Grain-oriented electrical steel sheet and method for producing same

Abstract

The invention relates to a grain-oriented electrical steel sheet and a method for manufacturing the same. A grain-oriented electrical steel sheet in which a plurality of magnetic domain control processing lines extending in a direction intersecting the rolling direction are formed on the surface, the grain-oriented electrical steel sheet being annealed by holding at 800 DEG C for 240 minutes or more, cooling to 200 DEG C at 25 DEG C / h or less, and then cooling to 50 DEG C or less at an average cooling rate of 100 DEG C / h or less, with the magnetic domain image of the surface being a first magnetic domain image, and the grain-oriented electrical steel sheet being obtained by annealing the grain-oriented electrical steel sheet. An alternating-current magnetic field is applied to magnetize to a magnetic flux density of 1.9 T or more, and a magnetic domain image at the same position as the first magnetic domain image after demagnetization by attenuating the alternating-current magnetic field is set as a second magnetic domain image; a region in which the magnetic domain width derived from the second magnetic domain image is greater than the magnetic domain width derived from the first magnetic domain image by 100 [mu] m or more is defined as a first region, and a region other than the first region is defined as a second region. The linear density per mm / mm2 of the magnetic domain control processing lines in the second region is smaller than the linear density per mm / mm2 of the magnetic domain control processing lines in the first region.

Description

Technical Field

[0001] This invention relates to directional electromagnetic steel sheets and their manufacturing methods.

[0002] This application is based on and claims priority to Japanese Patent Application No. 2023-166134 filed in Japan on September 27, 2023, the contents of which are incorporated herein by reference. Background Technology

[0003] Directional electromagnetic steel sheets contain less than 7% by mass of Si and have secondary recrystallized grains with easy magnetization axes. <001> {110} oriented along the rolling direction <001> Directional electromagnetic steel sheets are steel sheets with a secondary recrystallization texture aggregated on the Goss orientation. They are primarily used as the cores of power transformers. For directional electromagnetic steel sheets, it is necessary to reduce energy loss (iron loss).

[0004] To reduce iron loss, techniques for narrowing the domain width of directional electromagnetic steel sheets (domain refinement techniques based on domain control processing) have been known previously. Domain width can be narrowed by inducing thermal strain by irradiating the surface of the directional electromagnetic steel sheet with a laser or electron beam in a direction intersecting the rolling direction. Alternatively, domain width can also be narrowed by forming grooves on the surface of the directional electromagnetic steel sheet in a direction intersecting the rolling direction. Methods for forming these grooves include laser or electron beam irradiation, machining methods based on gears, and chemical processing methods such as etching.

[0005] In recent years, various improved techniques for magnetic domain refinement have been proposed in order to provide directional electromagnetic steel sheets with good iron loss characteristics (for example, see Patent Documents 1 to 3).

[0006] In addition, in Patent Document 4, since there are problems such as reduced permeability and increased magnetostriction and noise due to the strain even when local strain is applied for magnetic domain refinement, a low-iron-loss directional electromagnetic steel sheet and an advantageous manufacturing method for it are proposed, which alleviate the problems of reduced permeability and increased magnetostriction caused by the linear grooves used for magnetic domain refinement and local strain.

[0007] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2012-57219 Patent Document 2: Japanese Patent Application Publication No. 2012-12664 Patent Document 3: Japanese Patent Application Publication No. 2012-57218 Patent Document 4: Japanese Patent Application Publication No. H11-293340 Summary of the Invention

[0008] The problem that the invention aims to solve If domain control treatment is applied to directional electromagnetic steel sheets, their magnetostrictive properties change due to the closed magnetic domains. This deteriorates the noise characteristics of the directional electromagnetic steel sheets. Noise characteristics refer to the level of noise generated by electrical products (such as transformers and motors) made from directional electromagnetic steel sheets. Magnetostriction refers to the phenomenon of slight deformation of the shape when a strongly magnetic body is magnetized. If a directional electromagnetic steel sheet is excited by alternating current, the magnitude of magnetostriction changes with the magnetization intensity, thereby generating vibration. The magnitude of this magnetostriction is 10. -6 Although the magnitude is very small, this magnetostriction causes the iron core to vibrate, which propagates to external structures such as the transformer's container and becomes noise. In other words, while magnetic domain control is effective in reducing the iron loss of directional electromagnetic steel sheets, it also deteriorates their noise characteristics.

[0009] In recent years, directional electromagnetic steel sheets have been required to achieve not only low iron loss but also low noise. However, to date, no magnetic domain refinement technology has been proposed that can fully realize both low noise and low iron loss.

[0010] Furthermore, while Patent Document 4 mentions noise, it fails to adequately achieve both low noise and low iron loss. Patent Document 4 discloses that the average β angle near the center of the grain's rolling direction is 0°, and by applying magnetic domain control processing only to the corresponding regions where iron loss reduction based on magnetic domain control is significant, both low noise and low iron loss can be achieved. However, the magnetic domain widths within each grain are approximately the same, and the β angle near the center of the grain's rolling direction may not be 0°. Therefore, even with the method disclosed in Patent Document 4, adequately achieving both low noise and low iron loss is not possible.

[0011] The purpose of this invention is to provide a directional electromagnetic steel sheet with low iron loss and low noise when used in electrical products, as well as a method for manufacturing the same.

[0012] Methods for solving problems The inventors have studied directional electromagnetic steel sheets with low iron loss and excellent noise characteristics. The results show that domain control treatment is effective in reducing the iron loss of directional electromagnetic steel sheets, but on the other hand, it deteriorates the noise characteristics of the sheets. Therefore, by setting non-domain control regions, the deterioration of noise characteristics can be suppressed.

[0013] The present invention was made in view of the above insights.

[0014] [1] One aspect of the present invention is a directional electromagnetic steel sheet having multiple domain control processing lines extending in a direction intersecting the rolling direction formed on its surface. The magnetic domain image of the surface is designated as a first magnetic domain image. An annealing process is performed, which involves holding the surface at 800°C for at least 240 minutes, cooling it to 200°C at a rate of 25°C / h or less, and then cooling it to 50°C or less at an average cooling rate of 100°C / h or less. The surface is then magnetized with an alternating magnetic field to a magnetic flux density of 1.9T or more, and demagnetized by attenuation of the alternating magnetic field. A second magnetic domain image is defined as a region where the domain width derived from the second magnetic domain image is at least 100 μm larger than the domain width derived from the first domain image. All other regions are designated as the second region. The unit of the domain control processing lines in the second region is mm / mm. 2 The linear density is less than the unit mm / mm of the domain control processing lines in the first region. 2 The linear density.

[0015] [2] In the directional electromagnetic steel plate described in [1], the difference between the linear density of the domain control processing lines in the second region and the linear density of the domain control processing lines in the first region can be 0.20 mm / mm. 2 above.

[0016] [3] In the directional electromagnetic steel plate described in [1] or [2], the multiple magnetic domain control processing lines may be thermal strain, or grooves and thermal strain.

[0017] [4] In any of the directional electromagnetic steel plates described in [1] to [3], the multiple magnetic domain control processing lines are thermal strains with tensile stress of more than 40 MPa.

[0018] [5] Another aspect of the present invention relates to a method for manufacturing a directional electromagnetic steel plate, comprising: a first domain image acquisition step, acquiring a domain image of the surface of the directional electromagnetic steel plate before domain control processing; a domain width distribution acquisition step, acquiring a domain width distribution in the directional electromagnetic steel plate based on the domain image before domain control processing obtained in the first domain image acquisition step; a domain control processing line formation step, forming a domain control processing line on the surface of the directional electromagnetic steel plate; a second domain image acquisition step, acquiring a domain image of the surface of the directional electromagnetic steel plate after domain control processing on which the domain control processing line is formed; and a domain image comparison step, comparing the domain image before domain control processing with the domain image after domain control processing. The comparison process involves adding a domain control processing line forming step. As needed, domain control processing lines are further formed on the surface of the directional electromagnet plate after the domain image comparison step. In the domain control processing line forming step, based on the domain width distribution obtained in the domain width distribution acquisition step, the domain control processing lines are formed in regions where the domain width exceeds 500 μm. In the domain image comparison step, when a region where the domain width derived from the domain image before domain control processing is more than 100 μm larger than the domain width derived from the domain image after domain control processing is designated as a first region, and other regions are designated as second regions, the unit of the domain control processing lines in the second region is mm / mm. 2 The line density of the magnetic domain control processing lines in the first region is in mm / mm. 2 In the process of forming additional magnetic domain control processing lines, if the line density of the second region is the same as or greater than that of the first region, the magnetic domain control processing line is formed in the first region. The process of obtaining the second magnetic domain image, comparing the magnetic domain image, and forming the additional magnetic domain control processing line is repeated until the line density of the magnetic domain control processing line in the second region is less than that of the magnetic domain control processing line in the first region.

[0019] [6] In the manufacturing method of the directional electromagnetic steel plate, the magnetic domain control processing line can also be formed by irradiation with a laser or electron beam in the magnetic domain control processing line forming process.

[0020] Invention Effects According to the above-described manner of the present invention, it is possible to provide a directional electromagnetic steel sheet with low iron loss (low iron loss) and low noise when used in electrical products (excellent noise characteristics), and a method for manufacturing the same. Attached Figure Description

[0021] Figure 1A This is a schematic diagram illustrating an example of a directional electromagnetic steel plate according to this embodiment.

[0022] Figure 1B This is a schematic diagram illustrating an example of a directional electromagnetic steel plate according to this embodiment.

