Grain-oriented electrical steel sheet and method for producing grain-oriented electrical steel sheet

Abstract

This grain-oriented electrical steel sheet is provided with a plurality of magnetic domain controlling lines on the surface thereof. If a rectangular evaluation region in which the length of a side parallel to the rolling direction of the grain-oriented electrical steel sheet is 50 mm and the length of a side parallel to the direction perpendicular to the rolling direction of the grain-oriented electrical steel sheet is 100 mm is set in the grain-oriented electrical steel sheet, and virtual lines that are parallel to the direction perpendicular to the rolling direction and have a length of 100 mm are set at intervals of 5 mm within the evaluation region in the direction parallel to the rolling direction, with respect to at least one of the virtual lines, the standard deviation of the intervals between magnetic domain control points, which are intersection points of the virtual line and the magnetic domain controlling lines, is 1.25 mm or more, and the average |βL| of the absolute values of β angles measured between two magnetic domain control points, between which the interval has a maximum value DL, is 1.5° or more.

Description

Grain-oriented electrical steel sheet and method for manufacturing grain-oriented electrical steel sheet

[0001] This disclosure relates to a grain-oriented electrical steel sheet and a method for manufacturing the grain-oriented electrical steel sheet. This application claims priority to Japanese Patent Application No. 2023-166141, filed on September 27, 2023, the contents of which are incorporated herein by reference.

[0002] Grain-oriented electrical steel sheets are steel sheets containing 7 mass% or less of Si and having a secondary recrystallization texture consisting of an accumulation of {110}<001>-oriented grains (Goss-oriented grains) as secondary recrystallized grains with the easy axis of magnetization <001> oriented in the rolling direction. Grain-oriented electrical steel sheets are mainly used as iron cores for power transformers. Reduction of energy loss (iron loss) is required for grain-oriented electrical steel sheets.

[0003] A technique for narrowing the magnetic domain width of grain-oriented electrical steel sheets (magnetic domain refinement technique by magnetic domain control treatment) has long been known to reduce iron loss. The magnetic domain width can be narrowed by irradiating the surface of the grain-oriented electrical steel sheet with a laser or electron beam in a direction intersecting the rolling direction to introduce thermal strain. The magnetic domain width can also be narrowed by forming grooves in the surface of the grain-oriented electrical steel sheet in a direction intersecting the rolling direction. Groove formation methods include laser or electron beam irradiation, mechanical processing such as gear machining, and chemical processing such as etching.

[0004] In recent years, various improved techniques for magnetic domain refining have been proposed in order to provide grain-oriented electrical steel sheets with good iron loss characteristics (see, for example, Patent Documents 1 to 3). Furthermore, Patent Document 4 proposes a low-iron-loss grain-oriented electrical steel sheet and an advantageous manufacturing method thereof that alleviates the problems of reduced magnetic permeability and increased magnetostriction caused by linear grooves and local strain for magnetic domain refining, since even when local strain is applied for magnetic domain refining, this strain can cause problems such as increased noise due to the reduced magnetic permeability and increased magnetostriction.

[0005] Japanese Patent Publication No. 2012-57219 Japanese Patent Publication No. 2012-12664 Japanese Patent Publication No. 2012-57218 Japanese Patent Publication No. H11-293340

[0006] When magnetic domain control treatment is applied to grain-oriented electrical steel sheet, the magnetostriction characteristics of the grain-oriented electrical steel sheet change due to the closure magnetic domains. This causes the noise characteristics of the grain-oriented electrical steel sheet to deteriorate. The noise characteristics refer to the level of noise generated by electrical products (e.g., transformers, motors, etc.) manufactured using grain-oriented electrical steel sheet as a material. Magnetostriction is a phenomenon in which the external shape of a ferromagnetic material is slightly deformed when it is magnetized. When grain-oriented electrical steel sheet is excited with an alternating current, the magnitude of magnetostriction changes with the change in the strength of the magnetization, causing vibration. The magnitude of this magnetostriction is 10 －６ Although the magnitude of the magnetostriction is very small, it generates vibrations in the iron core, which then propagate to external structures such as transformer tanks, resulting in noise. While magnetic domain control treatment is effective in reducing the iron loss of grain-oriented electrical steel sheets, it also worsens the noise characteristics of grain-oriented electrical steel sheets. In recent years, there has been an increasing demand for grain-oriented electrical steel sheets to reduce not only iron loss but also noise. However, no magnetic domain refining technology capable of sufficiently achieving both low noise and low iron loss has been proposed to date. Furthermore, Patent Document 4 mentions noise, but is unable to sufficiently achieve both low noise and low iron loss. Patent Document 4 discloses that the β angle near the center of the crystal grains in the rolling direction is on average 0°, and that by applying magnetic domain control treatment only to this region where magnetic domain control has a significant effect on iron loss reduction, both low noise and low iron loss can be achieved. However, since the β angle near the center of the crystal grain in the rolling direction is not necessarily 0°, even if magnetic domain control treatment is performed using the method disclosed in Patent Document 4, it is not possible to sufficiently achieve both low noise and low iron loss.

[0007] An object of the present disclosure is to provide a grain-oriented electrical steel sheet that can achieve both low iron loss and low noise, and a method for manufacturing the same.

[0008] The gist of the present disclosure is as follows.

[0009] (1) A grain-oriented electrical steel sheet according to one aspect of the present disclosure is a grain-oriented electrical steel sheet having a plurality of magnetic domain control treatment lines on a surface thereof, wherein a rectangular evaluation area is set in the grain-oriented electrical steel sheet, the length of a side parallel to the rolling direction of the grain-oriented electrical steel sheet being 50 mm and the length of a side parallel to a direction perpendicular to the rolling direction of the grain-oriented electrical steel sheet being 100 mm, and further, when imaginary lines parallel to the direction perpendicular to the rolling direction and having a length of 100 mm are set inside the evaluation area at intervals of 5 mm in a direction parallel to the rolling direction, the standard deviation of intervals between magnetic domain control points, which are intersections of the imaginary line and the magnetic domain control treatment lines, is 1.25 mm or more for at least one of the imaginary lines, and the intervals are equal to or smaller than a maximum value D Ｌ The average value of the absolute value of the β angle measured between the two magnetic domain control points |β Ｌ (2) Preferably, in the grain-oriented electrical steel sheet according to (1) above, the standard deviation of the spacing between the magnetic domain control points is 1.25 mm or more, and the spacing is greater than or equal to the maximum value D Ｌ the average value |β of the absolute values ​​of the β angles measured between the two magnetic domain control points Ｌ (3) Preferably, in the grain-oriented electrical steel sheet according to (1) or (2) above, the maximum value D | of the intervals between the magnetic domain control points is 1.5° or more. Ｌ and the minimum value D of the spacing between the magnetic domain control points. Ｓ Relative to D Ｌ / D Ｓ (4) In the grain-oriented electrical steel sheet according to any one of (1) to (3) above, the D Ｌ / D Ｓ (5) In the grain-oriented electrical steel sheet according to (3) or (4), the |β Ｌ | and the interval is the minimum value D Ｓ The average value of the absolute value of the β angle measured between the two magnetic domain control points |β Ｓ | and satisfy the following formula: 0.5°≦|β Ｌ |-|β Ｓ| (6) Preferably, in the grain-oriented electrical steel sheet according to any one of (1) to (5) above, the magnetic domain control treatment line is thermal strain. (7) Preferably, in the grain-oriented electrical steel sheet according to (6) above, the maximum value of the tensile stress introduced into the thermal strain in the magnetic domain control treatment line is non-uniform for each measurement point of the tensile stress. (8) Preferably, in the grain-oriented electrical steel sheet according to (7) above, when a rectangular evaluation area is set on the surface, the length of a side parallel to the rolling direction is 50 mm and the length of a side parallel to the direction perpendicular to the rolling direction of the grain-oriented electrical steel sheet is 100 mm, and further, imaginary lines parallel to the direction perpendicular to the rolling direction and each having a length of 100 mm are set within the evaluation area at 5 mm intervals in a direction parallel to the rolling direction, each of a plurality of intersections of the imaginary lines and the plurality of magnetic domain control treatment lines is set as a magnetic domain control point, and the maximum value of the tensile stress in unit MPa measured at each of the magnetic domain control points is defined as TS ｍ , the TS ｍ The variance of σ(TS ｍ ) ２ Then, σ(TS ｍ ) ２ (9) Preferably, in the grain-oriented electrical steel sheet according to (8) above, the arithmetic mean value of the maximum values ​​of the tensile stress in unit MPa introduced into the thermal strain, measured at each of the magnetic domain control points having a β angle of less than 2°, is defined as TS ｍ（β＜２） The arithmetic mean value of the maximum value of the tensile stress in unit MPa introduced into the thermal strain, measured at each of the magnetic domain control points where the β angle is 2° or more, is defined as TS ｍ（β≧２） When this is done, TS ｍ（β＜２） >TS ｍ（β≧２）(10) Preferably, in the grain-oriented electrical steel sheet according to any one of (1) to (5) above, the magnetic domain control treatment lines are grooves. (11) Preferably, in the grain-oriented electrical steel sheet according to (10) above, the maximum value of the groove depth in the magnetic domain control treatment lines is non-uniform for each measurement point of the groove depth. (12) Preferably, in the grain-oriented electrical steel sheet according to (10) above, when a rectangular evaluation area is set on the surface, the length of a side parallel to the rolling direction is 50 mm and the length of a side parallel to the direction perpendicular to the rolling direction of the grain-oriented electrical steel sheet is 100 mm, and further, imaginary lines parallel to the direction perpendicular to the rolling direction and each having a length of 100 mm are set inside the evaluation area at 5 mm intervals in a direction parallel to the rolling direction, each of the plurality of intersections of the imaginary lines and the plurality of magnetic domain control treatment lines is set as a magnetic domain control point, and the maximum value of the groove depth in unit μm measured at each of the magnetic domain control points is defined as D ｍ , the above-mentioned D ｍ The variance of σ (D ｍ ) ２ When this is done, σ(D ｍ ) ２ (13) Preferably, in the grain-oriented electrical steel sheet according to (10) or (11) above, the arithmetic mean value of the maximum groove depths in μm measured at each of the magnetic domain control points where the β angle is less than 2° is D ｍ（β＜２） The arithmetic mean value of the maximum value of the groove depth in the unit μm measured at each of the magnetic domain control points where the β angle is 2° or more is defined as D ｍ（β≧２） When this is done, D ｍ（β＜２） >D ｍ（β≧２）(14) A method for manufacturing a grain-oriented electrical steel sheet according to another aspect of the present disclosure includes the steps of acquiring a magnetic domain image of an original sheet of the grain-oriented electrical steel sheet, determining a magnetic domain control treatment area based on a distribution of magnetic domain widths in the magnetic domain image, and applying a magnetic domain control treatment to the magnetic domain control treatment area determined based on the distribution of magnetic domain widths, wherein a rectangular evaluation area is set in the grain-oriented electrical steel sheet, the length of a side parallel to the rolling direction of the grain-oriented electrical steel sheet is 50 mm and the length of a side parallel to a direction perpendicular to the rolling direction of the grain-oriented electrical steel sheet is 100 mm, and virtual lines parallel to the direction perpendicular to the rolling and each having a length of 100 mm are set within the evaluation area at 5 mm intervals in a direction parallel to the rolling direction, and the standard deviation of the intervals along the virtual line between at least one of the virtual lines and the magnetic domain control treatment line formed by the magnetic domain control treatment is 1.25 mm or more. (15) Preferably, in the method for producing a grain-oriented electrical steel sheet according to (14) above, in the step of determining the magnetic domain control treatment region, a region where the magnetic domain width is equal to or greater than a predetermined value is determined as the magnetic domain control treatment region. (16) Preferably, in the method for producing a grain-oriented electrical steel sheet according to (14) or (15) above, in the step of acquiring the magnetic domain image, the distribution of the magnetic domain width is derived from the magnetic domain image using a two-dimensional Fourier transform. (17) Preferably, in the method for producing a grain-oriented electrical steel sheet according to any one of (14) to (16) above, in the step of applying the magnetic domain control treatment, the magnetic domain control treatment is applied by irradiation with a laser or an electron beam.

