section, and there may be a region where the adhesion of the insulating coating is insufficient.On the contrary, in the anisotropic electrical steel sheet 1 according to the present embodiment, in the groove G formed in the base steel sheet 2, at the end portion of the groove, which is a 5 mm region from the end E (the position at which the groove depth is 0.0 μm) of the groove to the center portion in the longitudinal direction of the groove, the groove depth decreases so that it becomes shallower, the groove width decreases so that it becomes narrower, as it approaches the end (end E) in the longitudinal direction of the groove, and therefore the groove depth and the groove width satisfy a predetermined relationship, thereby improving the adhesion of the insulating coating.More specifically, in the case where the groove depths D1-D5 and the groove widths W1-W5 at positions 1-5 mm from the end of the groove at the end portion of the groove satisfy the following formulas (1) and (2) (provided that D5≠D1 and W5≠W1), and at the end portion of the groove, the groove width at the portion where the groove depth is 0.05 × Dc is denoted by W0.05, and the groove width at the portion where the groove depth is 0.50 × Dc is denoted by W0.50, said W0.05 and W0.50 satisfy the following formulas (3) and (4), respectively, whereby the adhesion of the insulating coating or the like is improved.D5 ≥ D4 ≥ D3 ≥ D2 ≥ D1 … (1),W5 ≥ W4 ≥ W3 ≥ W2 ≥ W1 … (2),0.004 ≤ W0.05 / Wc ≤ 0.210 … (3),0.180 ≤ W0.50 / Wc ≤ 0.810 … (4).

[0020] The reason why the adhesion of the insulating coating is improved when the groove shape satisfies formulas (1)-(4) at the end section of the groove is unclear. However, it is believed that when formulas (1)-(4) are satisfied, the groove width or groove depth at the end section of the groove changes smoothly, and the coating solution is easily applied to each corner of the groove. In addition, when the above formulas are satisfied, the magnetic induction also increases, since the amount of reduction of the base metal due to the groove can be reduced.

[0021] As described above, in the base steel sheet 2 of the anisotropic electrical steel sheet 1 according to the present embodiment, the groove depth and the groove width decrease so that they become shallower and narrower as they approach the end in the longitudinal direction of the groove. As can be seen from formulas (1) and (2), the groove depth and the groove width can change continuously (D5>D4>D3>D2>D1), but there may be a region where the depth and width do not change within a certain range (for example, D5=D4≥D3=D2≥D1 can be satisfied). In the case where formula (1) and / or formula (2) are not satisfied, the groove depth or width quickly changes at the end in the longitudinal direction of the groove, and it is considered that the adhesion of the insulation coating is deteriorated since it is difficult to apply the coating solution in this region.

[0022] In addition, as illustrated in formulas (3) and (4), in the base steel sheet 2 of the anisotropic electrical steel sheet 1 according to the present embodiment, the groove width also narrows in the portion where the groove depth is shallow. If formula (3) and / or formula (4) are not satisfied, that is, the change rate of the groove depth is significantly different from the change rate of the groove width at the end portion of the groove, it is considered that there are regions where the groove width is small (the groove is narrow), but the groove depth is large (the groove is deep), and in these regions, it is difficult to apply the coating solution, resulting in deterioration of the adhesion of the insulation coating.

[0023] W0.05 and W0.50 preferably satisfy the formulas (3') and (4'), more preferably satisfy the formulas (5) and (6), and even more preferably satisfy the formulas (5') and (6'): 0.005 ≤ W0.05 / Wc ≤ 0.200 … (3') 0.200 ≤ W0.50 / Wc ≤ 0.800 … (4') 0.008 ≤ W0.05 / Wc ≤ 0.160 … (5) 0.380 ≤ W0.50 / Wc ≤ 0.710 … (6) 0.010 ≤ W0.05 / Wc ≤ 0.150 … (5') 0.400 ≤ W0.50 / Wc ≤ 0.700 … (6'). In this case, the effect of additional improvement of the adhesion of the insulating coating is obtained.

[0024] The groove shape, excluding the end portion of the groove, is not limited. It is preferable that the average groove depth Dc in the central portion in the longitudinal direction of the groove be 5.0-40.0 μm, and the average groove width Wc be 10.0-200.0 μm. Within this range, the effect of reducing magnetic loss due to magnetic domain refinement is enhanced.

[0025] The interval S between the plurality of grooves G in the rolling direction RD is preferably 2-10 mm. The interval S between the grooves is the distance from the center of one groove in the width direction to the center of the adjacent groove in the width direction. The intervals of the plurality of grooves G may not be equal intervals, provided that each interval is within the above-described range, but are preferably equal intervals. In addition, the angle between the direction along which the groove extends (the longitudinal direction of the groove) and the rolling direction is preferably 60-120 degrees. Since the direction along which the groove extends is preferably closer to the direction orthogonal to the rolling direction, this direction is more preferably 75-115 degrees relative to the rolling direction. The plurality of grooves are preferably substantially parallel to each other.If the groove direction and spacing are within the range described above, the effect of reducing magnetic losses is enhanced. The groove shape is not limited, and, for example, its cross-section can be nearly rectangular or nearly triangular. Furthermore, its cross-section can be shaped like an arc or something similar, forming part of a circle.

