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. In the grain-oriented electrical steel sheet, a plurality of magnetic domain control processing lines extending in a direction intersecting the rolling direction are provided on the surface, a square evaluation region having a length of 50 mm on one side and parallel to the rolling direction on the other side is set on the surface, and a plurality of magnetic domain control processing lines extending in the direction intersecting the rolling direction are provided inside the evaluation region. When imaginary lines parallel to the rolling direction and having a length of 50 mm are set at 5 mm intervals in a direction perpendicular to the rolling direction, in at least one of the imaginary lines, the maximum value of the interval in the rolling direction between adjacent intersection points among a plurality of intersection points of the imaginary line and the plurality of magnetic domain control processing lines exceeds 20 mm. The average magnetic domain width measured along the imaginary line is 600 [mu] m or less, and the plurality of magnetic domain control processing lines are tensile stress introduction lines into which a tensile stress of 40 MPa or more is introduced.

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. 2023-166093, 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] 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 Summary of the Invention

[0007] 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.

[0008] 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.

[0009] 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.

[0010] Methods for solving problems The inventors have studied methods for reducing iron loss and suppressing the deterioration of noise characteristics.

[0011] The results showed that, when performing magnetic domain control processing based on tensile stress, directional electromagnetic steel sheets with low iron loss and excellent noise characteristics can be obtained by expanding the interval of magnetic domain control processing in at least a portion of specific regions.

[0012] This invention was made in view of the above-mentioned insights. The main points of this invention are as follows.

[0013] [1] One aspect of the directional electromagnetic steel sheet of the present invention is that it has a plurality of magnetic domain control processing lines extending in a direction intersecting the rolling direction on its surface, and a square evaluation area with one side having a length of 50 mm and one side being parallel to the rolling direction is set on the surface. In the case that imaginary lines with a length of 50 mm are set at 5 mm intervals in a direction perpendicular to the rolling direction, in at least one of the imaginary lines, the maximum value of the interval between adjacent intersections of the imaginary line and the plurality of magnetic domain control processing lines in the rolling direction exceeds 20 mm, and the average value of the magnetic domain width measured along the imaginary line is 600 μm or less. The plurality of magnetic domain control processing lines are tensile stress introduction lines that introduce tensile stress of 40 MPa or more.

[0014] [2] In the directional electromagnetic steel plate described in [1], the average value of the magnetic domain width measured along the imaginary line may be less than 500 μm.

[0015] [3] In the directional electromagnetic steel sheet described in [1], the average value of the magnetic domain width measured along the imaginary line in each of the two or more rolling directions where the maximum value of the interval exceeds 20 mm is 600 μm or less.

[0016] [4] In the directional electromagnetic steel sheet described in [3], the average value of the magnetic domain width measured along the imaginary line in each of the two or more said rolling directions where the maximum value of the interval exceeds 20 mm is 500 μm or less.

[0017] [5] Another aspect of the directional electromagnetic steel sheet of the present invention is that it has a plurality of magnetic domain control processing lines extending in a direction intersecting the rolling direction on its surface, and a square evaluation area with one side having a length of 50 mm and one side being parallel to the rolling direction is set on the surface. In the case that imaginary lines with a length of 50 mm are set at 5 mm intervals in a direction perpendicular to the rolling direction, in at least one of the imaginary lines, the maximum value of the interval between adjacent intersections of the imaginary line and the plurality of magnetic domain control processing lines in the rolling direction exceeds 20 mm, and the maximum value of the magnetic domain width measured along the imaginary line is 1200 μm or less.

[0018] [6] In the directional electromagnetic steel plate described in [5], the maximum value of the magnetic domain width measured along the imaginary line may be less than 800 μm.

[0019] [7] In the directional electromagnetic steel sheet described in [5], the maximum value of the magnetic domain width measured along the imaginary line in each of the two or more said rolling directions where the maximum value of the interval exceeds 20 mm is 1200 μm or less.

[0020] [8] In the directional electromagnetic steel sheet described in [7], the maximum value of the magnetic domain width measured along the imaginary line in each of the two or more said rolling directions where the maximum value of the interval exceeds 20 mm is 800 μm or less.

[0021] [9] In any of the directional electromagnetic steel plates described in [1] to [8], the multiple magnetic domain control processing lines may be thermal strain.

[0022]

[10] In the directional electromagnetic steel plate described in [9], the maximum value of the tensile stress introduced in the thermal strain in the magnetic domain control processing line is not uniform at each measurement point of the tensile stress.

[0023]

[11] In the directional electromagnetic steel plate described in

[10] , the intersection points of the imaginary line and the multiple magnetic domain control processing lines are respectively taken as magnetic domain refinement points, and the maximum value of the tensile stress per unit MPa introduced into the thermal strain measured at the magnetic domain refinement points is set as TS. m , the TS m Let the variance be σ(TS) m ) 2 When σ(TS) is satisfied m ) 2 >5.0.

[0024]

[12] In the directional electromagnetic steel plate described in

[10] , when the multiple intersection points of the imaginary line and the multiple magnetic domain control processing lines are respectively set as magnetic domain refinement points, the arithmetic mean of the maximum value of the tensile stress per unit MPa introduced in the thermal strain measured at the magnetic domain refinement points with a β angle less than 2° is set as TS. m(β<2) The arithmetic mean of the maximum tensile stress per unit MPa introduced in the thermal strain, measured at the magnetic domain refinement points with a β angle of 2° or higher, is set as TS. m(β≥2) When, satisfy TS m(β<2) >TS m(β≥2) .

[0025]

[13] In the directional electromagnetic steel sheet described in

[11] , the arithmetic mean of the maximum tensile stress per unit MPa introduced into the thermal strain, measured at each of the magnetic domain refinement points where the β angle is less than 2°, can be set as TS. m(β<2) The arithmetic mean of the maximum tensile stress per unit MPa introduced in the thermal strain, measured at the magnetic domain refinement points with a β angle of 2° or higher, is set as TS. m(β≥2) When, satisfy TS m(β<2) >TS m(β≥2) .

[0026]

[14] Another method for manufacturing a directional electromagnetic steel plate according to the present invention is a method for manufacturing a directional electromagnetic steel plate according to any one of [1] to [8], comprising: a magnetic domain image acquisition step, acquiring a magnetic domain image of the surface of the directional electromagnetic steel plate; a region determination step, determining a region in the directional electromagnetic steel plate with a magnetic domain width exceeding 500 μm based on the magnetic domain image obtained in the magnetic domain image acquisition step; and a magnetic domain control processing line formation step, forming a magnetic domain control processing line on the surface of the directional electromagnetic steel plate after the region determination step, wherein the magnetic domain control processing line is formed in the region with a magnetic domain width exceeding 500 μm in the magnetic domain control processing line formation step.

