Grain-oriented electrical steel sheet and its manufacturing method

Abstract

In a surface of this grain-oriented magnetic steel plate, a ratio (a groove presence ratio), of a total length of magnetic-domain control processing lines aligned in a rolling direction and forming an angle of 0° to 45° with respect to a rolling perpendicular direction, occupied by a section (a groove formation line) where a groove having a depth of 5 μm to 50 μm and a width of 10 μm to 300 μm is present, is equal to or greater than 50% in a first region, which is a region where a β angle is equal to or less than 1°, the β angle being a deviation angle from a crystal grain Goss orientation around the axis of the rolling perpendicular direction. The groove presence ratio is less than 50% in a second region, which is a region where the β angle is greater than 2°.

Description

[Technical Field]

[0001] The present disclosure 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. 2022-052345, filed on March 28, 2022, the contents of which are incorporated herein by reference. [Background technology]

[0002] Grain-oriented electrical steel sheets contain 7 mass% or less of Si, and secondary recrystallized grains are formed in the {110} <001> This steel sheet has a secondary recrystallization texture concentrated in the Goss orientation. Grain-oriented electrical steel sheets are mainly used as iron cores for power transformers, and there is a growing need for reduced noise as well as reduced energy loss (iron loss).

[0003] To reduce iron loss, a magnetic domain refining technique has long been known in which the surface of grain-oriented electrical steel sheet is irradiated with a laser or electron beam in a direction intersecting the rolling direction to narrow the magnetic domain width. In recent years, various improved techniques for magnetic domain refining have been proposed in order to provide grain-oriented electrical steel sheet with good iron loss characteristics (see, for example, Patent Documents 1 to 5). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-57219 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-12664 [Patent Document 3] Japanese Patent Application Laid-Open No. 2012-77380 [Patent Document 4] Japanese Patent Application Laid-Open No. 2012-126973 [Patent Document 5] Patent No. 3148092 [Patent Document 6] International Publication No. 2016 / 056501 [Patent Document 7] International Publication No. 2013-160955 [Patent Document 8] Japanese Patent Application Laid-Open No. 2015-206114 [Patent Document 9] Japanese Patent Application Laid-Open No. 2012-57219 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when grain-oriented electrical steel sheets are subjected to magnetic domain refinement, the magnetostriction characteristics change due to closure domains, resulting in problems such as increased transformer noise. Because there is a trade-off between reducing iron loss and reducing noise in grain-oriented electrical steel sheets, an optimal magnetic domain refinement technology that can achieve both is needed. None of Patent Documents 1 to 9 discloses a magnetic domain refinement method that can reduce iron loss without increasing noise. The inventors considered that, since the magnetic domain width and β angle are not uniform in grain-oriented electrical steel sheets before magnetic domain refinement treatment, it would be effective to perform magnetic domain refinement treatment only on specific locations. However, such a magnetic domain refinement treatment method is not disclosed in any of the patent documents.

[0006] An object of the present disclosure is to provide a grain-oriented electrical steel sheet that can achieve both low iron loss and low noise, and a method for manufacturing the same. [Means for solving the problem]

[0007] (1) In a grain-oriented electrical steel sheet according to one embodiment of the present invention, the groove presence ratio, which is the ratio of the area on the surface of the grain-oriented electrical steel sheet where grooves having a depth of 5 μm to 50 μm and a width of 10 μm to 300 μm exist, which form an angle of 0° to 45° with respect to the direction perpendicular to the rolling direction and are aligned in the rolling direction, are present, is 50% or more in a first region, which is a region where the β angle, which is the deviation angle from the Goss orientation of the crystal grains around an axis perpendicular to the rolling direction, is 1° or less, and is less than 50% in a second region, which is a region where the β angle is more than 2°. (2) Preferably, in the grain-oriented electrical steel sheet described in (1) above, the groove presence ratio is 20% or more and 80% or less in a third region, which is a region where the β angle is more than 1° and not more than 2°, and the groove presence ratio in the first region ≧ the groove presence ratio in the third region ≧ the groove presence ratio in the second region. (3) Preferably, in the grain-oriented electrical steel sheet according to (1) or (2) above, the grooves, each having a depth of 5 μm to 50 μm and a width of 10 μm to 300 μm, are present at intervals of 1 to 20 mm in the rolling direction.

[0008] (4) A method for manufacturing a grain-oriented electrical steel sheet according to another embodiment of the present invention includes: an image acquisition step of acquiring a magnetic domain image of the grain-oriented electrical steel sheet; a determination step of determining, based on the spatial distribution of magnetic domain widths in the magnetic domain image and the β angle, which is the angle of deviation of the crystal grains from the Goss orientation around an axis in the direction perpendicular to the rolling direction, locations to form grooves having a depth of 5 μm to 50 μm and a width of 10 μm to 300 μm among magnetic domain control treatment lines that form an angle of 0° to 45° with the direction perpendicular to the rolling direction of the grain-oriented electrical steel sheet and are aligned in the rolling direction; and a groove formation step of forming grooves in the magnetic domain control treatment lines at the locations determined in the determination step. (5) Preferably, in the method for manufacturing a grain-oriented electrical steel sheet according to (4) above, the determining step determines a location of the magnetic domain control treatment line where the β angle is 1° or less as the location where the groove is to be formed. (6) Preferably, in the method for producing a grain-oriented electrical steel sheet according to (4) or (5) above, the determining step derives the spatial distribution of the magnetic domain width from the magnetic domain image using a two-dimensional Fourier transform. [Effects of the Invention]

[0009] According to the grain-oriented electrical steel sheet according to the embodiment of the present invention, it is possible to achieve both low iron loss and low noise.

