Grain-oriented electrical steel sheet and its manufacturing method

Abstract

This grain-oriented electromagnetic steel sheet comprises a base material steel sheet, a forsterite film that is optionally formed on the base material steel sheet, and an insulating film that is formed on the base material steel sheet or the forsterite film. The base material steel sheet has a plurality of grooves extending in a direction intersecting a rolling direction. A groove depth and a groove width at a plurality of positions on groove edge parts satisfy a prescribed relationship, where: the groove depth is a distance within the grooves, on a straight line that extends along a plate thickness direction of the base material steel sheet from a virtual line obtained by extending the surface of the base material steel sheet, from the virtual line to the grooves; the groove width is the rolling-direction width of the grooves; and the groove edge parts are regions within 5 mm from groove edges toward groove-longitudinal-direction central parts, the groove longitudinal direction being the direction in which the grooves extend, and the groove edges being positions at which the groove depth is 0.0 μm.

Description

[Technical Field]

[0001] The present invention relates to a grain-oriented electrical steel sheet and a method for manufacturing the same. This application claims priority based on Japanese Patent Application No. 2023-111726, filed on July 6, 2023, the contents of which are incorporated herein by reference. [Background technology]

[0002] Grain-oriented electrical steel sheets are soft magnetic materials that are primarily used as iron core materials for transformers, and therefore require magnetic properties such as high magnetic flux density and low core loss. Iron loss is the loss consumed as thermal energy when an iron core is excited by an AC magnetic field, and from the perspective of energy conservation, iron loss should be as low as possible. The level of iron loss is affected by factors such as magnetic susceptibility, sheet thickness, film tension, impurity content, electrical resistivity, crystal grain size, and magnetic domain width. Even now, when various technologies have been developed for grain-oriented electrical steel sheets, research and development into reducing iron loss continues in order to increase energy conversion efficiency. One method proposed for reducing iron loss is to irradiate steel sheets with a laser. This technique is said to reduce eddy current loss, which is a part of iron loss, by introducing strain into the surface of the steel sheet through laser irradiation and dividing the magnetic domain width.

[0003] For example, Patent Document 1 discloses a method for producing a steel sheet by irradiating a surface of the steel sheet with a focused continuous wave laser beam while scanning the surface in a direction inclined from the rolling direction of the steel sheet, and by shifting the scanning area of ​​the continuous wave laser beam at predetermined intervals, and the method is repeated. The average power of the continuous wave laser beam is represented by P (W), the scanning speed by Vc (mm / s), the predetermined interval by PL (mm), and the input energy Ua is represented by Ua = P / (Vc × PL) (mJ / mm 2 ), 1.0 mm ≦ PL ≦ 3.0 mm, and 0.8 mJ / mm 2 ≦Ua≦2.0mJ / mm 2The present invention discloses a method for producing a grain-oriented electrical steel sheet in which magnetic domains are controlled by irradiation with laser light, which satisfies the above conditions. Patent Document 1 shows that it is possible to easily reduce iron loss in both the L-direction and C-direction of a grain-oriented electrical steel sheet while ensuring high productivity.

[0004] However, for example, when manufacturing a wound core, grain-oriented electrical steel sheets are bent and shaped, which requires stress relief annealing. Therefore, in the method of introducing strain into the surface by laser irradiation as described above, the strain introduced into the grain-oriented electrical steel sheets is released by stress relief annealing. As a result, the effect of magnetic domain refinement by laser irradiation is lost. For this reason, it has been proposed to form grooves on the steel sheet surface to subdivide the magnetic domain width in the same way as introducing strain, thereby reducing eddy current loss. In such cases, the grooves do not disappear even after stress relief annealing, so the effect of magnetic domain refinement is not lost. Methods for forming grooves in steel sheets include, for example, an electrolytic etching method in which grooves are formed on the surface of a grain-oriented electrical steel sheet by electrolytic etching, a gear pressing method in which grooves are formed on the surface of a grain-oriented electrical steel sheet by mechanically pressing a gear onto the surface of the grain-oriented electrical steel sheet, and a laser irradiation method in which grooves are formed by melting and evaporating the steel sheet (laser-irradiated portion) by laser irradiation. For example, Patent Document 2 discloses a method for improving the iron loss characteristics of grain-oriented electrical steel sheet that can withstand stress relief annealing, in which a laser beam is controlled and irradiated to form recesses with a width of 0.5 mm or less in the rolling direction and a depth of 10 μm or more.

[0005] Generally, grain-oriented electrical steel sheets have an insulating coating formed on their surfaces to provide electrical insulation, tensile strength, heat resistance, and other properties. As described in Patent Document 2, grain-oriented electrical steel sheets have grooves formed substantially parallel to the width of the steel sheet, thereby dividing the magnetic domain width and reducing iron loss. Meanwhile, the width and depth of the longitudinal ends of the formed grooves (near the beginning and end) vary compared to the center. This makes it difficult to apply a coating solution to every corner of the groove ends, resulting in insufficient adhesion of the insulating coating at the groove ends. Because the length of the region where the width and depth change at the groove ends is a relatively small proportion of the overall length of the groove, poor adhesion of the insulating coating in this region is not thought to have a significant impact on magnetic properties. However, poor adhesion of the insulating coating at the groove ends may expose the steel substrate to the surface, potentially causing rust. Furthermore, when grain-oriented electrical steel sheets are stacked, significant interlaminar currents may flow in these exposed steel substrate regions, potentially increasing iron loss. However, Patent Document 2 does not consider such exposure of the base steel or the occurrence of rust.

[0006] As a technique for controlling the shape of the groove ends, for example, Patent Document 3 discloses a technique for suppressing etching of the widthwise ends of a steel strip in a manufacturing method for grain-oriented silicon steel sheet in which linear or dotted grooves are formed on the surface of the steel strip, thereby making the groove depth at the widthwise ends 70% or less of the groove depth at the widthwise center.