[0027]

[15] In the manufacturing method of the directional electromagnetic steel plate described in

[14] , 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.

[0028] 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

[0029] Figure 1A This is a schematic diagram illustrating an example of a directional electromagnetic steel plate according to this embodiment.

[0030] Figure 1B This is a schematic diagram illustrating an example of a directional electromagnetic steel plate according to this embodiment.

[0031] Figure 1C This is a schematic diagram illustrating an example of a directional electromagnetic steel plate according to this embodiment.

[0032] Figure 2 It is a graph showing the relationship between the domain width before laser irradiation and the domain width after laser irradiation.

[0033] Figure 3A This is a diagram illustrating an example of the distribution of magnetic domain widths in a directional electromagnet before domain refinement.

[0034] 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.

[0035] Figure 3C This is a diagram illustrating an example of a magnetic domain image acquired by an image acquisition device.

[0036] Figure 3D It is a schematic representation Figure 3C The image.

[0037] Figure 4 This is a block diagram illustrating an example of the hardware configuration of an image acquisition device.

[0038] Figure 5 This is a block diagram illustrating an example of the hardware configuration of an analysis device.

[0039] Figure 6 This is a schematic diagram illustrating an example of the configuration of a laser irradiation device.

[0040] Figure 7 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.

[0041] Figure 8 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.

[0042] Figure 9 This is a schematic diagram of a cross-section of a directional electromagnetic steel plate with thermal strain as the magnetic domain control processing line.

[0043] Figure 10 This is a planar schematic diagram illustrating the method for measuring the magnetic domain control intensity at the intersection of the magnetic domain control processing line and the imaginary line.

[0044] Figure 11 It is a graph that schematically shows the relationship between the size of the domain width and the domain control saturation intensity.

[0045] Figure 12 It is a graph that schematically shows the relationship between the size of the β angle and the domain-controlled saturation intensity. Detailed Implementation

[0046] 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.

[0047] like Figure 1AAs shown, the directional electromagnetic steel plate 1 of this embodiment has multiple domain control processing lines 11 extending in a direction intersecting the rolling direction RD on its surface. An evaluation area with a length of 50 mm on one side and parallel to the rolling direction RD on the other side is set on the surface. Inside the evaluation area, imaginary lines VL with a length of 50 mm and parallel to the rolling direction RD are set at 5 mm intervals in a direction perpendicular to the rolling direction RD. In at least one imaginary line VL, the maximum value (dmax) of the interval (d1~d7) between adjacent intersection points of the imaginary line VL and multiple intersection points VP of the multiple domain control processing lines 11 in the rolling direction RD is more than 20 mm, and the average value of the domain width measured along the imaginary line VL is 600 μm or less, or the maximum value of the domain width is 1200 μm or less.

[0048] In addition, the magnetic domain control processing line 11 is a tensile stress introduction line that introduces tensile stress of 40 MPa or more.

[0049] As described below, the directional electromagnetic steel sheet of this embodiment may have a magnesium olivine coating and / or an insulating coating on the surface of the steel sheet used as the base material.

[0050] 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, intersection spacing, 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] The thickness of the directional electromagnetic steel sheet 1 is not limited, but is preferably 0.15 mm to 0.30 mm. By setting it 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.

[0057] (Magnetic domain control processing line 11) Multiple magnetic domain control lines 11 disposed on the surface of the directional electromagnetic steel plate 1 have 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 inside 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".

[0058] 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.

[0059] like Figure 1A As 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.

[0060] Furthermore, as long as dmax (the maximum value of the interval between adjacent intersections in the rolling direction among the multiple intersections of the imaginary line and the multiple magnetic domain control processing lines) exceeds 20 mm, it can be as follows: Figure 1B As shown, the magnetic domain control processing line 11 is uninterrupted in the middle (i.e., all magnetic domain control processing lines are formed throughout the width direction of the steel plate), or it can be as follows: Figure 1C As shown, the domain control processing line 11 includes a curved portion (i.e., it may not be composed of only straight lines).

[0061] The type of magnetic domain control processing line 11 is not particularly limited as long as it is a tensile stress introduction line with a tensile stress of 40 MPa or more. A preferred example is thermal strain. Thermal strain can be formed, for example, by methods such as laser irradiation, electron beam irradiation, and ion implantation.

[0062] 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 by the directional electromagnetic steel plate 1.

[0063] Regarding the magnitude of the tensile stress, at least a portion of the magnetic domain control processing line 11 has a tensile stress of 40 MPa or more in any direction, preferably 60 MPa or more, and more preferably 80 MPa or more. When the tensile stress in at least one direction is 40 MPa or more, it is considered to satisfy the requirement of "tensile stress in any direction is 40 MPa or more," and also satisfies the requirement of this embodiment that "multiple magnetic domain control processing lines are tensile stress introduction lines with a tensile stress of 40 MPa or more." Furthermore, for example, at least a portion of the magnetic domain control processing line 11 has a tensile stress in any direction that is preferably 300 MPa or less, 200 MPa or less, 180 MPa or less, or 150 MPa or less. The tensile stress in any direction within the magnetic domain control processing line 11 may be the same or may vary.

[0064] 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.

[0065] 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.

[0066] The number of measurement sites is set to, for example, 10. At at least one point 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 among the multiple magnetic domain control processing lines possessed by the directional electromagnetic steel plate 1 is 40 MPa or more. Therefore, if the purpose is to determine whether the maximum value of the tensile stress is 40 MPa or more, the measurement of the tensile stress can be stopped at the moment when a measurement point where the tensile stress relative to any direction is 40 MPa or more is found. However, after calculating σ(TS) as described later... m ) 2 TS m(β<2) , or TS m(β≥2) In this case, the tensile stress at each measurement point is determined without stopping the measurement.

[0067] 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. By observing the captured magnetic domain images, the location of thermal strain can be determined. 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.

[0068] (The interval between the intersections of the imaginary line parallel to the rolling direction and the magnetic domain control processing line) (domain width) As described above, the 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. Furthermore, the smaller the spacing between the domain control processing lines, the greater the effect on improving iron loss. Therefore, in typical domain control processing, the spacing between each domain control processing line is formed to be no more than 20 mm.

[0069] In contrast, in the directional electromagnetic steel sheet of this embodiment, a square evaluation area with one side length of 50 mm and one side parallel to the rolling direction RD is set on the surface. Inside the evaluation area, imaginary lines VL with a length of 50 mm and parallel to the rolling direction RD are set at 5 mm intervals in a direction perpendicular to the rolling direction. In at least one imaginary line VL, the maximum value of the interval between adjacent intersection points VP of the imaginary line VL and multiple domain control processing lines 11 in the rolling direction RD exceeds 20 mm. That is, in at least a portion, the interval between the domain control processing lines in the rolling direction exceeds 20 mm. Figure 1A The example shown depicts a state where only one imaginary line VL is drawn. When multiple imaginary lines VL are set, it is possible to... Figure 1A The required number of other imaginary lines are set parallel to the imaginary line VL.