[0023] Figure 2 It is a graph showing the relationship between the domain width before laser irradiation and the domain width after laser irradiation.

[0024] Figure 3A This is a diagram illustrating an example of the distribution of magnetic domain widths in a directional electromagnet before domain refinement.

[0025] Figure 3B This is a diagram illustrating an example of the distribution of magnetic domain widths in a directional electromagnetic steel sheet after domain refinement.

[0026] Figure 3C This is a diagram illustrating an example of a magnetic domain image acquired by an image acquisition device.

[0027] Figure 3D It is a schematic representation Figure 3C The image.

[0028] Figure 4 This is a block diagram illustrating an example of the hardware configuration of an image acquisition device.

[0029] Figure 5 This is a block diagram illustrating an example of the hardware configuration of an analysis device.

[0030] Figure 6 This is a schematic diagram illustrating an example of the configuration of a laser irradiation device.

[0031] Figure 7 This is a flowchart illustrating an example of a method for manufacturing a directional electromagnetic steel sheet according to this embodiment.

[0032] Figure 8 This is a schematic diagram illustrating a method for cutting out multiple partial regions from a magnetic domain image of a directional electromagnetic steel plate.

[0033] Figure 9 This is an example of obtaining multiple partial Fourier images by performing two-dimensional Fourier transforms on multiple partial regions cut out from the magnetic domain image of a directional electromagnetic steel plate. Detailed Implementation

[0034] A directional electromagnetic steel sheet (the directional electromagnetic steel sheet of this embodiment) and its manufacturing method according to one embodiment of the present invention will be described.

[0035] like Figure 1AAs shown, the directional electromagnetic steel plate 1 of this embodiment is a directional electromagnetic steel plate on which multiple magnetic domain control processing lines 11 extending in a direction intersecting with the rolling direction RD are formed on the surface.

[0036] Furthermore, in this embodiment, the directional electromagnetic steel plate 1 is configured such that, when the magnetic domain image on the surface is designated as the first magnetic domain image, and the magnetic domain image at the same position as the first magnetic domain image after annealing, magnetization, and demagnetization under specified conditions is designated as the second magnetic domain image, and the region where the magnetic domain width derived from the second magnetic domain image is 100 μm or more larger than the magnetic domain width derived from the first magnetic domain image is designated as the first region 21, and the other regions are designated as the second region 22, the unit of the magnetic domain control processing line in the second region 22 is mm / mm. 2 The line density is greater than that of the domain control processing lines in the first region 21 per unit mm / mm 2 Its linear density is low.

[0037] As described below, the directional electromagnetic steel plate 1 of this embodiment may have a magnesium olivine coating and / or an insulating coating on the surface of the steel plate, which serves as the base material steel plate.

[0038] The following will explain each point separately. However, when the directional electromagnetic steel sheet has a base steel sheet and a forsterite coating and / or an insulating coating, the following specifications regarding chemical composition, domain control treatment lines, and domain width pertain to the base steel sheet. However, the specifications regarding sheet thickness pertain to the entire directional electromagnetic steel sheet including the base steel sheet, the forsterite coating, and / or the insulating coating.

[0039] Directional electromagnetic steel sheet (Chemical composition) The chemical composition of the directional electromagnetic steel plate 1 is not limited, and it can be the same as that of the known directional electromagnetic steel plate 1. For example, as a chemical composition, the directional electromagnetic steel plate 1 may contain, by mass%, Si: 2.50~7.00%, Mn: 0~1.00%, C: 0~0.085%, acid-soluble Al: 0~0.065%, N: 0~0.012%, Cr: 0~0.300%, Cu: 0~0.400%, P: 0~0.500%, Sn: 0~0.300%, Sb: 0~0.300%, Ni: 0~1.000%, S: 0~0.015%, Se: 0~0.015%, Bi: 0~0.020%, Nb: 0~0.030%, V: 0~0.030%, Mo: 0~0.030%, Ta: 0~0.030%, W: 0~0.030%, B: 0~0.080%, Ti: 0~0.015%. The balance of the chemical composition includes Fe and impurities.

[0040] The chemical composition of the directional electromagnetic steel sheet 1 can be determined using general analytical methods for steel. For example, the chemical composition can be determined using ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry). Specifically, a test piece is taken from the center of the sample along its thickness direction, and the chemical composition of the directional electromagnetic steel sheet 1 can be determined using a Shimadzu ICPS-8100 (measuring device) under conditions based on pre-made calibration lines. The contents of C and S, which are difficult to determine by ICP-AES, can be determined using the combustion-infrared absorption method. The N content can be determined using the inactive gas melting-thermal conductivity method.

[0041] When a forsterite coating and / or an insulating coating are formed on the directional electromagnetic steel plate 1, the chemical composition of the directional electromagnetic steel plate 1 (i.e., the chemical composition of the base steel plate) can be analyzed after removing the forsterite coating and / or the insulating coating from the directional electromagnetic steel plate 1.

[0042] Insulating coatings can be removed, for example, by immersing the sample in a sodium hydroxide solution followed by immersion in dilute sulfuric acid and nitric acid. Furthermore, the temperature and concentration of the sodium hydroxide, dilute sulfuric acid, and nitric acid solutions, as well as the immersion time, are appropriately adjusted to prevent excessive dissolution of the steel substrate of the sample. An example of the conditions for removing the insulating coating is described below. First, the sample is immersed in a 20% sodium hydroxide solution at 80°C for 15 minutes. Then, the sample is dried. Next, the sample is immersed in a 10% dilute sulfuric acid solution at 80°C for 4 minutes. Then, the residue adhering to the sample surface is removed with a cloth or similar means. Finally, the sample is immersed in a 10% nitric acid solution at room temperature while stirring for approximately 10 seconds.

[0043] For example, forsterite coatings can be removed by immersing the sample in sulfuric acid followed by immersion in nitric acid. The temperature and concentration of the sulfuric acid and nitric acid, the immersion time, and other conditions are appropriately adjusted to prevent excessive dissolution of the steel matrix of the sample. An example of the conditions for removing the forsterite coating is described below. First, the sample is immersed in 10% sulfuric acid at 80°C for 3 minutes. Then, the surface of the sample is washed with water using a cloth or similar means to remove any adhering sludge. The sample is then dried. Next, the sample is immersed in 10% nitric acid at room temperature with stirring for approximately 5 seconds.

[0044] The thickness of the directional electromagnetic steel sheet 1 is not limited, but is preferably 0.15 mm to 0.30 mm. By setting the sheet thickness to 0.30 mm or less, classical eddy current losses can be suppressed, further improving iron loss. On the other hand, by making the sheet thickness 0.15 mm or more, rolling efficiency can be improved, thus increasing productivity.

[0045] (Magnetic domain control processing line 11) In the directional electromagnetic steel plate 1 of this embodiment, multiple magnetic domain control processing lines 11 extending in a direction intersecting the rolling direction are formed on the surface.

[0046] The magnetic domain control processing line 11, disposed on the surface of the directional electromagnetic steel plate 1, has the function of refining 180° magnetic domains. By refining the magnetic domains, the iron loss of the directional electromagnetic steel plate 1 can be reduced. A magnetic domain refers to a collection of magnetic dipoles existing within a strongly magnetic body, and is a small region where the magnetic moment is consistent in one direction. A 180° magnetic domain refers to a region where the magnetization direction is crystalline. <100> A magnetic domain is oriented and sandwiched between two 180° domain walls that are approximately parallel to the rolling direction RD. The distance between adjacent domain walls of a 180° domain (domain wall spacing) is called the width of the 180° domain. Hereinafter, unless otherwise specified, the width of the 180° domain will be simply referred to as the "domain width".

[0047] The extension direction of the domain control processing line 11 is not particularly limited as long as it intersects the rolling direction (as long as it is not parallel to the rolling direction). The domain control processing line 11 can also be approximately right-angled with the rolling direction RD (approximately parallel to the right-angled rolling direction TD). That is, the angle between the domain control processing line 11 and the right-angled rolling direction TD can be substantially 0°. On the other hand, as... Figure 1A As illustrated, the angle between the domain control processing line 11 and the rolling right-angle direction TD can also exceed 0°. For example, the angle between the domain control processing line 11 and the rolling right-angle direction TD can be set to any value within the range of 0° to 45°. The angle between the domain control processing line 11 and the rolling right-angle direction TD can also be set to 1° or more, 3° or more, or 5° or more. The angle between the domain control processing line 11 and the rolling right-angle direction TD can also be set to 40° or less, 35° or less, or 30° or less.

[0048] like Figure 1AAs illustrated, the angles formed by all the domain control processing lines 11 and the rolling right-angle direction TD can be the same. That is, all the domain control processing lines 11 can extend parallel to each other. On the other hand, the angles formed by the domain control processing lines 11 and the rolling right-angle direction TD can also deviate. That is, some or all of the multiple domain control processing lines 11 can extend non-parallel to each other. The average value of the angles formed by the domain control processing lines 11 and the rolling right-angle direction TD can also be set to 1° or more, 3° or more, or 5° or more. The average value of the angles formed by the domain control processing lines 11 and the rolling right-angle direction TD can also be set to 40° or less, 35° or less, or 30° or less. Regarding the average value of the angle, the angles formed by a single domain control processing line and the rolling right-angle direction TD at multiple locations, or the angles formed by multiple domain control processing lines and the rolling right-angle direction TD at one or more locations, can be measured, and their average value can be calculated.

[0049] In addition, such as Figure 1B As shown, the magnetic domain control processing line 11 may include curved sections (i.e., may consist of only straight lines) or may be interrupted in the middle (i.e. may be formed throughout the width direction of the steel plate).