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

[0008] Patent Document 5 also discloses a grain-oriented electrical steel sheet that includes linear grooves formed on one or both surfaces of the electrical steel sheet in a direction intersecting the rolling direction, the grooves including a sloping portion (GS) and a flat portion (US) in a cross section including the longitudinal direction of the groove and the normal direction to the rolling surface of the steel sheet, and the lengths of the sloping portion and the flat portion satisfy a predetermined relationship. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent No. 4669565 [Patent Document 2] Japanese Patent Publication No. 6-57335 [Patent Document 3] Japanese Patent No. 4016431 [Patent Document 4] Japanese Patent No. 6418322 [Patent Document 5] Japan Patent Application No. 2022-503782 Summary of the Invention [Problem to be solved by the invention]

[0010] However, in Patent Document 3, the reason for suppressing etching of the widthwise ends of the steel strip and making the groove depth at the widthwise ends 70% or less of the groove depth at the widthwise center is to prevent the steel strip from breaking in subsequent processes when linear grooves are introduced by electrolytic etching, and there is no mention of the adhesion or rust resistance of the insulating coating at the groove ends. Furthermore, Patent Document 4 makes no mention of the width and depth of the groove at the groove end, and as a result of investigations by the inventors, it was found that it is not necessarily possible to improve the adhesion and rust resistance of the insulating coating at the groove end. Furthermore, Patent Document 5 does not mention anything about the width of the groove at the groove end, and as a result of investigations by the present inventors, it was found that it is not necessarily possible to improve the adhesion or rust resistance of the insulating coating at the groove end, and that it is not necessarily possible to suppress the reduction in magnetic flux density due to the formation of the groove.

[0011] As described above, in the past, in grain-oriented electrical steel sheets in which magnetic domain refinement is performed by forming grooves, techniques have been proposed for improving the adhesion and rust resistance of the insulating coating at the groove ends, but it cannot be said that sufficient research has been conducted on these techniques. Therefore, an object of the present invention is to provide a grain-oriented electrical steel sheet that has high adhesion of an insulating coating even at the groove ends and is excellent in rust resistance. [Means for solving the problem]

[0012] The inventors have investigated methods for improving the adhesion of insulating coatings at the groove ends, and have found that the adhesion and rust resistance of insulating coatings and the like can be improved by shaping the grooves so that the depth and width become shallower and narrower toward the end of the groove in the longitudinal direction (groove longitudinal direction) and by shaping the grooves so that the depth and width satisfy a certain relationship.

[0013] The present invention has been made based on the above findings. The gist of the present invention is as follows. [1] A grain-oriented electrical steel sheet according to one aspect of the present invention comprises a base steel sheet, and optionally a forsterite film formed on the base steel sheet, and an insulating film formed on the base steel sheet or on the forsterite film, wherein the base steel sheet has a plurality of grooves extending in a direction intersecting the rolling direction, the direction in which the grooves extend is defined as the groove longitudinal direction, the distance from an imaginary line extending from the surface of the base steel sheet to the groove 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, and a position where the groove depth is 0.0 μm is defined as the groove length. , the end of the groove, and a region 5 mm from the end of the groove toward the center in the longitudinal direction of the groove is defined as the groove end, and the depth of the groove at a position 1 mm from the end of the groove in the longitudinal direction of the groove at the groove end is defined as D1, the width of the groove is defined as W1, the depth of the groove at a position 2 mm from the end of the groove is defined as D2, the width of the groove is defined as W2, the depth of the groove at a position 3 mm from the end of the groove is defined as D3, the width of the groove is defined as W3, the depth of the groove at a position 4 mm from the end of the groove is defined as D4, the width of the groove is defined as W4, the depth of the groove at a position 5 mm from the end of the groove is defined as D5, the width of the groove is defined as W5, and The range is ±10mm from the center. When the average groove width at the center is Wc and the average groove depth is Dc, D1, D2, D3, D4, D5, W1, W2, W3, W4, and W5 satisfy the following formulas (1) and (2). When the groove width at a portion where the groove depth is 0.05×Dc at the groove end is W0.05 and the groove width at a portion where the groove depth is 0.50×Dc is W0.50, W0.05 and W0.50 satisfy the following formulas (3) and (4). death , The Dc is 5.0 to 40.0 μm, the Wc is 10.0 to 200.0 μm, the intervals between the plurality of grooves in the rolling direction are 2 to 10 mm, and the angle between the longitudinal direction of the groove and the rolling direction is 60 to 120 degrees. . 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] In the grain-oriented electrical steel sheet described in [1], the W0.05 and W0.50 may satisfy the following formulas (5) and (6). 0.008≦W0.05 / Wc≦0.160 (5) 0.380≦W0.50 / Wc≦0.710 (6) [3] In the grain-oriented electrical steel sheet according to [1], the D1, D2, D3, D4, and D5 may satisfy the following formula (1'). D5>D4>D3>D2>D1 (1') [4] In the grain-oriented electrical steel sheet according to [2], the D1, D2, D3, D4, and D5 may satisfy the following formula (1'). D5>D4>D3>D2>D1...(1' ) [ 5 A method for producing a grain-oriented electrical steel sheet according to one aspect of the present invention comprises: a groove forming step of irradiating a steel sheet with a laser while scanning the steel sheet in a direction intersecting the rolling direction to form grooves extending in the rolling direction; a decarburization annealing step of decarburization annealing the steel sheet after the groove forming step; a finish annealing step of finish annealing the steel sheet after the decarburization annealing step; and an insulating film forming step of performing a process of forming an insulating film on the steel sheet after the finish annealing step to become a base steel sheet, to obtain a grain-oriented electrical steel sheet having the base steel sheet, a forsterite film arbitrarily formed on the base steel sheet, and the insulating film formed on the base steel sheet or on the forsterite film, wherein in the groove forming step, the extending direction of the groove is defined as the groove longitudinal direction, and the groove is defined as a virtual extension of the surface of the base steel sheet. The distance from the imaginary line to the groove on the straight line extending from the imaginary line in the thickness direction of the base steel plate 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 region 5 mm from the groove end toward the center in the longitudinal direction of the groove is defined as the groove end, and the groove depth at a position 1 mm from the groove end in the longitudinal direction of the groove, in μm, is defined as D1, the groove width is defined as W1, the groove depth at a position 2 mm from the groove end is defined as D2, the groove width is defined as W2, the groove depth at a position 3 mm from the groove end is defined as D3, the groove width is defined as W3, the groove depth at a position 4 mm from the groove end is defined as D4, the groove width is defined as W4, the groove depth at a position 5 mm from the groove end is defined as D5, the groove width is defined as W5, and the groove length in the longitudinal direction of the groove is defined as The range is ±10mm from the center.When the average groove width at the center is Wc and the average groove depth is Dc, the laser is irradiated to form the groove so that D1, D2, D3, D4, D5, W1, W2, W3, W4, and W5 satisfy the following formulas (1) and (2) by changing the distance between the focal point of the laser and the surface of the base steel sheet at the groove end portion according to the distance from the groove end, and so that W0.05 and W0.50 satisfy the following formulas (3) and (4) at the groove end portion where the groove depth is 0.05×Dc and W0.50, respectively. death , In the groove forming step, the laser irradiation conditions are set to a laser output of 200 to 3000 W, a focused spot diameter of 10 to 1000 μm, which is a diameter including 86% of the laser output in the rolling direction, a focused spot diameter of 10 to 1000 μm in the sheet width direction, and a scanning speed of 2 to 50 m / s, and grooves are formed so that Dc is 5.0 to 40.0 μm and Wc is 10.0 to 200.0 μm, and the grooves are formed so that the intervals between the plurality of grooves in the rolling direction are 2 to 10 mm, and the angle between the groove longitudinal direction and the rolling direction is 60 to 120 degrees. . 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) [ 6 ][ 5 In the method for producing a grain-oriented electrical steel sheet according to the present invention, in the groove forming step, the grooves may be formed so that the W0.05 and the W0.50 satisfy the following formulas (5) and (6). 0.008≦W0.05 / Wc≦0.160 (5) 0.380≦W0.50 / Wc≦0.710 (6 ) [Effects of the Invention]