[0010] According to the method for manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention, it is possible to provide a grain-oriented electrical steel sheet that achieves both low iron loss and low noise. [Brief explanation of the drawings]

[0011] [Figure 1A] 1 is a graph showing an example of the spatial distribution of magnetic domain width in a grain-oriented electrical steel sheet before magnetic domain refinement treatment. [Figure 1B] 1 is a graph showing an example of the spatial distribution of magnetic domain width in a grain-oriented electrical steel sheet after magnetic domain refinement treatment. [Figure 1C] 1C is a graph showing regions in which the magnetic domain width is refined to 50 μm or more before and after the magnetic domain refinement process shown in FIGS. 1A and 1B. [Figure 2A] 1 is a graph showing the relationship between the magnetic domain width before and after groove formation. [Figure 2B] 1 is a graph showing the relationship between the β angle of a grain-oriented electrical steel sheet and the width of a 180° magnetic domain. [Figure 3] 1 is a block diagram showing a hardware configuration of an image acquisition device according to an embodiment of the present invention. [Figure 4] FIG. 2 is a block diagram showing the hardware configuration of the analysis device according to the present embodiment. [Figure 5] 1 is a schematic diagram showing a configuration of a laser irradiation device according to an embodiment of the present invention. [Figure 6] 1 is a flowchart showing a method for manufacturing a grain-oriented electrical steel sheet according to the present embodiment. [Figure 7] FIG. 10 is a schematic diagram illustrating a method for extracting a plurality of partial regions from a magnetic domain image of a grain-oriented electrical steel sheet. [Figure 8] 10 is an example of a plurality of partial Fourier images obtained by performing a two-dimensional Fourier transform on each of a plurality of partial regions cut out from a magnetic domain image of a grain-oriented electrical steel sheet. [Figure 9] FIG. 2 is a schematic diagram showing groove formation lines among magnetic domain control treatment lines of a grain-oriented electrical steel sheet. [Figure 10] FIG. 2 is a schematic diagram illustrating a method for identifying a first region, a second region, and a third region. [Figure 11] FIG. 4 is a schematic diagram illustrating a method for measuring the groove presence ratio in each of the first region, the second region, and the third region. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0013] First, we compare the magnetic domain structures of grain-oriented electrical steel sheets before and after magnetic domain refinement treatment. Figure 1A shows the spatial distribution of the width of the 180° magnetic domains (hereinafter simply referred to as "magnetic domain width") in a grain-oriented electrical steel sheet before magnetic domain refinement treatment. Figure 1B shows the spatial distribution of the magnetic domain width after magnetic domain refinement treatment was performed on the surface of the grain-oriented electrical steel sheet of Figure 1A. The magnetic domain refinement treatment here was performed by forming grooves along magnetic domain control treatment lines that made an angle of 0° to 45° with the rolling direction (RD).

[0014] Here, the "180° magnetic domain" means that the magnetization direction is <100> It refers to a magnetic domain sandwiched between two 180° magnetic domain walls that are oriented in the rolling direction and are nearly parallel to the rolling direction. The "width" of a 180° magnetic domain refers to the distance between adjacent magnetic domain walls (magnetic domain wall spacing).

[0015] The spatial distribution of the magnetic domain width shown in FIGS. 1A and 1B was derived from a magnetic domain image of the grain-oriented electrical steel sheet using a two-dimensional Fourier transform, which will be described later.

[0016] Figure 1C shows regions where the magnetic domain width has been refined by 50 μm or more before and after the magnetic domain refinement process shown in Figures 1A and 1B, and visualizes the values ​​of the original magnetic domain width at which refinement occurred.

[0017] Figure 1C shows that the areas where the effect of magnetic domain refinement was 50 μm or more were areas where the original magnetic domain width was wide, and that the effect of magnetic domain refinement was particularly pronounced in areas where the original magnetic domain width was approximately 500 μm or more. In other words, the effect of magnetic domain refinement differs depending on the original magnetic domain width.

[0018] Figure 2A shows the relationship between the magnetic domain width before and after groove formation at the same position. The grooves were formed with a depth of 20 μm, a width of 100 μm, and a groove pitch of 4 mm.

[0019] From FIG. 2A, it can be seen that even if grooves are formed in a region with a magnetic domain width of approximately 500 μm or less, no effect of magnetic domain refinement is apparent.

[0020] From the above, it is believed that the iron loss reduction effect can be obtained by subdividing regions with originally wide magnetic domain widths, and that even if magnetic domain subdivision is performed on regions with originally narrow magnetic domain widths, the iron loss reduction effect cannot be obtained, and that this will result in increased hysteresis loss, worsening noise characteristics, and a decrease in magnetic permeability.

[0021] To reduce the iron loss of grain-oriented electrical steel sheets, secondary recrystallized grains in the steel sheets are formed in the {110} <001> However, when grain-oriented electrical steel sheets are manufactured industrially, grains with orientations that deviate from the ideal Goss orientation are generated during the secondary recrystallization process. The deviation of grains from the Goss orientation around the transverse direction (TD) axis corner This is called the β angle. As shown in Figure 9, the transverse direction (TD) is the direction perpendicular to the rolling direction (RD) and parallel to the sheet surface of the grain-oriented electrical steel sheet. Figure 2B shows the relationship between the β angle of grain-oriented electrical steel sheet and the 180° magnetic domain width before laser irradiation. Figure 2B shows that the original magnetic domain width is wide (approximately 500 μm or more) in regions where the β angle is 2° or less, and therefore it is effective to perform magnetic domain refinement treatment preferentially in regions where the β angle is 2° or less, more preferably in regions where the β angle is 1° or less.

[0022] Also, a technique for reducing iron loss is known in which grooves having a predetermined depth and a predetermined width are formed at predetermined intervals in the rolling direction (RD) within a range of 0° to 45° with respect to the transverse direction (TD) on the surface of a grain-oriented electrical steel sheet (see Patent Document 5).

[0023] Therefore, in this embodiment, magnetic domain control is performed so that grooves having a predetermined depth and a predetermined width are formed preferentially in areas on the surface of the grain-oriented electrical steel sheet where the β angle is 1° or less.

[0024] Next, the configuration of a device that realizes magnetic domain control of the grain-oriented electrical steel sheet according to this embodiment will be described with reference to FIGS.

[0025] 3 shows the hardware configuration of an image acquisition device 30 that acquires magnetic domain images of grain-oriented electrical steel sheets. The image acquisition device 30 includes a light source unit 31, a magneto-optical (MO) sensor 33, an image sensor 35, and a signal processing unit 37.

[0026] The light source unit 31 has a light source made up of a light emitting diode (LED), and irradiates the MO sensor 33 with light having a uniform polarization plane.

[0027] The MO sensor 33 is a device for measuring the structure of magnetic materials and has an observation surface on which a magnetic sample to be measured is placed. Light emitted from the light source unit 31 passes through the interior of the MO sensor 33 and is reflected by a reflective layer. The reflected light passes through the interior of the MO sensor 33 again and is output from the MO sensor 33. When a grain-oriented electrical steel sheet is placed on the observation surface of the MO sensor 33 as a magnetic sample, a leakage magnetic field corresponding to the direction of spontaneous magnetization of the grain-oriented electrical steel sheet is generated inside the MO sensor 33. This leakage magnetic field rotates the polarization plane of the reflected light.