[0050] At least a portion of the domain control processing line 11 is thermal strain. The thermal strain disappears through stress-relief annealing or heat treatment based on this, thus changing the domain width before and after heat treatment under specified conditions. Alternatively, thermal strain, as well as slots and other domain control processing lines, can be used in combination.

[0051] When the domain control processing line 11 is a slot, the domain control processing line 11 can be determined visually. When the directional electromagnetic steel plate 1 has an insulating film, the magnetic domain control processing line 11 can be visually determined by removing the insulating film using a known stripping agent.

[0052] When the domain control processing line 11 is subjected to thermal strain, it is sometimes impossible to visually determine the domain control processing line 11. In such cases, for example, using... Figure 4 The image acquisition device 30, configured as illustrated, captures magnetic domain images, and the location of thermal strain can be determined by observing the captured magnetic domain images. During capture, a DC magnetic field is applied along the normal direction ND of the rolled surface of the directional electromagnetic steel plate 1 as needed while capturing the magnetic domain images.

[0053] (The spacing of the magnetic domain control processing line 11 along the rolling direction RD) In the multiple domain control processing lines 11, the spacing of adjacent domain control processing lines 11 along the rolling direction RD is not particularly limited. The smaller the spacing, the greater the effect of improving (reducing) iron loss. On the other hand, the larger the spacing, the better the noise characteristics. The spacing can be appropriately selected according to the characteristics required for the directional electromagnetic steel sheet 1. For example, the spacing of adjacent domain control processing lines 11 along the rolling direction RD can be set to 1.0 mm or more, 2.0 mm or more, 3.0 mm or more, or 5.0 mm or more. The spacing of adjacent domain control processing lines 11 along the rolling direction RD can also be set to 10.0 mm or less, 9.0 mm or less, 8.0 mm or less, or 7.0 mm or less.

[0054] The spacing of adjacent domain control processing lines 11 along the rolling direction RD can be constant or may vary. In the case of variation, for example, the average spacing of adjacent domain control processing lines 11 along the rolling direction RD can be set to 1.0 mm or more, 2.0 mm or more, 3.0 mm or more, or 5.0 mm or more. Alternatively, the average spacing of adjacent domain control processing lines 11 along the rolling direction RD can be set to 10.0 mm or less, 9.0 mm or less, 8.0 mm or less, or 7.0 mm or less. Regarding the spacing, it is sufficient to draw one or more straight lines L along the rolling direction RD and measure the distance between two adjacent points LP at the intersection points LP of the straight line L and the domain control processing lines. When calculating the average spacing, multiple distances between adjacent points LP are measured and averaged.

[0055] The angle between the domain control processing line 11 and the rolling right-angle direction TD can be measured using a known angle measurement method after the domain control processing line 11 and the rolling right-angle direction TD have been determined according to the steps described above and below.

[0056] The spacing of the domain control processing line 11 along the rolling direction RD can be measured using a known length measurement method after the domain control processing line 11 and the rolling direction RD have been determined through the steps described above and below.

[0057] Here, the spacing of the domain control processing lines 11 along the rolling direction RD is the distance from the center of the width of the domain control processing line in the rolling direction RD to the center of the width of the adjacent domain control processing line in the rolling direction RD.

[0058] As described above, at least a portion of the domain control processing line 11 is thermally strained. That is, the domain control processing line 11 is thermally strained, or thermally strained and other domain control processing lines such as trenches. Thermal strain can be formed, for example, using methods such as laser irradiation, electron beam irradiation, and ion implantation. Trenches can be formed, for example, using methods such as laser irradiation, electron beam irradiation, machining, and etching.

[0059] Furthermore, when the magnetic domain control processing line is thermal strain, it is preferable to introduce tensile stress into the thermal strain. The greater the tensile stress, the better the effect on improving iron loss. On the other hand, the smaller the tensile stress, the better the noise characteristics. It is possible to appropriately select the tensile stress corresponding to the characteristics required for the directional electromagnetic steel plate 1.

[0060] The magnitude of the tensile stress is not particularly limited. For example, in at least a portion of the domain control processing line 11, the tensile stress relative to any direction is preferably 40 MPa or more, 60 MPa or more, or 80 MPa or more. When the tensile stress relative to at least one direction is 40 MPa or more, it is considered to satisfy the requirement of "tensile stress relative to any direction is 40 MPa or more". Furthermore, for example, in at least a portion of the domain control processing line 11, the tensile stress relative to any direction is preferably 300 MPa or less, 200 MPa or less, 180 MPa or less, or 150 MPa or less. The tensile stress relative to any direction in the domain control processing line 11 can be the same or may vary.

[0061] The magnitude of the tensile stress introduced in the thermal strain was determined using the EBSD Wilkinson method and the Cross Court manufactured by BLG Vantage. The EBSD Wilkinson method is described in detail in AJ Wilkinson, et al. “High-resolution elastic strain measurement from electron backscatter diffraction patterns: New levels of sensitivity” Ultramicroscopy Vol 106, No.4-5, March 2006, pp.307-313.

[0062] When determining the magnitude of tensile stress introduced by thermal strain using the EBSD Wilkinson method and a Cross Court manufactured by BLG Vantage, the domain control processing line 11 is first determined according to the steps described above. Next, the directional electromagnetic steel sheet 1 is cut through and perpendicular to the domain control processing line 11. This cut surface is used as the measurement surface. For the cross-section of the measurement surface containing the domain control processing line 11, analysis is performed using the EBSD Wilkinson method and a Cross Court manufactured by BLG Vantage to extract the tensile stress components relative to any direction and determine their magnitude. For example, tensile stress components can be extracted in the rolling surface normal direction ND, in the direction parallel to the domain control processing line 11, and in the direction perpendicular to both the rolling surface normal direction ND and the domain control processing line 11.

[0063] The number of measurement sites is set to, for example, 10. At at least one location on the directional electromagnetic steel plate 1, if the tensile stress relative to any direction is 40 MPa or more (i.e., if the tensile stress relative to at least one direction is 40 MPa or more), it is determined that the maximum value of the tensile stress relative to any direction in the magnetic domain control processing lines of the directional electromagnetic steel plate 1 is 40 MPa or more (multiple magnetic domain control processing lines represent thermal strain with tensile stress of 40 MPa or more). The measurement of tensile stress may also be stopped when a measurement point where the tensile stress relative to any direction is found to be 40 MPa or more.

[0064] The greater the depth and width of the slots used for magnetic domain control processing, the better the effect on improving iron loss. On the other hand, the smaller the depth and width of the slots, the better the noise characteristics. The shape of the slots can be appropriately selected to correspond to the characteristics required by the directional electromagnetic steel plate 1.

[0065] The depth of the groove is not particularly limited, but is preferably 5μm to 50μm. The groove depth can also be set to 6μm or more, 7μm or more, or 10μm or more. Alternatively, the groove depth can be set to 48μm or less, 45μm or less, or 40μm or less.

[0066] The width of the groove (width of the opening) is not particularly limited, but is preferably set to 10μm to 300μm. The groove width can also be specified as 20μm or more, 30μm or more, or 50μm or more. Alternatively, the groove width can be specified as 280μm or less, 250μm or less, or 200μm or less. The depth and width of the groove can be the same or varied. In the case of variation, it is preferable that the average value of the depth and width of multiple grooves is within the above-mentioned range.

[0067] The surface shape of the sample is determined by using a known three-dimensional measuring machine, thereby enabling the measurement of the depth and width of the groove. In the case where the directional electromagnetic steel plate 1 has an insulating coating, the three-dimensional measurement of the sample surface is performed after removing the insulating coating according to the steps described above.

[0068] (Methods for determining the rolling direction RD and the rolling right-angle direction TD) The rolling direction RD and the rolling right-angle direction TD of the directional electromagnetic steel sheet 1 are determined by the following methods.

[0069] (1) In the case where the sample is cut from a coil-shaped directional electromagnetic steel sheet 1, the width direction of the coil is regarded as the rolling right-angle direction TD. In addition, the direction perpendicular to the rolling right-angle direction TD and the normal direction ND of the rolling surface is regarded as the rolling direction RD.

[0070] (2) In the case where the sample is cut from a part of an electrical product, the rolling direction RD and the rolling right-angle direction TD are determined based on the rolling marks on the surface of the directional electromagnetic steel sheet 1. The direction of extension of the rolling marks is regarded as the rolling direction RD. The direction perpendicular to the rolling direction RD and the normal direction ND of the rolled surface is regarded as the rolling right-angle direction TD.

[0071] (3) When it is difficult to determine the rolling direction RD and the right-angle rolling direction TD based on the rolling marks on the surface of the directional electromagnetic steel sheet 1, the rolling direction RD and the right-angle rolling direction TD are determined based on the crystal orientation of the directional electromagnetic steel sheet 1. Specifically, the crystal orientation of the directional electromagnetic steel sheet 1 to be evaluated is measured at multiple points. Then, the easy magnetization axis, which has the closest angle to a right angle between the crystal orientation at that measurement point and the normal direction ND (thickness direction) of the rolling surface, is selected. <001> The direction in which the deviation angle is minimized is considered the rolling direction RD, and the direction perpendicular to the rolling direction RD and the normal direction ND of the rolling surface is considered the rolling right-angle direction TD.