[0014] According to the above aspect of the present invention, a grain-oriented electrical steel sheet having high adhesion of the insulating coating even at the groove ends and excellent rust resistance can be obtained. [Brief explanation of the drawings]

[0015] [Figure 1] 10A and 10B are diagrams showing examples of groove formation in the grain-oriented electrical steel sheet according to the present embodiment. [Figure 2A]FIG. 2 is a schematic diagram of a cross section of the grain-oriented electrical steel sheet according to the present embodiment, parallel to the rolling direction and the sheet thickness direction, including a groove. [Figure 2B] 1 is a schematic diagram of a cross section of a grain-oriented electrical steel sheet according to an embodiment of the present invention, the cross section being parallel to the sheet thickness direction and the direction in which the grooves extend and passing through the center of the width of the grooves. FIG. [Figure 3A] FIG. 1 is a schematic diagram of a cross section of the grain-oriented electrical steel sheet according to the present embodiment, parallel to the rolling direction and the sheet thickness direction, including the grooves, after the insulating coating has been removed to measure the width and depth of the grooves. [Figure 3B] FIG. 1 is a schematic diagram of a cross section of a grain-oriented electrical steel sheet according to an embodiment of the present invention, parallel to the sheet thickness direction and the direction in which the grooves extend, and passing through the center of the groove width, after the insulating coating has been removed to measure the groove width and depth. DETAILED DESCRIPTION OF THE INVENTION

[0016] A grain-oriented electrical steel sheet according to one embodiment of the present invention (grain-oriented electrical steel sheet according to this embodiment) and a method for manufacturing the same will be described.

[0017] As shown in FIGS. 1, 2A, and 2B, the grain-oriented electrical steel sheet 1 according to this embodiment includes a base steel sheet 2 and an insulating coating 3 formed on the base steel sheet 2. Alternatively, although not shown in the figure, a forsterite film may be present between the base steel sheet 2 and the insulating film 3. That is, the steel sheet may include a base steel sheet 2, a forsterite film formed on the base steel sheet 2, and an insulating film 3 formed on the forsterite film. In the grain-oriented electrical steel sheet 1 according to this embodiment, the base steel sheet 2 has a plurality of grooves extending in a direction intersecting the rolling direction. Each of the grooves has a predetermined shape, which will be described later, at the groove end portion, which is a region extending 5 mm from the groove end E toward the center in the longitudinal direction of the groove. This will be explained in detail below.

[0018] For the purpose of explanation, in this embodiment, the direction in which the groove extends is referred to as the groove longitudinal direction. The groove depth is the distance from an imaginary line extending from the surface of the base steel sheet to the groove (groove bottom), and the width of the groove in the rolling direction is referred to as the groove width. The position where the groove depth is 0.0 μm is referred to as the groove end, and the region 5 mm from the groove end toward the center in the groove longitudinal direction is referred to as the groove end. In addition, the groove depth at a position 1 mm from the groove end in the groove longitudinal direction at the groove end, in μm, is referred to as D1, the groove width is referred to as W1, the groove depth at a position 2 mm from the groove end is referred to as D2, the groove width is referred to as W2, the groove depth at a position 3 mm from the groove end is referred to as D3, the groove width is referred to as W3, the groove depth at a position 4 mm from the groove end is referred to as D4, the groove width is referred to as W4, and the groove depth at a position 5 mm from the groove end is referred to as D5, the groove width is referred to as W5. Furthermore, the average width of the groove at the center in the longitudinal direction of the groove is defined as Wc, and the average depth of the groove is defined as Dc.

