Grain-oriented electrical steel sheet and method for manufacturing the same

Abstract

A grain-oriented electromagnetic steel sheet according to an embodiment of the present invention has magnetic domain refining process lines indicating the portions at which a magnetic domain refining process is carried out on magnetic domain control process lines that form an angle of 0-45° with respect to the direction perpendicular to the rolling direction and that are arranged in the rolling direction. The regions, of the magnetic domain control process lines, in which the magnetic domain refining process lines are absent and that have a length of 1 mm or more preferably have an average magnetic domain width of 500 μm or less. Alternatively, the regions, of the magnetic domain control process lines, in which the magnetic domain refining process lines are absent and that include two or more magnetic walls preferably have an average magnetic domain width of 500 μm or less.

Description

[Technical Field]

[0001] This disclosure relates to grain-oriented electrical steel sheets and methods for manufacturing the same. This application claims priority based on Japanese Patent Application No. 2022-052343, filed in Japan on March 28, 2022, and the contents of that application are incorporated herein by reference. [Background technology]

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

[0003] To reduce iron loss, a technique called magnetic domain subdivision has long been known, which involves irradiating the surface of grain-oriented electrical steel sheets with lasers or electron beams in a direction intersecting the rolling direction to narrow the magnetic domain width. In recent years, various improved techniques related to magnetic domain subdivision have been proposed to provide grain-oriented electrical steel sheets with good iron loss characteristics (see, for example, Patent Documents 1 to 3). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2012-57219 [Patent Document 2] Japanese Patent Publication No. 2012-12664 [Patent Document 3] Japanese Patent Publication No. 2012-57218 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] However, when the domain refinement treatment is performed on the grain-oriented electrical steel sheet, the magnetic distortion characteristics change due to the reflux domains, resulting in a problem that the noise of the transformer increases. Thus, since the reduction of iron loss and the reduction of noise in the grain-oriented electrical steel sheet are in a trade-off relationship, an optimal domain refinement technology that can achieve both is required.

[0006] In view of the above problems, an object of the present disclosure is to provide a grain-oriented electrical steel sheet and a method for manufacturing the same that can achieve both low iron loss and low noise.

Means for Solving the Problems

[0007] (1) The grain-oriented electrical steel sheet according to one aspect of the present invention has a region where a domain refinement treatment line, which represents a portion subjected to a domain refinement treatment, exists at an angle of 0° to 45° with respect to the rolling right angle direction and is arranged along the rolling direction. (2) Preferably, in the grain-oriented electrical steel sheet according to (1) above, the average domain width in a region that is a region without the domain refinement treatment line among the domain control treatment lines and has a length of 1 mm or more is 500 μm or less. (3) Preferably, in the grain-oriented electrical steel sheet according to (1) or (2) above, the average domain width in a region that is a region without the domain refinement treatment line among the domain control treatment lines and contains two or more magnetic walls is 500 μm or less. (4) Preferably, in the grain-oriented electrical steel sheet according to any one of (1) to (3) above, the domain refinement treatment lines exist in a non-single period. (5) Preferably, in the grain-oriented electrical steel sheet according to any one of (1) to (4) above, the ratio of the domain refinement treatment lines to the total extension of the domain control treatment lines is 10% or more and 90% or less. (6) Preferably, in the grain-oriented electrical steel sheet according to any one of (1) to (5) above, the domain refinement treatment lines are grooves. (7) Preferably, in the grain-oriented electrical steel sheet according to any one of (1) to (5) above, the domain refinement treatment lines are thermal strains.

[0008] (8) A method for manufacturing a grain-oriented electrical steel sheet according to an 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 the magnetic domain widths of the magnetic domain image, the location to which the magnetic domain subdivision process is applied among magnetic domain control processing lines that form an angle of 0° to 45° with respect to the direction perpendicular to the rolling of the grain-oriented electrical steel sheet and are aligned in the rolling direction; and a magnetic domain subdivision step of applying the magnetic domain subdivision process to the location among the magnetic domain control processing lines determined in the determination step. (9) Preferably, in the method for manufacturing grain-oriented electrical steel sheets described in (8) above, the determination step determines that locations where the magnetic domain width is greater than or equal to a predetermined value are to be used as locations to apply the magnetic domain subdivision process. (10) Preferably, in the method for manufacturing grain-oriented electrical steel sheets described in (8) or (9) above, the determination step derives the spatial distribution of the magnetic domain width from the magnetic domain image using a two-dimensional Fourier transform. (11) Preferably, in the method for manufacturing grain-oriented electrical steel sheets described in any one of items (8) to (10) above, the magnetic domain subdivision step is performed by irradiating with a laser or electron beam. (12) Preferably, in the method for manufacturing grain-oriented electrical steel sheets described in any one of items (9) to (11) above, the predetermined value is set to a value within the range of 400 μm to 600 μm. [Effects of the Invention]

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

[0010] According to the method for manufacturing grain-oriented electrical steel sheets as embodied in the present invention, it is possible to provide grain-oriented electrical steel sheets that achieve both low iron loss and low noise. [Brief explanation of the drawing]

[0011] [Figure 1A] This graph shows an example of the spatial distribution of magnetic domain widths in grain-oriented electrical steel sheets before magnetic domain subdivision processing. [Figure 1B]This graph shows an example of the spatial distribution of magnetic domain widths in grain-oriented electrical steel sheets after magnetic domain subdivision treatment. [Figure 1C] Figures 1A and 1B are graphs showing the regions where the magnetic domain width was subdivided by 50 μm or more before and after the magnetic domain subdivision process. [Figure 2] This graph shows the relationship between the magnetic domain width before laser irradiation and the magnetic domain width after laser irradiation. [Figure 3] This is a block diagram showing the hardware configuration of the image acquisition device according to this embodiment. [Figure 4] This is a block diagram showing the hardware configuration of the analysis device according to this embodiment. [Figure 5] This is a schematic diagram showing the configuration of the laser irradiation device according to this embodiment. [Figure 6] This flowchart shows the manufacturing method for grain-oriented electrical steel sheets according to this embodiment. [Figure 7] This is a schematic diagram illustrating a method for extracting multiple subregions from a magnetic domain image of grain-oriented electrical steel sheets. [Figure 8] This is an example of multiple partial Fourier images obtained by applying a two-dimensional Fourier transform to each of several subregions extracted from a magnetic domain image of a grain-oriented electrical steel sheet. [Figure 9] This is a schematic diagram representing the magnetic domain subdivision processing lines that are subject to magnetic domain subdivision among the magnetic domain control processing lines of grain-oriented electrical steel sheets. [Figure 10] This is a schematic diagram of an example of a magnetic domain image of grain-oriented electrical steel sheet. [Modes for carrying out the invention]

[0012] Embodiments of the present invention will be described below with reference to the drawings.