[0070] Furthermore, in the directional electromagnetic steel sheet of this embodiment, in the imaginary line VL where the maximum value of the interval in the rolling direction RD exceeds 20 mm, at least one of the following listed requirements is satisfied.

[0071] (1) The average value of the domain width measured along the imaginary line VL is less than 600 μm.

[0072] (2) The maximum value of the magnetic domain width measured along the imaginary line VL is less than 1200 μm.

[0073] Both of the above requirements (1) and (2) can be satisfied. That is, the average value of the domain width measured along the imaginary line VL is 600 μm or less, and the maximum value is 1200 μm or less.

[0074] As mentioned above, while domain control processing is effective in reducing iron losses in directional electromagnetic steel sheets, it also deteriorates their noise characteristics. Therefore, by reducing the density of the domain control processing lines, 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] A maximum interval of more than 20 mm at the intersection points means that there are areas in the steel plate where the interval of the rolling direction of the magnetic domain control processing line exceeds 20 mm, which is more preferable from the point of view of low noise.

[0076] 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.

[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] Therefore, in order to reduce iron loss while minimizing the deterioration of noise characteristics, domain control processing is mainly performed on regions with wider domain widths where the domain refinement effect is significant. While it is preferable to perform domain control processing only on regions with wider domain widths, it is permissible to perform domain control processing on regions with narrower domain widths because the smaller the proportion, the smaller the deterioration of noise characteristics. Furthermore, for regions with wider domain widths, it is preferable to perform domain control processing on the entire region, but regions without domain control processing may be included within the range where sufficient iron loss reduction is achieved.

[0079] The inventors' further research results on the magnetic domain refinement effect, such as... Figure 2As shown, in regions where the domain width is approximately 500 μm or less, the domain width is approximately the same before and after the domain control treatment. That is, it can be considered that the domain refinement effect based on domain control is almost negligible in regions where the domain width is approximately 500 μm or less. Therefore, in the directional electromagnetic steel sheet of this embodiment, in order to reduce the density of the domain control treatment lines and sufficiently obtain the effect of reducing iron loss, domain control is not intentionally performed in such regions where the domain width is 500 μm or less, and the domain control treatment lines are mainly formed in regions where the domain width exceeds 500 μm. As a result, in the directional electromagnetic steel sheet of this embodiment, in the imaginary lines VL where the maximum value of the interval in the rolling direction RD exceeds 20 mm, the average value of the domain width measured along the imaginary lines is 600 μm or less, or the maximum value is 1200 μm or less. That is, in the directional electromagnetic steel sheet 1 that satisfies at least one of requirements (1) and (2), the domain width is set to a small value throughout the entire imaginary lines VL. Therefore, it is possible to achieve both low noise and low iron loss in a balanced way.

[0080] In the directional electromagnetic steel sheet of this embodiment, it is preferable that, in two or more imaginary lines VL, the maximum value of the interval between adjacent intersections of a plurality of intersections VP in the rolling direction exceeds 20 mm, and at least one of the following listed requirements is satisfied.

[0081] (1) The average domain width measured along each imaginary line VL is less than 600 μm.

[0082] (2) The maximum value of the magnetic domain width measured along each imaginary line VL is less than 1200 μm.

[0083] Both of the above requirements (1) and (2) can be satisfied. That is, the average value of the domain width measured along the imaginary line VL is 600 μm or less, and the maximum value is 1200 μm or less.

[0084] In regions where the maximum interval between intersections of multiple imaginary lines exceeds 20 mm, it means that there are regions in the rolling direction of the magnetic domain control processing lines at multiple locations on the steel plate with an interval exceeding 20 mm, which is more preferable from the point of view of low noise.

[0085] The average value of the magnetic domain width described above is further preferably 500 μm or less, 450 μm or less, 400 μm or less, 380 μm or less, 350 μm or less, or 300 μm or less. Furthermore, the maximum value of the magnetic domain width is further preferably 1000 μm or less, 800 μm or less, 600 μm or less, 500 μm or less, 450 μm or less, or 400 μm or less.

[0086] The interval of the rolling direction at the intersection of the imaginary line and the multiple domain control processing lines, the average value of the domain width measured along the imaginary line, and the maximum value are obtained by the following method.

[0087] For example, rectangular specimens with side lengths of 100 mm (or more) can be cut from the directional electromagnetic steel sheet 1 for measurement. When the directional electromagnetic steel sheet 1 is a roll, the specimen can be collected 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 specimen can be collected from any part of the part. When the part is small, as long as one side of the specimen is 50 mm or more, one side of the specimen can be less than 100 mm. In this case, to minimize the influence of mechanical strain on the specimen, it is preferable to collect the specimen using methods such as wire cutting.

[0088] For this sample, a magnetic domain image is obtained using an image acquisition device that includes a light source, a magneto-optical sensor (MO sensor), an image sensor, and a signal processing unit.

[0089] In the magnetic domain image, an evaluation area is set as a square with one side length of 50 mm and one side parallel to the rolling direction. Inside the evaluation area, imaginary lines VL with a length of 50 mm and parallel to the rolling direction are set at 5 mm intervals in a direction perpendicular to the rolling direction.

[0090] The interval between the intersection points of the imaginary line VL and the multiple magnetic domain control processing lines 11 is measured, and the maximum value is taken as the maximum value of the interval between adjacent intersection points in the rolling direction.

[0091] The average and maximum domain widths measured along the imaginary line are determined using multiple sub-imaginary lines that intersect the imaginary line VL perpendicularly to the direction perpendicular to the plate surface (thickness direction). The sub-imaginary lines are 5 mm long and spaced 2 mm apart in the rolling direction. Each sub-imaginary line is positioned to intersect the imaginary line VL at its center. The number of domains contained in each sub-imaginary line is measured, and the value obtained by dividing the length of the sub-imaginary line by the number of domains it contains is considered the domain width on the sub-imaginary line. The average domain width on the sub-imaginary lines is set as the average domain width measured along the imaginary line, and the maximum domain width on the sub-imaginary lines is set as the maximum domain width measured along the imaginary line.

[0092] That is, in this embodiment, "along the imaginary line VL" means that the center of the secondary imaginary line is located on the imaginary line at equal intervals.