[0028] The image sensor 35 is a complementary metal-oxide-semiconductor (CMOS) image sensor that forms an image of the reflected light from the MO sensor 33 on its light-receiving surface, photoelectrically converts the image, and outputs the photoelectrically converted analog signal to the signal processing unit 37. By detecting the reflected light with its polarization plane rotated by the image sensor 35, the spatial distribution of the leakage magnetic field can be obtained, and the magnetic domain structure of the grain-oriented electrical steel sheet can be clarified.

[0029] The signal processing unit 37 includes an amplifier, an AD converter, a digital signal processor (DSP), etc. The analog signal output from the image sensor 35 is amplified by the amplifier and converted into a digital signal by the AD converter. This digital signal is subjected to predetermined digital processing by the DSP to generate an image signal. The image signal generated by the signal processing unit 37 is output to an analysis device 40 (see FIG. 4) via a cable or wireless communication.

[0030] 4 shows the hardware configuration of an analysis device 40 that analyzes the magnetic domain structure of grain-oriented electrical steel sheets. The analysis device 40 is a computer device such as a personal computer (PC), and includes a calculation unit 41, a memory 43, a display unit 45, an input unit 47, and a communication I / F 49.

[0031] The calculation unit 41 has a central processing unit (CPU) and analyzes the magnetic domain structure from the magnetic domain image of the grain-oriented electrical steel sheet and determines the locations where grooves should be formed in accordance with a program stored in the memory 43. The processing executed by the calculation unit 41 will be described in detail later.

[0032] The memory 43 includes a read-only memory (ROM) and a random access memory (RAM). The ROM stores programs executed by the CPU of the calculation unit 41 and data required for executing these programs. The programs and data stored in the ROM are loaded into the RAM and executed.

[0033] The memory 43 may include a magnetic memory such as a hard disk drive (HDD) or an optical memory such as an optical disk. Alternatively, the program and data may be stored in a computer-readable recording medium that is detachable from the analysis device 40. Alternatively, the program executed by the calculation unit 41 may be received from a network via the communication I / F 49.

[0034] The display unit 45 has a display such as a liquid crystal display (LCD), a plasma display, or an organic electroluminescence (EL) display, and displays an image based on the image signal output from the image acquisition device 30, and also displays the analysis results of the magnetic domain structure by the calculation unit 41.

[0035] The input unit 47 has input devices such as a mouse, a keyboard, etc. The communication I / F 49 is an interface for transmitting and receiving data to and from external devices via a network such as a local area network (LAN), a wide area network (WAN), or the Internet.

[0036] Instead of general-purpose hardware such as a CPU, the calculation unit 41 may be dedicated hardware such as an application specific integrated circuit (ASIC) or a field programmable gate array (FPGA) specialized for analyzing magnetic domain structures.

[0037] 3 and 4 show the case where the image acquisition device 30 and the analysis device 40 are separate devices, but a system in which the image acquisition device 30 and the analysis device 40 are integrated may also be employed.

[0038] As a means for forming grooves on the surface of the grain-oriented electrical steel sheet, known means such as laser irradiation, electron beam irradiation, machining, etc. The configuration of a laser irradiation device for forming grooves by laser irradiation will be described below.

[0039] 5 shows the configuration of a laser irradiation device 500. The laser irradiation device 500 includes a polygon mirror 501, a light source device 503, a collimator 505, a condenser lens 507, a motor 509, a sensor 511, a control unit 513, and a strip threading device 515.

[0040] The threading device 515 threads the grain-oriented electrical steel sheet 50 in the rolling direction (RD).

[0041] The polygon mirror 501 has, for example, a regular polygonal prism shape, and a plurality of plane mirrors are provided on each of the plurality of side surfaces constituting the regular polygonal prism. A laser beam LB is incident on the plane mirror of the polygon mirror 501 in one direction (horizontal direction) from a light source device 503 via a collimator 505 and is reflected by the plane mirror.

[0042] The polygon mirror 501 is rotatable around a rotation axis O1 by being driven by a motor 509. The angle of incidence of the laser beam LB with respect to the plane mirror changes sequentially according to the rotation angle of the polygon mirror 501, thereby sequentially changing the reflection direction of the laser beam LB, and allowing the laser beam LB to scan along the magnetic domain control treatment lines 52 of the grain-oriented electrical steel sheet 50. Here, the magnetic domain control treatment lines 52 are multiple straight lines that form an angle of 0° to 45° with respect to the transverse direction (TD) of rolling on the surface of the grain-oriented electrical steel sheet 50 and are aligned in the rolling direction (RD). Preferably, the multiple magnetic domain control treatment lines 52 extend parallel to one another. Also, preferably, the multiple magnetic domain control treatment lines 52 are aligned at equal intervals. The interval P between adjacent magnetic domain control treatment lines 52 represents the groove formation interval.

[0043] The light source device 503 outputs a laser beam LB under the control of the control unit 513 in a predetermined irradiation method (for example, a continuous irradiation method or a pulse irradiation method).

[0044] The condenser lens 507 is provided in the optical path of the laser beam LB reflected from the polygon mirror 501, and constitutes a condensing optical system with a predetermined focal length. The laser beam LB reflected from the polygon mirror 501 is condensed onto the surface of the grain-oriented electromagnetic steel sheet 50 via the condenser lens 507, thereby forming grooves along the magnetic domain control treatment lines 52 on the surface of the grain-oriented electromagnetic steel sheet 50.

[0045] The motor 509 is connected to the polygon mirror 501 and drives the polygon mirror 501 to rotate under the control of the control unit 513 .

[0046] The sensor 511 is connected to the drive shaft of the motor 509, detects the rotation angle of the polygon mirror 501 rotated by the motor 509, and outputs a signal indicating the detected rotation angle (hereinafter referred to as a rotation angle signal) to the control unit 513.

[0047] The control unit 513 is made up of a processor and is connected to the light source device 503, the motor 509, the sensor 511, and the strip threading device 515. The control unit 513 receives a speed signal from the strip threading device 515 and outputs a signal to the motor 509 to instruct the motor 509 to rotate the polygon mirror 501.

[0048] Furthermore, the control unit 513 controls the power of the laser beam LB output by the light source device 503 to be turned on and off based on a groove formation signal indicating the location of the magnetic domain control processing line 52 where a groove is to be formed and the rotation angle signal output from the sensor 511. When the laser irradiation device 500 is electrically connected to the analysis device 40, the groove formation signal is input from the analysis device 40 to the laser irradiation device 500. Note that the groove formation signal may also be input to the laser irradiation device 500 by an operator.