[0010] According to the above-described aspects of the present disclosure, it is possible to provide a grain-oriented electrical steel sheet that can achieve both low iron loss and low noise, and a method for manufacturing the same.

[0011] 4A and 4B are plan views of grain-oriented electrical steel sheets according to an embodiment of the present disclosure; FIG. 4B is a plan view of a grain-oriented electrical steel sheet according to an embodiment of the present disclosure; FIG. 4C is a plan view of a normal grain-oriented electrical steel sheet; FIG. 4D is a graph showing the relationship between β angle and magnetic domain width; FIG. 4E is a diagram showing an example of the distribution of magnetic domain widths of a grain-oriented electrical steel sheet before magnetic domain refinement treatment; FIG. 4F is a diagram showing an example of the distribution of magnetic domain widths of a grain-oriented electrical steel sheet after magnetic domain refinement treatment; FIG. 4G is a graph showing the difference between FIG. 4A and FIG. 4B; FIG. 4G is a diagram showing the relationship between the magnetic domain widths before and after magnetic domain control treatment; FIG. 4G is a block diagram showing an example of the hardware configuration of an image acquisition device; FIG. 4C is a block diagram showing an example of the hardware configuration of an analysis device; 1 is a graph showing a relationship between the size of the magnetic domain width and the magnetic domain control saturation strength; FIG. 2 is a graph showing a relationship between the size of the β angle and the magnetic domain control saturation strength; FIG. 3 is a cross-sectional schematic diagram of a grain-oriented electrical steel sheet in which the magnetic domain control treatment lines are thermally strained; FIG. 4 is a cross-sectional schematic diagram of a grain-oriented electrical steel sheet in which the magnetic domain control treatment lines are grooves; FIG. 5 is a plan view schematic diagram illustrating a method for measuring the magnetic domain control strength at the intersection of the magnetic domain control treatment lines and the virtual line when the magnetic domain control treatment lines are thermally strained; and FIG. 6 is a plan view schematic diagram illustrating a method for measuring the magnetic domain control strength at the intersection of the magnetic domain control treatment lines and the virtual line when the magnetic domain control treatment lines are grooves.

[0012] (1. Grain-oriented electrical steel sheet 1) The grain-oriented electrical steel sheet 1 according to this embodiment has a plurality of magnetic domain control treatment lines 11 on its surface, as illustrated in Fig. 1. In the grain-oriented electrical steel sheet 1 according to this embodiment, a rectangular evaluation area is set in which the length of the side parallel to the rolling direction RD of the grain-oriented electrical steel sheet 1 is 50 mm and the length of the side parallel to the direction transverse to rolling TD of the grain-oriented electrical steel sheet 1 is 100 mm, and virtual lines VL, each 100 mm long and parallel to the direction transverse to rolling TD, are set within the evaluation area at intervals of 5 mm in a direction parallel to the rolling direction. In this case, for at least one virtual line VL, the standard deviation of the intervals between the magnetic domain control points VP, which are the intersections of the virtual line VL and the magnetic domain control treatment lines 11, is 1.25 mm or more, and the intervals are equal to or smaller than the maximum value D Ｌ is the average absolute value of the β angle measured between two magnetic domain control points. Ｌ | is 1.5° or more.

[0013] (Magnetic Domain Control Processing Lines 11) The multiple magnetic domain control processing lines 11 provided on the surface of the grain-oriented electrical steel sheet 1 function to subdivide the 180° magnetic domains. Subdividing the magnetic domains can reduce the iron loss of the grain-oriented electrical steel sheet 1. A magnetic domain is a collection of magnetic dipoles present inside a ferromagnetic material, and is a small region in which the magnetic moments are aligned in one direction. A 180° magnetic domain is a magnetic domain whose magnetization direction is the <100> orientation of the crystal and is sandwiched between two 180° magnetic domain walls that are approximately parallel to the rolling direction RD. The distance between adjacent domain walls of a 180° magnetic domain (domain wall spacing) is referred to as the width of the 180° magnetic domain. Hereinafter, unless otherwise specified, the width of a 180° magnetic domain will be simply referred to as the "magnetic domain width."

[0014] Suitable examples of the magnetic domain control processed wire 11 are thermal distortion and grooves. By subdividing the magnetic domains, it is possible to suppress the iron loss of the grain-oriented electrical steel sheet 1. However, the magnetic domain control processed wire 11 changes the magnetostriction characteristics of the grain-oriented electrical steel sheet 1 due to closure domains. This deteriorates the noise characteristics of the grain-oriented electrical steel sheet 1.

[0015] The magnetic domain control treatment lines 11 are formed in a direction intersecting the rolling direction RD of the grain-oriented electrical steel sheet 1. In a typical grain-oriented electrical steel sheet 1 such as the one illustrated in Fig. 2, the magnetic domain control treatment lines 11 are formed across the entire width of the grain-oriented electrical steel sheet 1. However, in the grain-oriented electrical steel sheet 1 according to this embodiment such as the one illustrated in Fig. 1A, it is not essential to provide the magnetic domain control treatment lines 11 across the entire width of the grain-oriented electrical steel sheet 1.

[0016] In the grain-oriented electrical steel sheet 1 exemplified in FIG. 1A , the magnetic domain control treatment lines 11 are straight. On the other hand, as shown in FIG. 1B , the magnetic domain control treatment lines 11 may be curved. The magnetic domain control treatment lines 11 may have a shape including straight portions and bent portions. Furthermore, the magnetic domain control treatment lines 11 may be on one or both sides of the grain-oriented electrical steel sheet 1. When the magnetic domain control treatment lines 11 are on both sides of the grain-oriented electrical steel sheet 1, it is sufficient that the various aspects of the grain-oriented electrical steel sheet 1 according to this embodiment are applied to at least one side of the grain-oriented electrical steel sheet 1.

[0017] (Evaluation area) In the grain-oriented electrical steel sheet 1 according to this embodiment, in order to set the virtual line VL described later, a rectangular evaluation area is set in the grain-oriented electrical steel sheet 1, with the length of the side parallel to the rolling direction RD of the grain-oriented electrical steel sheet 1 being 50 mm and the length of the side parallel to the direction perpendicular to the rolling direction TD of the grain-oriented electrical steel sheet 1 being 100 mm.

[0018] (Imaginary lines VL parallel to the rolling direction TD and 100 mm long) In the grain-oriented electrical steel sheet 1 according to this embodiment, imaginary lines VL are used for convenience to define the density of the magnetic domain control treatment lines 11. The imaginary lines VL are set within the aforementioned evaluation region at intervals of 5 mm in a direction parallel to the rolling direction. FIG. 1A shows, as an example, a state in which only one imaginary line VL is drawn. When multiple imaginary lines VL are set, a required number of other imaginary lines can be set parallel to the imaginary line VL in FIG. 1A. The length of the imaginary line VL is 100 mm. The imaginary line VL extends parallel to the rolling direction TD. The intersections of the imaginary lines VL and the magnetic domain control treatment lines 11 are defined as magnetic domain control points VP. The spacing between the magnetic domain control points VP is an indicator of the density of the magnetic domain control treatment lines 11.

[0019] (Standard Deviation of Spacing Between Magnetic Domain Control Points VP) In the grain-oriented electrical steel sheet 1 according to this embodiment, the standard deviation of the spacing between magnetic domain control points VP on at least one imaginary line VL is 1.25 mm or more. The spacing d between magnetic domain control points VP is the distance between two adjacent magnetic domain control points VP along the imaginary line VL. For example, the imaginary line VL of the grain-oriented electrical steel sheet 1 illustrated in FIG. 1A has five magnetic domain control points VP. If the standard deviation of the spacings d1 to d4 between these magnetic domain control points VP is 1.25 mm or more, the grain-oriented electrical steel sheet 1 of FIG. 1A satisfies the requirement of the present disclosure regarding the spacing between magnetic domain control points VP.

[0020] A grain-oriented electrical steel sheet 1 capable of arranging one or more virtual lines VL such that the standard deviation of the spacing between magnetic domain control points VP is 1.25 mm or more will include an area X where the magnetic domain control processing lines 11 are intentionally not provided, for example by interrupting the magnetic domain control processing lines, as illustrated in Figure 1A.

[0021] The standard deviation of the spacing between the magnetic domain control points VP can vary depending on the positions of the evaluation area and the virtual line VL. In the grain-oriented electrical steel sheet 1 illustrated in FIG. 1A , it is also possible to position the evaluation area and the virtual line VL so that the standard deviation of the spacing between the magnetic domain control points VP is less than 1.25 mm. However, a grain-oriented electrical steel sheet 1 in which one or more virtual lines VL can be arranged at any location so that the standard deviation of the spacing between the magnetic domain control points VP is 1.25 mm or more is considered to satisfy the requirements of the present disclosure regarding the spacing between the magnetic domain control points VP. Therefore, the grain-oriented electrical steel sheet 1 of FIG. 1A satisfies the requirements of the present disclosure regarding the spacing between the magnetic domain control points VP.

[0022] On the other hand, the grain-oriented electrical steel sheet 1 shown in Figure 2 in which multiple magnetic domain control treatment lines 11 extending across the entire width of the grain-oriented electrical steel sheet 1 are arranged at equal intervals does not include an area X where no magnetic domain control treatment lines 11 are provided. The grain-oriented electrical steel sheet 1 in Figure 2 cannot have imaginary lines VL arranged such that the standard deviation of the spacing between magnetic domain control points VP is 1.25 mm or more. Therefore, the grain-oriented electrical steel sheet 1 in Figure 2 does not satisfy the requirements of the present disclosure regarding the spacing between magnetic domain control points VP.

[0023] (β angle) In the grain-oriented electrical steel sheet 1 according to this embodiment, the β angle measured at the magnetic domain control treatment line 11 is set to be within a predetermined range. The β angle is the angle of deviation of crystal grains from the Goss orientation around the axis of the direction transverse to the rolling direction TD. It is known that controlling the β angle is effective in controlling the magnetic properties of the grain-oriented electrical steel sheet 1. The angle of deviation of crystal grains from the Goss orientation around the axis of the normal direction ND of the rolling surface is called the α angle, and the angle of deviation of crystal grains from the Goss orientation around the axis of the rolling direction RD is called the γ angle.

[0024] In the grain-oriented electrical steel sheet 1 (original sheet 2 described later) before the magnetic domain control treatment shown in Figure 12, there is a close relationship between the β angle and the magnetic domain width. Figure 3 is a graph showing an example of the relationship between the β angle and the average value of the magnetic domain width in the grain-oriented electrical steel sheet 1 before the magnetic domain control treatment. In the grain-oriented electrical steel sheet 1 before the magnetic domain control treatment, the smaller the β angle, the larger the magnetic domain width. However, the relationship shown in Figure 3 does not hold true in the grain-oriented electrical steel sheet 1 after the magnetic domain control treatment. This is because the magnetic domain control treatment reduces the magnetic domain width in regions where the magnetic domain width was wide before the magnetic domain control treatment, but does not change the orientation of the crystal grains (α angle, β angle, γ angle).

[0025] (|β Ｌ In the grain-oriented electrical steel sheet 1 according to this embodiment, the β angle measured between the two magnetic domain control points VP having the longest distance on the imaginary line VL where the standard deviation of the distance between the magnetic domain control points VP is 1.25 mm or more is specified. Specifically, when the distance is equal to or greater than the above-mentioned maximum value D Ｌ The average value of the absolute value of the β angle |β measured between two magnetic domain control points VP Ｌ| is 1.5° or more. As shown in FIG. 1A , in the grain-oriented electrical steel sheet 1 according to this embodiment, on the virtual line VL where the standard deviation of the spacing between the magnetic domain control points VP is 1.25 mm or more, there are regions X where the magnetic domain control treatment has not been performed, and there are locations where adjacent magnetic domain control points VP are widely separated. On the other hand, in the grain-oriented electrical steel sheet 1 after the normal magnetic domain control treatment, in which multiple magnetic domain control treatment lines 11 extending across the entire width are arranged at equal intervals, there are no regions X where the magnetic domain control treatment has not been performed. Furthermore, even if there are regions X where the magnetic domain control treatment has not been performed in the grain-oriented electrical steel sheet 1 after the normal magnetic domain control treatment, that is, even if the grain-oriented electrical steel sheet 1 is a grain-oriented electrical steel sheet 1 in which multiple magnetic domain control treatment lines 11 are arranged randomly and unequally, the magnetic domain width in the region X is wide and the β angle is small. Therefore, if a normal grain-oriented electrical steel sheet 1 were to have a region X where no magnetic domain control treatment had been performed, the average value of the absolute values ​​of the β angles on the imaginary line VL passing through that region would be small, and the magnetic domain width would be large. A person skilled in the art would try to make the region X where no magnetic domain control treatment had been performed as small as possible. However, in the grain-oriented electrical steel sheet 1 according to this embodiment, the magnetic domain width in the region X where no magnetic domain control treatment had been performed is narrow, and the |β measured in the region X Ｌ | is considered to be a large value.