[0026] The groove extends in the width direction of the anisotropic electrical steel sheet and extends linearly. The grooves can be formed over the entire width direction of the anisotropic electrical steel sheet or can be formed in a portion of the width direction of the sheet.

[0027] The groove depths (D1-D5) and groove widths (W1-W5) at the groove end portion are measured using a laser microscope (a three-dimensional laser microscope using a confocal optical system and a diaphragm). If the anisotropic electrical steel sheet has an insulating coating, the groove depth and groove width on the surface of the base steel sheet excluding the insulating coating are measured. Specifically, the insulating coating of the anisotropic electrical steel sheet can first be removed, for example, by the following method. The anisotropic electrical steel sheet with the insulating coating is immersed in an aqueous sodium hydroxide solution consisting of 30 wt% NaOH and 70 wt% H2O at 80°C for 20 minutes and then washed with water. Finally, drying is performed using a warm air blower for 1 minute.After the insulating coating is removed in the manner described above, a measured cross-sectional curve forming the groove profile is obtained in a cross-section parallel to the sheet thickness direction and the groove direction and passing through the groove width center by measurement using a laser microscope. After a low-pass filter with a cutoff value of λs is applied to the measured cross-sectional curve to obtain the cross-sectional curve, band-pass filters with cutoff values ​​of λf and λc are applied to this cross-sectional curve to remove the long-wave component and the short-wave component from the cross-sectional curve. As a result, as illustrated in Fig. 3B, a WCL waviness curve is obtained that characterizes the groove profile in a cross-section parallel to the sheet thickness direction and the groove direction and passing through the groove width center.The waviness curve is a type of profile curve suitable for simplifying the shape of the profile itself using a smooth line. In the WCL waviness curve, an imaginary line IL, which is an extension of the surface of the base steel sheet, is drawn in the direction of the groove (the horizontal direction in the plane of the drawing), and the starting point of this imaginary line IL, i.e., the position where the groove depth is 0.0 μm, is defined as the end E of the groove. The straight-line distance between the imaginary line IL and the base steel sheet 2 is determined at a position of 1 mm from the end E of the groove in the direction of the groove (in the right direction in the plane of the drawing) and is set as the groove depth D1. In addition, at the position where the groove depth D1 is determined, a measured section curve forming the groove profile is obtained in a section parallel to the rolling direction and the sheet thickness direction through measurement using a laser microscope.In the case where, after a low-pass filter with a cutoff value of λs is applied to the measured cross-section curve in order to obtain the cross-section curve, band-pass filters with cutoff values ​​of λf and λc are applied to the cross-section curve in order to remove the long-wave component and the short-wave component from the cross-section curve, a WCT waviness curve is obtained, which characterizes the groove profile in a cross-section parallel to the rolling direction and the sheet thickness direction, as illustrated in Fig. 3A. On the WCT waviness curve, the length of the imaginary line IL, which is a continuation of the surface of the base steel sheet in the rolling direction, is determined and is taken as the width W1 of the groove. In the same way, the depths D2, D3, D4 and D5 of the groove and the widths W2, W3, W4 and W5 of the groove are obtained, respectively, at positions of 2 mm, 3 mm, 4 mm and 5 mm from the end E of the groove in the direction of passage of the groove.

[0028] In addition, the average groove depth Dc and the average groove width Wc at the center section in the longitudinal direction of the groove are measured in the same way as the groove depth and groove width at the end section using a laser microscope. The groove depths and groove widths are measured at any five locations in the central section (range ±10 mm at the center) of one groove in the longitudinal direction of the groove, and the corresponding average values ​​are taken as the average groove depth Dc and the average groove width Wc.

[0029] In addition, at the end portion of the groove, the groove width W0.05 is measured at the portion where the groove depth is 0.05 × Dc, and the groove width W0.50 is measured at the portion where the groove depth is 0.50 × Dc using a laser microscope. Based on the waviness curve WCL, which characterizes the groove profile in a section parallel to the sheet thickness direction and the groove passing direction and passing through the center of the groove width, as illustrated in Fig. 3B, straight lines are obtained from the end E of the groove at the positions where the groove depths are 0.05 × Dc and 0.50 × Dc. At each position, a measured sectional curve forming the groove profile is obtained in a section parallel to the rolling direction and the sheet thickness direction by measurement using a laser microscope.If, after a low-pass filter with a cutoff value of λs is applied to the measured cross-section curve to obtain the cross-section curve, band-pass filters with cutoff values ​​of λf and λc are applied to this cross-section curve to remove the long-wave and short-wave components from the cross-section curve, a WCT waviness curve is obtained in the cross-section parallel to the rolling direction and the sheet thickness direction. On each WCT waviness curve, the length of an imaginary line IL, which is an extension of the base steel sheet surface in the rolling direction, is determined and taken as W0.05 and W0.50.