[0013] First, we compare the magnetic domain structure of grain-oriented electrical steel sheets before and after magnetic domain refinement treatment. Figure 1A shows the spatial distribution of the width of 180° magnetic domains (hereinafter simply referred to as "magnetic domain width") of the grain-oriented electrical steel sheet before magnetic domain refinement treatment. Figure 1B shows the spatial distribution of magnetic domain width after magnetic domain refinement treatment has been applied to the surface of the grain-oriented electrical steel sheet shown in Figure 1A. The magnetic domain refinement treatment here was performed by irradiating with a continuous wave laser along a magnetic domain control treatment line that is almost perpendicular to the rolling direction (RD).

[0014] Here, "180° magnetic domain" refers to a magnetic domain where the magnetization direction is the same as that of the crystal. <100> This represents a magnetic domain that is situated between two 180° domain walls that are both oriented and nearly parallel to the rolling direction. The "width" of a 180° domain refers to the distance between adjacent domain walls (domain wall spacing).

[0015] The spatial distribution of magnetic domain widths shown in Figures 1A and 1B were derived from magnetic domain images of grain-oriented electrical steel sheets using the two-dimensional Fourier transform described later.

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

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

[0018] Figure 2 shows the relationship between the magnetic domain width before and after laser irradiation at the same location. Here, the irradiation conditions are: average irradiation energy density Ua (mJ / mm²). 2 ), and irradiation pitch PL (mm), respectively, Ua = 1.5 mJ / mm 2 PL=4mm.

[0019] Figure 2 shows that even when laser irradiation is applied to a region with a magnetic domain width of approximately 500 μm or less, the effect of magnetic domain refinement does not appear.

[0020] From the above, it is thought that the effect of reducing iron loss is obtained by subdividing magnetic domains in regions where the original magnetic domain width is wide, and that applying the magnetic domain subdivision treatment to regions where the original magnetic domain width is narrow does not result in a reduction of iron loss, but rather leads to an increase in hysteresis loss and a deterioration of noise characteristics.

[0021] Therefore, in this embodiment, the magnetic domain control is performed so as to preferentially apply the magnetic domain subdivision process to regions of the grain-oriented electrical steel sheet with wide original magnetic domain widths (for example, regions of approximately 500 μm or more). Preferably, in this embodiment, the magnetic domain control is performed so as to apply the magnetic domain subdivision process only to regions of the grain-oriented electrical steel sheet with wide original magnetic domain widths (for example, regions of approximately 500 μm or more). However, considering the operational accuracy of the magnetic domain control device, it is acceptable for regions with narrow magnetic domain widths and the magnetic domain subdivision processing lines to overlap slightly.

[0022] Next, with reference to Figures 3 to 5, the configuration of the device that realizes magnetic domain control of grain-oriented electrical steel sheets according to this embodiment will be described.

[0023] Figure 3 shows the hardware configuration of an image acquisition device 30 for acquiring magnetic domain images of grain-oriented electrical steel sheets. The image acquisition device 30 comprises a light source unit 31, a magneto-optical (MO) sensor 33, an image sensor 35, and a signal processing unit 37.

[0024] The light source unit 31 has a light source consisting of light-emitting diodes (LEDs) and irradiates the MO sensor 33 with light that has a aligned plane of polarization.

[0025] The MO sensor 33 is a device for measuring the structure of a magnetic material and has an observation surface on which the magnetic material sample to be measured is placed. Light emitted from the light source unit 31 passes through the inside of the MO sensor 33 and is reflected by the reflective layer, and the reflected light passes through the inside of the MO sensor 33 again and is output to the outside of 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 material sample, a leakage magnetic field is generated inside the MO sensor 33 according to the direction of the spontaneous magnetization of the grain-oriented electrical steel sheet, and this leakage magnetic field rotates the polarization plane of the reflected light.

[0026] The image sensor 35 is a Complementary Metal-Oxide-Semiconductor (CMOS) image sensor that focuses the reflected light from the MO sensor 33 onto the light-receiving surface, performs photoelectric conversion, and outputs the resulting analog signal to the signal processing unit 37. By detecting the reflected light with a rotated plane of polarization using the image sensor 35, the spatial distribution of the leakage magnetic field can be obtained, revealing the magnetic domain structure of the grain-oriented electrical steel sheet.

[0027] 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 then 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 the analysis device 40 (see Figure 4) via cable or wireless communication.

[0028] Figure 4 shows the hardware configuration of an analysis device 40 for analyzing 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 comprises a calculation unit 41, memory 43, display unit 45, input unit 47, and communication I / F 49.

[0029] The calculation unit 41 has a Central Processing Unit (CPU) and, according to a program stored in memory 43, analyzes the magnetic domain structure from the magnetic domain image of the grain-oriented electrical steel sheet and determines the locations to which magnetic domain subdivision processing is applied. The processing performed by the calculation unit 41 will be described in detail later.

[0030] Memory 43 includes Read Only Memory (ROM) and Random Access Memory (RAM). ROM stores programs executed by the CPU of the arithmetic unit 41 and data necessary for the execution of these programs. Programs and data stored in ROM are loaded into RAM and executed.

[0031] The memory 43 may include magnetic memory such as a hard disk drive (HDD), or optical memory such as an optical disc. Alternatively, programs and data may be stored on a computer-readable recording medium that is detachable from the analysis device 40. Alternatively, programs executed by the arithmetic unit 41 may be received from a network via the communication interface 49.

[0032] The display unit 45 has a display such as a liquid crystal display (LCD), plasma display, or organic electroluminescent (EL) display, and displays an image based on the image signal output from the image acquisition device 30, and also displays the results of the magnetic domain structure analysis by the calculation unit 41.

[0033] The input unit 47 has input devices such as a mouse and keyboard. The communication interface 49 is an interface for sending and receiving data with external devices via a network such as a Local Area Network (LAN), Wide Area Network (WAN), or the Internet.

[0034] Furthermore, instead of general-purpose hardware such as a CPU, dedicated hardware such as an application-specific integrated circuit (ASIC) or a field-programmable gate array (FPGA) specialized for analyzing magnetic domain structures may be used as the calculation unit 41.

[0035] Although Figures 3 and 4 show cases where the image acquisition device 30 and the analysis device 40 are separate devices, a system in which the image acquisition device 30 and the analysis device 40 are integrated may also be used.

[0036] Known methods such as laser irradiation and electron beam irradiation can be used to perform magnetic domain refinement treatment on the surface of grain-oriented electrical steel sheets. The following describes the configuration of a laser irradiation apparatus that performs magnetic domain refinement treatment by laser irradiation.

[0037] Figure 5 shows the configuration of the laser irradiation device 500. The laser irradiation device 500 comprises a polygon mirror 501, a light source device 503, a collimator 505, a focusing lens 507, a motor 509, a sensor 511, a control unit 513, and a plate feeding device 515.