[0026] |β Ｌ It is more preferable that |β is 1.5° or more, 2.0° or more, or 2.5° or more. Ｌ The upper limit of | is not particularly limited, but is more preferably 10.0° or less, 7.0° or less, or 5.0° or less, for example.

[0027] (Basic Principle and Effects) The present inventors have been able to set a virtual line VL where the standard deviation of the intervals between the magnetic domain control points VP is 1.25 mm or more, and to measure |β on the virtual line VL. ＬIt has been discovered that a grain-oriented electrical steel sheet 1 in which | is 1.5° or more can achieve both low iron loss and low noise. This is because, in such grain-oriented electrical steel sheet 1, magnetic domain control treatment is applied only to portions that contribute to reducing iron loss, and magnetic domain control treatment lines 11 are not provided in portions where magnetic domain control treatment is not required. The basic principles and effects of the present disclosure will be described below with reference to Figures 4A to 4C, etc.

[0028] First, the inventors compared the magnetic domain structure of the grain-oriented electrical steel sheet 1 before and after magnetic domain control treatment. Fig. 4A shows an example of the magnetic domain width distribution of the grain-oriented electrical steel sheet 1 before magnetic domain control treatment. Fig. 4B shows the magnetic domain width distribution after magnetic domain control treatment was performed on the surface of the grain-oriented electrical steel sheet 1 of Fig. 4A. The magnetic domain control treatment here was performed by irradiating the surface with a continuous wave laser in a direction tilted by 2° with respect to the rolling direction RD. The magnetic domain width distributions shown in Figs. 4A and 4B were derived from magnetic domain images of the grain-oriented electrical steel sheet 1 using a two-dimensional Fourier transform, which will be described later.

[0029] Furthermore, Figure 4C shows the difference between Figures 4A and 4B. Figure 4C shows regions where the magnetic domain width has been subdivided by 50 μm or more before and after the magnetic domain control process shown in Figures 4A and 4B. Figure 4C visualizes the regions where the magnetic domain width has been subdivided by the magnetic domain control process. In Figures 4A to 4C, the unit of values ​​is μm.

[0030] 4C shows that the regions where magnetic domain refining of 50 μm or more has occurred as a result of the magnetic domain control treatment are the dark areas in FIG. 4A, i.e., regions where the magnetic domain width was wide before the magnetic domain control treatment. It can be seen that the magnetic domain refining effect is particularly pronounced in regions where the original magnetic domain width was approximately 500 μm or more. On the other hand, the effect of the magnetic domain control treatment is hardly apparent in the light areas in FIG. 4A, i.e., regions where the magnetic domain width was narrow before the magnetic domain control treatment. It can be seen that the effect of the magnetic domain control treatment varies depending on the magnetic domain width before the magnetic domain control treatment.

[0031] The present inventors further investigated in detail the relationship between the amount of reduction in magnetic domain width caused by the magnetic domain control treatment and the magnetic domain width before the magnetic domain control treatment. Figure 5 shows the relationship between the magnetic domain width before the magnetic domain control treatment and the magnetic domain width before the magnetic domain control treatment at the same position. The magnetic domain control treatment was performed by laser irradiation. During the laser irradiation, the average irradiation energy density Ua (mJ / mm ２ ), and irradiation pitch PL (mm), respectively, Ua = 1.5 mJ / mm ２ , PL=4 mm.

[0032] 5, it can be seen that the magnetic domain refinement effect of the magnetic domain control treatment is difficult to achieve in regions with narrow magnetic domain widths. In particular, in regions with magnetic domain widths of approximately 500 μm or less, the magnetic domain widths were substantially the same before and after the magnetic domain control treatment. Therefore, it is believed that the iron loss reduction effect of the magnetic domain control treatment is large in regions where the magnetic domain width before the magnetic domain control treatment was wide, but is insufficient in regions where the magnetic domain width before the magnetic domain control treatment was sufficiently narrow. It is believed that the magnetic domain control treatment line 11 formed in regions with narrow magnetic domain widths leads to deterioration of noise characteristics due to closure domains.

[0033] Based on the above findings, it is believed that in the magnetic domain control treatment of conventional grain-oriented electrical steel sheets 1, magnetic domain control is performed even in areas where magnetic domain control is not required, which contributes to increased noise. It has also been found that performing magnetic domain control treatment preferentially in areas with wide magnetic domain widths (i.e., areas with small β angles) is extremely effective in achieving both low iron loss and low noise. Magnetic domain control treatment in areas with wide magnetic domain widths can reduce iron loss. Furthermore, minimizing magnetic domain control treatment in areas with narrow magnetic domain widths (i.e., areas with large β angles) can prevent deterioration of noise characteristics.

[0034] In the grain-oriented electrical steel sheet 1 according to this embodiment, magnetic domain control treatment lines 11 are not provided in regions where the magnetic domain width was narrow before the magnetic domain control treatment. Therefore, the grain-oriented electrical steel sheet 1 according to this embodiment includes a region X where no magnetic domain control treatment lines 11 are provided. When an evaluation region and a virtual line VL are set in this region X, the standard deviation of the spacing between magnetic domain control points VP along the virtual line VL is 1.25 mm or more. By not providing magnetic domain control treatment lines 11, the noise characteristics of the grain-oriented electrical steel sheet 1 according to this embodiment are improved.

[0035] Furthermore, the regions X where the magnetic domain control treatment lines 11 are not provided are regions where the magnetic domain width was narrow and the β angle was large before the magnetic domain control treatment. Therefore, in the grain-oriented electrical steel sheet 1 according to this embodiment, the β angle is also large in the regions X where the magnetic domain control treatment lines 11 are not provided. In the grain-oriented electrical steel sheet 1 according to this embodiment, the regions X where the magnetic domain control treatment lines 11 are not provided do not impair iron loss.

[0036] Additionally, in the grain-oriented electrical steel sheet 1 according to this embodiment, the magnetic domain control treatment is performed in the regions with wide magnetic domain widths before the magnetic domain control treatment is performed, and therefore the iron loss of the grain-oriented electrical steel sheet 1 according to this embodiment is improved by the magnetic domain control treatment.

[0037] The above has described the most basic aspect of the grain-oriented electrical steel sheet 1 according to this embodiment. A more preferred aspect will now be described.

[0038] (Number of virtual lines VL for which the standard deviation of the spacing between magnetic domain control points VP is 1.25 mm or more) According to the results of studies by the present inventors, in the original sheet 2 before the magnetic domain control treatment, regions with narrow magnetic domain widths (regions that do not require magnetic domain control treatment) were scattered across the entire surface of the original sheet 2. It is preferable to avoid all of the regions with narrow magnetic domain widths scattered across the entire surface of the original sheet 2 and perform appropriate magnetic domain control. Thus, it is desirable that in the grain-oriented electrical steel sheet 1 after the magnetic domain control treatment, regions X where no magnetic domain control treatment lines 11 are provided are scattered across the entire surface.

[0039] Therefore, in the grain-oriented electrical steel sheet 1 according to this embodiment, when imaginary lines VL parallel to the direction transverse to the rolling direction TD and 100 mm long are set at intervals of 5 mm inside the evaluation region, the standard deviation of the intervals between the magnetic domain control points VP is 1.25 mm or more, and the intervals are equal to or greater than the maximum value D Ｌ The average value of the absolute value of the β angle measured between two magnetic domain control points |β Ｌ It is preferable that | is 1.5° or more. That is, the standard deviation of the intervals between the magnetic domain control points VP is 1.25 mm or more and |β Ｌ It is preferable that the grain-oriented electrical steel sheet 1 includes an area X where no magnetic domain control processing line 11 is provided, to the extent that two or more imaginary lines VL can be set such that |β is 1.5° or more. Ｌ It is more preferable that the number of imaginary lines VL where | is 1.5° or more is 3 or more, 4 or more, 5 or more, or 10 or more.

[0040] (D Ｌ / D Ｓ The grain-oriented electrical steel sheet 1 according to this embodiment is characterized in that the magnetic domain control treatment is selectively performed on regions with a wide magnetic domain width before magnetic domain control. In this case, more significant effects can be obtained by performing the above treatment on a steel sheet having a coarse crystal grain size than on a steel sheet having a typical crystal grain size.

[0041] For example, generally, when an attempt is made to increase the degree of orientation concentration in the Goss orientation in order to increase magnetic flux density, the grain size tends to become larger due to the manufacturing method. Steel sheets with such coarse grain sizes have excellent magnetic flux density, but because the grains are too large, they tend to have high iron loss unless magnetic domain control treatment is performed. Therefore, magnetic domain control is essentially required. However, as mentioned above, while conventional magnetic domain control treatments are effective in reducing the iron loss of grain-oriented electrical steel sheets, they tend to deteriorate the noise characteristics of the grain-oriented electrical steel sheets.

[0042] On the other hand, if a steel sheet having a coarse crystal grain size is subjected to a magnetic domain control treatment selectively in the region where the magnetic domain width is wide before magnetic domain control, as in the present embodiment, a grain-oriented electrical steel sheet can be obtained that not only has excellent magnetic flux density but also can achieve both low iron loss and low noise.

[0043] If the magnetic domain control treatment specific to the present embodiment is performed on a steel sheet having a coarse crystal grain size, the steel sheet has the coarse crystal grain size, and among the above-mentioned characteristics, in particular, the maximum value D Ｌ and the minimum value D Ｓ Relative to D Ｌ / D Ｓ The value of changes.

[0044] Specifically, in the grain-oriented electrical steel sheet 1 according to this embodiment, the maximum value D of the interval between the magnetic domain control points Ｌ and the minimum value D of the spacing between magnetic domain control points Ｓ Relative to D Ｌ / D Ｓ It is preferable that D is 2 or more. This further improves both the iron loss characteristics and the noise characteristics. It is more preferable that D Ｌ / D Ｓ is 4 or more. Ｌ / D Ｓ There is no upper limit to the value of D. Ｌ / D Ｓ The upper limit may be set to 24.

[0045] (|β Ｌ | and | β Ｓ On the imaginary line VL where the standard deviation of the intervals between the magnetic domain control points VP is 1.25 mm or more, |β Ｌ | and the interval is the minimum value D Ｓ The average value of the absolute value of the β angle measured between two magnetic domain control points VP is |β Ｓ It is more preferable that | and | satisfy the following formula: 0.5°≦|β Ｌ |-|β Ｓ | |β Ｌ |-|β ＳWhen | is 0.5° or more, it indicates that the region to be subjected to the magnetic domain control treatment is selectively determined by the β angle. Since the magnetic domain control treatment is concentrated on the region where the magnetic domain width before magnetic domain control is wide and the iron loss reduction effect is large, further improvement in noise characteristics is achieved. |β Ｌ |-|β Ｓ The upper limit of | is not limited.

[0046] (Mode of magnetic domain control processing line 11) The type of magnetic domain control processing line 11 is not particularly limited, but suitable examples are thermal distortion and / or grooves. Thermal distortion can be formed by means of, for example, laser irradiation, electron beam irradiation, ion implantation, etc. Grooves can be formed by means of, for example, laser irradiation, electron beam irradiation, machining, etc.

[0047] Thermal distortion disappears by stress relief annealing or a heat treatment equivalent thereto. Therefore, when the grain-oriented electrical steel sheet 1 is heat treated, it is preferable to form the magnetic domain control treatment lines 11 as grooves. On the other hand, since thermal distortion can be easily formed, when simplification of the manufacturing process is required, it is preferable to form the magnetic domain control treatment lines 11 as thermal distortion. The grain-oriented electrical steel sheet 1 may have both thermal distortion and grooves.