[0072] (domain width) In the directional electromagnetic steel sheet of this embodiment, a magnetic domain image obtained from the surface is designated as the first magnetic domain image. An annealing process is performed, in which the directional electromagnetic steel sheet is held at 800°C for at least 240 minutes, cooled to 200°C at a rate of 25°C / h or less, and then cooled to 50°C or less at an average cooling rate of 100°C / h or less. An alternating magnetic field is applied to the directional electromagnetic steel sheet, magnetizing it to a magnetic flux density of 1.9T or more (magnetization is performed with a magnetic flux density of 1.9T). The alternating magnetic field is then attenuated to demagnetize the sheet, resulting in a magnetic domain image at the same position as the first magnetic domain image. A region where the domain width derived from the second magnetic domain image is at least 100 μm larger than the domain width derived from the first magnetic domain image is designated as the first region. All other regions are designated as the second region. The linear density (mm / mm) of the magnetic domain control processing lines in the second region is defined as follows: 2 The linear density of the magnetic domain control processing lines in the first region (mm / mm) is higher than that in the first region. 2 )Small.

[0073] As described above, the magnetic domain control processing lines 11 provided on the surface of the directional electromagnetic steel plate 1 have the function of refining the 180° magnetic domains. Therefore, it is effective in reducing the iron loss of the directional electromagnetic steel plate.

[0074] On the other hand, while domain control is effective in reducing iron loss in directional electromagnetic steel sheets, it also deteriorates their noise characteristics. Therefore, by setting up non-domain control regions, the deterioration of noise characteristics can be suppressed. In other words, both low noise and low iron loss can be achieved in a balanced way.

[0075] The inventors further investigated and analyzed the changes in magnetic domains before and after domain control in directional electromagnetic steel sheets. The results clearly identified regions where magnetic domain width narrowed and regions where it remained almost unchanged after domain control. In other words, it was found that the domain thinning effect differed depending on the original domain width. More specifically, it was observed that in regions with narrower domain widths, the domain thinning effect based on domain control was less pronounced.

[0076] For example, such as Figure 2 As shown, the following examples were found: in regions where the domain width before domain control is less than about 500 μm, the domain width before and after domain control is roughly the same. In regions where the domain width before domain control is less than about 500 μm, it can be considered that the domain refinement effect of domain control is almost negligible.

[0077] Based on the above insights, prioritizing domain control processing in regions with wider domain widths is extremely effective in achieving both low iron loss and low noise. Domain control processing in regions with wider domain widths can reduce iron loss. It can be considered that domain control processing lines formed in regions with narrower domain widths lead to a deterioration in noise characteristics caused by closed domains. Therefore, by minimizing domain control processing in regions with narrower domain widths, the deterioration of noise characteristics can be prevented.

[0078] The directional electromagnetic steel sheet of this embodiment is a directional electromagnetic steel sheet in which magnetic domain control processing is selectively performed in regions with wide magnetic domain widths and a large magnetic domain refinement effect to minimize the deterioration of noise characteristics and reduce iron loss. Although it is preferable to perform magnetic domain control processing only in regions with wide magnetic domain widths, it is permissible to perform magnetic domain control processing in regions with narrow magnetic domain widths because the smaller the proportion, the smaller the deterioration of noise characteristics. In addition, it is preferable to perform magnetic domain control processing on all regions with wide magnetic domain widths, but regions without magnetic domain control processing may also be included as long as the relationship between the linear density of the magnetic domain control processing lines after annealing under the above-specified conditions is satisfied.

[0079] However, in the directional electromagnetic steel plate after magnetic domain control treatment, the magnetic domain width becomes narrower in areas with wider magnetic domain widths. Therefore, it is not easy to directly determine whether magnetic domain control treatment was only performed in areas with a greater magnetic domain refinement effect (it can be determined indirectly based on noise characteristics and magnetic properties).

[0080] On the other hand, in regions where the domain width is relatively wide but narrows due to the formation of domain control processing lines (via domain control), the effect of domain control disappears and the domain width widens (returning to its original direction) if heat treatment such as stress-relief annealing is performed. Conversely, in regions where the domain width was already relatively narrow before the formation of domain control processing lines, the domain width hardly widens even after heat treatment such as stress-relief annealing.

[0081] That is, after the domain control processing lines are formed, the domain width is not different (it narrows as a whole) in the state of the directional electromagnetic steel sheet without stress-relief annealing, so it is impossible to determine the domain width before the formation of the domain control processing lines. However, by performing stress-relief annealing (or equivalent annealing) on ​​the directional electromagnetic steel sheet, it is possible to determine whether the region before the formation of the domain control processing lines was a region with a wider domain width (region with a greater domain refinement effect) or a region with a narrower domain width (region with a smaller domain refinement effect based on domain control).

[0082] Furthermore, by observing the changes in domain width and the formation position of domain control processing lines before and after stress-relief annealing, it is possible to determine whether the domain control processing lines are formed in areas with a greater domain refinement effect or in areas with a smaller domain refinement effect based on domain control. In other words, it is possible to determine whether a directional electromagnetic steel sheet has undergone domain control processing to minimize the deterioration of noise characteristics and reduce iron loss.

[0083] The directional electromagnetic steel sheet of this embodiment is a directional electromagnetic steel sheet that has undergone magnetic domain control treatment to minimize the deterioration of noise characteristics and reduce iron loss. Specifically, as described above, the magnetic domain image on the surface is designated as the first magnetic domain image. The magnetic domain image at the same position as the first magnetic domain image is designated as the second magnetic domain image. The magnetic domain image after undergoing an annealing process equivalent to stress-relief annealing, in which the temperature of the directional electromagnetic steel sheet is held at 800°C for 240 minutes or more, cooled to 200°C at an average cooling rate of 25°C / h or less, and then cooled to 50°C or less at an average cooling rate of 100°C / h or less, magnetized to a magnetic flux density of 1.9T or more by applying an alternating magnetic field, and demagnetized by attenuating the alternating magnetic field, is designated as the second magnetic domain image. The region where the magnetic domain width derived from the second magnetic domain image is 100 μm or more larger than the magnetic domain width derived from the first magnetic domain image is designated as the first region. When the other regions are designated as the second region, the unit of the magnetic domain control processing line in the second region is mm / mm. 2 The linear density is greater than that of the domain control processing lines in the first region per mm / mm. 2 Its linear density is low.

[0084] The linear density of the domain control processing lines in the second region is less than that in the first region, which means that the domain control processing lines are mainly formed in regions with wider domain widths (regions with greater domain refinement effects).

[0085] Preferably, the difference between the linear density of the domain control processing lines in the second region and the linear density of the domain control processing lines in the first region is 0.20 mm / mm. 2 The above (i.e., the linear density of the domain control processing lines in the second region - the linear density of the domain control processing lines in the first region ≤ -0.20 mm / mm) 2 In this case, forming domain control processing lines in regions with wider domain widths (regions with greater domain refinement effects) can further minimize the deterioration of noise characteristics and reduce iron losses.

[0086] The preferred linear density of the domain control processing lines in the first region is 0.05 mm / mm. 2 The above is more preferably 0.10 mm / mm 2 above.

[0087] Furthermore, the linear density of the magnetic domain control processing lines in the second region is preferably 0.40 mm / mm. 2 Hereinafter, 0.20 mm / mm is preferred. 2 Below. The linear density of the magnetic domain control processing lines in the second region can be 0.00 mm / mm. 2 .

[0088] It can be considered that in regions where the domain width expansion based on stress-relief annealing is greater than 100 μm, domain control processing can achieve a certain degree of iron loss reduction. In addition, in regions where the domain width expansion based on stress-relief annealing is less than 100 μm, domain control processing has a smaller effect on reducing iron loss and deteriorates noise characteristics. The region where the domain width derived from the second domain image is more than 100 μm larger than the domain width derived from the first domain image is defined as the first region.

[0089] The domain width can be determined using the following method.

[0090] For example, a sample with one side length of 100 mm (or more) can be cut from the directional electromagnetic steel sheet 1 for testing. When the directional electromagnetic steel sheet 1 is a roll, the sample can be taken from any part of the roll. Similarly, when the directional electromagnetic steel sheet 1 is a part assembled into electrical products such as transformers or motors, the sample can also be taken from any part of the part. When the part is small, the length of one side of the sample can be less than 100 mm. In this case, the total sample area is 10000 mm². 2 That concludes the above. At this point, to minimize the influence of mechanical strain and other factors on the sample, it is preferable to acquire the sample using methods such as wire cutting. For this sample, a magnetic domain image (first magnetic domain image) is acquired using an image acquisition device equipped with a light source, a magneto-optical sensor (MO sensor), an image sensor, and a signal processing unit. Furthermore, this magnetic domain image is output via cable or wireless communication to an analysis device, which is a computer device such as a personal computer (PC) equipped with a computing unit, memory, display unit, input unit, and communication interface. In the computing unit, the magnetic domain structure is analyzed based on the magnetic domain image using the line segment method.

[0091] An example of determination using the line segment method will be given. Figure 3C The magnetic domain images were obtained using a CMOS-MagView camera manufactured by Matesy GmbH. Additionally, Figure 3D It is shown schematically to illustrate the measurement. Figure 3C The image.

[0092] In the line segment method, line segments Ls perpendicular to the magnetic domains are drawn for evaluation. The line segments are spaced in groups of three per 1 cm along the rolling direction RD. The domain width is derived based on the interval w of the intersection point Ip of the 180° domain wall and the line segment Ls. However, in the presence of closed domains 301 and noise 302, they are not counted as domain walls. Furthermore, after calculating the average domain width, the average interval is determined based on the length of each line segment Ls and the number of intersection points Ip.