[0019] <Grain-oriented electrical steel sheet> [Base material steel plate] (groove) In grain-oriented electrical steel sheets, grooves are formed parallel to the width of the steel sheet to reduce iron loss. However, conventionally, the width and depth of the longitudinal edges of the grooves (near the start and end) differ from those of the center, resulting in insufficient adhesion of the insulating coating in some areas. In contrast, in the grain-oriented electrical steel sheet 1 according to this embodiment, at the groove end portion of the groove G formed in the base steel sheet 2, which is a region extending 5 mm from the end E of the groove (the position where the groove depth is 0.0 μm) toward the center in the longitudinal direction of the groove, the groove depth becomes shallower and the groove width becomes narrower as it approaches the tip (end E) in the longitudinal direction of the groove, and the groove depth and groove width are shaped to satisfy a predetermined relationship, thereby improving the adhesion of the insulating coating. More specifically, when groove depths D1 to D5 and groove widths W1 to W5 at positions 1 to 5 mm from the groove end at the groove end satisfy the following formulas (1) and (2) (where D5 ≠ D1 and W5 ≠ W1), and when the groove width at the groove end where the groove depth is 0.05 × Dc is W0.05 and the groove width at the groove end where the groove depth is 0.50 × Dc is W0.50, the adhesion of an insulating coating or the like is improved by W0.05 and W0.50 satisfying the following 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)

[0020] Although it is not clear why the adhesion of the insulating coating improves when the groove shape satisfies formulas (1) to (4) at the groove ends, it is thought that this is because when formulas (1) to (4) are satisfied, the groove width and depth at the groove ends change gradually, making it easier to apply the coating solution to every corner of the groove. Furthermore, when the above conditions are satisfied, the amount of base steel lost by the grooves is reduced, which also has the effect of increasing magnetic flux density.

[0021] As described above, in the base steel sheet 2 of the grain-oriented electrical steel sheet 1 according to this embodiment, the groove depth becomes shallower and the groove width becomes narrower toward the end in the longitudinal direction of the groove. As can be seen from equations (1) and (2), the groove depth and groove width may change continuously (D5>D4>D3>D2>D1), but there may also be a region where they do not change within a certain range (for example, D5=D4≧D3=D2≧D1). If formula (1) and / or formula (2) are not satisfied, the depth and width of the groove will change suddenly at the end of the groove in the longitudinal direction, making it difficult to apply the coating solution in that area, which is thought to result in a decrease in the adhesion of the insulating coating.

[0022] Furthermore, as shown in formulas (3) and (4), in the base steel sheet 2 of the grain-oriented electrical steel sheet 1 according to this embodiment, the width of the groove is narrower in areas where the groove depth is shallower. If formula (3) and / or formula (4) are not satisfied, that is, if the degree of change in groove depth and the degree of change in groove width at the groove end differ greatly, there will be areas where the groove width is narrow but the groove depth is deep, making it difficult to apply the coating solution in those areas, which is thought to result in reduced adhesion of the insulating coating.

[0023] W0.05 and W0.50 preferably satisfy the formulas (3') and (4'), more preferably satisfy the formulas (5') and (6), and further 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 adhesiveness of the insulating film is further improved.

[0024] The shape of the grooves other than the groove ends is not limited, but it is preferable that the average groove depth Dc at the center in the longitudinal direction of the groove is 5.0 to 40.0 μm and the average groove width Wc is 10.0 to 200.0 μm. By setting the range to this, the effect of reducing iron loss due to magnetic domain refinement is increased.

[0025] The intervals S between the plurality of grooves G in the rolling direction RD are preferably 2 to 10 mm. The groove interval S 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 between the plurality of grooves G do not have to be equal as long as they are within the above range, but are preferably equal. The angle between the groove extension direction (groove longitudinal direction) and the rolling direction is preferably 60 to 120 degrees. Since it is preferable that the angle is closer to a direction perpendicular to the rolling direction, it is more preferable that the angle is 75 to 115 degrees with respect to the rolling direction. It is preferable that the multiple grooves are approximately parallel to each other. When the groove extension direction and spacing are within the above ranges, the iron loss reduction effect is increased. The shape of the groove is not limited, and for example, the cross section may be approximately rectangular or approximately triangular. The cross section may also be arch-shaped, constituting a part of a circle.

[0026] The grooves are linear and extend in the width direction of the grain-oriented electrical steel sheet. The grooves may be formed over the entire width direction of the grain-oriented electrical steel sheet, or may be formed only in a part of the width direction.

[0027] The groove depths (D1 to D5) and widths (W1 to W5) at the groove ends are measured using a laser microscope (a 3D laser microscope using a pinhole confocal optical system). If the grain-oriented electrical steel sheet has an insulating coating, the groove depth and width are measured on the surface of the base steel sheet excluding this coating. Specifically, the insulating film on the grain-oriented electrical steel sheet can be removed by, for example, the following method: The grain-oriented electrical steel sheet with the insulating film is immersed in an 80°C aqueous sodium hydroxide solution consisting of 30% by mass of NaOH and 70% by mass of HO for 20 minutes, and then rinsed with water. Finally, the sheet is dried for 1 minute using a hot air blower. After removing the insulating coating as described above, a measured profile curve defining the groove contour is obtained by measurement using a laser microscope in a cross section parallel to the thickness direction and the groove extension direction and passing through the center of the groove width. A low-pass filter with a cutoff value λs is applied to this measured profile curve to obtain a profile curve, and bandpass filters with cutoff values ​​λf and λc are then applied to the profile curve to remove long and short wavelength components. This results in a waviness curve (WCL) defining the groove contour in a cross section parallel to the thickness direction and the groove extension direction and passing through the center of the groove width, as shown in Figure 3B. A waviness curve is a type of profile curve suitable for simplifying the contour shape itself with a smooth line. On the waviness curve WCL, an imaginary line IL is drawn in the extension direction of the groove (left and right on the paper) extending from the surface of the base steel sheet, and the start point of the imaginary line IL, i.e., the position where the groove depth is 0.0 μm, is defined as the groove end E. At a position 1 mm from the groove end E in the extension direction of the groove (rightward on the paper), the linear distance between the imaginary line IL and the base steel sheet 2 is found, and this is defined as the groove depth D1. Furthermore, at the position where the groove depth D1 was determined, a measured profile curve forming the groove outline in a cross section parallel to the rolling direction and plate thickness direction is obtained by measurement using a laser microscope. A low-pass filter with cutoff value λs is applied to this measured profile curve to obtain a profile curve, and then bandpass filters with cutoff values ​​λf and λc are applied to the profile curve to remove long and short wavelength components from the profile curve, resulting in a waviness curve WCT forming the groove outline in a cross section parallel to the rolling direction and plate thickness direction, as shown in Figure 3A. In the waviness curve WCT, the length of an imaginary line IL extending along the surface of the base steel plate in the rolling direction is determined, and this is defined as the groove width W1. In a similar manner, groove depths D2, D3, D4, and D5 and groove widths W2, W3, W4, and W5 are determined at positions 2 mm, 3 mm, 4 mm, and 5 mm from the end E of the groove in the extension direction of the groove.