[0038] The sheet feeding device 515 feeds the grain-oriented electrical steel sheet 50 in the rolling direction (RD).

[0039] The polygon mirror 501 is, for example, shaped like a regular polygonal prism, and multiple plane mirrors are provided on each of the multiple sides that make up the regular polygonal prism. A laser beam LB is incident on the plane mirrors of the polygon mirror 501 from the light source device 503 via the collimator 505 in one direction (horizontal direction) and is reflected by the plane mirrors.

[0040] The polygon mirror 501 is rotatable around the rotation axis O1 by drive from the motor 509. As the angle of incidence of the laser beam LB to the plane mirror changes sequentially according to the rotation angle of the polygon mirror 501, the reflection direction of the laser beam LB changes sequentially, allowing scanning along the magnetic domain control processing lines 52 of the grain-oriented electrical steel sheet 50. Here, the magnetic domain control processing lines 52 are multiple straight lines on the surface of the grain-oriented electrical steel sheet 50 that form an angle of 0° to 45° with respect to the direction perpendicular to the rolling direction (TD) and are aligned in the rolling direction (RD). Preferably, the multiple magnetic domain control processing lines 52 extend parallel to each other. Also preferably, the multiple magnetic domain control processing lines 52 are arranged at equal intervals. The interval P between adjacent magnetic domain control processing lines 52 represents the irradiation pitch.

[0041] The light source device 503 outputs a laser beam LB in a predetermined irradiation method (for example, a continuous irradiation method or a pulsed irradiation method) under the control of the control unit 513.

[0042] The focusing lens 507 is positioned in the optical path of the laser beam LB reflected from the polygon mirror 501, and constitutes a focusing optical system with a predetermined focal length. The laser beam LB reflected from the polygon mirror 501 is focused onto the surface of the grain-oriented electrical steel sheet 50 via the focusing lens 507, thereby forming grooves along the magnetic domain control processing lines 52 on the surface of the grain-oriented electrical steel sheet 50, or introducing thermal strain.

[0043] The motor 509 is connected to the polygon mirror 501 and rotates the polygon mirror 501 under the control of the control unit 513.

[0044] Sensor 511 is connected to the drive shaft of motor 509 and detects the rotation angle of polygon mirror 501, which is rotated by motor 509, and outputs a signal indicating the detected rotation angle (hereinafter referred to as the rotation angle signal) to control unit 513.

[0045] The control unit 513 consists of a processor and is connected to the light source device 503, motor 509, sensor 511, and sheet metal feed device 515. The control unit 513 receives a speed signal input from the sheet metal feed device 515 and outputs a signal to the motor 509 instructing it to rotate the polygon mirror 501.

[0046] Furthermore, the control unit 513 controls the on / off state of the laser beam LB output by the light source device 503 based on the magnetic domain subdivision signal, which represents the portion of the magnetic domain control processing line 52 to which magnetic domain subdivision processing is applied, 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 magnetic domain subdivision signal is input from the analysis device 40 to the laser irradiation device 500. Alternatively, the magnetic domain subdivision signal may be input to the laser irradiation device 500 by an operator.

[0047] Next, with reference to Figure 6, the manufacturing method of the grain-oriented electrical steel sheet 50 according to this embodiment will be described.

[0048] First, the image acquisition device 30 acquires a magnetic domain image of the grain-oriented electrical steel sheet 50 (step S62). Next, the calculation unit 41 of the analysis device 40 derives the spatial distribution of 180° magnetic domain widths (magnetic domain widths) from the magnetic domain image, and determines that the areas in the magnetic domain control processing lines 52 of the grain-oriented electrical steel sheet 50 where the magnetic domain width is greater than or equal to a predetermined value (for example, about 500 μm or more) are areas to which magnetic domain subdivision processing is applied (step S64).

[0049] In this embodiment, the portion of the magnetic domain control processing line 52 to which magnetic domain subdivision processing is applied is called the "magnetic domain subdivision processing line." Details of the processing in step S64, which is performed by the calculation unit 41, will be described later.

[0050] In step S64, the operator may visually observe the magnetic domain image displayed on the display unit 45 to determine the location of the magnetic domain subdivision processing line, and input a magnetic domain subdivision signal representing the location of the magnetic domain subdivision processing line to the laser irradiation device 500.

[0051] Next, the magnetic domain subdivision process is preferentially applied to the locations of the magnetic domain control processing lines 52 of the grain-oriented electrical steel sheet 50 determined in step S64 (step S66). Preferably, the magnetic domain subdivision process is applied only to the locations determined in step S64. The magnetic domain subdivision process in step S66 may be performed by irradiation with a laser beam LB from a laser irradiation device 500, or other means such as irradiation with an electron beam may be employed.

[0052] Next, the process of step S64, which is performed by the calculation unit 41 of the analysis device 40, will be described.

[0053] The calculation unit 41 uses the line segment method or Fourier transform to derive the spatial distribution of magnetic domain widths of the grain-oriented electrical steel sheet 50, and determines that the areas in the magnetic domain control processing line 52 of the grain-oriented electrical steel sheet 50 where the magnetic domain width is greater than a predetermined value (for example, about 500 μm) are areas to which magnetic domain subdivision processing is applied.

[0054] In the line segment method, the magnetic domain is evaluated by drawing line segments perpendicular to the domain. The line segments are drawn so that there are three segments per centimeter in a direction parallel to the domain, and the domain width is derived from the distance between the intersection points of the 180° domain wall and the line segments.

[0055] 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 will explain how to derive the spatial distribution of magnetic domain widths of grain-oriented electrical steel sheets using the short-interval two-dimensional Fourier transform (hereinafter referred to as "ST2DFT"), which is an extension of the short-interval Fourier transform, one of the signal processing methods that has been used for a long time for the time-frequency analysis of audio signals, to a two-dimensional domain.

[0056] The image signal acquired by the image acquisition device 30 represents the image (magnetic domain image), which is denoted as x(k,l) as a data sequence in two-dimensional coordinates (kl coordinates). In this embodiment, the magnetic domain image to be analyzed is an image binarized by two colors, such as grayscale, or an image represented by three or more gradations (multi-gradation).

[0057] To derive the spatial distribution of the magnetic domain width of the directional electromagnetic steel sheet 50, the calculation unit 41 executes the following steps (A-1), (A-2), and (A-3). (A-1) Step of cutting out a plurality of partial regions from the magnetic domain image; (A-2) Step of performing ST2DFT; (A-3) Step of deriving the spatial distribution of the magnetic domain width. Hereinafter, each step will be described in detail.

[0058] (A-1) Step of cutting out a plurality of partial regions from the magnetic domain image To cut out a plurality of partial regions from the magnetic domain image and analyze their respective frequency structures, the window function Wa(k, l) of a rectangular window with the range of the k direction being 0 ≦ k ≦ N k -1 and the range of the l direction being 0 ≦ l ≦ N l -1 is used (N k and N l are natural numbers). As the window function Wa(k, l), a Hamming window, a Hanning window, a Blackman window, etc. can be applied.