[0093] Regarding the domain width of the second magnetic domain image of the directional electromagnetic steel sheet, for a sample from which the first magnetic domain image was obtained, an annealing process was performed: holding the sample at 800°C for at least 240 minutes, cooling it to 200°C at a rate of 25°C / h or less, and then cooling it to 50°C or less at an average cooling rate of 100°C / h or less. The sample was then magnetized with an alternating magnetic field until the magnetic flux density reached 1.9T or more, and demagnetized by attenuating the alternating magnetic field. A magnetic domain image (second magnetic domain image) was then acquired using an image acquisition device equipped with a light source, a magneto-optical sensor (MO sensor), an image sensor, and a signal processing unit. The domain width of this magnetic domain image can be measured using the same method as described above.

[0094] By comparing the domain width derived from the first domain image and the domain width derived from the second domain image, the first region and the second region can be defined.

[0095] The linear densities of the first and second regions are obtained using the following method.

[0096] In the sample where the domain width was measured, the total length (mm) of the domain control processing lines contained in the first and second regions was measured respectively, and then divided by the area (mm) of each region. 2 Therefore, it can be calculated.

[0097] The determination of any of the above parameters is performed on a sample of a specified size taken from the directional electromagnetic steel sheet 1. When the directional electromagnetic steel sheet 1 is a roll, the sample can be taken from any part of the roll. Similarly, when the directional electromagnetic steel sheet 1 is a part assembled into electrical products such as transformers or motors, the sample can be taken from any part of that part. When the part is small, the length of one side of the sample can be reduced, but the total area of ​​the sample remains the same. When taking the sample, to minimize the influence of mechanical strain on the sample, it is preferable to take the sample using methods such as wire cutting.

[0098] (Laminated) The surface of the directional electromagnetic steel sheet 1 may have a forsterite coating (i.e., the directional electromagnetic steel sheet may be composed of a base steel sheet and a forsterite coating formed on the surface of the base steel sheet). Furthermore, the directional electromagnetic steel sheet 1 may have an insulating coating on the surface of the base steel sheet or on the surface of the forsterite coating (i.e., the directional electromagnetic steel sheet may be composed of a base steel sheet, a forsterite coating formed on the surface of the base steel sheet, and an insulating coating formed on the surface of the forsterite coating, or it may be composed of a base steel sheet and an insulating coating formed on the surface of the base steel sheet).

[0099] The magnesium olivine coating and the insulating coating can be formed on one side or both sides of the directional electromagnetic steel plate 1.

[0100] Forsterite coatings are, for example, inorganic coatings primarily composed of magnesium silicate. For example, a forsterite coating is formed by reacting an annealing release agent containing magnesium oxide (MgO) applied to the surface of a base steel sheet with the components of the base steel sheet surface during final annealing. The forsterite coating, for example, has a composition derived from the annealing release agent and the base steel sheet (more specifically, a composition primarily composed of Mg₂SiO₄). On the other hand, when an annealing release agent primarily composed of Al₂O₃ is used in the final annealing, a forsterite coating sometimes does not form.

[0101] The insulating coating imparts electrical insulation and tensile strength to the directional electromagnetic steel sheet 1. By applying tension to the directional electromagnetic steel sheet 1, the movement of magnetic domain walls within it becomes easier, thereby reducing iron losses. Furthermore, the insulating coating can impart various properties to the directional electromagnetic steel sheet 1, such as corrosion resistance, heat resistance, and slip resistance. The insulating coating can be, for example, a known coating formed by applying a coating solution primarily composed of phosphate and colloidal silica to the surface of a magnesium olivine coating and then sintering it.

[0102] [Manufacturing Method] The directional electromagnetic steel sheet of this embodiment is suitable regardless of the manufacturing method, as long as it possesses the aforementioned characteristics. However, the following method allows for stable manufacturing and is therefore preferred.

[0103] That is, the directional electromagnetic steel plate of this embodiment can be manufactured by a manufacturing method including the following steps (I) to (VI).

[0104] (I) First magnetic domain image acquisition process: to acquire the magnetic domain image of the surface of the directional electromagnetic steel plate before magnetic domain control processing; (II) Domain width distribution acquisition process: Based on the domain image before domain control processing obtained in the first domain image acquisition process, the distribution of domain width in the directional electromagnetic steel plate is obtained. (III) Magnetic domain control processing line forming process, wherein magnetic domain control processing lines are formed on the surface of the directional electromagnetic steel plate; (IV) Second magnetic domain image acquisition process, acquiring a magnetic domain image of the surface of the directional electromagnetic steel plate after magnetic domain control processing in which the magnetic domain control processing line is formed; (V) A domain image comparison step, which compares the domain image before the domain control processing with the domain image after the domain control processing; and (VI) An additional magnetic domain control processing line forming step is performed, wherein, as needed, magnetic domain control processing lines are formed on the surface of the directional electromagnetic steel plate after the magnetic domain image comparison step.

[0105] Each process step is explained.

[0106] First, the directional electromagnetic steel plate (original plate) provided for the first magnetic domain image acquisition process can be a known directional electromagnetic steel plate.

[0107] For example, as a chemical composition, the base plate may contain, by mass%, Si: 2.50~7.00%, Mn: 0~1.00%, C: 0~0.085%, acid-soluble Al: 0~0.065%, N: 0~0.012%, Cr: 0~0.300%, Cu: 0~0.400%, P: 0~0.500%, Sn: 0~0.300%, Sb: 0~0.300%, Ni: 0~1.000%, S: 0~0.015%, Se: 0~0.015%, Bi: 0~0.020%, Nb: 0~0.030%, V: 0~0.030%, Mo: 0~0.030%, Ta: 0~0.030%, W: 0~0.030%, B: 0~0.080%, Ti: 0~0.015%. The balance of the chemical composition includes Fe and impurities.

[0108] A magnesium olivine coating can be formed on the surface of the directional electromagnetic steel sheet that becomes the base plate.

[0109] (First magnetic domain image acquisition process) In the first magnetic domain image acquisition process, a magnetic domain image of the surface of the directional electromagnetic steel plate before magnetic domain control processing is acquired.

[0110] As described below, in the manufacturing method of the directional electromagnetic steel sheet of this embodiment, the magnetic domain control processing lines are formed such that the line density of the magnetic domain control processing lines in the second region is less than the line density of the magnetic domain control processing lines in the first region. At this time, it is necessary to determine the first region and the second region. Therefore, in the first magnetic domain image acquisition step, a magnetic domain image before magnetic domain control processing is acquired from the magnetic domain image used when determining the first region and the second region.

[0111] The acquisition of magnetic domain images can be performed according to the methods described later.

[0112] (Process for obtaining magnetic domain width distribution) In the domain width distribution acquisition process, the domain width distribution in the directional electromagnetic steel plate (the domain width distribution before the formation of the domain control processing line) is obtained based on the domain image before the domain control processing obtained in the first domain image acquisition process.

[0113] Based on this distribution, in the domain control processing line process, the position where the domain control processing line is formed can be determined, and when determining the first region and the second region in the domain image comparison process described later, the distribution of domain width derived from the domain image before the domain control processing, which serves as a reference, can be obtained.

[0114] (Magnetic domain control processing line formation process) In the domain control processing line formation process, the domain control processing lines are mainly formed in regions where the domain width, as determined in the region determination process, exceeds 500 μm. This results in multiple domain control processing lines extending in a direction intersecting the rolling direction being formed on the surface of the directional electromagnetic steel sheet. As described above, it can be considered that the domain refinement effect is smaller in regions with narrower domain widths, and almost no domain refinement effect based on domain control is obtained in regions with domain widths of approximately 500 μm or less. Therefore, it is preferable not to perform domain control in these regions. While it is preferable not to form domain control processing lines in regions with domain widths of 500 μm or less, this is permissible if the proportion is small. By forming these domain control processing lines, the domain width in their vicinity can be narrowed.

[0115] However, this effect disappears due to stress-relief annealing, and thus the domain width widens by stress-relief annealing in regions where thermal strain-based domain control processing lines are formed.

[0116] At least a portion of the domain control processing line is thermally strained. Alternatively, thermal strain and other domain control processes such as slots can be used in combination. In the case of thermal strain, the domain control processing line is formed by irradiation with a laser or electron beam. The irradiation conditions can be within a known range.

[0117] When the groove is used, methods such as irradiating with lasers or electron beams, machining methods based on gears, and chemical processing methods based on etching can be cited.

[0118] The formation direction of the magnetic domain control processing line (or the scanning direction if it is a laser, etc.), the spacing of the rolling direction RD of the magnetic domain control processing line, the width of the magnetic domain control processing line, and the depth of the magnetic domain control processing line if it is a groove, are controlled by known methods to make it fall within the range of the directional electromagnetic steel plate described in this embodiment.

[0119] (Second domain image acquisition process) In the second magnetic domain image acquisition step, a magnetic domain image after magnetic domain control processing is acquired on the surface of the directional electromagnetic steel plate on which magnetic domain control processing lines are formed. That is, a magnetic domain image after magnetic domain control processing is acquired from the magnetic domain images used when determining the first region and the second region.

[0120] The acquisition of magnetic domain images can be performed according to the methods described later.

[0121] Additionally, at this stage, the distribution of domain width in the directional electromagnetic steel plate (the distribution of domain width after forming the domain control processing line) can also be obtained based on the obtained domain image after domain control processing.

[0122] (Magnetic domain image comparison process) In the domain image comparison process, when a region whose domain width derived from the domain image before domain control processing is more than 100 μm larger than the domain width derived from the domain image after domain control processing is designated as the first region, and the region outside of this region is designated as the second region, the unit of the domain control processing lines in the second region is mm / mm. 2 Linear density and the magnetic domain control processing lines in the first region, in units of mm / mm 2 The linear densities were compared.