[0093] There is no limitation on the location where the evaluation area and the imaginary line VL are set. The evaluation area and the imaginary line VL can be set anywhere where the maximum value of the interval between adjacent intersections VP in the rolling direction falls within the scope of this invention. For example, the imaginary line VL can be set in a region where the magnetic domain control processing line 11 is not provided. On the other hand, if it is not possible to find a location where the maximum value of the interval between adjacent intersections falls within the scope of this invention, it is inferred that the requirements of this invention are not met.

[0094] Furthermore, the magnetic domain image is output via cable or wireless communication to an analysis device, which is a computer device 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.

[0095] 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.

[0096] 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.

[0097] In the directional electromagnetic steel sheet of the present invention, the maximum value of the tensile stress introduced in the thermal strain, which is an indicator of the strength of magnetic domain control, in the magnetic domain control processing line is non-uniform at each measurement point of the tensile stress.

[0098] The greater the intensity of domain control, the better the domain refinement effect. However, a greater intensity of domain control also tends to lead to increased hysteresis loss and deterioration of noise characteristics. Furthermore, according to the present invention, the domain control saturation intensity is not uniform in directional electromagnetic steel sheets. Therefore, it is preferable to make the domain control intensity non-uniform based on the domain control saturation intensity.

[0099] Domain control saturation intensity refers to the domain control intensity at which the effect of domain refinement is substantially saturated. When the domain control intensity is below the domain control saturation intensity, a higher domain control intensity results in a greater reduction in iron loss. However, when the domain control intensity exceeds the domain control saturation intensity, even increasing the domain control intensity yields almost no improvement in iron loss reduction. On the other hand, even when the domain control intensity exceeds the domain control saturation intensity, a higher domain control intensity leads to greater hysteresis loss and a worsening of noise characteristics. Therefore, the domain control intensity is preferably set within a range that does not exceed the domain control saturation intensity.

[0100] More preferably, the following state is adopted: multiple intersection points of the imaginary line and multiple magnetic domain control processing lines are respectively designated as magnetic domain refinement points, and the maximum value of the tensile stress per unit MPa introduced in thermal strain, measured at each magnetic domain refinement point, is designated as TS. m , the TS m Let the variance be σ(TS) m ) 2 When σ(TS) is satisfied m ) 2 >5.0.

[0101] "The maximum value of the tensile stress introduced in thermal strain" refers to the maximum value of the tensile stress measured in an arbitrary cross-section. Since tensile stress varies within a single cross-section, a specific point is determined for each cross-section to define the "maximum value of the tensile stress introduced in thermal strain." For example... Figure 9 As schematically shown, the thermal strain 541 extends to a certain extent within the cross-section. The tensile stress is greatest at the location directly irradiated by the laser, and smaller at locations farther away. That is, the measured value of tensile stress is different at each measurement location within the cross-section. The distribution and maximum value of the tensile stress within the cross-section can be derived using the tensile stress measurement method described later.

[0102] When the domain control intensity is uniform, the maximum value of the tensile stress introduced in the thermal strain 541 becomes constant throughout the entire domain control processing line 11. On the other hand, when the domain control intensity is non-uniform, the maximum value of the tensile stress introduced in the thermal strain in the domain control processing line is not uniform at each measurement point of the tensile stress. Hereinafter, the maximum value of the tensile stress introduced in the thermal strain will sometimes be simply referred to as "tensile stress".

[0103] Furthermore, the inventors discovered a strong correlation between domain control saturation intensity and the β angle. The β angle refers to the deviation angle of a grain from its Goss orientation around the rolling right-angle direction (TD). At locations with smaller β angles, the domain control saturation intensity is greater. Additionally, a correlation exists between the β angle and domain width in directional electromagnetic steel sheets before domain control treatment. In these sheets, a larger β angle corresponds to a smaller domain width. However, in directional electromagnetic steel sheets after domain control treatment, the correlation between domain width and the β angle decreases. This is because the domain control treatment changes the domain width but not the β angle.

[0104] Therefore, it is preferable to select the optimal domain control intensity based on the domain width or the β angle. For example, it is preferable to perform domain refinement with a higher domain control intensity in regions with a larger domain width and a smaller β angle, and to perform domain refinement with a lower domain control intensity in regions with a smaller domain width and a larger β angle. Furthermore, as mentioned above, domain refinement is not performed in regions where the original domain width is narrow.

[0105] Preferably, TS is defined as the arithmetic mean of the maximum tensile stress per unit MPa introduced by thermal strain, measured at magnetic domain refinement points where the β angle is less than 2°. m(β<2) The arithmetic mean of the maximum tensile stress per unit MPa introduced in thermal strain, measured at each of the domain refinement points with a β angle of 2° or higher, is set as TS. m(β≥2) When, satisfy TS m(β<2) >TS m(β≥2) .

[0106] In this case, the iron loss of the directional electromagnetic steel sheet after domain control is further reduced. On the other hand, the increase in hysteresis loss and the deterioration of noise characteristics of the directional electromagnetic steel sheet after domain control are further suppressed.

[0107] use Figure 10 Explanation of TS m and σ(TS) m ) 2 An example of a determination method. Figure 10 The dashed lines in the diagram are multiple imaginary lines VL set at 5mm intervals parallel to the rolling direction RD of the directional electromagnetic steel sheet. Figure 10 The × and ○ marks represent the intersections of the imaginary line VL and the thermal strain 541, which serves as the magnetic domain control processing line. Furthermore, the β angle at locations marked with × is 2° or more, while the β angle at locations marked with ○ is less than 2°. However, in σ(TS) m ) 2 When calculating, the β angle at the intersection point does not need to be considered.

[0108] First, the rolling direction RD of the directional electromagnetic steel sheet is determined. The rolling direction RD can be determined by the method described later. Next, imaginary lines VL are set parallel to the rolling direction RD of the directional electromagnetic steel sheet at 5 mm intervals. Then, the intersection point of the imaginary line VL and the thermal strain 541, which serves as the magnetic domain control processing line, is determined. When the thermal strain 541 cannot be visually identified by the naked eye, it is determined based on a magnetic domain image. The shape of the sample is preferably a rectangle with a size of 100 mm or more along the rolling direction RD and a size of 100 mm or more along the rolling right-angle direction TD. One side of the rectangle is preferably parallel to the rolling direction RD.

[0109] Then, for all intersections of the measurement area, TS m Perform measurements and calculate TS. m variance σ(TS) m ) 2 Tensile stress TS introduced in thermal strain m The measurements were performed 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.

[0110] When determining the magnitude of tensile stress introduced into thermal strain using the EBSD Wilkinson method and a Cross Court manufactured by BLG Vantage, the thermal strain 541, which serves as the domain control processing line, 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. This cut surface is used as the measurement surface. For the cross section containing the domain control processing line within the measurement surface, 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 direction normal to the rolling surface, in the direction parallel to the domain control processing line, and in the direction perpendicular to both the rolling surface normal and the domain control processing line.