[0030] When multiple grooves are formed on the base steel sheet, it is preferable that all the grooves satisfy formulas (1) to (4). In addition, it is more preferable to satisfy formulas (3') and (4'), or formulas (5) and (6), or formulas (5') and (6'). When grooves are repeatedly formed at equal intervals in the rolling direction under the same conditions, it is considered that when one groove satisfies formulas (1) to (4), the other grooves also satisfy formulas (1) to (4). However, when grooves are formed up to the end of the width of the base steel sheet, the end E of the groove does not exist at the end portion of the groove. Therefore, the above measurement is not carried out (the grooves are not regarded as grooves to be measured). (Chemical composition)

[0031] The chemical composition of the base steel sheet of the anisotropic electrical steel sheet is not limited, provided that it is equivalent to the chemical composition of the base steel sheet of the known anisotropic electrical steel sheet. For example, the chemical composition may contain Si: 2.50-4.50%, Mn: 0.010-0.150%, C: 0-0.085%, acid-soluble Al: 0-0.065%, N: 0-0.012%, Cr: 0-0.30%, Cu: 0-0.40%, P: 0-0.50%, Sn: 0-0.30%, Sb: 0-0.30%, Ni: 0-1.00%, S: 0-0.015%, Se: 0-0.015%, Bi: 0-0.10%, Nb: 0-0.10%, V: 0-0.10%, Mo: 0-0.10%, Ta: 0-0.10%, W: 0-0.10%, B: 0-0.080%, Ti: 0-0.10% by weight. In addition, the anisotropic electrical steel sheet may contain the chemical composition described above and the remainder is Fe and impurities.

[0032] The chemical composition of the anisotropic electrical steel sheet (base steel sheet) can be measured using conventional steel analysis methods. For example, chemical components can be measured using inductively coupled plasma atomic emission spectrometry (ICP-AES). If the forsterite film and insulating coating described below are formed, it is sufficient to remove the insulating coating from the anisotropic electrical steel sheet using the above-described method, remove the forsterite film using a known method such as pickling, and then analyze the chemical components of the base steel sheet.Specifically, for example, chemical components can be analyzed by taking a test specimen with a square side of 35 mm (35 mm × 35 mm) from the center position of the base steel sheet after removing the coating and film as necessary and performing measurement under the condition based on a calibration curve created in advance using an ICPS-8100 measuring instrument manufactured by Shimadzu Corporation or the like. Carbon and sulfur (C and S), which are difficult to measure using ICP-AES, can be measured by the combustion infrared absorption method, and N can be measured using the inert gas fusion thermal conductivity measurement method. (Sheet thickness).

[0033] The base steel sheet thickness of anisotropic electrical steel sheets is not limited and is preferably 0.15-0.30mm. If the base steel sheet thickness is greater than 0.30mm, the classic eddy current loss and magnetic loss will increase. On the other hand, if the sheet thickness is less than 0.15mm, the rolling efficiency will decrease, which is disadvantageous in terms of productivity and cost. [Forsterite Film] [Insulation Coating]

[0034] The anisotropic electrical steel sheet according to the present embodiment may include a base steel sheet and an insulating coating formed on the surface of the base steel sheet, or a forsterite film may be formed on the surface of the base steel sheet. In this case, the insulating coating may be formed on the surface of the forsterite film. That is, the anisotropic electrical steel sheet according to the present embodiment may include a base steel sheet, a forsterite film formed on the base steel sheet, and an insulating coating formed on the forsterite film. The forsterite film and the insulating coating may be formed on one surface or may be formed on both surfaces. The forsterite film is an inorganic film containing magnesium silicate as the main component.The forsterite film is formed by the reaction of the magnesium oxide (MgO)-containing annealing separator applied to the surface of the base steel sheet with the surface component of the base steel sheet during final annealing. Its composition (specifically, the composition containing Mg2SiO4 as the main component) is derived from the annealing separator and the base steel sheet component. However, if the annealing separator mainly containing Al2O3 is used during final annealing, the forsterite film may not be formed. The insulating coating has the function of imparting electrical insulation properties and tension to the anisotropic electrical steel sheet. Tension is applied to the anisotropic electrical steel sheet to promote the movement of domain walls in the anisotropic electrical steel sheet, thereby reducing the magnetic loss of the anisotropic electrical steel sheet.In addition, depending on the insulating coating, various properties such as rust resistance, heat resistance, and slip resistance can be obtained in addition to the electrical insulation properties and tension as described above. In the anisotropic electrical steel sheet according to the present embodiment, the insulating coating, for example, can be a known coating formed by applying a coating solution containing phosphate and colloidal silica as the main components to the surface of a base steel sheet or a forsterite film and calcining this coating solution (processing to form an insulating coating). <Manufacturing method>.