[0123] Linear density is determined by measuring the total length (mm) of the domain control processing lines contained in the first and second regions, respectively, and dividing it by the area (mm) of each region. 2 To calculate.

[0124] If the comparison of online densities shows that the linear density of the domain control processing lines in the second region is less than that in the first region, then the additional domain control processing line formation process as the next process can be omitted.

[0125] On the other hand, if the comparison result of the line density is that the line density of the magnetic domain control processing line in the second region is the same as or greater than the line density of the magnetic domain control processing line in the first region, then the additional magnetic domain control processing line forming process is carried out as the next process.

[0126] (Additional magnetic domain control processing line formation process) In the process of forming additional magnetic domain control processing lines, if it is determined in the magnetic domain image comparison process that the line density of the magnetic domain control processing lines in the second region is the same as or greater than the line density of the magnetic domain control processing lines in the first region, magnetic domain control processing lines are further formed in the first region to increase the line density of the first region.

[0127] In the manufacturing method of the directional electromagnetic steel sheet of this embodiment, the linear density of the magnetic domain control processing lines in the second region is made smaller than the linear density of the magnetic domain control processing lines in the first region.

[0128] However, during the formation stage of the domain control processing lines, the distribution of domain widths in the first and second regions after the formation of the domain control processing lines is unknown. Therefore, after the formation of the domain control processing lines, the domain images before and after the formation of the domain control processing lines are compared, and the line densities of the domain control processing lines in the first and second regions are compared.

[0129] As a result, if the line density of the domain control processing lines in the second region is less than that in the first region, the process ends there. On the other hand, if the line density is not less than that in the first region, an additional domain control processing line formation process is performed.

[0130] In addition, after the additional domain control processing line formation process, a new domain image of the surface of the directional electromagnetic steel plate with the domain control processing lines formed is obtained (for the second domain image acquisition process). Then, the domain images before the domain control processing line formation and the domain images after the additional domain control processing line formation process are compared, and the line densities of the domain control processing lines in the first and second regions are compared.

[0131] As a result, if the line density of the domain control processing lines in the second region is less than that in the first region, the process ends there. On the other hand, if the line density is not less than that of the domain control processing lines in the first region, an additional domain control processing line formation process is performed again.

[0132] That is, the second domain image acquisition process, the domain image comparison process, and the additional domain control processing line formation process are repeated until the line density of the domain control processing lines in the second region is less than the line density of the domain control processing lines in the first region.

[0133] That is, such as Figure 7 As shown, sometimes a directional electromagnetic steel plate is obtained through S1→S2→S3→S4→S5, but sometimes it is obtained through S1→S2→S3→S4→S5→S6→S4→S5. Additionally, sometimes the directional electromagnetic steel plate is obtained through S1→S2→S3→S4→S5→S6→S4→S5→S6→S4→S5. Furthermore, sometimes S4→S5→S6 is repeated.

[0134] (Specific methods for obtaining magnetic domain images, obtaining the distribution of magnetic domain widths, and forming magnetic domain control processing lines) The acquisition of magnetic domain images and the distribution of magnetic domain widths can be achieved through the following methods.

[0135] A magnetic domain image of the surface can be acquired, for example, using an image acquisition device. Then, the distribution of the widths (domain widths) of the 180° domains is derived from the magnetic domain image. The distribution of domain widths in the original substrate can be derived, for example, using an analysis device.

[0136] Based on the distribution of the domain width, regions with domain widths exceeding a specified value (e.g., exceeding approximately 500 μm if a domain control processing line is formed in a region with a domain width exceeding 500 μm in a subsequent process) can be identified as regions that should undergo domain control processing (hereinafter sometimes simply referred to as processing areas).

[0137] The processing area can also be determined by the operator visually observing the magnetic domain image displayed on the display of the analysis device.

[0138] Figure 4 An example of the hardware configuration of an image acquisition device 30 for acquiring magnetic domain images of the original board (directional electromagnetic steel board 1 before magnetic domain control processing) is shown. The image acquisition device 30 includes a light source unit 31, a magneto-optical sensor (MO sensor 33), an image sensor 35, and a signal processing unit 37.

[0139] The light source unit 31 has a light source composed of light-emitting diodes (LEDs) that illuminates the MO sensor 33 with light of the same polarization plane.

[0140] The MO sensor 33 is a device for measuring the magnetic domain structure of a magnetic material. The MO sensor 33 has an observation surface on which the magnetic material sample to be measured is placed. Light irradiated from the light source 31 passes through the interior of the MO sensor 33 and is reflected by a reflective layer. The reflected light then passes through the interior of the MO sensor 33 again and is output to the exterior. When the original plate, which is the magnetic material sample, is placed on the observation surface of the MO sensor 33, a leakage magnetic field corresponding to the spontaneous magnetization of the original plate is generated inside the MO sensor 33. Through this leakage magnetic field, the polarization plane of the reflected light rotates.

[0141] Image sensor 35 is a complementary metal-oxide-semiconductor (CMOS) image sensor. Image sensor 35 images the reflected light from MO sensor 33 onto the light-receiving surface and performs photoelectric conversion, outputting the photoelectric converted analog signal to signal processing unit 37. By using image sensor 35 to detect the reflected light after the polarization plane is rotated, the distribution of the leakage magnetic field can be obtained, thereby clarifying the magnetic domain structure of the original plate.

[0142] The signal processing unit 37 includes an amplifier, an analog-to-digital converter (ADC), and a digital signal processor (DSP). The analog signal output from the image sensor 35 is amplified by the amplifier. Then, the analog signal is converted into a digital signal by the ADC. An image signal is generated by performing digital processing on the digital signal using the DSP. The image signal generated by the signal processing unit 37 is output to the analysis device 40 (see reference 37) via cable or wireless communication. Figure 5 ).

[0143] Figure 5 The hardware configuration of the analysis device 40 for analyzing the magnetic domain structure of the original board is shown. The analysis device 40 is a computer device such as a personal computer (PC). The analysis device 40 includes an arithmetic unit 41, a memory 43, a display unit 45, an input unit 47, and a communication interface 49.

[0144] The arithmetic unit 41 has a central processing unit (CPU). The arithmetic unit 41 analyzes the domain structure based on the domain image of the original board according to a program stored in the memory 43. Then, the arithmetic unit 41 determines the area, i.e., the processing region, where domain control processing is applied. The processing performed by the arithmetic unit 41 will be described in detail later.

[0145] 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 arithmetic unit 41, as well as the data required to execute these programs. The programs and data stored in the ROM are loaded into the RAM and executed.

[0146] The memory 43 may also be a magnetic storage device such as a hard disk drive (HDD) or an optical storage device such as an optical disc. Alternatively, the memory 43 may store programs and data in a computer-readable recording medium that is removable from and detachable from the analysis device 40. Alternatively, the memory 43 may receive programs executed by the arithmetic unit 41 from a network via a communication interface 49.

[0147] The display unit 45 includes a liquid crystal display (LCD), a plasma display, or an organic electroluminescent display (EL). The display unit 45 displays images based on image signals output from the image acquisition device 30. Additionally, the display unit 45 displays the analysis results of the magnetic domain structure obtained by the calculation unit 41.

[0148] The input unit 47 includes input devices such as a mouse and keyboard. The communication interface 49 is an interface for sending and receiving data with external devices via networks such as a local area network (LAN), a wide area network (WAN), and the Internet.

[0149] As the computing unit 41, it can also replace general-purpose hardware such as a CPU with dedicated hardware such as an application-specific integrated circuit (ASIC) or a field-programmable gate array (FPGA) specifically designed for the analysis of magnetic domain construction.

[0150] Figure 4 as well as Figure 5 The illustration shows a case where the image acquisition device 30 and the analysis device 40 are different devices, but a system integrating the image acquisition device 30 and the analysis device 40 can also be used.

[0151] As a method for introducing thermal strain onto the surface of the original plate, known methods such as laser irradiation, electron beam irradiation, and ion implantation can be used. As a method for forming grooves on the surface of the original plate, known methods such as laser irradiation, electron beam irradiation, and machining can be used. The configuration of the laser irradiation device 500 for introducing thermal strain by laser irradiation will be described below.

[0152] Figure 6 This describes the configuration of the 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 through plate device 515.

[0153] The plate-passing device 515 causes the original plate to pass through the rolling direction RD.

[0154] The polygon mirror 501 is, for example, in the shape of a regular polygonal column. Multiple plane mirrors are respectively provided on the multiple sides of the polygon mirror 501 that constitute the regular polygonal column. The laser beam LB is incident from the light source device 503 through the collimator 505 in one direction (horizontal direction) onto the plane mirror of the polygon mirror 501 and is reflected by the plane mirror.

[0155] The polygon mirror 501 can be rotated about the rotation axis O1 by the drive of the motor 509. The incident angle of the laser beam LB relative to the plane mirror changes sequentially according to the rotation angle of the polygon mirror 501. As a result, the reflection direction of the laser beam LB changes sequentially, enabling it to scan the surface of the original plate. Figure 6 The symbol P represents the spacing between adjacent magnetic domain control processing lines 11, i.e., the irradiation spacing of the laser beam LB.

[0156] Under the control of the control unit 513, the light source device 503 outputs a laser beam LB in a prescribed irradiation mode (e.g., continuous irradiation mode or pulse irradiation mode).