[0048] In the grain-oriented electrical steel sheet according to the present disclosure, it is preferable that the maximum value of the tensile stress introduced into the groove depth or thermal strain, which is an indicator of the strength of the magnetic domain control, is non-uniform at each measurement point of the groove depth or tensile stress. The greater the strength of the magnetic domain control, the greater the effect of magnetic domain refinement. However, the greater the strength of the magnetic domain control, the more likely it is that hysteresis loss will increase and noise characteristics will deteriorate. According to the inventors' new findings, the magnetic domain control saturation strength is not uniform in grain-oriented electrical steel sheets. Therefore, it is preferable to make the magnetic domain control strength non-uniform depending on the magnetic domain control saturation strength. The magnetic domain control saturation strength is the magnetic domain control strength at which the effect of the magnetic domain refinement treatment is substantially saturated. When the magnetic domain control strength is equal to or less than the magnetic domain control saturation strength, the greater the magnetic domain control strength, the greater the reduction in iron loss. However, when the magnetic domain control strength exceeds the magnetic domain control saturation strength, increasing the magnetic domain control strength hardly improves the iron loss reduction effect. On the other hand, even if the magnetic domain control strength exceeds the magnetic domain control saturation strength, the greater the magnetic domain control strength, the greater the hysteresis loss and the worse the noise characteristics become. Therefore, it is highly preferable that the magnetic domain control strength be set within a range that does not exceed the magnetic domain control saturation strength.

[0049] When the magnetic domain control processing line is a thermal strain, each of the multiple intersections of the virtual line and the multiple magnetic domain control processing lines is defined as a magnetic domain control point, and the maximum value of the tensile stress in unit MPa introduced into the thermal strain, measured at each of the magnetic domain control points, is defined as TS ｍ , T.S. ｍ The variance of σ(TS ｍ ) ２ Then, σ(TS ｍ ) ２ It is more preferable that the value is >5.0.

[0050] The "maximum value of tensile stress introduced into thermal strain" is the maximum value of tensile stress measured at an arbitrary measurement cross section. Tensile stress varies across a measurement cross section, and therefore, a single "maximum value of tensile stress introduced into thermal strain" is identified for a measurement cross section. As shown schematically in FIG. 15 , thermal strain 541 has a certain degree of spread across the cross section. The tensile stress is greatest at the location directly irradiated with the laser, and is smaller at locations distant from that location. In other words, the measured value of tensile stress differs for each measurement location on the cross section. Using the tensile stress measurement method described below, the distribution and maximum value of tensile stress across the cross section can be derived.

[0051] When the magnetic domain control strength is uniform, the maximum value of the tensile stress introduced into the thermal strain 541 is a constant value throughout the entire magnetic domain control processing line 11. On the other hand, when the magnetic domain control strength is non-uniform, the maximum value of the tensile stress introduced into the thermal strain in the magnetic domain control processing line is non-uniform for each measurement point of the tensile stress. Hereinafter, the maximum value of the tensile stress introduced into the thermal strain may be simply referred to as "tensile stress."

[0052] The inventors also found that the magnetic domain control saturation strength has a strong correlation with the β angle. The β angle is the angle of deviation from the Goss orientation of the crystal grains around the axis transverse to the rolling direction (TD). The magnetic domain control saturation strength is high where the β angle is small. Furthermore, in grain-oriented electrical steel sheets before magnetic domain control treatment, there is a correlation between the β angle and the magnetic domain width. In grain-oriented electrical steel sheets before magnetic domain control treatment, the larger the β angle, the smaller the magnetic domain width. However, in grain-oriented electrical steel sheets after magnetic domain control treatment, the correlation between the magnetic domain width and the β angle becomes weaker. This is because the magnetic domain control treatment changes the magnetic domain width but does not change the β angle.

[0053] Therefore, it is preferable to select an optimum magnetic domain control strength depending on the magnetic domain width or β angle. For example, it is preferable to perform a magnetic domain refinement process with a high magnetic domain control strength in a location where the magnetic domain width is large and the β angle is small, and to perform a magnetic domain refinement process with a low magnetic domain control strength in a location where the magnetic domain width is small and the β angle is large. Also, as described above, the magnetic domain refinement process is not performed on areas where the original magnetic domain width is narrow. Specifically, the arithmetic mean value of the maximum tensile stress in unit MPa introduced into the thermal strain, measured at each of the magnetic domain control points with a β angle of less than 2°, is defined as TS ｍ（β＜２） The arithmetic mean value of the maximum value of the tensile stress in unit MPa introduced into the thermal strain, measured at each of the magnetic domain control points with a β angle of 2° or more, is defined as TS ｍ（β≧２） When this is done, TS ｍ（β＜２） >TS ｍ（β≧２） In this case, the iron loss of the grain-oriented electrical steel sheet after magnetic domain control is further reduced. On the other hand, the increase in hysteresis loss and the deterioration of noise characteristics of the grain-oriented electrical steel sheet after magnetic domain control are further suppressed.

[0054] TS ｍ and σ(TS ｍ ) ２ An example of a method for measuring σ(TS) will be described with reference to FIG. 17. The dashed lines in FIG. 17 are multiple imaginary lines VL set at 5 mm intervals in parallel along the direction transverse to the rolling direction TD of the grain-oriented electrical steel sheet. The x and o marks in FIG. 17 are intersections of the imaginary lines VL and the thermal strain 541, which is the magnetic domain control treatment line. The β angle at the location marked with an x ​​is 2° or more, and the β angle at the location marked with an o is less than 2°. However, σ(TS ｍ ) ２ In calculating the angle, the β angle at the intersection point does not need to be taken into consideration.

[0055] First, the transverse direction TD of the grain-oriented electrical steel sheet is identified. The transverse direction TD can be identified by the method described below. Next, imaginary lines VL are set at 5 mm intervals parallel to the transverse direction TD of the grain-oriented electrical steel sheet. Then, the intersections of the imaginary lines VL and the thermal strain 541, which is the magnetic domain control treatment line, are identified. If the thermal strain 541 cannot be seen with the naked eye, the thermal strain 541 is identified based on a magnetic domain image. The shape of the measurement area is preferably a rectangle whose size along the rolling direction RD is 50 mm or more and whose size along the transverse direction TD is 100 mm or more. One side of the rectangle is preferably parallel to the rolling direction RD.

[0056] Then, a rectangular evaluation area was set on the surface, with the length of the side parallel to the rolling direction being 50 mm and the length of the side parallel to the direction perpendicular to the rolling being 100 mm. Furthermore, imaginary lines parallel to the direction perpendicular to the rolling and 100 mm long were set inside the evaluation area at 5 mm intervals in the direction parallel to the rolling direction. When the TS at the intersections of all the imaginary lines in the set area and the magnetic domain control processing lines was measured, ｍ Measure TS ｍ Variance σ(TS ｍ ) ２ The tensile stress TS introduced in the thermal strain is calculated. ｍ is measured by the EBSD Wilkinson method and a Cross Court manufactured by BLG Vantage.

[0057] When measuring the magnitude of the tensile stress introduced by thermal strain using the EBSD Wilkinson method and BLG Vantage's Cross Court, first, the thermal strain 541, which is the magnetic domain control treatment line, is identified using the procedure described above. Next, the grain-oriented electrical steel sheet 1 is cut through the magnetic domain control treatment line and perpendicular to the magnetic domain control treatment line. This cut surface is used as the measurement surface. The cross section of the magnetic domain control treatment line included in the measurement surface is analyzed using the EBSD Wilkinson method and BLG Vantage's Cross Court to extract tensile stress components in any direction and measure their magnitude. For example, tensile stress components in the direction normal to the rolling surface, the direction parallel to the magnetic domain control treatment line, and the direction perpendicular to the rolling surface normal and the magnetic domain control treatment line can be extracted. The maximum value TS of the tensile stress identified at each of the multiple measurement points Ｍ Variance σ(TS Ｍ ) ２ is derived in accordance with the method for deriving population variance described in paragraph 2.36 of JIS Z 8101-1:2015 "Statistics - Terms and symbols - Part 1: General statistical terms and terms used in probability."

[0058] Also, TS ｍ（β＜２） and T.S. ｍ（β≧２） is measured by the following method. First, the β angles at the intersections are measured to identify intersections with β angles of 2° or more and intersections with β angles of less than 2°. The β angles of grain-oriented electrical steel sheets are measured by the side reflection Laue method. The side reflection Laue method is widely known as a method for measuring crystal orientation. Next, the maximum tensile stress TS is measured at each of all intersections with β angles of 2° or more. ｍ The arithmetic mean value of these values ​​is calculated. This value is called TS ｍ（β≧２） Furthermore, at each of the intersections where the β angle is less than 2°, the maximum value of the tensile stress TS ｍ The arithmetic mean value of these values ​​is calculated. This value is called TS ｍ（β＜２） The maximum value TS of the tensile stress introduced into the thermal strain 541 at the intersection ｍ The measurement method is as described above.

[0059] When the magnetic domain control treatment lines are grooves, a rectangular evaluation area is set on the surface with a side parallel to the rolling direction having a length of 50 mm and a side parallel to the direction perpendicular to the rolling having a length of 100 mm, and further, imaginary lines parallel to the direction perpendicular to the rolling and having a length of 100 mm are set inside the evaluation area at 5 mm intervals in a direction parallel to the rolling direction, and each of the multiple intersections of the imaginary lines and the multiple magnetic domain control treatment lines is set as a magnetic domain control point, and the maximum value of the groove depth in units of μm measured at each of the magnetic domain control points is defined as D ｍ , D ｍ The variance of σ (D ｍ ) ２ When this is done, σ(D ｍ ) ２ In this case, the magnetic domain control strength is changed based on the size of the magnetic domain width or the size of the β angle, and the increase in hysteresis loss and the deterioration of noise characteristics of the grain-oriented electrical steel sheet after magnetic domain control are further suppressed.

[0060] Furthermore, the arithmetic mean value of the maximum value of the groove depth in the unit of μm measured at each of the magnetic domain control points where the β angle is less than 2° is defined as D ｍ（β＜２） The arithmetic mean value of the maximum value of the groove depth in the unit μm measured at each of the magnetic domain control points where the β angle is 2° or more is defined as D ｍ（β≧２） When this is done, D ｍ（β＜２） >D ｍ（β≧２） It is even more preferable to satisfy the following. In this case, in the magnetic domain control processed wire, the magnetic domain control strength is high where the β angle is small, and the magnetic domain control strength is low where the β angle is large. Therefore, the iron loss of the grain-oriented electrical steel sheet after magnetic domain control is further reduced. On the other hand, the increase in hysteresis loss and the deterioration of noise characteristics of the grain-oriented electrical steel sheet after magnetic domain control are further suppressed.

[0061] D ｍ and σ(D ｍ ) ２An example of a method for measuring σ(D) is shown in FIG. 18. The dashed lines in FIG. 18 are multiple imaginary lines VL set at 5 mm intervals in parallel along the direction transverse to the rolling direction TD of the grain-oriented electrical steel sheet. The x and o marks in FIG. 18 are intersections of the imaginary lines VL and the grooves 542, which are magnetic domain control treatment lines. The β angle at the locations marked with x is 2° or more, and the β angle at the locations marked with o is less than 2°. However, σ(D ｍ ) ２ In calculating the angle, the β angle at the intersection point does not need to be taken into consideration.

[0062] First, the rolling direction of the grain-oriented electrical steel sheet is identified. Next, imaginary lines VL are set at 5 mm intervals parallel to the rolling direction TD of the grain-oriented electrical steel sheet. Then, the intersections of the imaginary lines VL and the magnetic domain control treatment lines are identified. When the magnetic domain control treatment lines are grooves 542 as shown in FIG. 16, the magnetic domain control treatment lines are easily visible with the naked eye. The shape of the measurement area is preferably a rectangle whose size along the rolling direction RD is 50 mm or more and whose size along the rolling direction TD is 100 mm or more. One side of the rectangle is preferably parallel to the rolling direction RD.