[0049] Next, a method for manufacturing the grain-oriented electrical steel sheet 50 according to this embodiment will be described with reference to FIG.

[0050] First, the image acquisition device 30 acquires a magnetic domain image of the grain-oriented electrical steel sheet 50 (step S62: image acquisition step). Next, the calculation unit 41 of the analysis device 40 derives the spatial distribution of the width of the 180° magnetic domain (magnetic domain width) from the magnetic domain image, and determines, among the magnetic domain control treatment lines 52 of the grain-oriented electrical steel sheet 50, locations having a β angle corresponding to an area where the magnetic domain width is equal to or greater than a predetermined value (for example, equal to or greater than about 500 μm), specifically, locations where the β angle is 1° or less, as locations where magnetic domain refinement treatment is to be applied by forming grooves (step S64: determination step).

[0051] In this embodiment, the portion of the magnetic domain control processing line 52 where the groove is formed is called a “groove forming line.” Details of the process of step S64 executed by the calculation unit 41 will be described later.

[0052] In step S64, the location of the groove formation line may be determined by the operator visually observing the magnetic domain image displayed on the display unit 45, and a groove formation signal representing the location of the groove formation line may be input to the laser irradiation device 500.

[0053] Next, magnetic domain refinement is performed by preferentially forming grooves having a predetermined depth and a predetermined width in the magnetic domain control treatment lines 52 of the grain-oriented electrical steel sheet 50 at the locations determined in step S64 (step S66: groove forming step). Preferably, the magnetic domain refinement is performed only at the locations determined in step S64. Step S66 may be performed by irradiating the area with a laser beam LB using a laser irradiation device 500, or by using other means such as electron beam irradiation, machining, or etching.

[0054] Next, the process of step S64 executed by the calculation unit 41 of the analysis device 40 will be described.

[0055] The calculation unit 41 derives the spatial distribution of the magnetic domain width of the grain-oriented electromagnetic steel sheet 50 using a line segment method or a Fourier transform, and determines that the locations where grooves should be formed preferentially are areas of the magnetic domain control processing lines 52 of the grain-oriented electromagnetic steel sheet 50 where the β angle is 1° or less, which corresponds to areas with a wide magnetic domain width.

[0056] In the line segment method, evaluation is performed by drawing line segments perpendicular to the magnetic domains, but the line segments are spaced three apart per cm in the direction parallel to the magnetic domains, and the magnetic domain width is calculated from the distance between the intersections of the 180° domain walls and the line segments.

[0057] The Fourier transform is particularly effective as a means of analyzing the magnetic domain structure of magnetic materials with periodic magnetic domain structures, such as grain-oriented electrical steel sheets. Below, we explain a method for deriving the spatial distribution of the magnetic domain width of grain-oriented electrical steel sheets using the short-term two-dimensional Fourier transform (hereinafter referred to as "ST2DFT"), which is an extension of the short-term Fourier transform, a signal processing method long used in the time-frequency analysis of audio signals, to the two-dimensional domain.

[0058] An image (magnetic domain image) represented by an image signal acquired by the image acquisition device 30 is expressed as a data string of two-dimensional coordinates (kl coordinates) as x(k,l). The magnetic domain image to be analyzed in this embodiment is an image binarized using two types of colors, such as grayscale, or an image expressed in three or more gradations (multi-gradation).

[0059] In order to derive the spatial distribution of the magnetic domain width of the grain-oriented electrical steel sheet 50, the calculation unit 41 executes the following steps (A-1), (A-2) and (A-3). (A-1) cutting out a plurality of subregions from a magnetic domain image; (A-2) performing ST2DFT; (A-3) Step to derive the spatial distribution of magnetic domain width. Each step will be described in detail below.

[0060] (A-1) Step of extracting multiple partial regions from a magnetic domain image To extract multiple partial regions from the magnetic domain image and analyze the frequency structure of each, the range of the k direction is set to 0≦k≦N. k -1, the range of the l direction is 0≦l≦N l -1 is used as the rectangular window function Wa(k,l) (N k and N l is a natural number). As the window function Wa(k,l), a Hamming window, a Hanning window, a Blackman window, etc. can be applied.

[0061] The observation position in the data sequence x(k,l) of the magnetic domain image is expressed as an index (n,m), and the shift amount of the window function Wa(k,l) in the k direction and the l direction is expressed as S k and S l If we write it as (n, m, S k , S l is an integer), and nS is calculated from the magnetic domain image as shown in equation (1). k ≦k≦nS k +N k -1, mS l ≦l≦mS l +N l Data sequence x of the partial region cut out from the range of -1 nm(k-nS k ,l-mS l ) is obtained.

number

[0062] Figure 7 shows an example in which partial regions corresponding to the observation positions (n, m) = (1, 1), (2, 2), (3, 3), ..., (P, Q) (P and Q are natural numbers) are cut out from the magnetic domain image G.

[0063] In this embodiment, N which defines the range of the window function Wa(k,l) k and N l are parameters corresponding to the number of pixels in the k direction and the number of pixels in the l direction in the partial region, respectively.

[0064] (A-2) Step of performing ST2DFT The data sequence of the subregion is x nm (n´, m´)=x nm (k-nS k ,l-mS l ) and x nm When a two-dimensional Fourier transform is performed on (n', m'), a partial Fourier image X(f k ,f l ,n,m) is obtained.

number

[0065] spatial frequency f k The resolution of Δf k , spatial frequency f l The resolution of Δf l When written as Δf k and Δf l is defined as equation (3).

number

[0066] For example, the data string x of each partial region shown in FIG. nm (k-nS k ,l-mS l ) is subjected to a two-dimensional Fourier transform, a partial Fourier image X(f k ,f l ,n,m) is obtained.

[0067] (A-3) Step of deriving the spatial distribution of magnetic domain width Partial Fourier image X(f k ,f l , n, m) is obtained, the partial Fourier image X(f k ,f l , n, m) spot peak position coordinates (k component f k max (n,m) and l component f l max (n, m)) is calculated. Note that the region near k=0 and l=0 is excluded from the calculation of the peak position because it is a region that is highly dependent on the contrast of the image.

[0068] Then, from the spatial frequency resolution defined by equation (3) and the peak position of the spot in the partial Fourier image, the spatial distribution L(n, m) of the magnetic domain width is derived as shown in equation (4).

number

[0069] In this way, by using ST2DFT, it is possible to quantitatively derive the spatial distribution L(n,m) of the magnetic domain width while preserving the position information of the magnetic domain image. Figures 1A to 1C above show the analysis results of the magnetic domain width derived by ST2DFT.