[0059] The observation position in the data sequence x(k, l) of the magnetic domain image is denoted by the index (n, m), and the shift amounts of the window function Wa(k, l) in the k direction and the l direction are denoted by S k and S l respectively. Then (n, m, S k , S l are integers), as shown in Equation (1), a data sequence x of a partial region cut out from the magnetic domain image within the range of nS k ≦ k ≦ nS k + N k -1, mS l ≦ l ≦ mS l + N l -1 is obtained. nm (k - nS k , l - mS l ) [Number]

[0060] Figure 7 shows examples of subregions extracted from the magnetic domain image G, corresponding to observation positions (n,m) = (1,1), (2,2), (3,3), ..., (P,Q) (where P and Q are natural numbers).

[0061] In this embodiment, the range of the window function Wa(k,l) is defined by N. k and N l These are parameters corresponding to the number of pixels in the k-direction and the number of pixels in the l-direction in the subregion, respectively.

[0062] (A-2) Steps to perform ST2DFT The data column of the subregion is x nm (n', m')=x nm (k-nS k ,l-mS l ) defined as x nm When a two-dimensional Fourier transform is applied to (n', m'), a partial Fourier image X(f) corresponding to the subregion of the observation position (n, m) is obtained, as shown in equation (2). k ,f l ,n,m) is obtained.

number

[0063] 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 It is defined as shown in equation (3).

number

[0064] For example, the data column x of each subregion shown in Figure 7 nm (k-nS k,l-mS l When a two-dimensional Fourier transform is applied to ), as shown in Figure 8, a partial Fourier image X(f k ,f l ,n,m) is obtained.

[0065] (A-3) Steps to derive the spatial distribution of magnetic domain widths Partial Fourier image X(f k ,f l When a partial Fourier image X(f, n, m) is obtained, k ,f l Coordinates of the peak position of the spot (k component f) k max (n,m) and l component f l max (n,m) is determined. Note that when deriving the peak position, the region near k=0 and l=0 is excluded because it is a part that depends heavily on the image contrast.

[0066] Then, from the spatial frequency resolution defined in 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

[0067] Thus, by using ST2DFT, it becomes possible to quantitatively derive the spatial distribution L(n,m) of the magnetic domain width while preserving the positional information of the magnetic domain image. Figures 1A to 1C above show the analysis results of the magnetic domain width derived by ST2DFT.

[0068] The calculation unit 41 derives the spatial distribution L(n,m) of the magnetic domain width and, as shown in Figure 9, determines that the locations of the magnetic domain widths of the grain-oriented electrical steel sheet 50 that are greater than or equal to a predetermined value (for example, about 500 μm or more) among the magnetic domain control processing lines 52 (dashed lines in Figure 9) are the magnetic domain subdivision processing lines 90 (solid lines in Figure 9) to which the magnetic domain subdivision processing is applied. The control unit 513 of the laser irradiation device 500 controls the power of the laser beam LB to turn on the magnetic domain subdivision processing lines 90 among the magnetic domain control processing lines 52, and preferably to turn off the power of the laser beam LB to the other locations. As a result, grooves are formed along the magnetic domain subdivision processing lines 90, or thermal strain is introduced. Note that the above-mentioned "predetermined value" does not need to strictly match 500 μm. By setting the predetermined value to approximately within the range of 400 μm to 600 μm, it is possible to provide grain-oriented electrical steel sheets that achieve both low iron loss and low noise. The lower limit of the specified value may be 425 μm, 450 μm, or 475 μm. The upper limit of the specified value may be 575 μm, 550 μm, or 525 μm.

[0069] In some cases, the magnetic domain subdivision lines 90 may be unclear in the magnetic domain image obtained by the procedure described above. In this case, the observation conditions may be adjusted so that the magnetic domain subdivision lines 90 can be clearly identified. For example, the magnetic domain subdivision lines 90 can be made clearer by applying a DC magnetic field along the direction perpendicular to the surface of the grain-oriented electrical steel sheet (thickness direction).

[0070] Next, the grain-oriented electrical steel sheet 50 according to this embodiment will be described. The grain-oriented electrical steel sheet 50 according to this embodiment has magnetic domain subdivision lines 90, as illustrated in Figure 9. The magnetic domain subdivision lines 90 are portions that have undergone magnetic domain subdivision processing. The magnetic domain subdivision lines 90 are, for example, grooves and thermal strains. When the magnetic domain subdivision lines 90 are grooves, they can be easily seen. Even when the magnetic domain subdivision lines 90 are in a form that is difficult to see, such as thermal strains, the magnetic domain subdivision lines 90 can be clearly observed by taking a magnetic domain image while applying a DC magnetic field along the direction perpendicular to the surface of the grain-oriented electrical steel sheet 50 (thickness direction).

[0071] The magnetic domain subdivision lines 90 are arranged on lines that form an angle of 0° to 45° with respect to the direction perpendicular to the rolling direction (TD), i.e., on the magnetic domain control lines 52, as illustrated in Figure 9. The magnetic domain control lines 52 are arranged on the surface of the grain-oriented electrical steel sheet 50 at an angle of 0° to 45° with respect to the direction perpendicular to the rolling direction (TD) and aligned along the rolling direction (RD). It is preferable that the magnetic domain control lines 52 are arranged parallel to each other. The magnetic domain control lines 52 correspond to the trajectory of the focal point of the laser beam LB during the manufacturing stage of the grain-oriented electrical steel sheet 50. The magnetic domain control lines 52 are The magnetic domain subdivision lines 90 are not actual physical entities in the grain-oriented electrical steel sheet 50, but are virtual lines along the magnetic domain subdivision lines 90. The magnetic domain control lines 52 can be identified by drawing lines along the magnetic domain subdivision lines 90 using the procedure described above. The angle between the direction perpendicular to rolling (TD) and the direction of extension of the magnetic domain subdivision lines 90 is the same as the angle between the direction perpendicular to rolling (TD) and the direction of extension of the magnetic domain control lines 52 on which the magnetic domain subdivision lines 90 are provided.

[0072] The magnetic domain subdivision lines 90 form an angle of 0° to 45° with respect to the rolling direction (TD) of the grain-oriented electrical steel sheet 50. If the angle between the magnetic domain subdivision lines 90 and the rolling direction (TD) exceeds 45°, the effect of reducing iron loss cannot be obtained. The angle between the magnetic domain subdivision lines 90 and the rolling direction (TD) may be 1° or more, 5° or more, or 10° or more. The angle between the magnetic domain subdivision lines 90 and the rolling direction (TD) may be 40° or less, 30° or less, or 20° or less.