[0063] Then, a rectangular evaluation area was set with a side length of 50 mm parallel to the rolling direction and a side length of 100 mm parallel to the direction perpendicular to the rolling direction, and further, virtual lines parallel to the direction perpendicular to the rolling direction and having a length of 100 mm were set inside the evaluation area at 5 mm intervals in a direction parallel to the rolling direction. In this case, the maximum value D of the groove depth at the intersection of all the virtual lines and the magnetic domain control processing line in the set area was ｍ The maximum groove depth D ｍ Variance σ (D ｍ ) ２ The maximum groove depth D is calculated. ｍThe measurement method is as follows. Measurements are performed using a Bruker Control GT-I white light interference microscope. The lens used is a 5x objective (numerical aperture 0.12, optical resolution 2.2 μm) with an internal 1x magnification. The light source is a white LED, and the camera is a monochrome CCD (1200 x 1000 pixels). The pixel size is 1.37 μm, and after performing tilt correction by fitting to a least-squares plane using the analysis software Vision64 Map Premium 9.2, a Gaussian filter with a cutoff value of 2.5 mm is used to remove long-wavelength undulations. If necessary, the pixel size may be resampled to 10 μm during analysis. Additionally, areas that are clearly deemed to be abnormal may be excluded from the analysis. The lens type, filter value, and correction method may be changed depending on the properties of the sample. If grooves are formed in the grain-oriented electrical steel sheet but the unevenness cannot be measured from the surface due to an insulating coating or the like, the insulating coating or the like is removed using a known method and the above measurement is carried out.

[0064] First, by measuring the β angles at the intersections, intersections with β angles of 2° or more and intersections with β angles of less than 2° are identified. Next, D at all intersections with β angles of 2° or more is determined. ｍ The arithmetic mean value of ｍ（β≧２） Furthermore, the β angle is less than 2° at all intersection points. ｍ The arithmetic mean value of ｍ（β＜２） The maximum depth of the groove at the intersection D ｍ The measurement method is as described above.

[0065] (2. Manufacturing Apparatus for Manufacturing Grain-Oriented Electrical Steel Sheet 1) Next, an example of a manufacturing apparatus for the grain-oriented electrical steel sheet 1 according to this embodiment will be described. However, the manufacturing apparatus described below is merely illustrative. The grain-oriented electrical steel sheet 1 according to this embodiment can be manufactured using any apparatus.

[0066] 6 shows an example of the hardware configuration of an image acquisition device 30 that acquires magnetic domain images of the original sheet 2, i.e., the grain-oriented electrical steel sheet 1 before the magnetic domain control process. 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.

[0067] The light source unit 31 has a light source made up of a light emitting diode (LED), and irradiates the MO sensor 33 with light having a uniform polarization plane.

[0068] 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 a magnetic sample to be measured is placed. Light emitted from the light source unit 31 passes through the interior of the MO sensor 33 and is reflected by the reflective layer. The reflected light passes through the interior of the MO sensor 33 again and is output to the outside of the MO sensor 33. When the original plate 2, which is a magnetic sample, is placed on the observation surface of the MO sensor 33, a leakage magnetic field corresponding to the direction of spontaneous magnetization of the original plate 2 is generated inside the MO sensor 33. This leakage magnetic field rotates the polarization plane of the reflected light.

[0069] The image sensor 35 is a complementary metal-oxide-semiconductor (CMOS) image sensor. The image sensor 35 forms an image of the reflected light from the MO sensor 33 on its light-receiving surface, performs photoelectric conversion, and outputs the photoelectrically converted analog signal to a signal processing unit 37. By detecting the reflected light with a rotated polarization plane using the image sensor 35, the distribution of the leakage magnetic field can be obtained, and the magnetic domain structure of the original plate 2 can be clarified.

[0070] The signal processing unit 37 includes an amplifier, an AD converter, a digital signal processor (DSP), etc. The analog signal output from the image sensor 35 is amplified by the amplifier. The analog signal is then converted into a digital signal by the AD converter. This digital signal is subjected to predetermined digital processing using the DSP to generate an image signal. The image signal generated by the signal processing unit 37 is output to an analysis device 40 (see FIG. 7 ) via a cable or wireless communication.

[0071] 7 shows the hardware configuration of an analysis device 40 that analyzes the magnetic domain structure of the original sheet 2. The analysis device 40 is a computer device such as a personal computer (PC), and includes a calculation unit 41, a memory 43, a display unit 45, an input unit 47, and a communication I / F 49.

[0072] The calculation unit 41 has a central processing unit (CPU). The calculation unit 41 analyzes the magnetic domain structure from the magnetic domain image of the original sheet 2 in accordance with a program stored in the memory 43. The calculation unit 41 then determines the magnetic domain control processing region 21, which is the location where the magnetic domain control processing is to be applied. The processing executed by the calculation unit 41 will be described in detail later.

[0073] The memory 43 includes a read-only memory (ROM) and a random access memory (RAM). The ROM stores programs executed by the CPU of the calculation unit 41 and data necessary for executing these programs. The programs and data stored in the ROM are loaded into the RAM and executed.

[0074] The memory 43 may include a magnetic memory such as a hard disk drive (HDD) or an optical memory such as an optical disk. Alternatively, the memory 43 may store programs and data in a computer-readable recording medium that is detachable from the analysis device 40. Alternatively, the memory 43 may receive the programs executed by the calculation unit 41 from a network via the communication I / F 49.

[0075] The display unit 45 has a display such as a liquid crystal display (LCD), a plasma display, or an organic electroluminescence (EL) display. The display unit 45 displays an image based on the image signal output from the image acquisition device 30. The display unit 45 also displays the analysis results of the magnetic domain structure by the calculation unit 41.

[0076] The input unit 47 has input devices such as a mouse, a keyboard, etc. The communication I / F 49 is an interface for transmitting and receiving data to and from external devices via a network such as a local area network (LAN), a wide area network (WAN), or the Internet.

[0077] As the calculation unit 41, instead of general-purpose hardware such as a CPU, dedicated hardware such as an application specific integrated circuit (ASIC) or a field programmable gate array (FPGA) specialized for analyzing magnetic domain structures may be adopted.

[0078] 6 and 7 show the case where the image acquisition device 30 and the analysis device 40 are separate devices, but a system in which the image acquisition device 30 and the analysis device 40 are integrated may also be employed.

[0079] Known means such as laser irradiation, electron beam irradiation, ion implantation, etc. can be used as a means for introducing thermal strain into the surface of the original plate 2. Known means such as laser irradiation, electron beam irradiation, mechanical processing, etc. can be used as a means for forming grooves in the surface of the original plate 2. The configuration of a laser irradiation device 500 that introduces thermal strain by laser irradiation will be described below.

[0080] 8 shows 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 strip threading device 515. The strip threading device 515 threads the original sheet 2 in the rolling direction RD.

[0081] The polygon mirror 501 has, for example, a regular polygonal prism shape. A plurality of plane mirrors are provided on each of the plurality of side surfaces constituting the regular polygonal prism-shaped polygon mirror 501. A laser beam LB is emitted from a light source device 503, passes through a collimator 505, and is incident on the plane mirror of the polygon mirror 501 in one direction (horizontal direction) and is reflected by the plane mirror.

[0082] The polygon mirror 501 can be rotated around a rotation axis O1 by being driven by a motor 509. The angle of incidence of the laser beam LB with respect to the plane mirror changes sequentially according to the rotation angle of the polygon mirror 501. This sequentially changes the reflection direction of the laser beam LB, enabling scanning of the surface of the original plate 2. The symbol P in Figure 8 represents the interval between adjacent magnetic domain control processing lines 11, i.e., the irradiation pitch of the laser beam LB.

[0083] The light source device 503 outputs a laser beam LB in a predetermined irradiation method (for example, a continuous irradiation method or a pulse irradiation method) under the control of the control unit 513 .

[0084] The condenser lens 507 is provided in the optical path of the laser beam LB reflected from the polygon mirror 501. The condenser lens 507 constitutes a condensing optical system with a predetermined focal length. The laser beam LB reflected from the polygon mirror 501 is condensed onto the surface of the original plate 2 via the condenser lens 507, thereby introducing thermal strain into the surface of the original plate 2.

[0085] The motor 509 is connected to the polygon mirror 501. The motor 509 drives the polygon mirror 501 to rotate under the control of the control unit 513.

[0086] The sensor 511 is connected to the drive shaft of the motor 509. The sensor 511 detects the rotation angle of the polygon mirror 501 rotated by the motor 509. Furthermore, the sensor 511 outputs a signal indicating the detected rotation angle (hereinafter referred to as a rotation angle signal) to the control unit 513.

[0087] The control unit 513 is made up of a processor. The control unit 513 is connected to the light source device 503, the motor 509, the sensor 511, and the strip threading device 515. The control unit 513 receives a speed signal from the strip threading device 515. The control unit 513 also outputs a signal to the motor 509 to instruct the motor 509 to rotate the polygon mirror 501.

[0088] Furthermore, the control unit 513 controls the power of the laser beam LB output by the light source device 503 to be turned on and off based on a stress application signal representing the magnetic domain control processing region 21 and a rotation angle signal output from the sensor 511. When the laser irradiation device 500 is electrically connected to the analysis device 40, the stress application signal is input from the analysis device 40 to the laser irradiation device 500. The stress application signal may be input to the laser irradiation device 500 by an operator.

[0089] (3. Manufacturing Method of Grain-Oriented Electrical Steel Sheet 1) Next, a manufacturing method of the grain-oriented electrical steel sheet 1 according to this embodiment will be described. According to the manufacturing method of the grain-oriented electrical steel sheet 1 according to this embodiment, the grain-oriented electrical steel sheet 1 according to this embodiment can be suitably manufactured. However, the manufacturing method described below is merely one example of a suitable manufacturing method of the grain-oriented electrical steel sheet 1, and does not limit the grain-oriented electrical steel sheet 1. For ease of explanation, manufacturing apparatuses will be referred to as appropriate in the description of the manufacturing method. However, the manufacturing apparatuses referred to below are merely suitable examples for carrying out the manufacturing method of the grain-oriented electrical steel sheet 1 according to this embodiment.

[0090] As shown in the flowchart of Figure 9, the manufacturing method of the grain-oriented electrical steel sheet 1 according to this embodiment includes step S62 of acquiring a magnetic domain image of the original sheet 2 of the grain-oriented electrical steel sheet 1, step S64 of determining the magnetic domain control processing area 21 shown in Figure 12 based on the distribution of magnetic domain widths in the magnetic domain image, and step S66 of applying magnetic domain control processing to the magnetic domain control processing area 21 determined based on the distribution of magnetic domain widths. Furthermore, in the manufacturing method of the grain-oriented electrical steel sheet 1 according to this embodiment, a rectangular evaluation area is set in the grain-oriented electrical steel sheet 1, with the length of the side parallel to the rolling direction RD of the grain-oriented electrical steel sheet 1 being 50 mm and the length of the side parallel to the direction transverse to rolling TD of the grain-oriented electrical steel sheet 1 being 100 mm, and further, virtual lines VL parallel to the direction transverse to rolling TD and 100 mm long are set at 5 mm intervals within the evaluation area, and in at least one virtual line VL, the standard deviation of the spacing between the magnetic domain control points VP, which are the intersections of the virtual line VL and the magnetic domain control processing line 11, is 1.25 mm or more.

[0091] First, a magnetic domain image of the original sheet 2 is acquired (see S62 in FIG. 9 ). The original sheet 2 refers to the grain-oriented electrical steel sheet 1 before the magnetic domain control process is applied. The magnetic domain image can be acquired, for example, by the image acquisition device 30. Next, the distribution of the widths of the 180° magnetic domains (magnetic domain widths) is derived from the magnetic domain image. The distribution of the magnetic domain widths in the original sheet 2 can be derived, for example, by using the calculation unit 41 of the analysis device 40.

[0092] Then, regions where the magnetic domain width is equal to or greater than a predetermined value (for example, equal to or greater than approximately 500 μm, or more than 500 μm) are determined to be magnetic domain control treatment regions 21 (see S64 in FIG. 9). Figure 12 shows the original sheet 2 of the grain-oriented electrical steel sheet 1 in FIG. 1. The shaded regions in Figure 12 are magnetic domain control treatment regions 21. The white regions in Figure 12 are non-magnetic domain control treatment regions 22. The magnetic domain width of the magnetic domain control treatment regions 21 is equal to or greater than the predetermined value, and the magnetic domain width of the non-magnetic domain control treatment regions 22 is less than the predetermined value.