[0111] The maximum tensile stress TS was determined at multiple measurement points. Mvariance σ(TS) M ) 2 The parent variance is derived according to the method described in paragraph 2.36 of JIS Z 8101-1:2015 "Statistics - Terms and notation - Part 1: General statistical terms and terms used in probability".

[0112] In addition, TS can be determined by the following methods. m(β<2) and TS m(β≥2) .

[0113] First, intersections with a β angle greater than 2° and intersections with a β angle less than 2° are determined by measuring the β angle at the intersection points. The β angle in directional electromagnetic steel sheets is measured using the side-reflection Laue method. The side-reflection Laue method is well-known as a method for determining crystal orientation.

[0114] Next, the maximum tensile stress TS is determined at all intersections where the β angle is greater than 2°. m And calculate the arithmetic mean of these values. This value is considered TS. m(β≥2) .

[0115] Furthermore, the maximum tensile stress TS is determined at all intersection points where the β angle is less than 2°. m And calculate the arithmetic mean of these values. Consider this value as TS. m(β<2) The maximum tensile stress TS introduced in the thermal strain 541 at the intersection point. m The determination method is as described above.

[0116] 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 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 by 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.

[0117] The spacing between adjacent domain control processing lines 11 along the rolling direction RD can be constant or it can vary. In the case of variation, for example, the average value of the spacing P between 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 value of the spacing between 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.

[0118] In the directional electromagnetic steel sheet 1 of this embodiment, the spacing of VP in the imaginary line VL, which serves as the measurement position for the domain width, deviates. That is, even if the average spacing of the domain control processing lines 11 is within the range described above, since the imaginary line VL, which serves as the measurement position for the domain width, passes through an area where no domain control processing lines 11 are provided, the maximum value of the spacing between the intersection of the imaginary line VL and the domain control processing lines 11 in the rolling direction exceeds 20 mm.

[0119] 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 through the steps described above and below.

[0120] 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.

[0121] 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.

[0122] (Methods for determining the rolling direction RD and the rolling right-angle direction TD) The rolling direction RD and the rolling right-angle direction (plate width direction) TD of the directional electromagnetic steel plate 1 are determined by the following methods.

[0123] (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 rolling surface normal direction ND is regarded as the rolling direction RD.

[0124] (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.

[0125] (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 (plate width direction) TD.

[0126] (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).

[0127] The magnesium olivine coating and the insulating coating can be formed on one side or both sides of the directional electromagnetic steel plate 1.

[0128] 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.

[0129] 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.

[0130] [Manufacturing Method] The directional electromagnetic steel sheet of this embodiment can achieve its effect regardless of the manufacturing method, as long as it has the above-mentioned characteristics. However, the following method can be used to manufacture it stably, and is therefore preferred.

[0131] That is, the directional electromagnetic steel plate of this embodiment can be manufactured by a manufacturing method including the steps (I) to (III) described below. In cases where the distribution of magnetic domain width is inferred by methods other than image acquisition, or where the distribution of magnetic domain width is clear, steps (I) and (II) may be omitted.

[0132] (I) Domain image acquisition process for obtaining domain images of directional electromagnetic steel plates.

[0133] (II) A region determination process for determining regions in a directional electromagnetic steel plate with a magnetic domain width exceeding 500 μm based on the magnetic domain image obtained in the magnetic domain image acquisition process.

[0134] (III) Domain control processing line forming process, which forms domain control processing lines on the surface of the directional electromagnetic steel plate after the region determination process.

[0135] Each process step is explained.

[0136] First, the directional electromagnetic steel sheet (original sheet) provided to the magnetic domain control processing line forming process, whether or not the magnetic domain image acquisition process is performed, or the magnetic domain image acquisition process and the region determination process are both performed, can be a known directional electromagnetic steel sheet.

[0137] 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.

[0138] In directional electromagnetic steel sheets that become the base plate, a magnesium olivine coating can be formed on the surface.

[0139] (Magnetic domain image acquisition process) (Regional process determination) In the magnetic domain image acquisition step, a magnetic domain image of the surface of the directional electromagnetic steel sheet is acquired before the magnetic domain control processing line formation step. In the region determination step, based on the magnetic domain image obtained in the magnetic domain image acquisition step, regions in the directional electromagnetic steel sheet with magnetic domain widths exceeding 500 μm are determined.

[0140] As mentioned above, the domain refinement effect is considered small in regions with narrow 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.

[0141] In the domain control line formation process, which is a subsequent process, domain control processing is mainly performed on areas with domain widths exceeding 500 μm. This reduces the number of domain control lines, suppresses the deterioration of noise characteristics, and reduces iron loss.

[0142] (Magnetic domain control processing line formation process) In the domain control processing line formation process, domain control processing lines are mainly formed in regions where the domain width exceeds 500 μm as determined in the region determination process. 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. At this time, the domain control processing lines are formed such that regions with an interval exceeding 20 mm in the rolling direction exist.

[0143] As a method, for example, the following approach can be cited: based on the distribution of domain widths obtained in the region determination process, a domain control processing line is formed in a direction intersecting the rolling direction at a position that has moved more than 20 mm along the rolling direction relative to the adjacent domain control processing line, or, as... Figure 1A As shown, when a magnetic domain control processing line is formed in a direction intersecting the rolling direction, even if the starting point is within 20 mm from the adjacent magnetic domain control processing line in the rolling direction, a magnetic domain control processing line is not formed in a certain range. Thus, a magnetic domain control processing line is formed at a certain position with an interval of more than 20 mm in the rolling direction between adjacent intersections.

[0144] Preferably, the domain control strength is determined based on the domain width and β angle of the directional electromagnetic steel sheet before domain refinement. Domain control strength refers to the amount of thermal strain. In this case, the maximum value of the tensile stress introduced by thermal strain in the domain control treatment line is not uniform at each measurement point of the tensile stress.

[0145] The greater the intensity of magnetic domain control, the better the effect of magnetic domain refinement. On the other hand, the greater the intensity of magnetic domain control, the more likely it is to lead to increased hysteresis loss and deterioration of noise characteristics. In addition, according to the inventors' novel insights, the saturation intensity of magnetic domain control is not uniform in directional electromagnetic steel sheets.

[0146] Domain control saturation intensity refers to the domain control intensity at which the effect of domain refinement processing becomes saturated. When the domain control intensity is below the domain control saturation intensity, a higher domain control intensity results in a greater reduction in iron loss. However, when the domain control intensity exceeds the domain control saturation intensity, even increasing the domain control intensity yields almost no improvement in iron loss reduction. On the other hand, even when the domain control intensity exceeds the domain control saturation intensity, a higher domain control intensity leads to greater hysteresis loss and a worsening of noise characteristics. Therefore, the domain control intensity is preferably set within a range that does not exceed the domain control saturation intensity.