[0028] The average groove depth Dc and average groove width Wc at the center in the longitudinal direction of the groove are measured using a laser microscope in the same manner as the groove depth and width at the groove ends. The groove depth and width are measured at five arbitrary points in the center in the longitudinal direction of one groove (within a range of ±10 mm from the center), and the average values ​​are taken as the average groove depth Dc and the average groove width Wc.

[0029] At the groove end, the groove width W0.05 at a portion where the groove depth is 0.05×Dc and the groove width W0.50 at a portion where the groove depth is 0.50×Dc are measured using a laser microscope. As shown in Figure 3B, the waviness curve WCL defining the groove profile in a cross section parallel to the thickness direction and the groove extension direction and passing through the center of the groove width is used to determine the linear distances from the groove end E to positions where the groove depths are 0.05 × Dc and 0.50 × Dc. At each position, a measured profile curve defining the groove profile in a cross section parallel to the rolling direction and thickness direction is obtained by measurement using a laser microscope. A low-pass filter with a cutoff value λs is applied to this measured profile curve to obtain a profile curve. Bandpass filters with cutoff values ​​λf and λc are then applied to the profile curve to remove long and short wavelength components, resulting in a waviness curve WCT for a cross section parallel to the rolling and thickness directions. The lengths of the imaginary lines IL extending along the surface of the base steel plate in the rolling direction are determined on each waviness curve WCT, and these are designated W0.05 and W0.50.

[0030] When a plurality of grooves are formed in the base steel sheet, it is preferable that all of the grooves satisfy the formulas (1) to (4), and it is even more preferable that the formulas (3') and (4'), or the formulas (5) and (6), or the formulas (5') and (6'), are satisfied. When grooves are repeatedly formed at equal intervals in the rolling direction under the same conditions, if one groove satisfies formulas (1) to (4), it is considered that the other grooves also satisfy formulas (1) to (4). However, if a groove is formed to the end of the width of the base steel plate, the groove end E does not exist at the end of that groove, and therefore the above-mentioned measurement is not performed (the groove is not considered to be the target of measurement).

[0031] (chemical composition) The chemical composition of the base steel sheet of the grain-oriented electrical steel sheet is not limited, and may be the same as that of the base steel sheet of a known grain-oriented electrical steel sheet. For example, the chemical composition may contain, in mass %, Si: 2.50 to 4.50%, Mn: 0.010 to 0.150%, C: 0 to 0.085%, acid-soluble Al: 0 to 0.065%, N: 0 to 0.012%, Cr: 0 to 0.30%, Cu: 0 to 0.40%, P: 0 to 0.50%, Sn: 0 to 0.30%, Sb: 0 to 0.30%, Ni: 0 to 1.00%, S: 0 to 0.015%, Se: 0 to 0.015%, Bi: 0 to 0.10%, Nb: 0 to 0.10%, V: 0 to 0.10%, Mo: 0 to 0.10%, Ta: 0 to 0.10%, W: 0 to 0.10%, B: 0 to 0.080%, and Ti: 0 to 0.10%. Alternatively, it may contain the above with the balance being Fe and impurities.

[0032] The chemical composition of grain-oriented electrical steel sheets (base steel sheets) can be measured using common steel analysis methods. For example, chemical components can be measured using inductively coupled plasma-atomic emission spectrometry (ICP-AES). When a forsterite film and an insulating film (described later) are formed, the chemical composition of the base steel sheet can be analyzed by removing the insulating film from the grain-oriented electrical steel sheet using the method described above, and then removing the forsterite film using a known method such as pickling. Specifically, for example, a 35 mm square (35 mm × 35 mm) test piece can be obtained from the center of the base steel sheet after removing the film if necessary, and analyzed using a measuring device such as Shimadzu's ICPS-8100 under conditions based on a pre-established calibration curve. C and S, which are difficult to measure using ICP-AES, can be measured using the combustion-infrared absorption method, and N can be measured using the inert gas fusion-thermal conductivity method.

[0033] (plate thickness) The thickness of the base steel sheet of the grain-oriented electrical steel sheet is not limited, but is preferably 0.15 to 0.30 mm. If the base steel sheet thickness exceeds 0.30 mm, classical eddy current loss increases, resulting in increased iron loss. On the other hand, if the thickness is less than 0.15 mm, the rolling efficiency decreases, which is disadvantageous in terms of productivity and cost.