[0093] The magnetic domain control processing region 21 may be determined by the operator visually observing the magnetic domain image displayed on the display unit 45, and a stress introduction signal representing the magnetic domain control processing region 21 may be input to the laser irradiation device 500.

[0094] Preferably, the magnetic domain control strength is determined according to the magnetic domain width of the grain-oriented electrical steel sheet before the magnetic domain refinement treatment. The magnetic domain control strength is the amount of thermal strain when the magnetic domain control method is thermal strain, or the groove depth when the magnetic domain control method is grooves. In this case, the maximum tensile strength or groove depth introduced by the thermal strain in the magnetic domain control treatment wire becomes non-uniform at each measurement point of the tensile strength or groove depth.

[0095] The stronger the magnetic domain control strength, the greater the effect of magnetic domain refinement. On the other hand, the stronger the magnetic domain control strength, the more likely it is to lead to increased hysteresis loss and deterioration of noise characteristics. Furthermore, according to new findings by the inventors, the magnetic domain control saturation strength is not uniform in grain-oriented electrical steel sheets.

[0096] The magnetic domain control saturation strength is the magnetic domain control strength at which the effect of the magnetic domain refinement process saturates. When the magnetic domain control strength is equal to or less than the magnetic domain control saturation strength, the greater the magnetic domain control strength, the greater the reduction in iron loss. However, when the magnetic domain control strength exceeds the magnetic domain control saturation strength, increasing the magnetic domain control strength does not improve the iron loss reduction effect. However, even when the magnetic domain control strength exceeds the magnetic domain control saturation strength, the greater the magnetic domain control strength, the greater the hysteresis loss and the worse the noise characteristics. Therefore, it is highly preferable to set the magnetic domain control strength within a range that does not exceed the magnetic domain control saturation strength.

[0097] Specifically, it is preferable to perform a magnetic domain refinement process with a high magnetic domain control strength in areas where the magnetic domain width is large and the β angle is small, and to perform a magnetic domain refinement process with a low magnetic domain control strength in areas where the magnetic domain width is small and the β angle is large. In areas where the β angle is large, the magnetic domain control effect is not obtained, so the magnetic domain control saturation strength is 0. In areas where the β angle is below a predetermined value, the magnetic domain control effect is obtained. For example, when the β angle is 2° or less, it is estimated that the magnetic domain control effect is obtained. Furthermore, in areas where the β angle is below a predetermined value, the larger the β angle, the greater the magnetic domain control saturation strength. Furthermore, in areas where the β angle is even smaller, the magnetic domain control saturation strength is approximately constant.

[0098] FIG. 18 shows a graph that schematically illustrates a method for determining the magnetic domain control strength based on the magnetic domain width. The vertical axis of FIG. 18 represents the magnetic domain control strength, and the horizontal axis represents the magnetic domain width. The solid line in FIG. 18 represents the magnetic domain control saturation strength. In regions where the magnetic domain width is small, the magnetic domain control effect is not obtained, so the magnetic domain control saturation strength is 0. In regions where the magnetic domain width exceeds 500 μm, the magnetic domain control effect is obtained. Furthermore, in regions where the magnetic domain width exceeds 500 μm, the magnetic domain control saturation strength increases as the magnetic domain width increases. Furthermore, in regions where the magnetic domain width exceeds approximately 1200 μm, the magnetic domain control saturation strength is approximately constant.

[0099] FIG. 14 shows a graph that schematically illustrates a method for determining the magnetic domain control strength based on the β angle. The vertical axis of FIG. 14 represents the magnetic domain control strength, and the horizontal axis represents the magnitude of the β angle. The solid line graph in FIG. 14 represents the magnetic domain control saturation strength. In regions where the β angle is large, the effect of magnetic domain control is not obtained, so the magnetic domain control saturation strength is 0. In regions where the β angle is below a predetermined value, the effect of magnetic domain control is obtained. For example, when the β angle is 2° or less, it is estimated that the effect of magnetic domain control is obtained. In regions where the β angle is below a predetermined value, the larger the β angle, the greater the magnetic domain control saturation strength. In regions where the β angle is even smaller, the magnetic domain control saturation strength is approximately constant.

[0100] It is most preferable that the relationship between the magnetic domain width at the location where magnetic domain control is performed and the magnetic domain control strength is on the solid line graph in Figure 14. Alternatively, it is most preferable that the relationship between the β angle at the location where magnetic domain control is performed and the magnetic domain control strength is on the solid line graph in Figure 14. The magnetic domain control saturation strength can be used as a target value for the magnetic domain control strength.

[0101] Furthermore, there is a minimum magnetic domain control strength, which is the minimum strength at which the magnetic domain control effect is exhibited. When magnetic domain control is performed, it is more preferable that the magnetic domain control strength is equal to or greater than the minimum magnetic domain control strength.

[0102] However, the magnetic domain control strength may vary slightly from the target value of the magnetic domain control saturation strength. In Figures 13 and 14, the region that is equal to or greater than the minimum magnetic domain control strength and that is within a certain range from the graph of the magnetic domain control saturation strength is referred to as the target range of the magnetic domain control strength. The magnetic domain control strength and the magnetic domain width of the magnetic domain control target portion are preferably within the shaded region surrounded by the dashed lines in Figures 13 and 14. When the maximum value of the tensile stress introduced into the thermal strain in the magnetic domain control treatment line is made non-uniform for each measurement point of the tensile stress, it is preferable to intentionally change the magnetic domain control strength. In this case, it is preferable to change it within the shaded region surrounded by the dashed lines. When the magnetic domain control treatment line is a thermal strain, the magnetic domain control strength can be changed by changing the irradiation conditions of the laser or electron beam. Specifically, the power, irradiation time, irradiation interval, etc. of the laser or electron beam are changed to obtain the average irradiation energy density Ua (mJ / mm) per unit area. ２ When the magnetic domain control treatment lines are grooves, the depth of the grooves formed in the grain-oriented electrical steel sheet can be changed by adjusting the time, intensity, shape, etc. of a method using a laser or electron beam, a method using mechanical processing such as gears, or a method using chemical processing such as etching.

[0103] Next, the magnetic domain control treatment is preferentially performed on the magnetic domain control treatment region 21 (see S66 in FIG. 9). Preferably, the magnetic domain control treatment is performed only on the magnetic domain control treatment region 21. If the magnetic domain control treatment line 11 is a thermal distortion, the magnetic domain control treatment may be performed by irradiation with a laser beam LB by a laser irradiation device 500, or other means such as ion implantation or electron beam irradiation may be employed. If the magnetic domain control treatment line 11 is a groove, the magnetic domain control treatment may be performed using a machining tool.

[0104] A detailed description will be given of an example of a method for determining the magnetic domain control processing area 21. The processing for identifying the magnetic domain control processing area 21 is executed by the calculation unit 41 of the analysis device 40, for example.

[0105] The calculation unit 41 derives the distribution of the magnetic domain width of the original sheet 2, for example, by using a two-dimensional Fourier transform. Then, the calculation unit 41 determines regions where the magnetic domain width is equal to or greater than a predetermined value (for example, equal to or greater than approximately 500 μm) as locations where the magnetic domain control process should be applied preferentially.

[0106] The two-dimensional Fourier transform is particularly effective as a means for analyzing the magnetic domain structure of a magnetic material having a periodic magnetic domain structure, such as the grain-oriented electrical steel sheet 1 and the original sheet 2. Below, we will explain a method for deriving the distribution of the magnetic domain width of the original sheet 2 using the short-term two-dimensional Fourier transform (hereinafter referred to as "ST2DFT"), which is an extension of the short-term Fourier transform, a signal processing method that has long been used in the time-frequency analysis of audio signals, to a two-dimensional region.

[0107] 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 (k-l coordinates) as x(k, l). The magnetic domain image to be analyzed in this embodiment is an image binarized using two types of colors, or an image expressed in three or more gradations (multi-gradation), such as grayscale.

[0108] In order to derive the distribution of magnetic domain widths of the original plate 2, the calculation unit 41 executes the following processes (A-1), (A-2), and (A-3): (A-1) Process of extracting multiple partial regions from the magnetic domain image (A-2) Process of performing ST2DFT (A-3) Process of deriving the distribution of magnetic domain widths The processes A-1 to A-3 will be explained in detail below.

[0109] (A-1) Processing for extracting multiple partial regions from a magnetic domain image In order to extract multiple partial regions from a magnetic domain image and analyze the frequency structure of each partial region, the range in the k direction is set to 0≦k≦N. ｋ -1, and the range in the l direction is 0≦l≦N ｌ -1 is used as the rectangular window function Wa(k, l) (N ｋ and N ｌ (k, l is a natural number). As the window function Wa(k, l), a Hamming window, a Hanning window, a Blackman window, etc. can be applied.

[0110] The observation position in the data sequence x(k, l) of the magnetic domain image is expressed by an index (n, m), and the shift amounts of the window function Wa(k, l) in the k direction and the l direction are respectively expressed as S ｋ and S ｌ When written as (n, m, S ｋ , S ｌ is an integer), and nS is calculated from the magnetic domain image as in equation (1). ｋ ≦k≦nS ｋ +N ｋ -1, mS ｌ ≦l≦mS ｌ +N ｌ Data string x of the partial region cut out from the range of -1 ｎｍ (k-nS ｋ , l-mS ｌ ) is obtained.

[0111]

[0112] Figure 10 shows an example in which partial regions corresponding to the observation positions (n, m) = (1, 1), (2, 2), (3, 3), ..., (P, Q) (P and Q are natural numbers) are cut out from the magnetic domain image G.

[0113] In this embodiment, N which determines the range of the window function Wa(k, l) ｋand N ｌ are parameters corresponding to the number of pixels in the k direction and the number of pixels in the l direction in the partial region, respectively.

[0114] (A-2) Processing to perform ST2DFT The data sequence of the partial region is x ｎｍ (n', m') = x ｎｍ (k-nS ｋ , l-mS ｌ ) and x ｎｍ When a two-dimensional Fourier transform is performed on (n', m'), a partial Fourier image X(f ｋ , f ｌ , n, m) are obtained.

[0115] where f ｋ and f ｌ is the spatial frequency.

[0116] spatial frequency f ｋ The resolution of Δf ｋ , spatial frequency f ｌ The resolution of Δf ｌ When written as Δf ｋ and Δf ｌ is defined as in equation (3).

[0117] Here, Δk and Δl are the spatial resolutions in the k and l directions, respectively, of the magnetic domain image.

[0118] For example, the data string x of each partial region shown in FIG. ｎｍ (k-nS ｋ , l-mS ｌ ) is subjected to a two-dimensional Fourier transform, a partial Fourier image X(f ｋ , f ｌ , n, m) are obtained.

[0119] (A-3) Processing to derive the distribution of magnetic domain widths Partial Fourier image X(f ｋ , f ｌ , n, m) is obtained, the partial Fourier image X(f ｋ , f ｌ, n, m) ｋ ｍａｘ (n, m) and l component f ｌ ｍａｘ (n, m)) can be obtained. Note that, in deriving the peak position, the region near k=0, l=0 is excluded because it is a portion that is highly dependent on the contrast of the image.

[0120] Then, from the spatial frequency resolution defined by equation (3) and the peak positions of the spots in the partial Fourier image, the distribution L(n, m) of the magnetic domain width is derived as shown in equation (4).

[0121]

[0122] In this way, by using ST2DFT, it is possible to quantitatively derive the magnetic domain width distribution L(n, m) while preserving the position information of the magnetic domain image. Figures 4A to 4C above show the analysis results of the magnetic domain width derived by ST2DFT.