[0035] The effect of the anisotropic electrical steel sheet according to the present embodiment can be obtained regardless of the manufacturing method, provided that the anisotropic electrical steel sheet has the above-described characteristics, but by means of the manufacturing method including the following steps, the anisotropic electrical steel sheet according to the present embodiment can be stably obtained, which is preferable: (I) a groove forming step of forming a plurality of grooves extending in a direction intersecting the rolling direction on the steel sheet at a predetermined interval in the rolling direction; (II) a decarburization annealing step of performing decarburization annealing on the steel sheet after the groove forming step; (III) a finish annealing step of performing finish annealing on the steel sheet after the decarburization annealing step;and(IV) an insulating coating forming step of forming an insulating coating on a steel sheet (there may be a case where a forsterite film is formed on a base steel sheet) which serves as a base steel sheet and is obtained after the final annealing step, to obtain an anisotropic electrical steel sheet having a base steel sheet, a forsterite film optionally formed on the base steel sheet, and an insulating coating formed on the base steel sheet or on the forsterite film. In addition, in the case where the steel sheet is a cold-rolled steel sheet, the steel sheet subjected to the groove forming step may be manufactured by a manufacturing method including the following steps:(V) a step of hot rolling with heating and hot rolling a slab to obtain a hot-rolled steel sheet;(VI) a hot-rolled steel sheet annealing step of annealing the hot-rolled steel sheet after the hot rolling step; and (VII) a cold rolling step of pickling the hot-rolled steel sheet after the hot-rolled steel sheet annealing step and cold rolling the hot-rolled steel sheet to obtain a cold-rolled steel sheet.

[0036] Next, a groove formation step characteristic of producing an anisotropic electrical steel sheet according to the present embodiment will be described. In other steps, known conditions may be set according to the target magnetic flux density before the groove is formed, and therefore, a description thereof will be omitted. However, in the final annealing step, in general, the final annealing is performed after an annealing separator mainly composed of MgO or Al2O3 is applied. For example, when an annealing separator containing MgO as the main component is used, a forsterite (Mg2SiO4) film layer is formed. When an annealing separator containing Al2O3 as the main component is used, the forsterite film may not be formed. Therefore, the annealing separator can be selected according to the need to form the forsterite film.

[0037] In addition, the chemical composition of the slab subjected to hot rolling can be determined by taking into account the change in the chemical composition at each stage in accordance with the chemical composition desired to be obtained in the anisotropic electrical steel sheet. For example, if the above-described chemical composition of the base steel sheet of the anisotropic electrical steel sheet according to the present embodiment is preferred, it is preferable to use a slab having the following chemical composition. Namely, the slab may contain in its chemical composition Si: 2.50-4.50%, Mn: 0.010-0.150%, C: 0.020-0.100%, acid-soluble Al: 0-0.065%, N: 0.002-0.030%, Cr: 0-0.30%, Cu: 0-0.40%, P: 0-0.50%, Sn: 0-0.30%, Sb: 0-0.30%, Ni: 0-1.00%, S: 0.001-0.050%, Se: 0-0.050%, Bi: 0-0.10%, Nb: 0-0.10%, V: 0-0.10%, Mo: 0-0.10%, Ta: 0-0.10%, W: 0-0.10%, B: 0-0.080%, Ti: 0-0.10% wt.%.In addition, the anisotropic electrical steel sheet may contain the above-described chemical composition and the rest - Fe and impurities. (Groove formation stage).

[0038] In the groove forming step, a plurality of grooves extending in a direction intersecting the rolling direction are formed at predetermined intervals in the rolling direction on a steel sheet, such as a hot-rolled steel sheet or a cold-rolled steel sheet. The groove extending in a direction intersecting the rolling direction can be formed by irradiating the steel sheet with a laser beam while scanning the steel sheet in a direction intersecting the rolling direction. Furthermore, the plurality of grooves are formed at predetermined intervals in the rolling direction by repeatedly irradiating portions with a laser beam while shifting the scanned portions by predetermined intervals in the rolling direction.During groove formation, a groove is formed by irradiation with a laser beam in such a way that D1, D2, D3, D4, D5, W1, W2, W3, W4 and W5 satisfy the following formulas (1) and (2), and in the case where the groove width in the section where the groove depth is 0.05 × Dc is denoted by W0.05, and the groove width in the section where the groove depth is 0.50 × Dc is denoted by W0.50, said W0.05 and W0.50 satisfy the following formulas (3) and (4), by changing the distance between the focal point of the laser beam and the surface of the base steel sheet in accordance with the distance from the end of the groove at the end section of the groove. Preferably, the grooves are formed in such a way that W0.05 and W0.50 satisfy the following formulas (3') and (4'), the following formulas (5) and (6), or the following formulas (5') and (6').By forming grooves satisfying formulas (1) to (4), it is possible to improve the adhesion of the insulating coating formed in the next step and produce an anisotropic electrical steel sheet with excellent adhesion of the insulating coating.D5 ≥ D4 ≥ D3 ≥ D2 ≥ D1 … (1),W5 ≥ W4 ≥ W3 ≥ W2 ≥ W1 … (2),0.004 ≤ W0.05 / Wc ≤ 0.210 … (3),0.180 ≤ W0.50 / Wc ≤ 0.810 … (4).0.005 ≤ W0.05 / Wc ≤ 0.200 … (3')0.200 ≤ W0.50 / Wc ≤ 0.800 … (4')0.008 ≤ W0.05 / Wc ≤ 0.160 … (5)0.380 ≤ W0.50 / Wc ≤ 0.710 … (6)0.010 ≤ W0.05 / Wc ≤ 0.150 … (5')0.400 ≤ W0.50 / Wc ≤ 0.700 … (6').