[0034] [Forsterite film] [Insulating film] The grain-oriented electrical steel sheet according to this embodiment may be composed of a base steel sheet and an insulating coating formed on the surface of the base steel sheet, or a forsterite coating 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 coating. That is, the grain-oriented electrical steel sheet according to this embodiment may be composed of a base steel sheet, a forsterite film formed on the base steel sheet, and an insulating film formed on the forsterite film. The forsterite film and the insulating film may be formed on one surface or both surfaces. The forsterite film is an inorganic film mainly composed of magnesium silicate. The forsterite film is formed during finish annealing by a reaction between an annealing separator containing magnesia (MgO) applied to the surface of the base steel sheet and the components on the surface of the base steel sheet, and has a composition derived from the components of the annealing separator and the base steel sheet (more specifically, a composition mainly composed of Mg2SiO4). On the other hand, when an annealing separator mainly containing Al2O3 is used in the final annealing, a forsterite film may not be formed. The insulating coating provides electrical insulation and tension to the grain-oriented electrical steel sheet. By applying tension to the grain-oriented electrical steel sheet, it is possible to reduce the iron loss of the grain-oriented electrical steel sheet by facilitating domain wall movement in the grain-oriented electrical steel sheet. Furthermore, in addition to the electrical insulation and tensile strength described above, the insulating film also provides various other properties such as rust resistance, heat resistance, and slipperiness. In the grain-oriented electrical steel sheet according to this embodiment, the insulating coating may be a known coating formed, for example, by applying a coating solution containing phosphate and colloidal silica as its main components to the surface of the base steel sheet or the forsterite coating and baking it (treatment for forming an insulating coating).

[0035] <Manufacturing method> The grain-oriented electrical steel sheet according to this embodiment can achieve the above-described effects as long as it has the characteristics regardless of the manufacturing method, but a manufacturing method including the following steps is preferred because it can be manufactured stably. (I) a groove forming step of forming a plurality of grooves extending in a direction intersecting the rolling direction in the steel sheet at predetermined intervals 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; (IV) An insulating film forming process in which an insulating film is formed on the steel sheet (in some cases, a forsterite film is formed on the base steel sheet) after the finish annealing process, which becomes the base steel sheet, to obtain a grain-oriented electrical steel sheet having the base steel sheet, a forsterite film formed on any of the base steel sheets, and the insulating film formed on the base steel sheet or the forsterite film. Furthermore, when the steel sheet to be subjected to the groove forming step is a cold-rolled steel sheet, it can be produced by a production method including the following steps. (V) a hot rolling step in which the slab is heated and hot-rolled to form 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; (VII) A cold rolling step of pickling and cold rolling the hot rolled steel sheet after the hot rolled steel sheet annealing step to obtain a cold rolled steel sheet.

[0036] The groove forming process, which is characteristic for obtaining the grain-oriented electrical steel sheet according to this embodiment, will be described below. The other processes will not be described here because they can be carried out by setting known conditions according to the target magnetic flux density before groove formation. However, in the final annealing process, an annealing separator consisting mainly of MgO or Al2O3 is generally applied before final annealing. For example, if an annealing separator consisting mainly of MgO is used, a forsterite (Mg2SiO4) film layer is formed. If an annealing separator consisting mainly of Al2O3 is used, a forsterite film may not be formed. Therefore, the annealing separator may be selected depending on whether or not the formation of a forsterite film is required.

[0037] The chemical composition of the slab to be subjected to hot rolling may be determined in accordance with the desired chemical composition of the grain-oriented electrical steel sheet, taking into consideration changes in the chemical composition in each process. For example, when obtaining the chemical composition of the base steel sheet of the grain-oriented electrical steel sheet according to the preferred embodiment described above, it is preferable to use a slab having the following chemical composition. That is, the chemical composition of the slab is, in mass%, 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 It may contain: Ni: 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%. It may also contain the above, with the balance being Fe and impurities.

[0038] (Groove formation process) In the groove forming process, a plurality of grooves extending in a direction intersecting the rolling direction are formed in a steel plate such as a hot-rolled steel plate or a cold-rolled steel plate at predetermined intervals in the rolling direction. The grooves extending in a direction intersecting the rolling direction can be formed by irradiating the surface with a laser while scanning in a direction intersecting the rolling direction. Furthermore, by repeatedly shifting the area scanned with the laser light at predetermined intervals in the rolling direction, a plurality of grooves are formed at predetermined intervals in the rolling direction. When forming a groove, the laser is irradiated to form a groove by changing the distance between the focus of the laser and the surface of the base steel sheet at the groove end depending on the distance from the end of the groove so that D1, D2, D3, D4, D5, W1, W2, W3, W4 and W5 satisfy the following formulas (1) and (2), and also so that when the groove width at the groove end where the groove depth is 0.05 × Dc is W0.05 and the groove width at the groove end where the groove depth is 0.50 × Dc is W0.50, W0.05 and W0.50 satisfy the following formulas (3) and (4). Preferably, the groove is formed so that W0.05 and W0.50 satisfy the following formulas (3') and (4'), (5) and (6), or (5') and (6'). By forming grooves that satisfy formulas (1) to (4), the adhesion of the insulating film formed in a subsequent process is improved, and a grain-oriented electrical steel sheet with excellent adhesion of the insulating film can be manufactured. 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 forming grooves by laser irradiation, by shifting the laser focus away from the surface of the steel sheet, the laser energy at the surface of the steel sheet is reduced, resulting in a shallower groove depth and narrower groove width. Therefore, the distance between the laser focus and the surface of the base steel sheet is changed depending on the distance from the edge of the groove. That is, at the start of laser irradiation of one groove, the laser focus is set to a position away from the surface of the steel sheet, and by gradually moving the focus to match the surface of the steel sheet as the scanning progresses, the groove depth and width can be changed within a certain range from the start point of the groove. Similarly, at the end of laser irradiation of one groove, the laser focus is moved to a position away from the surface of the steel sheet, thereby changing the groove depth and width within a certain range from the end point of the groove. In addition, the groove depth and width can be changed by changing the laser output, focal spot diameter, and scanning speed. The groove depth and groove width can be changed independently depending on the conditions to be changed, so the conditions are set in combination so that the groove depth and groove width satisfy formulas (1) to (4). Methods for moving the laser focus include displacing the position of an optical component.