[0123] FIG. 12 shows a plan view of an example of a master sheet 2. The master sheet 2 in FIG. 12 is the material of the grain-oriented electrical steel sheet 1 in FIG. 1. FIG. 12 shows a magnetic domain control processed region 21 and a non-magnetic domain control processed region 22 of the master sheet 2 identified based on a magnetic domain image. The magnetic domain control processed region 21 is a region where the magnetic domain width is equal to or greater than a predetermined value. The magnetic domain control processed region 21 of the master sheet 2 roughly corresponds to a region in the grain-oriented electrical steel sheet 1 where the β angle is small. Furthermore, the non-magnetic domain control processed region 22 of the master sheet 2 roughly corresponds to a region in the grain-oriented electrical steel sheet 1 where the β angle is large. The non-magnetic domain control processed region 22 is a region where the magnetic domain width is less than a predetermined value and where the β angle is large. Magnetic domain control processing is applied to the regions not surrounded by dashed lines in FIG. 12. In this case, a rectangular evaluation area is set in the grain-oriented electrical steel sheet 1, with the length of the side parallel to the rolling direction RD of the grain-oriented electrical steel sheet 1 being 50 mm and the length of the side parallel to the direction transverse to the rolling TD of the grain-oriented electrical steel sheet 1 being 100 mm, and further, imaginary lines VL, each 100 mm long and parallel to the direction transverse to the rolling TD, are set within the evaluation area at intervals of 5 mm in a direction parallel to the rolling direction, and in at least one of the imaginary lines VL, the standard deviation of the intervals along the imaginary line VL of the intersections between the imaginary line VL and the magnetic domain control treatment line 11 is set to 1.25 mm or more. Ｌ Therefore, the grain-oriented electrical steel sheet 1 shown in FIG. 1 is obtained, in which | is 1.5° or more.

[0124] When the calculation unit 41 derives the magnetic domain width distribution L(n, m), the calculation unit 41 determines regions where the magnetic domain width is equal to or greater than a predetermined value as magnetic domain control processing regions 21 (i.e., regions to which magnetic domain control processing is applied). The control unit 513 of the laser irradiation device 500 controls the power of the laser beam LB to be on for the magnetic domain control processing regions 21, and preferably to be off for the non-magnetic domain control processing regions 22 (i.e., regions other than the magnetic domain control processing regions 21). This introduces magnetic domain control processing lines 11 into the magnetic domain control processing regions 21 of the original sheet 2. Furthermore, the introduction of magnetic domain control processing lines 11 is minimized in the non-magnetic domain control processing regions 22 of the original sheet 2.

[0125] The above-described procedure can also be used to obtain a magnetic domain image of the grain-oriented electrical steel sheet 1 after the magnetic domain control treatment. In some cases, the magnetic domain control treatment lines 11 are unclear in the magnetic domain image of the grain-oriented electrical steel sheet 1. In this case, the observation conditions may be adjusted so that the magnetic domain control treatment lines 11 can be clearly seen. For example, the magnetic domain control treatment lines 11 can be made clear by applying a DC magnetic field in the direction perpendicular to the sheet surface (thickness direction) of the grain-oriented electrical steel sheet 1.

[0126] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited thereto and can be modified as appropriate without departing from the technical spirit of the invention. Below, more preferred examples of the grain-oriented electrical steel sheet 1 according to the present embodiment and the manufacturing method thereof will be described. Unless otherwise specified, the preferred aspects described below are applicable to both the grain-oriented electrical steel sheet 1 and the manufacturing method thereof. The grain-oriented electrical steel sheet according to the present embodiment may have a forsterite coating and / or an insulating coating on the surface of the base steel sheet, as described below. Each of these will be described below. However, when the grain-oriented electrical steel sheet has a base steel sheet and a forsterite coating and / or an insulating coating, the following specifications regarding the chemical composition, magnetic domain control treatment line, magnetic domain control region, and non-magnetic domain control treatment line apply to the base steel sheet. However, the specifications regarding the sheet thickness apply to the entire grain-oriented electrical steel sheet, including the base steel sheet and the forsterite coating and / or the insulating coating.

[0127] (Chemical Composition and Sheet Thickness) The chemical composition of the grain-oriented electrical steel sheet 1 and the base sheet 2 is not limited, and may be the same as that of a known grain-oriented electrical steel sheet 1. For example, the grain-oriented electrical steel sheet 1 and the base sheet 2 may have the following chemical composition, in mass %, Si: 2.500 to 7.000%, Mn: 0.00 to 1.000%, C: 0 to 0.085%, acid-soluble Al: 0 to 0.065%, N: 0 to 0.012%, Cr: 0 to 0.300%, Cu: 0 to 0.400%, P: 0 to 0.500%, Sn: 0 to 0.300%, Sb: 0 to 0.300%, and the like. : 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.

[0128] The thickness of the grain-oriented electrical steel sheet 1 and the base sheet 2 is not limited, but is preferably 0.15 mm to 0.30 mm, for example. By setting the thickness to 0.30 mm or less, classical eddy current loss can be suppressed and iron loss can be further improved. On the other hand, by setting the thickness to 0.15 mm or more, rolling efficiency can be improved, thereby improving productivity.

[0129] (Coating) The grain-oriented electrical steel sheet 1 and the base sheet 2 may have a forsterite coating. The grain-oriented electrical steel sheet 1 and the base sheet 2 may also have an insulating coating. The forsterite coating and the insulating coating may be formed on one side or both sides of the grain-oriented electrical steel sheet 1.

[0130] The forsterite coating is an inorganic coating containing, for example, magnesium silicate as a main component. The forsterite coating is formed, for example, during finish annealing, by a reaction between an annealing separator containing magnesia (MgO) applied to the surface of the base steel sheet and the components of the surface of the base steel sheet. The forsterite coating has a composition derived from the components of the annealing separator and the base steel sheet (more specifically, Mg ２ SiO ４ On the other hand, in the final annealing, ２ O ３When an annealing separator containing mainly SiO 2 is used, the forsterite film may not be formed.

[0131] The insulating coating has the function of imparting electrical insulation and tension to the grain-oriented electrical steel sheet 1. By applying tension to the grain-oriented electrical steel sheet 1 and facilitating domain wall movement in the grain-oriented electrical steel sheet 1, it is possible to reduce iron loss in the grain-oriented electrical steel sheet 1. The insulating coating also provides the grain-oriented electrical steel sheet 1 with various properties such as corrosion resistance, heat resistance, and slip resistance. The insulating coating may be a known coating formed, for example, by applying a coating solution containing phosphate and colloidal silica as main components to the surface of a forsterite coating and baking it.

[0132] The insulating coating is preferably formed after the final annealing and the magnetic domain control treatment. Alternatively, the insulating coating may be formed after the final annealing step and before the magnetic domain control treatment. If the insulating coating is formed before the magnetic domain control treatment, the insulating coating may peel off from the magnetic domain control treatment wire 11. Therefore, it is preferable to form an insulating coating again on the magnetic domain control treatment wire 11 after the magnetic domain control treatment.

[0133] (Angle Between Magnetic Domain Control Processing Line 11 and the Direction Transverse to Rolling TD) The angle between the magnetic domain control processing line 11 and the direction transverse to rolling TD is not particularly limited. On the other hand, as exemplified in FIG. 1A , the angle between the magnetic domain control processing line 11 and the direction transverse to rolling TD needs to be greater than 0°. For example, the angle between the magnetic domain control processing line 11 and the direction transverse to rolling TD may be any value within the range of 0° to 45°. The angle between the magnetic domain control processing line 11 and the direction transverse to rolling TD may be 2° or more, 3° or more, or 5° or more. The angle between the magnetic domain control processing line 11 and the direction transverse to rolling TD may be 40° or less, 35° or less, or 30° or less.

[0134] 1A , the angles formed by all the magnetic domain control process lines 11 and the direction transverse to the rolling direction TD may be the same. That is, all the magnetic domain control process lines 11 may extend parallel to one another. On the other hand, the angles formed by the magnetic domain control process lines 11 and the direction transverse to the rolling direction TD may vary. That is, some or all of the multiple magnetic domain control process lines 11 may extend non-parallel to one another. The average value of the angles formed by the magnetic domain control process lines 11 and the direction transverse to the rolling direction TD may be 2° or more, 3° or more, or 5° or more. The average value of the angles formed by the magnetic domain control process lines 11 and the direction transverse to the rolling direction TD may be 40° or less, 35° or less, or 30° or less. The average angle can be calculated by measuring the angle between one magnetic domain control processing line and the direction perpendicular to the rolling direction TD at multiple positions, or by measuring the angles between multiple magnetic domain control processing lines and the direction perpendicular to the rolling direction TD at one point or multiple positions and then calculating the average value.

[0135] (Interval P of Magnetic Domain Control Treatment) For example, the interval P of the magnetic domain control treatment, which is determined by the irradiation pitch P of the laser beam LB shown in FIG. 8 , is not particularly limited. The smaller the interval P of the magnetic domain control treatment, the greater the effect of improving iron loss. On the other hand, the larger the interval P of the magnetic domain control treatment, the more the noise characteristics improve. The interval can be selected appropriately depending on the characteristics required of the grain-oriented electrical steel sheet 1.

[0136] The interval P at which the magnetic domain control treatment is performed corresponds to the interval between the magnetic domain control treatment lines 11 and the imaginary lines along these in the grain-oriented electrical steel sheet 1 according to this embodiment. The imaginary lines along the magnetic domain control treatment lines 11 provided in the grain-oriented electrical steel sheet 1 are set across the entire width of the grain-oriented electrical steel sheet 1, and the interval between these lines is measured, thereby determining the interval P for the magnetic domain control treatment.

[0137] For example, the interval P of the magnetic domain control treatment may be 1.0 mm or more, 2.0 mm or more, 3.0 mm or more, or 5.0 mm or more. The interval P of the magnetic domain control treatment may be 10.0 mm or less, 9.0 mm or less, 8.0 mm or less, or 7.0 mm or less. The interval P of the magnetic domain control treatment is a value measured along the rolling direction RD. In FIG. 8 , for the sake of simplicity, the magnetic domain control treatment lines 11 are drawn substantially parallel to the direction transverse to the rolling direction TD, but in reality, as explained above, they are inclined at a predetermined angle with respect to the direction transverse to the rolling direction TD.

[0138] In the grain-oriented electrical steel sheet 1 illustrated in FIG. 1A , the interval P of the magnetic domain control treatment is constant. However, the interval P of the magnetic domain control treatment may vary. For example, the average value of the interval P of the magnetic domain control treatment may be 1.0 mm or more, 2.0 mm or more, 3.0 mm or more, or 5.0 mm or more. The average value of the interval P of the magnetic domain control treatment may be 10.0 mm or less, 9.0 mm or less, 8.0 mm or less, or 7.0 mm or less.

[0139] (Magnitude of tensile stress introduced by thermal strain) The magnetic domain control treatment wire 11 may be thermally strained. In the thermal strain, tensile stress is introduced. The larger the tensile stress, the greater the effect of improving iron loss. On the other hand, the smaller the tensile stress, the more improved the noise characteristics. The tensile stress can be appropriately selected according to the characteristics required of the grain-oriented electrical steel sheet 1.

[0140] The magnitude of the tensile stress is not particularly limited, but for example, in at least a portion of the magnetic domain control processing line 11, the tensile stress in any direction is preferably 40 MPa or more, 60 MPa or more, or 80 MPa or more. If the tensile stress in at least one direction is 40 MPa or more, the requirement of "tensile stress in any direction of 40 MPa or more" is considered to be met. Furthermore, for example, in at least a portion of the magnetic domain control processing line 11, the tensile stress in any direction 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 in the magnetic domain control processing line 11 may be uniform or may vary.

[0141] (Groove Depth and Width) The magnetic domain control treatment line 11 may be a groove. The greater the groove depth and width, the greater the effect of improving iron loss. On the other hand, the smaller the groove depth and width, the more the noise characteristics are improved. The shape of the groove can be selected appropriately depending on the characteristics required of the grain-oriented electrical steel sheet 1.

[0142] The depth of the groove is not particularly limited, but is preferably 5 μm to 50 μm, for example. The depth of the groove may be 6 μm or more, 7 μm or more, or 10 μm or more. The depth of the groove may be 48 μm or less, 45 μm or less, or 40 μm or less.

[0143] The width of the groove (width at the opening) is not particularly limited, but is preferably 10 μm to 300 μm, for example. The groove width may be specified as 20 μm or more, 30 μm or more, or 50 μm or more. The groove width may be specified as 280 μm or less, 250 μm or less, or 200 μm or less. The depth and width of the groove may be uniform or may vary. If there is variation, it is preferable that the average depth and width of multiple grooves be within the above range.