[0039] When a groove is formed by laser irradiation, the laser energy on the steel sheet surface is reduced by shifting the focal point of the laser beam away from the steel sheet surface, resulting in a shallower groove depth and a narrower groove width. Therefore, the distance between the focal point of the laser beam and the surface of the base steel sheet varies according to the distance from the groove end. That is, at the beginning of laser irradiation for forming a single groove, the focal point of the laser beam is set at a position offset from the steel sheet surface. During scanning, the focal point gradually moves until it aligns with the steel sheet surface, thereby enabling the groove depth and groove width to be varied within a certain range from the groove start point.Similarly, at the end of laser irradiation for forming one groove, the focal point of the laser beam is set to a position offset from the surface of the steel sheet, and during scanning, the focal point is gradually moved until it aligns with the surface of the steel sheet, thereby enabling the groove depth and groove width to be varied within a certain range from the groove end point. The groove depth and groove width can also be varied by changing the power or the diameter of the focused spot of the laser beam and the scanning speed. Since the groove depth and groove width can be independently varied by changing the conditions, the conditions are set in combination such that the groove depth and groove width satisfy expressions (1)-(4). Examples of the method for moving the focal point of the laser beam include a method for shifting the position of the optical component.

[0040] In the groove forming step, it is preferable to form a groove having an average groove depth Dc of 5.0-40.0 μm and an average groove width Wc of 10.0-200.0 μm in the center portion in the longitudinal direction of the groove, from the viewpoint of refining the magnetic domains. In the groove forming step, the laser irradiation conditions are not limited, but in the region other than the end portion of the groove, it is preferable that the laser beam power be 200-3000 W, the focused spot diameter, defined as the diameter in the rolling direction that contains 86% of the laser beam power, be 10-1000 μm, the focused spot diameter of the laser beam in the sheet width direction be 10-1000 μm, and the scanning speed be 2-50 m / s. In this case, it is easy to form grooves in which Dc and Wc are in the preferred range.

[0041] In addition, in the groove forming step, it is preferable to form grooves so that each interval between multiple grooves in the rolling direction is 2-10 mm, and the angle between the longitudinal direction of the groove and the rolling direction is 60-120 degrees (°). In this case, the effect of reducing magnetic loss is enhanced. Examples

[0042] The hot rolled steel sheet with a thickness of 2.6mm was obtained by performing a hot rolling step on a slab having a chemical composition containing Si: 3.30%, Mn: 0.120%, C: 0.060%, acid-soluble Al: 0.028%, N: 0.008%, Cr: 0.050%, Cu: 0.040%, P: 0.010%, Sn: 0.020%, Ni: 0.005% and S: 0.007% in mass%, and the balance was Fe and impurities. This hot rolled steel sheet was subjected to hot rolled steel sheet annealing under the conditions of heating to 1100°C and holding for 1 minute. The hot rolled steel sheet was pickled after the hot rolled steel sheet annealing and cold rolling, obtaining a cold-rolled steel sheet with a thickness of 0.22 mm. The obtained cold-rolled steel sheet was irradiated with a laser beam under various conditions illustrated in Table 1 for each test number, forming a plurality of grooves (the laser beam irradiation conditions were the same in one cold-rolled steel sheet).For the end section of the groove, the groove depth and width were gradually changed by shifting the position of the polygonal mirror. After forming the grooves, the cold-rolled steel sheet was subjected to decarburization annealing under conditions of heating up to 850°C and holding for 2 minutes. After decarburization annealing, an annealing separator containing magnesium oxide (MgO) as the main component was applied to the cold-rolled steel sheet, and the final annealing of the cold-rolled steel sheet was performed under conditions of heating up to 1200°C and holding for 20 hours. The result was a steel sheet in which a forsterite film was formed on the surface of a cold-rolled steel sheet (base steel sheet). Then, a coating solution containing colloidal silicon dioxide and aluminum phosphate was applied to the forsterite film and heat treated at 850°C for 1 minute to form an insulating coating.The thickness of the insulating coating was 5 μm. A specimen with a length of 60 mm in the width direction and 300 mm in the rolling direction was taken from the obtained anisotropic electrical steel sheet, and this specimen was subjected to a single sheet magnetic performance test (SST) in accordance with JIS C2556 (2015) to measure the B8 magnetic flux density generated when the specimen was magnetized at 800 A / m.

[0043] A test specimen with dimensions of 30 mm × 30 mm was selected from a section including the end section of the groove of the obtained anisotropic electrical steel sheet, the insulation coating was removed in the above-described manner, and then, for one groove as a typical representative, the average groove depth Dc and the average groove width Wc at the central section in the longitudinal direction of the groove, the groove depths D1-D5 and the groove widths W1-W5 at positions from 1 mm to 5 mm from the end of the groove at the end section of the groove were measured in the above-described manner. For the same groove, at the end section of the groove, the groove width was measured in the above-described manner at the section where the groove depth was 0.05 × Dc as W0.05, and the groove width was measured at the section where the groove depth was 0.50 × Dc. The results are shown in Table 2.