[0040] In the groove forming step, from the viewpoint of magnetic domain refinement, it is preferable to form grooves so that the average groove depth Dc at the center in the groove longitudinal direction is 5.0 to 40.0 μm and the average groove width Wc is 10.0 to 200.0 μm. In the groove forming step, the laser irradiation conditions are not limited, but in areas other than the groove ends, it is preferable that the laser output is 200 to 3000 W, the focused spot diameter, which is the diameter including 86% of the laser output in the rolling direction, is 10 to 1000 μm, the focused spot diameter in the plate width direction is 10 to 1000 μm, and the scanning speed is 2 to 50 m / s. In this case, it becomes easy to form grooves in which Dc and Wc fall within the preferred ranges.

[0041] In the groove forming step, it is preferable to form the grooves so that the intervals between the grooves in the rolling direction are 2 to 10 mm and the angle between the groove longitudinal direction and the rolling direction is 60 to 120 degrees (°). In this case, the iron loss reduction effect is increased. [Example]

[0042] A slab having a chemical composition containing, in mass%, 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%, S: 0.007%, with the remainder being Fe and impurities, was hot-rolled to form a hot-rolled steel sheet with a thickness of 2.6 mm. This hot-rolled steel sheet was annealed by heating to 1100°C and holding for 1 minute. The hot-rolled steel sheet after annealing was pickled and cold-rolled to obtain a cold-rolled steel sheet having a thickness of 0.22 mm. The obtained cold-rolled steel sheets were irradiated with a laser under the various conditions shown in Table 1 to form multiple grooves (the laser irradiation conditions were the same within a single cold-rolled steel sheet). The groove ends were gradually changed in depth and width by displacing the position of the polygon mirror. After the grooves were formed, the cold-rolled steel sheets were subjected to decarburization annealing by heating to 850°C and holding for 2 minutes. After decarburization annealing, the cold-rolled steel sheet was coated with an annealing separator mainly composed of magnesia (MgO), heated to 1200°C, and held for 20 hours for finish annealing. As a result, a steel sheet was obtained in which a forsterite film was formed on the surface of the cold-rolled steel sheet (base steel sheet). Next, a coating solution containing colloidal silica and aluminum phosphate was applied to the forsterite film, and the resulting insulating film was formed by heat treatment at 850°C for 1 minute. The insulating film had a thickness of 5 μm. A sample measuring 60 mm in the width direction and 300 mm in the rolling direction was taken from the obtained grain-oriented electrical steel sheet, and a single sheet magnetic property test (SST test) was performed on this sample in accordance with JIS C2556 (2015), and the magnetic flux density B8 generated when magnetized at 800 A / m was measured.

[0043] A 30 mm × 30 mm test piece was taken from the resulting grain-oriented electrical steel sheet in a portion including the groove ends, and the insulating coating was removed using the method described above. Then, for one representative groove, the average groove depth Dc at the center in the longitudinal direction of the groove, the average groove width Wc, and the groove depths D1 to D5 and groove widths W1 to W5 at positions 1 mm to 5 mm from the groove ends were measured using the method described above. Furthermore, for the same groove, the groove width W0.05 at the groove end where the groove depth was 0.05 × Dc, and the groove width W1 at the groove depth 0.50 × Dc were measured using the method described above. The results are shown in Table 2.

[0044] The adhesiveness of the insulating film and the rust resistance of the obtained grain-oriented electrical steel sheets were evaluated by the following methods. The results are shown in Table 3.

[0045] <Insulating film adhesion> A test piece of 80 mm x 80 mm was cut out from a portion of the obtained grain-oriented electrical steel sheet including the end of the groove, wrapped around a round bar of 20 mm diameter, and then flattened. The surface of the test piece after flattening was observed, and the area of ​​the insulating coating that had not peeled off from the steel sheet relative to the area of ​​the bent part was measured to calculate the remaining coating area ratio (%). The adhesion of the insulating coating of test pieces with a remaining coating area rate of 95% or more was rated as "excellent (Ex)", the adhesion of the insulating coating of test pieces with a remaining coating area rate of 90% or more but less than 95% was rated as "good (G)", and the adhesion of the insulating coating of test pieces with a remaining coating area rate of less than 90% was rated as "poor (P)".

[0046] <Rust resistance> A 30mm x 30mm test piece was taken from the portion of the resulting grain-oriented electrical steel sheet that included the groove end, and the test piece was left in an atmosphere of 50°C and 91% humidity for one week, and the test piece was evaluated based on the weight change before and after. Since the weight of the test piece increases when rust occurs, it was determined that the smaller the weight increase, the better the rust resistance. Specifically, the weight gain is 1.0 mg / m 2The rust resistance of the following test specimens was evaluated as "excellent (Ex)" and the weight gain was 5.0 mg / m 2 The rust resistance of the following test specimens was evaluated as "good (G)" and the weight increase was 5.0 mg / m 2 The rust resistance of over 100 test pieces was rated as "poor (P)."

[0047] [Table 1]

[0048] [Table 2]

[0049] [Table 3]

[0050] As can be seen from Tables 1 to 3, it was confirmed that the rust resistance and insulating coating adhesion of grain-oriented electrical steel sheets were improved by forming grooves that satisfied formulas (1) to (4). Furthermore, by forming grooves that satisfied formulas (3') and (4'), (5) and (6), or (5') and (6'), grain-oriented electrical steel sheets with further improved rust resistance and insulating coating adhesion were obtained. [Explanation of symbols]

[0051] 1 Grain-oriented electrical steel sheet 2 Base steel plate 3. Insulation coating G groove E End of groove D Groove depth (general term for D1, D2, D3, D4, D5, and Dc) W Groove width (general term for W1, W2, W3, W4, W5, and Wc) IL: An imaginary line extending from the surface of the base steel plate S groove spacing RD rolling direction TD Sheet width direction ND: Thickness direction of base steel plate [Industrial Applicability]

[0052] According to the present invention, it is possible to improve the rust resistance and insulating coating adhesion of a grain-oriented electrical steel sheet having grooves formed on the surface for the purpose of reducing iron loss. Therefore, by using the grain-oriented electrical steel sheet of the present invention, it is possible to prevent an increase in iron loss due to the generation of interlaminar current when steel sheets are stacked, and to prevent poor appearance.