[0157] A condenser lens 507 is positioned in the optical path of the laser beam LB reflected from the polygon mirror 501. The condenser lens 507 constitutes a condenser optical system with a specified focal length. The laser beam LB reflected from the polygon mirror 501 is focused onto the surface of the original plate by the condenser lens 507, thereby introducing thermal strain onto the surface of the original plate.

[0158] Motor 509 is connected to polygon mirror 501. Motor 509 rotates and drives polygon mirror 501 under the control of control unit 513.

[0159] Sensor 511 is connected to the drive shaft of motor 509. Sensor 511 detects the rotation angle of the polygon mirror 501 rotated by motor 509. Then, sensor 511 outputs a signal representing the detected rotation angle (hereinafter referred to as rotation angle signal) to control unit 513.

[0160] The control unit 513 is composed of a processor. The control unit 513 is connected to the light source device 503, the motor 509, the sensor 511, and the through-plate device 515. The control unit 513 receives speed signal input from the through-plate device 515. Furthermore, the control unit 513 outputs a signal to the motor 509 instructing the rotation drive of the polygon mirror 501.

[0161] Furthermore, the control unit 513 controls the switching on and off of the power of the laser beam LB output by the light source device 503 based on the stress introduction signal indicating the processing area 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 stress introduction signal is input from the analysis device 40 to the laser irradiation device 500. Alternatively, the stress introduction signal can also be input to the laser irradiation device 500 by the operator.

[0162] Next, an example of a method for determining the processing area will be described in detail. The process for determining the processing area is performed, for example, by the arithmetic unit 41 of the analysis device 40.

[0163] The arithmetic unit 41 uses, for example, the line segment method to derive the distribution of the magnetic domain width of the original board. Then, the arithmetic unit 41 identifies regions with magnetic domain widths above a predetermined value (e.g., exceeding approximately 500 μm) as areas where magnetic domain control processing is preferentially applied.

[0164] In the line segment method, evaluation is performed by drawing line segments perpendicular to the magnetic domains. The line segments are spaced in groups of three, with each segment spaced 1 cm apart, in a direction parallel to the magnetic domain. The domain width is derived based on the intervals between the intersection points of the 180° domain walls and the line segments.

[0165] Figure 3A The image shows an example of the distribution of magnetic domain widths of the directional electromagnetic steel plate 1 before magnetic domain control processing, obtained by further analyzing a magnetic domain image acquired using a CMOS-MagView manufactured by Matery GmbH through a two-dimensional Fourier transform. Figure 3B Showing the pair with Figure 3A The same principle can be obtained Figure 3AThe distribution of magnetic domain widths on the surface of the directional electromagnetic steel sheet 1 after magnetic domain control treatment. This magnetic domain control treatment is performed by continuous-wave laser irradiation along a direction approximately perpendicular to the rolling direction RD. Figures 3A-3B In this context, the unit of measurement is μm.

[0166] As an example of analysis using two-dimensional Fourier transform, a method for deriving the distribution of magnetic domain widths will be explained using the short-term Fourier transform (hereinafter referred to as "ST2DFT"), which is obtained by extending the short-term Fourier transform, one of the signal processing methods previously used in the time-frequency analysis of sound signals, to a two-dimensional region.

[0167] The image (magnetic domain image) represented by the 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). In this embodiment, the magnetic domain image being analyzed is an image binarized from two colors, or an image represented by three or more color levels such as grayscale (multi-color levels).

[0168] In order to derive the distribution of the domain width of the original plate 2, the arithmetic unit 41 performs the following processes (A-1), (A-2) and (A-3).

[0169] (A-1) Processing of segmenting multiple regions from a magnetic domain image (A-2) Perform ST2DFT processing (A-3) Processing to derive the distribution of domain widths The following section provides a detailed explanation of the processing of A-1 to A-3.

[0170] (A-1) Processing of segmenting multiple regions from a magnetic domain image To analyze the frequency structure of multiple regions segmented from the magnetic domain image, the range of the k-direction is set to 0 ≤ k ≤ N. k -1. Set the range of the l-direction to 0 ≤ l ≤ N l The window function Wa(k, l)(N) for a rectangular window of -1 k and N l (where k is a natural number). As a window function Wa(k, l), it can be used with Hamming windows, Hanning windows, Blackman windows, etc.

[0171] If the observation position in the data string x(k, l) of the magnetic domain image is represented by the index (n, m), and the offsets of the window function Wa(k, l) in the k and l directions are represented by S respectively... k and S l (n, m, S) kS l If nS is an integer, then as in equation (1), nS is obtained from the magnetic domain image. k ≤k≤nS k +N k -1, mS l ≤l≤mS l +N l The data string x in the range of -1 is a partial region of the data string. nm (k-nS k ,l-mS l ).

[0172] [Formula 1] Figure 8 Examples are shown of partial regions cut from the magnetic domain image G corresponding to the observation positions (n, m) = (1, 1), (2, 2), (3, 3), ..., (P, Q) (P and Q are natural numbers).

[0173] In this embodiment, N is used to determine the range of the window function Wa(k,l). k and N l These are the parameters corresponding to the number of pixels in the k-direction and the number of pixels in the l-direction of a given region, respectively.

[0174] (A-2) Perform ST2DFT processing If we define the data string of a portion of the region as x nm (n′,m′)=x nm (k-nS k ,l-mS l ), for x nm Performing a two-dimensional Fourier transform on (n′, m′) yields, as shown in equation (2), a partial Fourier image X(f) corresponding to a portion of the region at the observation position (n, m). k f l (n, m).

[0175] [Equation 2] Here, f k and f l It is spatial frequency.

[0176] If the spatial frequency f k The resolution is expressed as Δf k , space frequency f l The resolution is expressed as Δf l Then Δf k and Δf l Defined as in equation (3).

[0177] [Formula 3] Here, Δk and Δl represent the spatial resolution in the k-direction and the spatial resolution in the l-direction of the magnetic domain image, respectively.

[0178] For example, if for Figure 8 The data strings x for each of the shown regions nm (k-nS k ,l-mS l Performing a two-dimensional Fourier transform, then as follows Figure 9 As shown, a partial Fourier image X(f) is obtained for each observation position (n, m). k f l (n, m).

[0179] (A-3) Processing to derive the distribution of domain widths When a partial Fourier image X(f) is obtained k f l When n, m), calculate the partial Fourier image X(f k f l The coordinates of the peak position of the bright spot (k component f) of the bright spot (n, m). k max (n, m) and l-component f l max (n, m)). Regarding the derivation of the peak position, the region near k=0 and l=0 is largely dependent on the image contrast and is therefore excluded.

[0180] Then, based on the resolution of the spatial frequency defined by Equation (3) and the peak position of the bright spots in the partial Fourier image, the distribution of the magnetic domain width L(n, m) is derived as in Equation (4).

[0181] [Formula 4] Thus, by using ST2DFT, the distribution L(n, m) of the magnetic domain width can be quantitatively derived while preserving the positional information of the magnetic domain image.

[0182] When the arithmetic unit 41 outputs the distribution of magnetic domain widths, it defines the region with a magnetic domain width greater than or equal to a predetermined value as the processing region (i.e., the region where magnetic domain control processing is applied). The control unit 513 of the laser irradiation device 500 controls the laser beam LB to be powered on for the processing region, and preferably disables the laser beam LB for regions outside the processing region. This introduces the magnetic domain control processing line 11 into the processing region of the original board. Furthermore, the introduction of the magnetic domain control processing line 11 is suppressed in other regions.

[0183] Through the above steps, a magnetic domain image of the directional electromagnet plate 1 after magnetic domain control processing can also be obtained. Sometimes, the magnetic domain control processing lines 11 are not clear in the magnetic domain image of the directional electromagnet plate 1. In this case, the observation conditions can be adjusted to clearly identify the magnetic domain control processing lines 11. For example, by applying a DC magnetic field perpendicular to the surface (thickness direction) of the directional electromagnet plate 1, the magnetic domain control processing lines 11 can be made clearer.

[0184] (Insulating film formation process) When an insulating film is formed on the surface of a directional electromagnetic steel sheet, an insulating film forming process can be included, in which the insulating film is formed after final annealing using a known method. The insulating film forming process can be performed either before or after the magnetic domain control line forming process, as long as it is performed after final annealing. However, if the insulating film is formed before the magnetic domain control line forming process, the insulating film may sometimes peel off in the magnetic domain control line 11. Therefore, it is preferable to perform the process after the magnetic domain control line forming process. If the insulating film forming process is performed before the magnetic domain control line forming process, it is preferable to re-form the insulating film on the magnetic domain control line 11 after the magnetic domain control line forming process.

[0185] Example The effects of the present invention are illustrated more specifically through examples. However, the conditions in the examples are merely one example of conditions used to confirm the feasibility and effects of the present invention. The present invention is not limited to this one example of conditions. Various conditions can be used to achieve the purpose of the present invention without departing from its spirit. Directional electromagnetic steel sheets from the same batch with a thickness of 0.20 mm were used as the base sheet. The directional electromagnetic steel sheet has a base steel sheet containing 3.40% Si, a magnesium olivine coating, and an insulating coating.

[0186] Directional electromagnetic steel sheets No. 1 to No. 35 were cut from the directional electromagnetic steel sheet, and magnetic domain images of the surface of each directional electromagnetic steel sheet were obtained (magnetic domain images before magnetic domain control processing). In addition, based on the obtained magnetic domain images, the distribution of magnetic domain width in the directional electromagnetic steel sheet was obtained, and regions with magnetic domain widths exceeding 500 μm were identified.