[0044] The adhesion of the insulating coating and rust resistance of the obtained anisotropic electrical steel sheet were evaluated as follows. The results are shown in Table 3.<Adhesion of Insulating Coating>

[0045] A test specimen with dimensions of 80 mm × 80 mm was cut from a section including the end section of the groove of the anisotropic electrical steel sheet, wound on a round rod having a diameter of 20 mm, and then stretched to a flat state. The surface of the test specimen after flattening was observed, and the area of ​​the insulating coating that had not peeled off from the steel sheet was measured relative to the area of ​​the bent section to calculate the residual coating area ratio (%). The adhesion of the insulating coating of the test specimen in which the residual coating area ratio was 95% or more was rated as "Excellent (Ex)", the adhesion of the insulating coating of the test specimen in which the residual coating area ratio was 90% or more and less than 95% was rated as "Good (G)", and the adhesion of the insulating coating of the test specimen in which the residual coating area ratio was less than 90%, was rated as "Poor (P)".<Rust Resistance>

[0046] A test specimen with dimensions of 30 mm × 30 mm was taken from a section including the end section of the groove of the obtained anisotropic electrical steel sheet, and the test specimen was left for 1 week in an atmosphere at a temperature of 50 °C and a humidity of 91% and evaluated based on the change in weight of the test specimen before and after such leaving. When rust occurred, the weight of the test specimen increased. Therefore, it was determined that the rust resistance was better as the amount of weight increase became smaller. In particular, the rust resistance of the test specimen in which the amount of weight increase was 1.0 mg / m 2 or less, was rated as "Excellent (Ex)" for the rust resistance of the test specimen in which the weight increase amount was 5.0 mg / m 2 or less, was rated as "Good (G)", and the rust resistance of the test specimen in which the weight increase amounted to more than 5.0 mg / m2 , was rated "Poor (P)".

[0047] Table 1 № Groove formation stage Laser irradiation conditions Power Focused spot diameter in rolling direction The diameter of the focused spot in the direction across the width of the sheet Scanning speed Tue microns microns m / s 1 500 100 100 10 2 500 100 100 10 3 500 100 100 10 4 500 100 100 10 5 500 100 100 10 6 500 100 100 10 7 500 100 100 10 8 500 500 500 10 9 500 400 400 10 10 500 100 100 10 11 500 100 100 10 12 500 100 100 10 13 500 100 100 10

[0048] Table 2 № Groove The angle between the direction of the groove and the direction of rolling Spacing between grooves in rolling direction Central section in the longitudinal direction of the groove End section of the groove Average groove depth Dc Average groove width Wc D1 D2 D3 D4 D5 W1 W2 W3 W4 W5 D0,05 D0,50 W0,05 W0,50 W0.05 / Wc W0.50 / Wc degrees mm microns microns microns microns microns microns microns microns microns microns microns microns microns microns microns microns - - 1 95 4 20,1 39,0 4,2 8,1 12,4 17,5 19,8 10,5 15,4 20,4 24,1 33,4 1,0 10,1 1,2 19,9 0,031 0,510 2 95 4 19,5 42,0 3,3 7,1 10,5 16,4 18,7 9,7 17,8 21,5 25,7 30,4 1,0 9,8 5,8 20,1 0,138 0,479 3 95 4 21,4 40,1 5,5 10,4 13,7 18,7 20,1 5,4 14,9 19,7 26,7 37,4 1,1 10,7 3,1 17,4 0,077 0,434 4 95 4 19,9 38,9 6,1 9,7 11,1 18,8 19,8 10,4 18,7 27,9 35,7 38,1 1,0 10,0 3,4 25,1 0,087 0,645 5 95 4 20,3 40,5 5,1 11,4 14,8 17,9 20,0 11,4 18,2 28,1 37,6 40,2 1,0 10,2 3,5 15,1 0,086 0,373 6 95 4 19,7 41,2 3,8 10,8 16,7 17,4 19,0 15,7 25,7 37,8 39,7 41,1 1,0 9,9 0,3 22,4 0,007 0,544 7 95 4 21,7 41,1 3,1 6,7 9,8 10,5 18,2 12,4 15,3 16,7 19,5 30,8 1,1 10,9 10,1 20,1 0,246 0,489 8 95 4 18,7 100,1 2,1 5,7 8,9 10,5 14,9 10,5 24,8 35,7 47,9 75,8 0,9 9,4 0,3 41,5 0,003 0,415 9 95 4 24,8 87,9 7,8 10,2 15,4 21,4 23,0 4,1 12,8 27,9 55,4 61,8 1,2 12,4 5,4 15,1 0,061 0,172 10 95 4 18,8 42,5 2,4 5,1 8,7 9,1 15,9 15,7 21,9 29,7 34,8 41,0 0,9 9,4 5,5 38,7 0,129 0,911 11 95 4 25,1 50,3 5,9 15,4 12,3 20,8 24,1 11,8 23,4 24,7 37,4 45,1 1,3 12,6 7,1 25,8 0,141 0,513 12 95 4 18,4 36,7 2,4 5,1 9,3 12,7 17,4 5,7 14,2 12,7 27,4 34,3 0,9 9,2 2,4 13,4 0,065 0,365 13 95 4 20,0 50,0 19,8 20,1 19,9 20,2 20,0 50,1 49,9 50,0 51,0 49,5 1,0 10,0 2,5 13,4 0,050 0,268