[0073] In addition, in the grain-oriented electrical steel sheet 50, the angle between the magnetic domain control processing lines 52 and the direction perpendicular to the rolling direction (TD) may be uniform or vary. The angle between the magnetic domain control processing lines 52 and the direction perpendicular to the rolling direction (TD) may be 0° to 45° in only a part of the grain-oriented electrical steel sheet 50, or it may be 0° to 45° in all areas of the grain-oriented electrical steel sheet 50. Furthermore, the average value of the angle between the magnetic domain control processing lines 52 and the direction perpendicular to the rolling direction (TD) in the grain-oriented electrical steel sheet 50 may be 0° to 45°. The angle between the magnetic domain control processing lines 52 and the direction perpendicular to the rolling direction (TD), or its average value, may be 1° or more, 3° or more, or 5° or more. The angle between the magnetic domain control processing line 52 and the direction perpendicular to the rolling direction (TD), or its average value, may be 40° or less, 35° or less, or 30° or less.

[0074] In the grain-oriented electrical steel sheet 50 according to this embodiment, it is preferable that the average magnetic domain width in the region of the magnetic domain control processing line 52 that does not have a magnetic domain subdivision processing line 90 and has a length of 1 mm or more is 500 μm or less. The region of the magnetic domain control processing line 52 that does not have a magnetic domain subdivision processing line 90 is the region between multiple magnetic domain subdivision processing lines 90 that lie on the same line. The length of the region of the magnetic domain control processing line 52 that does not have a magnetic domain subdivision processing line 90 is the interval between multiple magnetic domain subdivision processing lines 90 that lie on the same line, and is a value measured along the magnetic domain subdivision processing line 90. Hereinafter, the region of the magnetic domain control processing line 52 that does not have a magnetic domain subdivision processing line 90 may be referred to as a non-magnetic domain subdivision processing line. For example, in the grain-oriented electrical steel sheet 10 illustrated in Figure 10, the non-magnetic domain subdivision processing line denoted by reference numeral 100A corresponds to "the region of the magnetic domain control processing line 52 that does not have a magnetic domain subdivision processing line 90 and has a length of 1 mm or more".

[0075] When the average magnetic domain width of a non-magnetic domain subdivided wire with a length of 1 mm or more is 500 μm or less, the iron loss of the grain-oriented electrical steel sheet 50 is further reduced, which is preferable. The average magnetic domain width of a non-magnetic domain subdivided wire with a length of 1 mm or more is more preferably 480 μm or less, 450 μm or less, or 400 μm or less.

[0076] Furthermore, in grain-oriented electrical steel sheets 50 in which the average magnetic domain width of non-magnetic domain subdivision processing lines with a length of 1 mm or more among the magnetic domain control processing lines 52 is 500 μm or less, the magnetic domain subdivision processing is minimized. As described above, in grain-oriented electrical steel sheets 50 before magnetic domain subdivision processing, regions with wide magnetic domain widths and regions with narrow magnetic domain widths are mixed. By identifying the distribution of magnetic domain widths in advance and minimizing the magnetic domain subdivision processing in regions with narrow magnetic domain widths, grain-oriented electrical steel sheets 50 in which the average magnetic domain width of non-magnetic domain subdivision processing lines with a length of 1 mm or more among the magnetic domain control processing lines 52 is 500 μm or less can be obtained. In such grain-oriented electrical steel sheets 50, the magnetic domain subdivision processing in regions with narrow magnetic domain widths, which have little effect on reducing iron loss, can be appropriately avoided, and the generation of recirculating magnetic domains caused by the magnetic domain subdivision processing can be reduced, further suppressing noise.

[0077] In the grain-oriented electrical steel sheet 50 according to this embodiment, it is preferable that the average magnetic domain width in the region of the magnetic domain control processing line 52 that does not have a magnetic domain subdivision processing line 90 and contains two or more magnetic domain walls 502 (i.e., 180° magnetic domain walls) is 500 μm or less. The region of the magnetic domain control processing line 52 that does not have a magnetic domain subdivision processing line 90 is the region between multiple magnetic domain subdivision processing lines 90 that lie on the same line, and is the non-magnetic domain subdivision processing line described above. For example, in the grain-oriented electrical steel sheet 10 illustrated in Figure 10, the non-magnetic domain subdivision processing line denoted by reference numeral 100A and the non-magnetic domain subdivision processing line denoted by reference numeral 100B correspond to "the region of the magnetic domain control processing line 52 that does not have a magnetic domain subdivision processing line 90 and contains two or more magnetic domain walls 502".

[0078] It is preferable that the average domain width in a non-domain-refined line containing two or more domain walls 502 is 500 μm or less, as this further reduces the iron loss of the grain-oriented electrical steel sheet 50. Furthermore, a grain-oriented electrical steel sheet 50 in which the average domain width in a non-domain-refined line containing two or more domain walls 502 is 500 μm or less can be obtained by performing domain control so that the domain-refining process is preferentially applied to regions where the original domain width of the grain-oriented electrical steel sheet is wide (for example, regions of approximately 500 μm or more). Therefore, when the average domain width in a non-domain-refined line containing two or more domain walls 502 is 500 μm or less, the domain-refining process is appropriately avoided in regions with narrow domain widths where the iron loss reduction effect is small, and the generation of recirculating domains caused by the domain-refining process is reduced, thus further suppressing the noise of the grain-oriented electrical steel sheet 50.

[0079] In the region where the magnetic domain subdivision lines 90 are present, the magnetic domain width is inevitably reduced. Therefore, the average magnetic domain width in the region where the magnetic domain subdivision lines 90 are present is not particularly limited. However, the average magnetic domain width in the region where the magnetic domain subdivision lines 90 are present may be defined as, for example, 500 μm or less, 480 μm or less, 450 μm or less, or 400 μm or less.

[0080] In this embodiment, the proportion of magnetic domain subdivision processing lines 90 within the magnetic domain control processing lines 52 is defined as the ratio of the length of magnetic domain subdivision processing lines 90 to the total length of magnetic domain control processing lines 52, and is preferably 10% or more and 90% or less.

[0081] Here, it is preferable that the ratio of the magnetic domain subdivision processing lines 90 to the total length of the magnetic domain control processing lines 52 be 10% or more because if it is less than 10%, the magnetic domain subdivision effect is difficult to obtain, and it is preferable that it be 90% or less because if it exceeds 90%, it is undesirable in terms of noise reduction.

[0082] From the viewpoint of reducing noise, it is preferable that the proportion of magnetic domain subdivision processing lines 90 within the magnetic domain control processing lines 52 be small. Furthermore, by setting the average magnetic domain width of non-magnetic domain subdivision processing lines with a length of 1 mm or more within the magnetic domain control processing lines 52 to 500 μm or less, or by setting the average magnetic domain width of non-magnetic domain subdivision processing lines containing two or more magnetic domain walls 502 to 500 μm or less, low iron loss can be achieved even if the proportion is small.