[0070] After deriving the spatial distribution L(n, m) of the magnetic domain width, the calculation unit 41 determines, as shown in Fig. 9, among the magnetic domain control processing lines 52 (dashed lines in Fig. 9) of the grain-oriented electrical steel sheet 50, locations having a β angle corresponding to regions where the magnetic domain width is equal to or greater than a predetermined value (for example, equal to or greater than approximately 500 µm), specifically locations where the β angle is 1° or less, as groove formation lines 90 (solid lines in Fig. 9) where grooves will be formed. The control unit 513 of the laser irradiation device 500 controls the power of the laser beam LB to be on for the groove formation lines 90 of the magnetic domain control processing lines 52, and preferably to be off for other locations. As a result, grooves are formed along the groove formation lines 90.

[0071] Next, a grain-oriented electrical steel sheet 50 according to this embodiment will be described. In the grain-oriented electrical steel sheet 50 according to this embodiment, as illustrated in Fig. 9, the surface of the grain-oriented electrical steel sheet 50 has a groove presence ratio, which is the ratio of grooves having a depth of 5 µm to 50 µm and a width of 10 µm to 300 µm to the total length of magnetic domain control treatment lines 52 that form an angle of 0° to 45° with the transverse direction (TD) of rolling and are aligned in the rolling direction (RD), of which the groove presence ratio is 50% or more in a first region, which is a region where the β angle, which is the deviation angle of the crystal grains from the Goss orientation around the axis of the transverse direction (TD), is 1° or less, and is less than 50% in a second region, which is a region where the β angle is more than 2°.

[0072] (Groove formation line 90 (a portion where a groove having a depth of 5 μm to 50 μm and a width of 10 μm to 300 μm exists)) As illustrated in FIG. 9 , the grain-oriented electrical steel sheet 50 according to this embodiment has a portion where grooves having a depth of 5 μm to 50 μm and a width of 10 μm to 300 μm are present. Here, the portion where grooves having a depth of 5 μm to 50 μm and a width of 10 μm to 300 μm are present is referred to as a "groove formation line 90." In order to promote magnetic domain refinement and reduce iron loss, it is preferable that the groove depth be 5 μm to 50 μm and the groove width be 10 μm to 300 μm (see Patent Document 5). Grooves with a depth and / or width outside the above-mentioned ranges are not considered to constitute the groove formation line 90. Grooves with a depth and / or width outside the above-mentioned ranges are not taken into account when calculating the groove presence ratio, which will be described later. The depth of the grooves constituting the groove formation line 90 may be specified as 6 μm or more, 7 μm or more, or 10 μm or more. The depth of the grooves constituting the groove formation line 90 may be specified as 48 μm or less, 45 μm or less, or 40 μm or less. The width of the grooves constituting the groove formation line 90 may be specified as 20 μm or more, 30 μm or more, or 50 μm or more. The width of the grooves constituting the groove formation line 90 may be specified as 280 μm or less, 250 μm or less, or 200 μm or less. The depth and width of the grooves may be uniform along the groove formation line 90 or may vary within the above-mentioned ranges.

[0073] Furthermore, in order to promote magnetic domain refinement and reduce iron loss, it is preferable that the spacing P between adjacent grooves measured along the rolling direction (RD) is 1 mm to 20 mm (see Patent Document 5). In a grain-oriented electrical steel sheet, the spacing P between adjacent grooves may be uniform or may vary. The spacing P between adjacent grooves may be 1 mm to 20 mm in only a portion of the grain-oriented electrical steel sheet, or the spacing P between adjacent grooves may be 1 mm to 20 mm in the entire region of the grain-oriented electrical steel sheet. Furthermore, the average value of the spacing P between adjacent grooves in the grain-oriented electrical steel sheet may be 1 to 20 mm. The spacing P between adjacent grooves or the average value of the spacing P between grooves may be 2 mm or more, 3 mm or more, or 5 mm or more. The average value of the spacing P between adjacent grooves or the average value of the spacing P between grooves may be 18 mm or less, 16 mm or less, or 15 mm or less.

[0074] A tension insulating coating may be formed on the surface of the grain-oriented electrical steel sheet. In this case, the groove depth, groove width, and groove spacing along the rolling direction are values ​​for grooves formed in the base steel sheet. When the grain-oriented electrical steel sheet has a tension insulating coating, the groove depth, groove width, and groove spacing along the rolling direction are measured after removing the tension insulating coating.

[0075] (Magnetic domain control processing line 52) As illustrated in FIG. 9 , the groove formation lines 90 are arranged on the magnetic domain control treatment lines 52. The magnetic domain control treatment lines 52 are aligned along the rolling direction (RD) on the surface of the grain-oriented electrical steel sheet 50, at an angle of 0° to 45° with respect to the transverse rolling direction (TD). The magnetic domain control treatment lines 52 are preferably aligned parallel to one another. When the grooves are formed by a laser, the magnetic domain control treatment lines 52 correspond to the locus of the focus of the laser beam LB during the manufacturing stage of the grain-oriented electrical steel sheet 50. The magnetic domain control treatment lines 52 do not actually exist in the grain-oriented electrical steel sheet 50, but are virtual lines that extend along the groove formation lines 90. The magnetic domain control treatment lines 52 can be identified by, for example, drawing lines along the groove formation lines 90. The angle between the transverse direction (TD) and the extension direction of the stress introduction wire 90 is the same as the angle between the transverse direction (TD) and the extension direction of the magnetic domain control processing line 52 on which the stress introduction wire 90 is provided.

[0076] In the grain-oriented electrical steel sheet 50, the angle formed between the magnetic domain control treatment lines 52 and the transverse direction (TD) may be uniform or may vary. The angle formed between the magnetic domain control treatment lines 52 and the transverse direction (TD) may be 0° to 45° in only a part of the grain-oriented electrical steel sheet 50, or the angle formed between the magnetic domain control treatment lines 52 and the transverse direction (TD) may be 0° to 45° in the entire region of the grain-oriented electrical steel sheet 50. Furthermore, the average value of the angle formed between the magnetic domain control treatment lines 52 and the transverse direction (TD) in the grain-oriented electrical steel sheet 50 may be 0° to 45°. The angle formed between the magnetic domain control treatment lines 52 and the transverse direction (TD) or its average value may be 1° or more, 3° or more, or 5° or more. The angle formed by the magnetic domain control treatment lines 52 and the direction perpendicular to the rolling direction (TD), or the average value thereof, may be 40° or less, 35° or less, or 30° or less.