[0049] Table 3 № Grade Note Adhesion of the insulating coating Rust resistance Magnetic induction Tl 1 Excellent Excellent 1,931 Example of the invention 2 Excellent Excellent 1,925 Example of the invention 3 Excellent Excellent 1,920 Example of the invention 4 Excellent Excellent 1,921 Example of the invention 5 Good Good 1,920 Example of the invention 6 Good Good 1,915 Example of the invention 7 Bad Bad 1,905 Comparative example 8 Bad Bad 1,908 Comparative example 9 Bad Bad 1,901 Comparative example 10 Bad Bad 1,895 Comparative example 11 Bad Bad 1,887 Comparative example 12 Bad Bad 1,884 Comparative example 13 Bad Bad 1,880 Comparative example

[0050] As can be seen from Tables 1-3, it was confirmed that the rust resistance and insulation coating adhesion of the anisotropic electrical steel sheet were improved by forming grooves satisfying formulas (1)-(4). In addition, by forming grooves satisfying formulas (3') and (4'), (5) and (6), or (5') and (6'), an anisotropic electrical steel sheet exhibiting further improved rust resistance and insulation coating adhesion was obtained.List of reference numbers

[0051] 1 - Anisotropic electrical steel sheet 2 - Base steel sheet 3 - Insulation coating G - Groove E - Groove end D - Groove depth (collective term for D1, D2, D3, D4, D5 and Dc) W - Groove width (collective term for W1, W2, W3, W4, W5 and Wc) IL - Imaginary line obtained by extending from the surface of the base steel sheet S - Groove interval RD - Rolling direction TD - Width direction of the sheet ND - Thickness direction of the base steel sheet Industrial applicability

[0052] According to the present invention, the rust resistance and adhesion of the insulating coating can be improved in an anisotropic electrical steel sheet having grooves formed on the surface to reduce magnetic loss. Therefore, when using the anisotropic electrical steel sheet according to the present invention, it is possible to prevent an increase in magnetic loss due to interlayer current generated during the lamination of steel sheets and prevent defects in appearance.

Claims

1. A sheet of anisotropic electrical steel containing: base steel sheet; a forsterite film, optionally formed on the base steel sheet; and an insulating coating formed on the base steel sheet or forsterite film, wherein the base steel sheet has a plurality of grooves running in the direction intersecting the rolling direction, in the case where the direction in which a plurality of grooves extend is defined as the longitudinal direction of the groove, the distance in the groove from an imaginary line, which is a continuation of the surface of the base steel sheet, to the groove, along a straight line from this imaginary line in the direction of the thickness of the base steel sheet, is defined as the groove depth, the groove width in the rolling direction is defined as the groove width, a position where the groove depth is 0.0 μm is defined as the end of the groove, and a 5 mm area extending from the end of the groove to the central portion in the longitudinal direction of the groove is defined as the end portion of the groove, in the longitudinal direction of the groove for the end portion of the groove, in units of μm, the groove depth at a position of 1 mm from the end of the groove is defined as D1, and the groove width at a position of 1 mm from the end of the groove is defined as W1, the groove depth at a position of 2 mm from the end of the groove is defined as D2, and the groove width at a position of 2 mm from the end of the groove is defined as W2, the groove depth at a position of 3 mm from the end of the groove is defined as D3, and the groove width at a position of 3 mm from the end of the groove is defined as W3, the groove depth at a position of 4 mm from the end of the groove is defined as D4, and the groove width at a position of 4 mm from the end of the groove is defined as W4, and the groove depth at a position of 5 mm from the end of the groove is defined as D5, and the groove width at a position of 5 mm from the end of the groove is defined as W5, the average groove width at the central section in the longitudinal direction of the groove is defined as Wc, and the average groove depth at the central section in the longitudinal direction of the groove is defined as Dc, the mentioned D1, D2, D3, D4, D5, W1, W2, W3, W4 and W5 satisfy formulas (1) and (2), and at the end section of the groove, in the case where the width of the groove in the section where the groove depth is 0.05 × Dc is determined as W0.05, and the width of the groove in the section where the groove depth is 0.50 × Dc is determined as W0.50, the said W0.05 and W0.50 satisfy formulas (3) and (4): D5 ≥ D4 ≥ D3 ≥ D2 ≥ D1 … (1) W5 ≥ W4 ≥ W3 ≥ W2 ≥ W1 … (2) 0.004 ≤ W0.05 / Wc ≤ 0.210 … (3) 0.180 ≤ W0.50 / Wc ≤ 0.810 ... (4).

2. A sheet of anisotropic electrical steel according to paragraph 1, wherein the mentioned W0.05 and W0.50 satisfy formulas (5) and (6): 0.008 ≤ W0.05 / Wc ≤ 0.160 … (5) 0.380 ≤ W0.50 / Wc ≤ 0.710 … (6).

3. A sheet of anisotropic electrical steel according to paragraph 1, wherein said D1, D2, D3, D4 and D5 satisfy formula (1'): D5 > D4 > D3 > D2 > D1 … (1').

4. A sheet of anisotropic electrical steel according to paragraph 2, wherein said D1, D2, D3, D4 and D5 satisfy formula (1'): D5 > D4 > D3 > D2 > D1 … (1').

5. Anisotropic electrical steel sheet according to any one of paragraphs 1-4, wherein Dc is 5.0-40.0 μm and Wc is 10.0-200.0 μm.