[0147] Specifically, it is preferable to perform domain refinement with higher domain control intensity in regions with larger domain widths and smaller β angles, and to perform domain refinement with lower domain control intensity in regions with smaller domain widths and larger β angles. In regions with larger β angles, no domain control effect is obtained, therefore the domain control saturation intensity is 0. In regions with β angles below a predetermined value, domain control effect is obtained. For example, it is inferred that domain control effect is obtainable when the β angle is below 2°. Furthermore, in regions with β angles below the predetermined value, the larger the β angle, the greater the domain control saturation intensity. Moreover, in regions with smaller β angles, the domain control saturation intensity remains approximately constant.

[0148] Figure 11A graph is shown to schematically illustrate a method for determining domain control strength based on domain width. Figure 11 The vertical axis represents the domain control strength, and the horizontal axis represents the domain width. Figure 11 The solid line represents the domain control saturation intensity. In regions with small domain widths, domain control is ineffective, resulting in a saturation intensity of 0. Domain control is achieved in regions with domain widths exceeding 500 μm. Furthermore, in regions with domain widths exceeding 500 μm, the wider the domain width, the greater the domain control saturation intensity. Moreover, in regions with domain widths exceeding approximately 1200 μm, the domain control saturation intensity remains approximately constant.

[0149] Figure 12 A graph is shown to schematically illustrate a method for determining the domain control intensity based on the β angle. Figure 12 The vertical axis represents the domain control intensity, and the horizontal axis represents the magnitude of the β angle. Figure 12 The solid line curve represents the domain control saturation intensity. In regions with large β angles, domain control is ineffective, resulting in a saturation intensity of 0. Domain control is effective in regions with β angles below a specified value. For example, when the β angle is below 2°, it is inferred that domain control is effective. Furthermore, in regions with β angles below the specified value, the larger the β angle, the greater the domain control saturation intensity. Moreover, in regions with smaller β angles, the domain control saturation intensity remains approximately constant.

[0150] The optimal relationship between the domain width and domain control intensity at the site where domain control is implemented is as follows: Figure 11 The curve is shown as a solid line in the graph. Alternatively, the optimal relationship between the β angle at the site where domain control is implemented and the domain control intensity is... Figure 12 The solid line in the graph shows that the domain control saturation intensity can be used as the target value for the domain control intensity.

[0151] Furthermore, there exists a minimum strength at which the domain control effect is detected, i.e., the minimum domain control strength. When performing domain control, the domain control strength is more preferably greater than or equal to the minimum domain control strength.

[0152] However, the domain control intensity can also deviate slightly from the target value of the domain control saturation intensity. Figure 11 and Figure 12 In this context, the region above the minimum domain control intensity, and the area within a certain range starting from the domain control saturation intensity curve, is defined as the target range of the domain control intensity. The domain control intensity and the domain width of the domain control target area are preferably within a certain range. Figure 11 and Figure 12The area inside the shaded region surrounded by dashed lines. When the maximum value of the tensile stress introduced in thermal strain in the magnetic domain control processing line is not uniform at each measurement point of the tensile stress, it is preferable to intentionally vary the magnetic domain control intensity, preferably within the shaded region surrounded by dashed lines.

[0153] The intensity of magnetic domain control can be varied according to the irradiation conditions of a laser or electron beam. Specifically, changing the power of the laser or electron beam, the irradiation time, the irradiation interval, etc., alters the average irradiation energy density Ua (mJ / mm²) per unit area. 2 That is, even if Ua is the same as above, the thermal strain of the steel plate will be slightly different depending on the combination of laser or electron beam power, irradiation time, irradiation interval, etc.

[0154] Magnetic domain control processing lines can be formed by irradiation with a laser or electron beam. The irradiation conditions can be within a known range.

[0155] The formation direction of the magnetic domain control processing line (or the scanning direction if it is a laser, etc.) and the spacing of the rolling direction RD of the magnetic domain control processing line can be controlled by known methods in a way that makes it fall within the range of the directional electromagnetic steel sheet described in this embodiment.

[0156] (Specific methods in the process of acquiring magnetic domain images ~ forming control lines for each magnetic domain) The acquisition of magnetic domain images and the determination of regions with domain widths exceeding 500 μm can be performed using the following methods.

[0157] The domain image 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 domain image. The distribution of domain widths in the original plate can be derived, for example, using an analysis device.

[0158] Regions with a domain width greater than a specified value (e.g., exceeding approximately 500 μm) are designated as regions for which domain control processing should be performed (hereinafter sometimes referred to as processing regions).

[0159] The processing area can also be determined by the operator visually observing the magnetic domain image displayed on the display of the analysis device.

[0160] 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.

[0161] 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.

[0162] 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.

[0163] 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.

[0164] 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 ).

[0165] 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.

[0166] 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 the 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.

[0167] 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.

[0168] 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.

[0169] 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.

[0170] 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.

[0171] 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.

[0172] 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.

[0173] 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. The following describes the configuration of a laser irradiation device 500 for introducing thermal strain via laser irradiation.

[0174] 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.

[0175] The plate-passing device 515 causes the original plate to pass through the rolling direction RD.

[0176] The polygonal 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 polygonal 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 polygonal mirror 501 and is reflected by the plane mirror.

[0177] The polygon mirror 501 can be rotated about the rotation axis O1 by being driven by 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.

[0178] 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).

[0179] 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.

[0180] Motor 509 is connected to polygon mirror 501. Motor 509 rotates and drives polygon mirror 501 under the control of control unit 513.

[0181] 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.

[0182] 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.

[0183] 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.

[0184] 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.

[0185] 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 determines the regions with magnetic domain widths above a predetermined value (e.g., exceeding approximately 500 μm) as the areas where magnetic domain control processing is preferentially applied.

[0186] 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.

[0187] 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 3A The 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.

[0188] 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.

[0189] 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).

[0190] 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).

[0191] (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.

[0192] (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.

[0193] 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) k S 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 ).

[0194] [Formula 1] Figure 7 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).

[0195] 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.

[0196] (A-2) Perform ST2DFT processing If we define a portion of the data string as x nm (n′,m′)=x nm (k-nS k ,l-mS l ), for x nmPerforming 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).

[0197] [Equation 2] Here, f k and f l It is spatial frequency.

[0198] If the spatial frequency f k The resolution is expressed as Δf k , spatial frequency f l The resolution is expressed as Δf l Then Δf k and Δf l Defined as in equation (3).

[0199] [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.

[0200] For example, if for Figure 7 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 8 As shown, a partial Fourier image X(f) is obtained for each observation position (n, m). k f l (n, m).