[0077] In this embodiment, the groove formation lines 90 may exist on the magnetic domain control treatment lines 52 in a non-single periodic manner. The presence of the groove formation lines 90 in a non-single periodic manner means that the groove formation lines 90 do not correspond to the case where there are an average of 10 or more groove formation lines 90 per cm and the standard deviation of the lengths of the non-groove formation lines between the groove formation lines 90 is 20 μm or less. In other words, in this embodiment, the groove formation lines 90 obtained by performing magnetic domain control using a normal pulsed laser on the entire surface of the steel sheet are not considered to exist in a non-single periodic manner. However, the pulsed laser may be selectively irradiated to a region with a β angle of 1° or less.

[0078] As described above, by determining the location of the grooves according to the β angle, the proportion of the magnetic domain control processing lines 52 where the grooves exist (groove formation lines 90) is relatively high in regions where the β angle is near 0°, and this proportion is relatively low in regions where the β angle is large. Specifically, if the proportion of the magnetic domain control processing lines 52 where the groove formation lines 90 exist (groove existence proportion) is defined as the ratio of the length of the groove formation lines 90 to the total length of the magnetic domain control processing lines 52, it is preferable that the groove formation lines 90 exist at a proportion of 50% or more in the first region, which is a region where the β angle is 1° or less, and that the groove formation lines 90 exist at a proportion of less than 50% in the second region, which is a region where the β angle is greater than 2°. The first region may be defined as a region where the β angle is 1.0° or less, a region where the β angle is 0.9° or less, or a region where the β angle is 0.8° or less. The second region may be defined as a region where the β angle is greater than 2.0°, a region where the β angle is 2.1° or greater, or a region where the β angle is 2.2° or greater.

[0079] In the third region, which is a region where the β angle is more than 1° and not more than 2°, the groove presence ratio is preferably 20% or more and 80% or less. Here, the groove presence ratios in the first to third regions each satisfy the following relationship. Groove presence rate in the first region ≧ Groove presence rate in the third region ≧ Groove presence rate in the second region The third region may be defined as a region where the β angle is greater than 1.0° and not more than 2.0°, a region where the β angle is 1.1° or more and 1.9° or less, or a region where the β angle is 1.2° or more and 1.8° or less.

[0080] In this embodiment, it is sufficient that a sample of a predetermined size (for example, 100 mm square or larger) taken from an arbitrary position on the grain-oriented electrical steel sheet 50 satisfies the above-mentioned groove presence ratio.

[0081] As described above, forming linear grooves according to the β angle of the grain-oriented electrical steel sheet 50 promotes magnetic domain refining, minimizes adverse effects such as increased hysteresis loss, worsening noise characteristics, and reduced magnetic permeability, and maximizes the effects of magnetic domain refining. This makes it possible to achieve both low iron loss and low noise.

[0082] (Measurement method) A method for measuring parameters related to the grain-oriented electrical steel sheet 50 according to this embodiment will be described below. Note that all parameters are measured on a sample of a predetermined size taken from the grain-oriented electrical steel sheet 50. For example, a rectangular sample with both sides measuring 100 mm (or 100 mm or more) can be cut out from the grain-oriented electrical steel sheet 50 and used for measurement. If the grain-oriented electrical steel sheet 50 is a coil, the sample may be taken from any location on the coil. Also, if the grain-oriented electrical steel sheet 50 is a component incorporated into an electrical product such as a transformer or motor, the sample may be taken from any location on the component. If the component is small, the length of one side of the sample may be less than 100 mm. In this case, the total sample area must be 10,000 mm. 2 At this time, it is desirable to collect the sample by a method such as wire cutting in order to minimize the influence of mechanical distortion on the sample.

[0083] (Angle between magnetic domain control processing line 52 and the direction perpendicular to rolling (TD)) The angle between the magnetic domain control treatment line 52 and the direction perpendicular to the rolling direction (TD) is measured as follows.

[0084] First, the groove formation line 90 on the sample is identified. The surface of the sample is measured using a three-dimensional measuring machine to identify the location of grooves with a depth of 5 μm to 50 μm and a width of 10 μm to 300 μm, which are considered to be the groove formation line 90. If the grain-oriented electrical steel sheet 50 has a tensile insulating coating, the tensile insulating coating is removed before three-dimensional measurement of the sample surface is performed. The tensile insulating coating can be removed, for example, by immersing the sample in a sodium hydroxide solution, followed by dilute sulfuric acid and nitric acid. The temperature and concentration of the sodium hydroxide, dilute sulfuric acid, and nitric acid solutions, as well as the immersion time, are adjusted appropriately to prevent excessive dissolution of the sample's base steel. An example of the conditions for removing the tensile insulating coating is as follows: First, the sample is immersed in a 20% sodium hydroxide solution at 80°C for 15 minutes. The sample is then dried. The sample is then immersed in a 10% dilute sulfuric acid solution at 80°C for 4 minutes. After that, remove the sludge adhering to the surface of the sample with a rag, etc. Furthermore, immerse the sample in 10% nitric acid at room temperature for about 10 seconds while stirring.

[0085] Next, the transverse direction (TD) is identified. (1) When the sample is cut out from a coil-shaped grain-oriented electrical steel sheet 50, the width direction of the grain-oriented electrical steel sheet 50 can be considered to be the transverse direction (TD) to the rolling direction. (2) When the sample is cut out from a part of an electrical product, the transverse direction (TD) is identified from the rolling defects on the surface of the grain-oriented electrical steel sheet 50. The direction in which the rolling defects extend is regarded as the rolling direction (RD), and the direction perpendicular to the rolling direction (RD) and parallel to the steel sheet surface is regarded as the transverse direction (TD). (3) When it is difficult to identify the transverse direction (TD) from the rolling defects on the surface of the grain-oriented electrical steel sheet 50, the transverse direction (TD) is identified from the crystal orientation of the grain-oriented electrical steel sheet 50. Specifically, the crystal orientation of the grain-oriented electrical steel sheet 50 to be evaluated is measured at multiple points. Then, the direction in which the deviation angle from the GOSS orientation at the measurement points is smallest is regarded as the rolling direction (RD), and the direction perpendicular to the rolling direction (RD) and parallel to the surface of the grain-oriented electrical steel sheet 50 is regarded as the transverse direction (TD). In either case, from the viewpoint of convenience of measurement, it is preferable to cut out the sample from the grain-oriented electrical steel sheet 50 so that one side of the sample coincides with the direction perpendicular to the rolling direction (TD).