[0187] Then, magnetic domain control treatment was performed on the directional electromagnetic steel sheet (original sheet) under various conditions. The principles for forming the magnetic domain control treatment lines are shown in Table 1. The direction, spacing, and type of the formed magnetic domain control treatment lines are shown in Table 2. In the case of thermal strain and groove formation, their ratio is approximately 1:1 based on the total length.

[0188] Then, a magnetic domain image of the surface of the directional electromagnetic steel plate after the formation of the magnetic domain control processing line is obtained (magnetic domain image after magnetic domain control processing), and the distribution of magnetic domain width is obtained from the magnetic domain image.

[0189] Using domain images before and after domain control processing, a region with a domain width greater than 100 μm derived from the domain image after domain control processing is designated as the first region, and the region outside of this region is designated as the second region. The unit of the domain control processing lines in the second region is mm / mm. 2 The linear density of the magnetic domain control processing lines in the first region is in mm / mm. 2 The linear densities were compared.

[0190] As a result of the comparison, the relationship between the line density of the second region and the line density of the first region is shown in Table 1. In the table, OK indicates that the line density of the second region is less than that of the first region, and NG indicates that the line density of the second region is greater than that of the first region, or the line density of the second region is the same as that of the first region.

[0191] Next, for a subset of examples, magnetic domain control processing lines are further formed (the formation of additional magnetic domain control processing lines). At this time, magnetic domain control processing lines are formed in the first region.

[0192] Furthermore, for the example where the additional magnetic domain control processing line was formed, the line densities of the first region and the second region were compared. As a result of the comparison, the relationship between the line density of the second region and the line density of the first region is shown in Table 1. In the table, OK indicates that the line density of the second region is less than that of the first region, and NG indicates that the line density of the second region is greater than that of the first region, or that the line density of the second region is the same as that of the first region.

[0193] As a result, directional electromagnetic steel sheets were manufactured.

[0194] For the obtained directional electromagnetic steel sheet, the maximum value of the tensile stress relative to any direction in the domain control treatment line was measured under the condition that the domain control treatment line was under thermal strain. The results are shown in Table 2.

[0195] In addition, a 100mm×100mm sample was collected from the obtained directional electromagnetic steel plate, and an image acquisition device equipped with a light source, a magneto-optical sensor (MO sensor), an image sensor and a signal processing unit was used to obtain a first magnetic domain image of the sample surface, and the magnetic domain width and the linear density of the magnetic domain control processing line were measured.

[0196] In addition, the sample was annealed by holding it at 800°C for 240 minutes, cooling it to 200°C at a rate of 25°C / h, and then cooling it to 50°C at an average cooling rate of 100°C / h. An alternating magnetic field was applied to magnetize it to a magnetic flux density of 1.9T (making the magnetic flux density 1.9T), and the alternating magnetic field was attenuated to demagnetize it.

[0197] Then, for the sample, a second magnetic domain image is obtained using the same method as when the first magnetic domain image was obtained, and the domain width and the linear density of the domain control processing lines are measured.

[0198] The results are shown in Table 3.

[0199] In addition, the noise characteristics and iron loss of the obtained directional electromagnetic steel sheet were evaluated according to the following criteria. The results are shown in Table 3.

[0200] [Noise Characteristics] The evaluation methods for noise characteristics and iron loss are as follows.

[0201] 205 sheets of 0.20mm thick directional electromagnetic steel were stacked to fabricate three-phase transformer cores. During fabrication, the width of the legs and yoke of the three-phase transformer cores was set to 150mm. The height and width of the three-phase transformer cores were both set to 750mm. The noise and iron loss of these three-phase transformer cores were measured. The measurement conditions were set to a frequency of 60Hz and an excitation flux density of 1.7T.

[0202] During noise measurement, microphones were placed at equal intervals at eight locations around the transformer where the three-phase transformer core was assembled. The distance between the transformer and the microphones was 30 cm. The noise measurement results from these microphones, corrected for A-characteristics and averaged, were used as the noise evaluation result (in dBA) for the directional electromagnetic steel plate. Examples with a noise evaluation result of 37.00 dBA or less were considered to have achieved low noise.

[0203] [Iron Loss] The iron loss was determined by measuring the voltage and current on the primary and secondary sides when excitation was performed at a frequency of 60 Hz and an excitation flux density of 1.7 T using a power analyzer. The calculated iron loss is recorded as the iron loss evaluation result (in W / kg) for the directional electromagnetic steel sheet in Table 3. Examples with an iron loss evaluation result of 1.03 W / kg or less were identified as examples that achieved low iron loss.

[0204] As shown in Tables 1-3, in the embodiments of the invention, the linear density of the second region is lower than that of the first region, resulting in lower iron loss and noise. Iron loss is particularly lower when the difference between the linear density of the second region and the first region is large. Furthermore, noise is lower when the magnetic domain control processing lines are slots and subjected to thermal strain.

[0205] On the other hand, in the comparative example, the linear density of the second region is not less than that of the first region, and one or both of iron loss and noise are higher.

[0206] [Table 1] [Table 2] [Table 3] Industrial applicability According to the present invention, a directional electromagnetic steel sheet with low iron loss (low iron loss) and low noise when manufactured into electrical products (excellent noise characteristics) and a method thereof are provided. Therefore, it has high industrial applicability.

[0207] Explanation of symbols 1. Directional Electromagnetic Steel Sheet 11 Magnetic Domain Control Processing Line 21 First District 22 Second Region RD rolling direction TD rolling right-angle direction (plate width direction) ND (Normal direction of the rolled surface) 30 Image Acquisition Device 31 Light Source Section 33 MO sensor 35 Image Sensor 37. Signal Processing Department 40 Analytical apparatus 41. Arithmetic Unit 43 Memory 45 Display Section 47 Input Section 49 Communication Interface 301 Closed Magnetic Domains 302 Noise Ls line segment IP intersection 500 laser irradiation device 501 Multifaceted Mirror 503 Light Source Device 505 Collimator 507 Condensing Lens 509 motor 511 sensor 513 Control Department 515 Through-plate device

Claims

1. A directional electromagnetic steel sheet, wherein multiple magnetic domain control lines extending in a direction intersecting the rolling direction are formed on its surface, wherein, The magnetic domain image of the surface is set as the first magnetic domain image. The magnetic domain image is defined as the second magnetic domain image, which is obtained by annealing the magnetic domains at 800°C for more than 240 minutes, cooling them to 200°C at a rate of less than 25°C / h, and then cooling them to 50°C at an average cooling rate of less than 100°C / h. The magnetic domains are then magnetized to a magnetic flux density of 1.9T or higher by applying an alternating magnetic field, and demagnetized by decaying the alternating magnetic field. When a region whose domain width derived from the second domain image is more than 100 μm larger than the domain width derived from the first domain image is designated as the first region, and all other regions are designated as the second region, The unit of the magnetic domain control processing line in the second region is mm / mm 2 The linear density is less than the unit mm / mm of the domain control processing lines in the first region. 2 The linear density.

2. The directional electromagnetic steel plate according to claim 1, wherein, The difference between the line density of the domain control processing lines in the second region and the line density of the domain control processing lines in the first region is 0.20 mm / mm. 2 above.

3. The directional electromagnetic steel plate according to claim 1 or 2, wherein, The multiple magnetic domain control processing lines are thermal strain, or slots and thermal strain.

4. The directional electromagnetic steel plate according to claim 1 or 2, wherein, The multiple magnetic domain control processing lines are thermal strains with tensile stress exceeding 40 MPa.

5. A method for manufacturing a directional electromagnetic steel plate, comprising: The first magnetic domain image acquisition process acquires a magnetic domain image of the surface of the directional electromagnetic steel plate before magnetic domain control processing. The magnetic domain width distribution acquisition process obtains the distribution of magnetic domain width in the directional electromagnetic steel plate based on the magnetic domain image before magnetic domain control processing obtained in the first magnetic domain image acquisition process. The magnetic domain control processing line forming process forms magnetic domain control processing lines on the surface of the directional electromagnetic steel plate. The second magnetic domain image acquisition process acquires a magnetic domain image of the surface of the directional electromagnetic steel plate on which the magnetic domain control processing lines are formed after magnetic domain control processing. The domain image comparison step compares the domain image before the domain control processing with the domain image after the domain control processing; and An additional magnetic domain control processing line forming step is performed, whereby, as needed, magnetic domain control processing lines are further formed on the surface of the directional electromagnetic steel plate after the magnetic domain image comparison step. In the domain control processing line formation step, based on the domain width distribution obtained in the domain width distribution acquisition step, the domain control processing line is formed in the region where the domain width exceeds 500 μm. In the domain image comparison process, when a region whose domain width derived from the domain image before the domain control processing is more than 100 μm larger than the domain width derived from the domain image after the domain control processing is designated as a first region, and all other regions are designated as a second region, the unit of the domain control processing line in the second region is mm / mm. 2 The line density and the magnetic domain control processing lines in the first region are in units of mm / mm. 2 Comparing the linear densities, In the additional magnetic domain control processing line formation step, when the line density of the second region is the same as or greater than the line density of the first region, the magnetic domain control processing line is formed in the first region, and the second magnetic domain image acquisition step, the magnetic domain image comparison step, and the additional magnetic domain control processing line formation step are repeated until the line density of the magnetic domain control processing line in the second region is less than the line density of the magnetic domain control processing line in the first region.

6. The method for manufacturing a directional electromagnetic steel plate according to claim 5, wherein, In the magnetic domain control processing line formation process, the magnetic domain control processing line is formed by irradiation with a laser or electron beam.

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