[0201] (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)). Furthermore, regarding the derivation of peak positions, the regions near k=0 and l=0 are largely dependent on the image contrast and are therefore excluded.

[0202] Then, based on the resolution of the spatial frequency defined by Equation (3) and the peak position of the bright spot in the partial Fourier image, the distribution L(n, m) of the magnetic domain width is derived as in Equation (4).

[0203] [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.

[0204] When the arithmetic unit 41 calculates the distribution of magnetic domain widths, it determines the regions with magnetic domain widths greater than or equal to a predetermined value as processing regions (i.e., regions 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.

[0205] 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.

[0206] (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.

[0207] Example The effects of the present invention will be illustrated more specifically through examples. However, the conditions in the examples are merely one example used to confirm the feasibility and effects of implementing the present invention. The present invention is not limited to this single example. Various conditions can be used to achieve the purpose of the present invention without departing from its spirit.

[0208] (Example 1) The directional electromagnetic steel sheets with a thickness of 0.23 mm, classified as 23P085 in Table 2 of JIS C 2553:2019 "Directional Electromagnetic Steel Strip", were used as the base sheets. Magnetic domain control treatment was applied to the base sheets in a manner that resulted in the shape of the magnetic domain control treatment lines shown in Table 1. Here, the shapes of the magnetic domain control treatment lines A~E and A-2 in the table are shown below.

[0209] A: Straight magnetic domain control processing lines are formed in regions where the magnetic domain width exceeds the specified value (500μm).

[0210] B: The magnetic domain control processing lines are formed in a straight line across the entire width of the original plate.

[0211] C: Forms regular dashed magnetic domain control processing lines.

[0212] D: Forms random, dashed magnetic domain control processing lines.

[0213] E: Magnetic domain control processing lines are formed only in the region within ±4 mm of the rolling direction RD, starting from the center of each grain. Additionally, the radius of curvature of the steel plate at the location of the grain during final annealing is 250 mm.

[0214] A-2: Forming a linear magnetic domain control processing line containing curves in regions where the magnetic domain width exceeds a specified value (500μm).

[0215] The regions with magnetic domain widths exceeding 500 μm were determined using the method described above.

[0216] In addition, the magnetic domain control processing line is a tensile stress introduction line based on thermal strain.

[0217] The magnetic domain control process is set to laser irradiation. During laser irradiation, the average irradiation energy density Ua (mJ / mm²) is... 2 (0.5~2.0 mJ / mm) 2 Internal changes: the irradiation spacing PL (mm) is set to 4mm for all cases.

[0218] The magnitude of the tensile stress introduced in each domain control processing line was determined using the method described above. Tensile stress was measured at 10 points along each domain control processing line, and the overall maximum value is recorded in Table 2.

[0219] The noise and iron loss of the directional electromagnetic steel plate after the magnetic domain control treatment were evaluated and recorded in Table 2.

[0220] The evaluation methods for noise and iron loss are as follows. First, 180 sheets of directional electromagnetic steel with a thickness of 0.23 mm were stacked to fabricate a three-phase transformer core. The width of the legs and yoke of the three-phase transformer core was 150 mm. The height and width of the three-phase transformer core were both 750 mm. The noise and iron loss of these three-phase transformer cores were measured. The measurement conditions were set at a frequency of 60 Hz and an excitation flux density of 1.8 T.

[0221] 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 obtained by performing A-characteristic correction and averaging on the noise measurement results from these microphones are recorded as the noise evaluation results (in dBA) of the directional electromagnetic steel plate in Table 2. Examples with noise evaluation results of 50.55 dBA or less were judged as examples that achieved low noise. Noise evaluation results judged as unqualified were marked with an underline.

[0222] The iron loss was determined by measuring the voltage and current on the primary and secondary sides of the directional electromagnetic steel sheet using a power analyzer when excitation was performed at a frequency of 60 Hz and an excitation flux density of 1.8 T, as described above. The calculated iron loss is recorded in Table 2 as the iron loss evaluation result (unit: W / kg) for the directional electromagnetic steel sheet. Examples with an iron loss evaluation result of 1.360 W / kg or less were deemed to have achieved low iron loss. Noise evaluation results deemed unqualified are underlined.

[0223] Furthermore, rectangular samples with a length of 100 mm on both sides were cut from the core of the three-phase transformer used for noise and iron loss measurement.

[0224] A square evaluation area with one side length of 50 mm and one side parallel to the rolling direction is set on the rectangular sample. Inside the evaluation area, imaginary lines VL with a length of 50 mm and parallel to the rolling direction are set at 5 mm intervals in a direction perpendicular to the rolling direction. The number of imaginary lines is 9.

[0225] In each of the nine imaginary lines VL, the maximum value of the interval between adjacent intersections in the rolling direction (intersection interval), the average value of the domain width measured along the imaginary line, and the maximum value of the domain width measured along the imaginary line were determined according to the above-described method.

[0226] Table 1 shows the number of imaginary lines whose maximum interval between intersection points exceeds 20 mm, the average value of the domain width in imaginary lines whose maximum interval between intersection points exceeds 20 mm, and the number of imaginary lines whose maximum value is below a specified value.

[0227] [Table 1] [Table 2] As shown in Tables 1 and 2, when a tensile stress introduction line (i.e., a domain control treatment line) with a tensile stress of 40 MPa or more is formed in a region where the domain width exceeds the specified value (500 μm) (samples No. 1-15, 20, 21), in at least one imaginary line, the maximum value of the interval between adjacent intersections of the imaginary line and the domain control treatment line in the rolling direction exceeds 20 mm, and the average value of the domain width measured along the imaginary line is 600 μm or less, or the maximum value is 1200 μm or less. As a result, iron loss is lower, and noise is also lower.

[0228] In contrast, when the domain control processing line is a regular or random dashed line, the maximum value of the interval between adjacent intersections of the imaginary line and the domain control processing line in the rolling direction, or the average and maximum values ​​of the domain width measured along the imaginary line, deviate from the scope of this invention. As a result, one or both of the iron loss characteristics and noise characteristics deteriorate.

[0229] (Example 2) The directional electromagnetic steel sheets with a thickness of 0.23 mm, classified as 23P085 in Table 2 of JIS C 2553:2019 "Directional Electromagnetic Steel Strip", were used as the base sheets. Magnetic domain control treatment was applied to the base sheets in a manner that resulted in the shape of the magnetic domain control treatment lines shown in Table 3. Here, the shapes of the magnetic domain control treatment lines A-3 to A-6 in the table are shown below.

[0230] A-3: To ensure that the average irradiation energy density Ua is between 0.75 and 1.75 mJ / mm². 2 It varies within a certain range.

[0231] A-4: To ensure that the average irradiation energy density Ua is between 0.5 and 2.0 mJ / mm². 2 It varies within a certain range.