6. A sheet of anisotropic electrical steel according to any one of paragraphs 1-4, wherein the interval between the plurality of grooves in the rolling direction is 2-10 mm, and the angle between the longitudinal direction of the groove and the rolling direction is 60-120 degrees.

7. A sheet of anisotropic electrical steel according to claim 5, wherein the interval between the plurality of grooves in the rolling direction is 2-10 mm, and the angle between the longitudinal direction of the groove and the rolling direction is 60-120 degrees.

8. A method for producing a sheet of anisotropic electrical steel, comprising: a step of forming grooves by irradiating a steel sheet with a laser beam while scanning the steel sheet in a direction intersecting the rolling direction to form a groove extending in the rolling direction; a decarburization annealing stage with decarburization annealing of the steel sheet after the groove formation stage; a final annealing step of performing final annealing of the steel sheet after the decarburization annealing step; and an insulating coating forming step of forming an insulating coating on a steel sheet that serves as a base steel sheet and is obtained after the final annealing step, to obtain an anisotropic electrical steel sheet having a base steel sheet, a forsterite film optionally formed on the base steel sheet, and an insulating coating formed on the base steel sheet or on the forsterite film, wherein at the stage of groove formation: in the case where the direction along which the groove runs is defined as the longitudinal direction of the groove, the distance in the groove from an imaginary line, which is a continuation of the surface of the base steel sheet, to the groove, along a straight line from this imaginary line in the direction of the thickness of the base steel sheet, is defined as the groove depth, the groove width in the rolling direction is defined as the groove width, a position where the groove depth is 0.0 μm is defined as the end of the groove, and a 5 mm area extending from the end of the groove to the central portion in the longitudinal direction of the groove is defined as the end portion of the groove, in the longitudinal direction of the groove for the end portion of the groove, in units of μm, the groove depth at a position of 1 mm from the end of the groove is defined as D1, and the groove width at a position of 1 mm from the end of the groove is defined as W1, the groove depth at a position of 2 mm from the end of the groove is defined as D2, and the groove width at a position of 2 mm from the end of the groove is defined as W2, the groove depth at a position of 3 mm from the end of the groove is defined as D3, and the groove width at a position of 3 mm from the end of the groove is defined as W3, the groove depth at a position of 4 mm from the end of the groove is defined as D4, and the groove width at a position of 4 mm from the end of the groove is defined as W4, and the groove depth at a position of 5 mm from the end of the groove is defined as D5, and the groove width at a position of 5 mm from the end of the groove is defined as W5, the average groove width at the central section in the longitudinal direction of the groove is defined as Wc, and the average groove depth at the central section in the longitudinal direction of the groove is defined as Dc, the groove is formed by irradiation with a laser beam in such a way that the mentioned D1, D2, D3, D4, D5, W1, W2, W3, W4 and W5 satisfy formulas (1) and (2), and at the end portion of the groove, in the case where the width of the groove at the portion where the groove depth is 0.05 × Dc is determined as W0.05, and the width of the groove at the portion where the groove depth is 0.50 × Dc is determined as W0.50, the said W0.05 and W0.50 satisfy the formulas (3) and (4), by changing the distance between the focal point of the laser beam and the surface of the base steel sheet in accordance with the distance from the end of the groove at the end portion of the groove: D5 ≥ D4 ≥ D3 ≥ D2 ≥ D1 … (1) W5 ≥ W4 ≥ W3 ≥ W2 ≥ W1 … (2) 0.004 ≤ W0.05 / Wc ≤ 0.210 … (3) 0.180 ≤ W0.50 / Wc ≤ 0.810 ... (4).

9. A method for manufacturing a sheet of anisotropic electrical steel according to paragraph 8, wherein at the stage of forming the grooves, the groove is formed in such a way that the mentioned W0.05 and W0.50 satisfy formulas (5) and (6): 0.008 ≤ W0.05 / Wc ≤ 0.160 … (5) 0.380 ≤ W0.50 / Wc ≤ 0.710 … (6).

10. The method for manufacturing an anisotropic electrical steel sheet according to claim 8 or 9, wherein at the stage of forming grooves, a groove in which Dc is 5.0-40.0 μm and Wc is 10.0-200.0 μm is formed under such laser beam irradiation conditions that the power of the laser beam is set to 200-3000 W, the diameter of the focused spot of the laser beam, defined as the diameter in the rolling direction that contains 86% of the power, is set to 10-1000 μm, the diameter of the focused spot of the laser beam in the direction along the width of the sheet is 10-1000 μm, and the scanning speed is set to 2-50 m / s.

11. A method for manufacturing an anisotropic electrical steel sheet according to claim 8 or 9, wherein at the stage of forming grooves, the groove is formed in such a way that the interval between a plurality of grooves in the rolling direction is 2-10 mm, and the angle between the longitudinal direction of the groove and the rolling direction is 60-120 degrees.

12. The method for manufacturing an anisotropic electrical steel sheet according to claim 10, wherein at the stage of forming the grooves, the groove is formed in such a way that the interval between the plurality of grooves in the rolling direction is 2-10 mm, and the angle between the longitudinal direction of the groove and the rolling direction is 60-120 degrees.

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