[0086] The magnetic domain control treatment lines 52 do not exist as real entities in the grain-oriented electrical steel sheet 50, but are virtual lines that extend along the groove formation lines 90. Therefore, the narrow angle formed by the groove formation lines 90 identified by the above-described procedure and the transverse direction (TD) of rolling can be considered to be the angle formed by the magnetic domain control treatment lines 52 and the transverse direction (TD) of rolling.

[0087] (Method for measuring β angle) The β angle of the grain-oriented electrical steel sheet 50 is measured by the side reflection Laue method, which is widely known as a method for measuring crystal orientation.

[0088] (Method for identifying the first, second, and third areas) The method for identifying the first, second, and third regions is as follows. As illustrated in FIG. 10, first, a virtual lattice L is set on the surface of the sample. This divides the surface of the sample into multiple cells C separated by the lattice L. The shape of the cells C is, for example, a square with sides of 2 mm. Then, the crystal orientation is measured using the real side reflection Laue method, with the center of each cell C set as a measurement point. This identifies the β angle of the measurement point, and determines whether the measurement point belongs to the first region A1, the second region A2, or the third region A3. Then, if a cell C is determined to be centered in the first region A1, then the entire cell C is considered to be in the first region A1. Similarly, if a cell C is determined to be centered in the second region A2, then the entire cell C is considered to be in the second region A2, and if a cell C is determined to be centered in the third region A3, then the entire cell C is considered to be in the third region A3. 10, measurement points deemed to be in the first region A1 are indicated by black circles P1, measurement points deemed to be in the second region A2 are indicated by gray circles P2, and measurement points deemed to be in the third region A3 are indicated by black circles P3. By the above-described procedure, the first region A1, the second region A2, and the third region A3 on the surface of the grain-oriented electrical steel sheet 50 can be identified as shown in FIGS. 10 and 11.

[0089] (Method of calculating the groove presence ratio in the first region, the second region, and the third region) 11, the magnetic domain control process lines 52 and groove formation lines 90 are identified in each of the first region A1, the second region A2, and the third region A3 using the procedure described in the description of the method for measuring the angle between the magnetic domain control process lines 52 and the transverse direction (TD) of rolling. The groove presence ratio in the first region A1 is the value obtained by dividing the total length of all groove formation lines 90 included in all first regions A1 of the sample by all magnetic domain control process lines 52 included in all first regions A1 of the sample. Similarly, the groove presence ratio in the second region A2 is the value obtained by dividing the total length of all groove formation lines 90 included in all second regions A2 of the sample by all magnetic domain control process lines 52 included in all second regions A2 of the sample, and the groove presence ratio in the third region A3 is the value obtained by dividing the total length of all groove formation lines 90 included in all third regions A3 of the sample by all magnetic domain control process lines 52 included in all third regions A3 of the sample.

[0090] The method for measuring the spacing of the groove formation lines 90 along the rolling direction (RD) is as follows: First, the rolling direction (RD) and the groove formation lines 90 are identified according to the procedure described in the description of the method for measuring the angle between the magnetic domain control treatment line and the transverse direction (TD). Next, the spacing of the groove formation lines 90 along the rolling direction (RD) is measured.

[0091] The method for determining whether the groove formation lines 90 exist in a non-single period is as follows. First, the magnetic domain control process lines 52 and the groove formation lines 90 included in the sample are identified using the procedure described above. As described above, the groove formation lines 90 are deemed to exist in a non-single period if "there are an average of 10 or more groove formation lines 90 per cm and the standard deviation of the lengths of the non-magnetic domain refinement process lines between the groove formation lines 90 exceeds 20 μm." Therefore, for the determination, it is determined whether there are an average of 10 or more groove formation lines 90 per cm in each of the multiple magnetic domain control process lines 52 included in the sample (e.g., a rectangular sample with both sides 100 mm long). For example, if the length of one magnetic domain control process line 52 included in the sample is X cm and the number of groove formation lines 90 included in that magnetic domain control process line 52 is y, it is determined that there are an average of y / X groove formation lines 90 per cm in that magnetic domain control process line 52. Furthermore, for each of the magnetic domain control processing lines 52 determined to contain an average of 10 or more groove forming lines 90 per cm, it is determined whether the standard deviation of the lengths of the non-magnetic domain refinement processing lines is 20 μm or less. If groove forming lines 90 are provided in a non-single period in 50% or more of all the magnetic domain control processing lines 52 contained in the sample, it is determined that the groove forming lines 90 exist in a non-single period in that sample. [Example]

[0092] The effects of one embodiment of the present invention will be explained in more detail using examples. However, the conditions in the examples are merely examples adopted to confirm the feasibility and effects of the present invention. The present invention is not limited to these examples. Various conditions may be adopted in the present invention as long as they do not deviate from the gist of the present invention and achieve the object of the present invention.

[0093] Magnetic domain refinement was carried out on grain-oriented electrical steel sheets from the same lot with a thickness of 0.23 mm, which are classified as 23P085 in Table 2 of JIS C 2553:2019 "Grain-oriented electrical steel strips," under the various conditions shown in Table 1. The noise and iron loss of the grain-oriented electrical steel sheets obtained after the magnetic domain refinement treatment were evaluated and are shown in Tables 2 and 3. In Table 2, inappropriate values ​​are underlined.

[0094] The noise and iron loss were evaluated as follows. First, a three-phase transformer core was created by laminating 180 grain-oriented electrical steel sheets with a thickness of 0.23 mm. The widths of the legs and yoke of the three-phase transformer core were both 150 mm. The height and width of the three-phase transformer core's outer dimensions were both 750 mm. The noise and iron loss of these three-phase transformer cores were measured. The measurement conditions were a frequency of 50 Hz and an excitation magnetic flux density of 1.5 T.

[0095] To measure the noise, microphones were placed at equal intervals around eight points around the transformer in which the three-phase transformer core was installed. The distance between the transformer and the microphones was 30 cm. The noise measurement results from these microphones were A-weighted corrected and averaged to obtain values, which are listed in Table 3 as the noise evaluation results (unit: dBA) for the grain-oriented electrical steel sheet. Examples with a noise evaluation result of 25.00 dBA or less were deemed to be examples in which low noise had been achieved. Noise evaluation results that were deemed to be unacceptable are underlined.