[0232] A-5: To ensure the average irradiation energy density Ua is between 0.75 and 1.75 mJ / mm². 2 Variations within the range, and application of... Figures 10-12 This explains the adjustment of the magnetic domain control intensity.

[0233] A-6: To maintain an average irradiation energy density Ua between 0.5 and 2.0 mJ / mm². 2 Variations within the range, and application of... Figures 10-12 The adjustment of the magnetic domain control intensity is explained.

[0234] The uniformity of the maximum tensile stress obtained by the above method, σ(TSm), is determined.2 TS m(β<2) TS m(β<2) The results are shown in Table 4.

[0235] In addition, the noise and iron loss of the directional electromagnetic steel sheet after the magnetic domain control treatment were evaluated in the same manner as in Example 1, and are recorded in Table 5.

[0236] [Table 3] [Table 4] [Table 5] As can be seen from Tables 3-5, in each example, the iron loss and noise are both low. Furthermore, when σ(TS) is satisfied... m ) 2 >5.0 and TS m(β<2) >TS m(β≥2) In cases involving one or both of them, iron loss is lower or noise is reduced.

[0237] 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.

[0238] Explanation of symbols 1. Directional Electromagnetic Steel Sheet 11. Magnetic domain control processing line (tensile stress introduction line) RD rolling direction TD rolling right-angle direction (plate width direction) ND (Normal direction of the rolled surface) VL Imaginary Line VP intersection 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 plate, characterized in that, The surface has multiple magnetic domain control processing lines extending in a direction intersecting the rolling direction. An evaluation area is defined on the surface as a square with one side length of 50 mm and one side parallel to the rolling direction. Inside the evaluation area, imaginary lines of 50 mm length and parallel to the rolling direction are defined at 5 mm intervals in a direction perpendicular to the rolling direction. In at least one of the imaginary lines, the maximum value of the interval between adjacent intersections of the imaginary line and the plurality of domain control processing lines in the rolling direction exceeds 20 mm, and the average value of the domain width measured along the imaginary line is less than 600 μm. The multiple magnetic domain control processing lines are tensile stress introduction lines that introduce tensile stress of more than 40 MPa.

2. The directional electromagnetic steel plate according to claim 1, characterized in that, The average value of the domain width measured along the imaginary line is less than 500 μm.

3. The directional electromagnetic steel plate according to claim 1, characterized in that, In each of the imaginary lines in two or more rolling directions where the maximum value of the interval exceeds 20 mm, the average value of the magnetic domain width measured along the imaginary line is less than 600 μm.

4. The directional electromagnetic steel plate according to claim 3, characterized in that, In each of the imaginary lines in two or more rolling directions where the maximum value of the interval exceeds 20 mm, the average value of the domain width measured along the imaginary line is less than 500 μm.

5. A directional electromagnetic steel plate, characterized in that, The surface has multiple magnetic domain control processing lines extending in a direction intersecting the rolling direction. An evaluation area is defined on the surface as a square with one side length of 50 mm and one side parallel to the rolling direction. Inside the evaluation area, imaginary lines of 50 mm length and parallel to the rolling direction are defined at 5 mm intervals in a direction perpendicular to the rolling direction. In at least one of the imaginary lines, the maximum value of the interval between adjacent intersections of the imaginary line and the plurality of magnetic domain control processing lines in the rolling direction exceeds 20 mm, and the maximum value of the magnetic domain width measured along the imaginary line is less than 1200 μm.

6. The directional electromagnetic steel plate according to claim 5, characterized in that, The maximum value of the domain width measured along the imaginary line is less than 800 μm.

7. The directional electromagnetic steel plate according to claim 5, characterized in that, In each of the imaginary lines in two or more rolling directions where the maximum value of the interval exceeds 20 mm, the maximum value of the magnetic domain width measured along the imaginary line is less than 1200 μm.

8. The directional electromagnetic steel plate according to claim 7, characterized in that, In each of the imaginary lines in two or more rolling directions where the maximum value of the interval exceeds 20 mm, the maximum value of the domain width measured along the imaginary line is less than 800 μm.

9. The directional electromagnetic steel plate according to any one of claims 1 to 8, characterized in that, The multiple magnetic domain control processing lines are thermal strain.

10. The directional electromagnetic steel plate according to claim 9, characterized in that, The maximum value of the tensile stress introduced into the thermal strain in the magnetic domain control processing line is not uniform at each measurement point of the tensile stress.

11. The directional electromagnetic steel plate according to claim 10, characterized in that, The intersection points of the imaginary line and the multiple magnetic domain control processing lines are respectively designated as magnetic domain refinement points. The maximum value of the tensile stress per unit MPa introduced into the thermal strain, measured at each of the magnetic domain refinement points, is set as TS. m , the TS m Let the variance be σ(TS) m ) 2 hour, Satisfying σ(TS) m ) 2 >5.

0.

12. The directional electromagnetic steel plate according to claim 10, characterized in that, When multiple intersection points of the imaginary line and the multiple magnetic domain control processing lines are respectively designated as magnetic domain refinement points, the arithmetic mean of the maximum tensile stress per unit MPa introduced into the thermal strain measured at magnetic domain refinement points with a β angle less than 2° is set as TS. m(β<2) The arithmetic mean of the maximum tensile stress per unit MPa introduced in the thermal strain, measured at the magnetic domain refinement points with a β angle of 2° or higher, is set as TS. m(β≥2) hour, Satisfy TS m(β<2) >TS m(β≥2) .

13. The directional electromagnetic steel plate according to claim 11, characterized in that, The arithmetic mean of the maximum tensile stress per unit MPa introduced into the thermal strain, measured at each of the domain refinement points where the β angle is less than 2°, is set as TS. m(β<2) The arithmetic mean of the maximum tensile stress per unit MPa introduced in the thermal strain, measured at the magnetic domain refinement points with a β angle of 2° or higher, is set as TS. m(β≥2) hour, Satisfy TS m(β<2) >TS m(β≥2) .

14. A method for manufacturing a directional electromagnetic steel sheet, as described in any one of claims 1 to 8, characterized in that, have: The magnetic domain image acquisition process acquires a magnetic domain image of the surface of the directional electromagnetic steel plate. The region determination process, based on the magnetic domain image obtained in the magnetic domain image acquisition process, determines the region in the directional electromagnetic steel plate with a magnetic domain width exceeding 500 μm; as well as The magnetic domain control processing line formation process involves forming magnetic domain control processing lines on the surface of the directional electromagnetic steel plate after the region determination process. In the domain control processing line formation process, the domain control processing line is formed in the region where the domain width exceeds 500 μm.

15. The method for manufacturing a directional electromagnetic steel plate according to claim 14, characterized in that, 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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