[0083] The ratio of the magnetic domain subdivision processing lines 90 to the total length of the magnetic domain control processing lines 52 is preferably 15% or more, 20% or more, or 30% or more. The ratio of the magnetic domain subdivision processing lines 90 to the total length of the magnetic domain control processing lines 52 is preferably 80% or less, 70% or less, or 60% or less.

[0084] Furthermore, in this embodiment, it is preferable that the magnetic domain subdivision lines 90 exist on the magnetic domain control lines 52 in a non-single periodic manner. Here, the existence of the magnetic domain subdivision lines 90 on the magnetic domain control lines 52 in a non-single periodic manner means that it does not fall under the case where "there are an average of 10 or more magnetic domain subdivision lines 90 per centimeter, and the standard deviation of the length of the non-magnetic domain subdivision lines between each magnetic domain subdivision line 90 is 20 μm or less." In other words, in this embodiment, the magnetic domain subdivision lines 90 obtained by performing magnetic domain control with a normal pulsed laser over the entire surface of the steel plate are not considered to "exist in a non-single periodic manner."

[0085] As described above, by applying magnetic domain refinement treatment only to the regions of the grain-oriented electrical steel sheet where the original magnetic domain width is wide, adverse effects such as increased hysteresis loss and deterioration of noise characteristics can be minimized, and the effect of magnetic domain refinement can be maximized. This makes it possible to achieve both low iron loss and low noise.

[0086] (Measurement method) The following describes a method for measuring parameters related to the grain-oriented electrical steel sheet 50 according to this embodiment. Note that all parameter measurements are performed on a sample of a predetermined size taken from the grain-oriented electrical steel sheet 50. For example, a rectangular sample with sides of 100 mm (or 100 mm or more) can be cut from the grain-oriented electrical steel sheet 50 and used for measurement. If the grain-oriented electrical steel sheet 50 is a coil, a sample can be taken from any point on the coil. Similarly, if the grain-oriented electrical steel sheet 50 is a component incorporated into electrical products such as transformers or motors, a sample can be taken from any point 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 should be 10,000 mm². 2 The above should be achieved. In this process, it is desirable to collect the sample using methods such as wire cutting to minimize the effects of mechanical distortion on the sample.

[0087] (Angle between the magnetic domain control processing line 52 and the direction perpendicular to the rolling direction (TD)) The method for measuring the angle between the magnetic domain control processing line 52 and the direction perpendicular to the rolling direction (TD) is as follows.

[0088] First, the magnetic domain subdivision lines 90 contained in the sample are identified. If the magnetic domain subdivision lines 90 are visible, such as grooves, no special processing for the magnetic domain subdivision lines 90 is required. If the magnetic domain subdivision lines 90 are difficult to see, such as due to thermal strain, a magnetic domain image is taken using an image acquisition device, for example, as illustrated in Figure 3. If necessary, a DC magnetic field is applied along the direction perpendicular to the plate surface (thickness direction) of the grain-oriented electrical steel sheet 50 while taking the magnetic domain image. By observing the magnetic domain image, the location of the magnetic domain subdivision lines 90 can be identified.

[0089] Next, we identify the direction perpendicular to the rolling direction (TD). (1) If the sample is cut from a coiled grain-oriented electrical steel sheet 50, the width direction of the grain-oriented electrical steel sheet 50 can be considered to be the direction perpendicular to the rolling direction (TD). (2) If the sample is cut from a component of an electrical product, the direction perpendicular to the rolling direction (TD) is determined from the rolling defects on the surface of the grain-oriented electrical steel sheet 50. The direction in which the rolling defects extend is considered to be the rolling direction (RD), and the direction perpendicular to the rolling direction (RD) and parallel to the surface of the steel sheet is considered to be the direction perpendicular to the rolling direction (TD). (3) If it is difficult to determine the direction perpendicular to the rolling direction (TD) from the rolling defects on the surface of the grain-oriented electrical steel sheet 50, the direction perpendicular to the rolling direction (TD) is determined 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. The direction in which the deviation angle from the GOSS orientation at the measurement point is minimized is considered 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 considered the direction perpendicular to the rolling direction (TD). In either case, from the viewpoint of ease of measurement, it is preferable to cut 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).

[0090] The magnetic domain control processing line 52 does not actually exist in the grain-oriented electrical steel sheet 50, but is a virtual line along the magnetic domain subdivision processing line 90. Therefore, the narrow angle between the magnetic domain subdivision processing line 90 identified in the procedure described above and the direction perpendicular to the rolling direction (TD) can be considered as the angle between the magnetic domain control processing line 52 and the direction perpendicular to the rolling direction (TD).

[0091] (Average magnetic domain width in areas with a length of 1 mm or more and without magnetic domain subdivision lines 90) The method for measuring the average domain width in non-domain subdivision processing lines with a length of 1 mm or more among the magnetic domain control processing lines 52 is as follows:

[0092] First, an image of the sample's magnetic domains is taken using an image acquisition device as illustrated in Figure 3. If necessary, the magnetic domain subdivision lines 90 of the sample are clarified by taking the image while applying a DC magnetic field along the direction perpendicular to the plate surface of the sample (thickness direction). Figure 10 shows an example of a magnetic domain image. In the magnetic domain image, magnetic domains 501A and 501B have a band shape. For clarity, adjacent magnetic domains are shown in different colors in Figure 10. That is, for the sake of explanation, magnetic domain 501A is hatched, while magnetic domain 501B adjacent to magnetic domain 501A is not hatched. The boundary between two adjacent magnetic domains 501A and 501B is the magnetic domain wall 502.

[0093] Next, we consider a virtual line along the magnetic domain subdivision processing line 90 included in the magnetic domain image. This virtual line corresponds to the magnetic domain control processing line 52. Then, we measure the length of the portion of the virtual line where the magnetic domain subdivision processing line 90 does not exist (hereinafter referred to as the "non-magnetic domain subdivision processing line"). The length of the non-magnetic domain subdivision processing line refers to the length along the virtual line, i.e., the magnetic domain subdivision processing line 90. This extracts all non-magnetic domain subdivision processing lines in the sample that are 1 mm or longer. For example, the non-magnetic domain subdivision processing line with code 100A is extracted because its length is 1 mm or longer. The non-magnetic domain subdivision processing lines with codes 100B and 100C are not extracted because their length is less than 1 mm. Furthermore, we count the total number of magnetic domains 501A and 501B contained in all non-magnetic domain subdivision processing lines with a length of 1 mm or longer. For example, the number of magnetic domains contained in the non-magnetic domain subdivision processing line with code 100A is 4. The average domain width of the non-magnetic domain refinement processed lines with a length of 1 mm or more among the magnetic domain control processed lines 52 is calculated by dividing the total length of all non-magnetic domain refinement processed lines with a length of 1 mm or more included in the sample by the total number of magnetic domains 501A and 501B included in these non-magnetic domain refinement processed lines.