[0096] As mentioned above, iron loss was determined by measuring the voltage and current on the primary and secondary sides with a power analyzer when excitation was performed at a frequency of 50 Hz and an excitation magnetic flux density of 1.5 T. The determined iron loss is shown in Table 3 as the iron loss evaluation results (unit: W / kg) of the grain-oriented electrical steel sheet. Examples with an iron loss evaluation result of 0.70 W / kg or less were determined to be examples in which low iron loss had been achieved. Noise evaluation results that were determined to be unacceptable are underlined.

[0097] Furthermore, the angle between the groove and the direction perpendicular to the rolling direction, the groove depth, groove width, groove spacing, and the groove presence ratio in the first, second, or third region of the grain-oriented electrical steel sheet that had undergone the magnetic domain refinement treatment were measured, and the results are shown in Table 2. In all examples, the grooves were formed so that the angle between the groove and the direction perpendicular to the rolling direction, the groove depth, groove width, and groove spacing were constant. The measurement method essentially followed the procedure described above. A rectangular sample with both sides measuring 100 mm was cut out from the iron core of a three-phase transformer used for measuring noise and iron loss, and used for the measurements.

[0098] According to the above-mentioned measurement method, the groove presence rate will be 0% in cases where the groove shape is inappropriate (i.e., cases where the groove depth or groove width is insufficient or excessive). However, for reference, Table 2 lists the groove presence rate when grooves with inappropriate shapes are considered to be groove formation lines.

[0099] [Table 1]

[0100] [Table 2]

[0101] [Table 3]

[0102] In Example 1, no magnetic domain refining treatment was performed. In Example 1, no groove forming lines were provided, so no deterioration in noise evaluation results was observed. On the other hand, in Example 1, low iron loss was not achieved.

[0103] (Example of an inappropriate angle) In Example 2, the angle between the magnetic domain control treatment line and the direction perpendicular to the rolling direction was excessive. In Example 2, the noise evaluation results were poor, and low iron loss was not achieved.

[0104] (Example of inappropriate groove depth) In Example 3, the groove depth was insufficient. In Example 3, low iron loss was not achieved. In Example 4, the groove depth was excessive. In Example 4, the noise evaluation results were poor, and low iron loss was not achieved.

[0105] (Example of inappropriate groove width) In Example 5, the groove width was insufficient. In Example 5, low iron loss was not achieved. In Example 6, the groove width was excessive. In Example 6, the noise evaluation results were poor, and low iron loss was not achieved.

[0106] (Example of inappropriate groove ratio in the first region) In Example 9, grooves were uniformly formed in the magnetic domain control processing line. In Example 9, the groove presence ratio was set to a low level in both the first region and the second region. In Example 9, noise was suppressed to a low level, but low iron loss was not achieved.

[0107] (Example of inappropriate groove ratio in the second region) In Example 10, grooves were uniformly formed in the magnetic domain control processing line. In Example 10, the groove presence ratio was set to a high level in both the first region and the second region. In Example 10, low iron loss was achieved, but the noise evaluation results were poor.

[0108] In Examples 7, 8, and 11 to 29, groove formation was preferentially performed in locations where the β angle was 1° or less. Furthermore, in Examples 7, 8, and 11 to 29, the groove shape at the groove formation line was also within an appropriate range. In Examples 7, 8, and 11 to 29, both low iron loss and low noise were achieved. Furthermore, in examples where the relationship of groove presence rate in the first region ≥ groove presence rate in the third region ≥ groove presence rate in the second region was satisfied, iron loss and noise were further reduced. [Explanation of symbols]

[0109] 30 Image acquisition device 31 Light source section 33 MO sensor 35 Image Sensor 37 Signal Processing Section 40 Analyzer 41 Arithmetic section 43 Memory 45 Display section 47 Input section 49 Communication I / F 50 Grain-oriented electrical steel sheet 52 Magnetic domain control processing line 90 Groove formation line (part where a groove having a depth of 5 μm to 50 μm and a width of 10 μm to 300 μm exists) 500 Laser irradiation device L lattice C Cell A1 1st area A2 2nd area A3 Third area P1 Measurement point determined to be in the first area P2 Measurement point determined to be in the second area P3 Measurement point determined to be in the third area RD rolling direction TD: Transverse direction to rolling

Claims

1. a groove presence ratio, which is the ratio of portions where grooves having a depth of 5 μm to 50 μm and a width of 10 μm to 300 μm exist, are present in the surface of the grain-oriented electrical steel sheet, the grooves forming an angle of 0° to 45° with respect to the direction perpendicular to the rolling and aligned in the rolling direction, is 50% or more in a first region, which is a region where a β angle, which is a deviation angle from the Goss orientation of crystal grains around an axis in the direction perpendicular to the rolling, is 1° or less; The grain-oriented electrical steel sheet, wherein the groove presence ratio is less than 50% in a second region, which is a region where the β angle exceeds 2°.

2. the groove presence ratio is 20% or more and 80% or less in a third region, which is a region where the β angle is more than 1° and 2° or less, the groove presence ratio in the first region ≧ the groove presence ratio in the third region ≧ the groove presence ratio in the second region The grain-oriented electrical steel sheet according to claim 1,

3. 3. The grain-oriented electrical steel sheet according to claim 1, wherein the grooves have a depth of 5 μm to 50 μm and a width of 10 μm to 300 μm and are present at intervals of 1 to 20 mm in the rolling direction.

4. an image acquisition step of acquiring a magnetic domain image of the grain-oriented electrical steel sheet; a determining step of determining, based on the spatial distribution of magnetic domain widths in the magnetic domain image and a β angle which is a deviation angle from the Goss orientation of crystal grains around an axis in the direction perpendicular to the rolling direction, locations where grooves having a depth of 5 μm to 50 μm and a width of 10 μm to 300 μm will be formed among magnetic domain control treatment lines which form an angle of 0° to 45° with the direction perpendicular to the rolling direction of the grain-oriented electrical steel sheet and are aligned in the rolling direction; a groove forming step of forming the groove at the location of the magnetic domain control processing line determined in the determining step; Including, the determining step determines a location of the magnetic domain control processing line where the β angle is 1° or less as a location where the groove is to be formed; Manufacturing method for grain-oriented electrical steel sheets.

5. The method for producing a grain-oriented electrical steel sheet according to claim 4 , wherein the determining step derives the spatial distribution of the magnetic domain width from the magnetic domain image using a two-dimensional Fourier transform.

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