Claims

1. A base steel plate; Optionally, a forsterite film formed on the base steel sheet; an insulating coating formed on the base steel sheet or the forsterite coating; Equipped with The base steel plate has a plurality of grooves extending in a direction intersecting the rolling direction, The direction in which the groove extends is defined as the groove longitudinal direction, The depth of the groove is the distance from a virtual line extending from the surface of the base steel plate to the groove, which is a straight line extending in the thickness direction of the base steel plate, to the virtual line, The width of the groove in the rolling direction is defined as the groove width, The position where the depth of the groove is 0.0 μm is defined as the end of the groove, and a region 5 mm from the end of the groove toward the center in the longitudinal direction of the groove is defined as a groove end portion, The groove depth at a position 1 mm from the end of the groove in the longitudinal direction of the groove at the groove end portion, in μm, is defined as D1, the groove width is defined as W1, the groove depth at a position 2 mm from the end of the groove is defined as D2, the groove width is defined as W2, the groove depth at a position 3 mm from the end of the groove is defined as D3, the groove width is defined as W3, the groove depth at a position 4 mm from the end of the groove is defined as D4, the groove width is defined as W4, and the groove depth at a position 5 mm from the end of the groove is defined as D5, the groove width is defined as W5, When the average width of the groove at the central portion within a range of the center ±10 mm in the longitudinal direction of the groove is Wc and the average depth of the groove is Dc, The D1, the D2, the D3, the D4, the D5, the W1, the W2, the W3, the W4, and the W5 satisfy the following formulas (1) and (2): When the width of the groove at a portion where the groove depth is 0.05×Dc at the groove end is W0.05 and the width of the groove at a portion where the groove depth is 0.50×Dc is W0.50, W0.05 and W0.50 satisfy the following formulas (3) and (4), The Dc is 5.0 to 40.0 μm, and the Wc is 10.0 to 200.0 μm, The intervals between the plurality of grooves in the rolling direction are 2 to 10 mm, and the angle between the longitudinal direction of the groove and the rolling direction is 60 to 120 degrees. A directional electrical steel sheet characterized by: 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. The W0.05 and the W0.50 satisfy the following formulas (5) and (6): The grain-oriented electrical steel sheet according to claim 1 , 0.008≦W0.05 / Wc≦0.160 (5) 0.380≦W0.50 / Wc≦0.710 (6)

3. The D1, D2, D3, D4, and D5 satisfy the following formula (1'): The grain-oriented electrical steel sheet according to claim 1 , D5>D4>D3>D2>D1...(1')

4. The D1, D2, D3, D4, and D5 satisfy the following formula (1'): The grain-oriented electrical steel sheet according to claim 2 , D5>D4>D3>D2>D1...(1')

5. a groove forming step of irradiating a steel sheet with a laser while scanning the steel sheet in a direction intersecting the rolling direction to form grooves 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 subjecting the steel sheet after the decarburization annealing step to finish annealing; an insulating film forming step of performing a process of forming an insulating film on the steel sheet after the finish annealing step that becomes a base steel sheet, to obtain a grain-oriented electrical steel sheet having the base steel sheet, a forsterite film optionally formed on the base steel sheet, and the insulating film formed on the base steel sheet or the forsterite film; Equipped with In the groove forming step, The direction in which the groove extends is defined as the groove longitudinal direction, The depth of the groove is the distance from a virtual line extending from the surface of the base steel plate to the groove, which is a straight line extending in the thickness direction of the base steel plate, to the virtual line, The width of the groove in the rolling direction is defined as the groove width, The position where the depth of the groove is 0.0 μm is defined as the end of the groove, and a region 5 mm from the end of the groove toward the center in the longitudinal direction of the groove is defined as a groove end portion, The groove depth at a position 1 mm from the end of the groove in the longitudinal direction of the groove at the groove end portion, in μm, is defined as D1, the groove width is defined as W1, the groove depth at a position 2 mm from the end of the groove is defined as D2, the groove width is defined as W2, the groove depth at a position 3 mm from the end of the groove is defined as D3, the groove width is defined as W3, the groove depth at a position 4 mm from the end of the groove is defined as D4, the groove width is defined as W4, and the groove depth at a position 5 mm from the end of the groove is defined as D5, the groove width is defined as W5, When the average width of the groove at the central portion within a range of the center ±10 mm in the longitudinal direction of the groove is Wc and the average depth of the groove is Dc, At the groove end, the distance between the focus of the laser and the surface of the base steel sheet is changed according to the distance from the end of the groove, so that D1, D2, D3, D4, D5, W1, W2, W3, W4, and W5 satisfy the following formulas (1) and (2), At the groove end, when the width of the groove at a portion where the groove depth is 0.05×Dc is W0.05 and the width of the groove at a portion where the groove depth is 0.50×Dc is W0.50, W0.05 and W0.50 are set so as to satisfy the following formulas (3) and (4): irradiating the laser to form the groove; In the groove forming process, the laser irradiation conditions are set to a laser output of 200 to 3000 W, a focused spot diameter which is a diameter including 86% of the laser output in the rolling direction of the laser of 10 to 1000 μm, a focused spot diameter in the sheet width direction of the laser of 10 to 1000 μm, and a scanning speed of 2 to 50 m / s, forming the groove so that the Dc is 5.0 to 40.0 μm and the Wc is 10.0 to 200.0 μm; The grooves are formed so that the intervals between the plurality of grooves in the rolling direction are 2 to 10 mm, and the angle between the longitudinal direction of the groove and the rolling direction is 60 to 120 degrees. A method for producing a grain-oriented electrical steel sheet. 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)

6. In the groove forming step, the groove is formed so that the W0.05 and the W0.50 satisfy the following formulas (5) and (6): The method for producing a grain-oriented electrical steel sheet according to claim 5 . 0.008≦W0.05 / Wc≦0.160 (5) 0.380≦W0.50 / Wc≦0.710 (6)

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