[0094] (Average domain width in a region containing two or more domain walls 502 and without domain subdivision lines 90) The method for measuring the average domain width in a non-domain-refined line containing two or more domain walls 502 is as follows:

[0095] First, an image acquisition device, as illustrated in Figure 3, is used to capture a magnetic domain image of the sample. If necessary, the magnetic domain subdivision lines 90 of the sample are clarified by applying a DC magnetic field along the direction perpendicular to the plate surface (thickness direction) while capturing the magnetic domain image. Figure 10 shows an example of a magnetic domain image. The boundary between adjacent magnetic domains 501A and 501B is the magnetic domain wall 502.

[0096] Next, we consider a virtual line along the magnetic domain subdivision processing line 90 included in the magnetic domain image. This virtual line corresponds to the magnetic domain control processing line 52. Then, we count the number of domain walls 502 contained in the portion of the virtual line where the magnetic domain subdivision processing line 90 does not exist (hereinafter referred to as the "non-magnetic domain subdivision processing line"). This extracts all non-magnetic domain subdivision processing lines contained in the sample that contain two or more domain walls 502. For example, the non-magnetic domain subdivision processing line with code 100A is extracted because it contains three domain walls 502. The non-magnetic domain subdivision processing line with code 100B is not extracted because it contains one domain wall 502. The non-magnetic domain subdivision processing line with code 100C is extracted because it contains two domain walls 502.

[0097] Furthermore, the total number of magnetic domains 501A and 501B in all non-domain subdivided lines containing two or more domain walls 502 is counted. For example, the non-domain subdivided line designated 100A contains four magnetic domains 501A and 501B. The non-domain subdivided line designated 100C contains three magnetic domains 501A and 501B. The average domain width in non-domain subdivided lines containing two or more domain walls 502 is calculated by dividing the total length of all non-domain subdivided lines containing two or more domain walls 502 in the sample by the total number of magnetic domains 501A and 501B in those non-domain subdivided lines.

[0098] The method for measuring the ratio of magnetic domain subdivision lines 90 to the total length of magnetic domain control lines 52 is as follows: First, the magnetic domain control lines 52 and magnetic domain subdivision lines 90 contained in the sample are identified using the procedure described above. Next, the total length of all magnetic domain control lines 52 and the total length of all magnetic domain subdivision lines 90 contained in the sample are calculated. Then, the ratio of magnetic domain subdivision lines 90 to the total length of magnetic domain control lines 52 is calculated by dividing the total length of all magnetic domain subdivision lines 90 contained in the sample by the total length of all magnetic domain control lines 52 contained in the sample.

[0099] The method for determining whether or not magnetic domain subdivision lines 90 exist in a non-single period is as follows. First, the magnetic domain control lines 52 and magnetic domain subdivision lines 90 contained in the sample are identified using the procedure described above. As described above, the existence of magnetic domain subdivision lines 90 in a non-single period means that the condition "there are an average of 10 or more magnetic domain subdivision lines 90 per centimeter, and the standard deviation of the length of non-magnetic domain subdivision lines between each magnetic domain subdivision line 90 is 20 μm or less" is not met. Therefore, in making the determination, it is determined whether or not there are an average of 10 or more magnetic domain subdivision lines 90 per centimeter in each of the multiple magnetic domain control lines 52 contained in the sample (for example, a rectangular sample with sides of 100 mm). For example, if the length of one magnetic domain control line 52 in the sample is X cm, and the number of magnetic domain subdivision lines 90 contained in that magnetic domain control line 52 is y, then it is determined that the magnetic domain control line 52 has an average of y / X magnetic domain subdivision lines 90 per centimeter. Furthermore, for each magnetic domain control line 52 that is determined to contain an average of 10 or more magnetic domain subdivision lines 90 per centimeter, it is determined whether the standard deviation of the length of non-magnetic domain subdivision lines is 20 μm or less. If, in more than 50% of all magnetic domain control lines 52 contained in the sample, the magnetic domain subdivision lines 90 are provided in a non-single period, then it is determined that the magnetic domain subdivision lines 90 exist in a non-single period in that sample. [Examples]

[0100] The effects of one aspect of the present invention will be further explained in detail by the examples. However, the conditions in the examples are merely examples of conditions adopted to confirm the feasibility and effects of the present invention. The present invention is not limited to these examples of conditions. The present invention can adopt various conditions as long as it does not depart from the spirit of the invention and achieves the objectives of the present invention.

[0101] Magnetic domain refinement treatment was performed on grain-oriented electrical steel sheets from the same lot, classified as 23P085 in Table 2 of JIS C 2553:2019 "Grain-oriented electrical steel strips," under various conditions shown in Table 1. The noise and iron loss of the resulting grain-oriented electrical steel sheets with refined magnetic domains were evaluated and are shown in Table 2. In all examples and comparative examples, the angle between the magnetic domain control treatment line and the direction perpendicular to the rolling direction was kept the same for all magnetic domain control treatment lines.

[0102] The evaluation method for noise and iron loss was as follows. First, a three-phase transformer core was created by laminating 180 sheets of grain-oriented electrical steel with a thickness of 0.23 mm. The width of both the legs and yoke of the three-phase transformer core was set to 150 mm. The height and width of the outer dimensions of the three-phase transformer core were both set to 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 1.7 T.

[0103] For noise measurement, microphones were placed at equal intervals around the transformer containing the three-phase transformer core. The distance between the transformer and the microphones was 30 cm. The noise measurement results from these microphones were A-weighted and averaged to obtain the noise evaluation results (unit dBA) for grain-oriented electrical steel sheets, which are listed in Table 2. Examples with a noise evaluation result of 33.5 dBA or less were judged to be examples where noise reduction was achieved. Noise evaluation results judged as unsatisfactory are underlined.

[0104] Iron loss was determined by measuring the primary and secondary voltages and currents using a power analyzer when excitation was performed at a frequency of 50 Hz and an excitation magnetic flux density of 1.7 T, as described above. The determined iron loss is listed in Table 2 as the iron loss evaluation results (unit: W / kg) for grain-oriented electrical steel sheets. Examples with an iron loss evaluation result of 1.00 W / kg or less were judged to be examples where low iron loss was achieved. Noise evaluation results that were judged to be unsatisfactory are underlined.

[0105] Furthermore, the average magnetic domain width measured in areas of 1 mm or longer in parts without magnetic domain refinement lines, and the average magnetic domain width measured in areas without magnetic domain refinement lines containing two or more magnetic domain walls, were measured and are listed in Table 2. The method for measuring the average magnetic domain width was as described above. Rectangular samples with sides of 100 mm were cut from the core of a three-phase transformer used for noise and iron loss measurements and used for the measurements.

[0106] [Table 1]

[0107] [Table 2]

[0108] In Example 1, magnetic domain subdivision processing was not performed. In Example 1, no stress introduction 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.

[0109] (Example of an inappropriate angle) In Examples 2 to 5, the angle between the magnetic domain control processing line and the direction perpendicular to the rolling direction was excessive. In these examples, iron loss exceeded 1.00 W / kg and noise exceeded 33.5 dBA. In other words, in Examples 2 to 5, despite the magnetic domain control processing being performed, there was almost no reduction in iron loss, and noise increased.

[0110] In Examples 6 to 10, the angle between the magnetic domain control processing line and the direction perpendicular to the rolling direction was appropriate. In these examples, the iron loss was lower than 1.00 W / kg, and the noise level was 33.5 dBA or less.

[0111] In Examples 11-15, 23, and 25, the angle between the magnetic domain control processing line and the direction perpendicular to the rolling direction was appropriate. In these examples, iron loss was 1.00 W / kg or less, and noise was 33.5 dBA or less. In other words, by setting the magnetic domain control processing line at an appropriate angle, it was possible to reduce iron loss without a significant increase in noise.

[0112] Furthermore, in these examples, the domain subdivision process was performed with a non-single period, resulting in a greater tendency to suppress noise compared to Examples 6-10. For example, comparing Example 7, where the domain subdivision process was performed with a constant pulse, with Example 11, where it was performed with a non-single period, the angle between the domain control processing line and the rolling perpendicular direction TD, and the ratio of the domain subdivision processing line to the total length of the domain control processing line, were the same between Example 7 and Example 11. However, the noise evaluation results were better for Example 11 than for Example 7.

[0113] In Examples 16-22, 24, and 26-28, the angle between the magnetic domain control processing line and the direction perpendicular to the rolling direction was set appropriately, and magnetic domain control processing was performed by selecting locations with a magnetic domain width of 500 μm or more. As a result, in Examples 16-22, 24, and 26-28, a higher reduction in iron loss was achieved compared to Examples 6-15, 23, and 25.

[0114] In addition, in Examples 16-22, 24, and 26-28, noise tended to be suppressed even more than in Examples 6-15, 23, and 25. For example, comparing Example 23, in which the magnetic domain subdivision process was performed in a non-single period, with Example 24, in which the magnetic domain subdivision process was selectively performed in areas where the magnetic domain width was 500 μm or more, the angle between the magnetic domain control processing line and the rolling direction TD, and the ratio of the magnetic domain subdivision processing line to the total length of the magnetic domain control processing line were substantially the same between Example 23 and Example 24. However, the noise evaluation results were better in Example 24 than in Example 23.

[0115] Furthermore, reducing the proportion of magnetic domain subdivision lines to the total length of magnetic domain control lines improves the noise evaluation value, but weakens the iron loss reduction effect. However, in Examples 16-22, 24, and 26-28, the average magnetic domain width in areas without magnetic domain subdivision lines was narrowed by selectively performing magnetic domain subdivision processing in areas where the magnetic domain width was 500 μm or more. As a result, in Examples 16-22, 24, and 26-28, the iron loss reduction effect was also extremely good despite the significant suppression of noise. [Explanation of Symbols]

[0116] 30 Image acquisition device 31 Light source section 33 MO Sensor 35 Image Sensors 37 Signal Processing Unit 40 Analyzer 41 Arithmetic section 43 memory 45 Display section 47 Input section 49 Communication I / F 50 Grain-oriented electrical steel sheet 501A, 501B magnetic domain 502 Domain wall 52 Magnetic Domain Control Processing Line 90 Magnetic Domain Refinement Processing Lines 100A, 100B, 100C Non-magnetic domain subdivision processing lines (regions within magnetic domain control processing lines that do not have magnetic domain subdivision processing lines) 500 Laser Irradiation Devices TD (Rolling direction perpendicular to the rolling direction) RD (Rolling Direction)

Claims

1. In the magnetic domain control processing lines that form an angle of 0° to 45° with respect to the direction perpendicular to the rolling direction and are aligned in the rolling direction, there are magnetic domain subdivision processing lines that represent the portion where magnetic domain subdivision processing has been applied. In the region of the aforementioned magnetic domain control processing line where there is no aforementioned magnetic domain subdivision processing line and the length is 1 mm or more, the average magnetic domain width is 500 μm or less. The ratio of the magnetic domain subdivision processing lines to the total length of the magnetic domain control processing lines is 10% or more and 90% or less. Grain-oriented electrical steel sheet.

2. In the magnetic domain control processing lines that form an angle of 0° to 45° with respect to the direction perpendicular to the rolling direction and are aligned in the rolling direction, there are magnetic domain subdivision processing lines that represent the portion where magnetic domain subdivision processing has been applied. In the region of the aforementioned magnetic domain control processing line where there is no aforementioned magnetic domain subdivision processing line, and where there are two or more magnetic domain walls, the average magnetic domain width is 500 μm or less. The ratio of the magnetic domain subdivision processing lines to the total length of the magnetic domain control processing lines is 10% or more and 90% or less. Grain-oriented electrical steel sheet.

3. The grain-oriented electrical steel sheet according to claim 1 or 2, wherein the magnetic domain subdivision lines exist in a non-single period.

4. The grain-oriented electrical steel sheet according to claim 1 or 2, wherein the magnetic domain subdivision lines are grooves.

5. The grain-oriented electrical steel sheet according to claim 1 or 2, wherein the magnetic domain subdivision lines are thermal strains.

6. A method for manufacturing grain-oriented electrical steel sheets according to claim 1 or 2, Image acquisition step to obtain magnetic domain images of grain-oriented electrical steel sheet, A determination step in which, based on the spatial distribution of magnetic domain widths in the aforementioned magnetic domain image, a magnetic domain subdivision process is applied to a portion of the magnetic domain control processing lines that form an angle of 0° to 45° with respect to the direction perpendicular to the rolling of the grain-oriented electrical steel sheet and are aligned in the rolling direction. A magnetic domain subdivision step in which the magnetic domain subdivision process is applied to the portion of the magnetic domain control processing line determined in the determination step, Includes, The aforementioned determination step determines that locations where the magnetic domain width is greater than or equal to a predetermined value are to be the locations to which the magnetic domain subdivision process is applied. The predetermined value shall be a value within the range of 400 μm to 600 μm. A method for manufacturing grain-oriented electrical steel sheets.

7. The method for manufacturing grain-oriented electrical steel sheets according to claim 6, wherein the determination step involves deriving the spatial distribution of the magnetic domain width from the magnetic domain image using a two-dimensional Fourier transform.

8. The method for manufacturing a grain-oriented electrical steel sheet according to claim 6, wherein the magnetic domain subdivision step is performed by irradiation with a laser or an electron beam.

Images