[0144] (Measurement Method) Hereinafter, a method for measuring various parameters of the grain-oriented electrical steel sheet 1 according to this embodiment will be described. Measurement of each parameter is performed on a sample taken from the grain-oriented electrical steel sheet 1. For example, a rectangular sample with both sides measuring 100 mm (or 100 mm or more) can be cut out from the grain-oriented electrical steel sheet 1 and used for measurement. When the grain-oriented electrical steel sheet 1 is a coil, the sample may be taken from any location on the coil. Also, when the grain-oriented electrical steel sheet 1 is used as a component incorporated into an electrical product such as a transformer or a motor, the sample may be taken from any location on the component. When the component is small in size, the length of one side of the sample along the rolling direction RD may be 50 mm or more and less than 100 mm, as long as the length of one side of the sample along the direction transverse to rolling TD is 100 mm or more. In this case, it is desirable to take the sample by a method such as wire cutting in order to minimize the influence of mechanical distortion on the sample.

[0145] (Method for Identifying Magnetic Domain Control Treatment Lines 11) When the magnetic domain control treatment lines 11 are grooves, the magnetic domain control treatment lines 11 can be identified visually. When the grain-oriented electrical steel sheet 1 has an insulating coating, the insulating coating can be removed using a known stripping agent, thereby making the magnetic domain control treatment lines 11 visible.

[0146] If the magnetic domain control treatment lines 11 are thermally strained, they may not be identifiable by visual inspection. In this case, a magnetic domain image is taken using, for example, an image acquisition device 30 as shown in FIG. 5 . If necessary, the magnetic domain image is taken while applying a DC magnetic field along the normal direction ND of the rolled surface of the grain-oriented electrical steel sheet 1. By observing the magnetic domain image, the location of the thermal strain can be identified.

[0147] (Method for determining the rolling direction RD and the transverse direction TD) The rolling direction RD and the transverse direction TD of the grain-oriented electrical steel sheet 1 are determined by the following means. (1) When the sample is cut out from a coil-shaped grain-oriented electrical steel sheet 1, the width direction of the coil is considered to be the transverse direction TD. Also, the direction perpendicular to the transverse direction TD and the normal direction ND to the rolling surface is considered to be the rolling direction RD. (2) When the sample is cut out from a part of an electrical product, etc., the rolling direction RD and the transverse direction TD are determined from rolling defects on the surface of the grain-oriented electrical steel sheet 1. The extension direction of the rolling defects is considered to be the rolling direction RD. The direction perpendicular to the rolling direction RD and the normal direction ND to the rolling surface is considered to be the transverse direction TD. (3) When it is difficult to identify the rolling direction RD and the direction transverse to the rolling direction TD from the rolling defects on the surface of the grain-oriented electrical steel sheet 1, the rolling direction RD and the direction transverse to the rolling direction TD are identified from the crystal orientation of the grain-oriented electrical steel sheet 1. Specifically, the crystal orientation of the grain-oriented electrical steel sheet 1 to be evaluated is measured at multiple points. Then, the direction in which the angle between the crystal orientation at the measurement point and the direction normal to the rolling surface ND (sheet thickness direction) is closest to a right angle and which has the smallest deviation angle from the axis of easy magnetization <001> is regarded as the rolling direction RD, and the direction perpendicular to the rolling direction RD and the direction normal to the rolling surface ND is regarded as the direction transverse to the rolling direction TD.

[0148] (Standard Deviation of Spacing Between Magnetic Domain Control Points VP) The standard deviation of spacing between magnetic domain control points is calculated according to the following procedure. First, a rectangular evaluation area is set on the grain-oriented electrical steel sheet 1, with the length of a side parallel to the rolling direction RD of the grain-oriented electrical steel sheet 1 being 50 mm and the length of a side parallel to the transverse direction TD of the grain-oriented electrical steel sheet 1 being 100 mm. Then, within the evaluation area, imaginary lines VL parallel to the transverse direction TD and 100 mm long are set on the surface of the grain-oriented electrical steel sheet 1 at 5 mm intervals. Next, magnetic domain control points VP are identified, which are the intersections of the imaginary lines VL and the magnetic domain control treatment lines 11. The transverse direction TD and the magnetic domain control treatment lines 11 are identified according to the procedure described above. Then, the spacing between adjacent magnetic domain control points VP is measured, and the standard deviation of these measurements is calculated.

[0149] The locations where the evaluation area and virtual line VL are set are not limited. The virtual line VL may be set at any location where the virtual line VL can be set so that the standard deviation of the spacing between the magnetic domain control points VP falls within the range of the present disclosure. For example, the virtual line VL may be set so that it passes through the area X where no magnetic domain control processing line 11 is provided. On the other hand, if a location where the virtual line VL can be set so that the standard deviation of the spacing between the magnetic domain control points VP falls within the range of the present disclosure cannot be found, it is presumed that the requirements of the present disclosure are not met.

[0150] (Minimum distance between magnetic domain control points VP D Ｓ and maximum value D Ｌ ) Minimum distance D between magnetic domain control processing points Ｓ and maximum value D Ｌ is calculated according to the following procedure. First, the above-mentioned imaginary line VL is set on the surface of the grain-oriented electrical steel sheet 1. Next, the magnetic domain control points VP, which are the intersections of the imaginary line VL and the magnetic domain control processing lines 11, are identified. The rolling direction RD and the magnetic domain control processing lines 11 are identified according to the above-mentioned procedure. Then, the distance between adjacent magnetic domain control points VP is measured, and the minimum and maximum values ​​of these measurements are obtained.

[0151] (Method for measuring β angles) β angles are measured using the side reflection Laue method. The side reflection Laue method is widely known as a method for measuring crystal orientation. However, the β angle is a value obtained by rounding off the measured value to one decimal place. In other words, the significant figures for the β angle are rounded to one decimal place.

[0152] (|β Ｌ | and |β Ｓ |) |β Ｌ | is measured by the following procedure. First, the distance is measured by the above-mentioned means to find the maximum value D Ｌ The β angle between these magnetic domain control points VP is determined by the midpoint P βＬ The measurement is made by the above-mentioned means at intervals of 1 mm from Ｌ In this case, two or more points where the distance is equal to the maximum value D Ｌ In this case, the β angle between the adjacent magnetic domain control points VP is calculated by dividing the β angle by the midpoint P of the magnetic domain control points VP. βＬ The average value of the absolute values ​​of the β angles is calculated as |β Ｌ |β Ｓ The procedure for measuring | is |β Ｌ First, by the above-mentioned means, the distance is determined to be the minimum value D Ｓ The β angle between these magnetic domain control points VP is determined by the midpoint P βＳ The measurement is carried out by the above-mentioned means at intervals of 1 mm from the Ｓ In this case, two or more points where the distance is the minimum value D Ｓ In this case, the β angle between the adjacent magnetic domain control points VP is defined as the angle between the midpoint P of the magnetic domain control points VP. βＳ The average value of the absolute values ​​of the β angles is calculated as |β Ｓ |You can just consider it that way.

[0153] In each of the multiple virtual lines VL, |β Ｌ In one or more virtual lines VL, the standard deviation of the intervals between the magnetic domain control points is 1.25 mm or more, and |β Ｌ If | is 1.5° or more, the steel sheet is considered to be a grain-oriented electrical steel sheet according to the present disclosure. The more the number of imaginary lines VL that satisfy the requirements of the present disclosure, the more preferable it is.

[0154] (Method for measuring the chemical composition of the master sheet 2 and the grain-oriented electrical steel sheet 1) The chemical compositions of the grain-oriented electrical steel sheet 1 and the master sheet 2 may be measured by a general steel analysis method. For example, the chemical compositions may be measured using ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry). Specifically, a test piece is obtained from the center of the sample in the thickness direction, and the chemical compositions of the grain-oriented electrical steel sheet 1 and the master sheet 2 can be measured by measuring the test piece using a measuring device such as an ICPS-8100 manufactured by Shimadzu Corporation under conditions based on a pre-created calibration curve. The contents of C and S, which are difficult to measure using ICP-AES, may be measured using a combustion-infrared absorption method. The content of N may be measured using an inert gas fusion-thermal conductivity method.

[0155] If a forsterite coating and / or an insulating coating is formed on the grain-oriented electrical steel sheet 1 and the base sheet 2, the forsterite coating and / or the insulating coating can be removed from the grain-oriented electrical steel sheet 1 and the base sheet 2 before analyzing the chemical composition of the grain-oriented electrical steel sheet 1 and the base sheet 2. The forsterite coating can be removed, for example, by immersing the sample in sulfuric acid and then in nitric acid. The conditions, such as the temperature and concentration of the sulfuric acid and nitric acid, and the immersion time, are adjusted appropriately so as not to excessively dissolve the base steel of the sample. An example of the conditions for removing the forsterite coating is as follows: 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 rag or the like to remove any sludge adhering to the surface. Then, the sample is dried. Next, the sample is immersed in 10% nitric acid at room temperature for about 5 seconds while stirring. The insulating coating can be removed, for example, by immersing the sample in a sodium hydroxide solution, followed by immersion in dilute sulfuric acid and nitric acid. The temperature and concentration of the sodium hydroxide, dilute sulfuric acid, and nitric acid solutions, as well as the immersion time, are adjusted appropriately so as not to excessively dissolve the steel substrate of the sample. An example of the conditions for removing the insulating coating is as follows: First, the sample is immersed in a 20% sodium hydroxide solution at 80°C for 15 minutes. The sample is then dried. Next, the sample is immersed in a 10% dilute sulfuric acid solution at 80°C for 4 minutes. After that, any sludge adhering to the sample surface is removed with a rag or similar. Next, the sample is immersed in a 10% nitric acid solution at room temperature for approximately 10 seconds while stirring.

[0156] (Method for measuring the angle between the magnetic domain control processing line 11 and the direction transverse to rolling TD) The angle between the magnetic domain control processing line 11 and the direction transverse to rolling TD can be measured using a known angle measuring means after the magnetic domain control processing line 11 and the direction transverse to rolling TD have been identified using the procedure described above.

[0157] (Method for measuring the spacing P of the magnetic domain control treatment) The spacing P of the magnetic domain control treatment is obtained by first identifying the magnetic domain control treatment line 11 and the rolling direction RD using the procedure described above, then setting a virtual line along the magnetic domain control treatment line 11, and measuring the spacing between the virtual lines using a known length measuring means.

[0158] (Method for measuring the magnitude of tensile stress induced by thermal strain) The magnitude of tensile stress induced by thermal strain is measured by the EBSD Wilkinson method and a Cross Court manufactured by BLG Vantage. The EBSD Wilkinson method is described in A. J. 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. 111-115, 2006. 307-313.

[0159] When measuring the magnitude of the tensile stress induced by thermal strain using the EBSD Wilkinson method and a Cross Court manufactured by BLG Vantage, first, the magnetic domain control treatment line 11 is identified using the procedure described above. Next, the grain-oriented electrical steel sheet 1 is cut through the magnetic domain control treatment line 11 and perpendicular to the magnetic domain control treatment line 11. This cut surface is used as the measurement surface. The cross section of the magnetic domain control treatment line 11 included in the measurement surface is analyzed using the EBSD Wilkinson method and a Cross Court manufactured by BLG Vantage, and tensile stress components in any direction are extracted and their magnitudes are measured. For example, tensile stress components can be extracted in the normal direction (ND) of the rolling surface, the direction parallel to the magnetic domain control treatment line 11, and the direction perpendicular to the normal direction (ND) of the rolling surface and the magnetic domain control treatment line 11.

[0160] The number of measurement points is, for example, 10. If the tensile stress in any direction is 40 MPa or more at at least one point of the grain-oriented electrical steel sheet 1 (i.e., if the tensile stress in at least one direction is 40 MPa or more), the maximum value of the tensile stress in any direction in the magnetic domain control treatment line of the grain-oriented electrical steel sheet 1 is determined to be 40 MPa or more. Therefore, if the purpose is to determine whether the maximum value of tensile stress is 40 MPa or more, the measurement of tensile stress may be stopped when a measurement point where the tensile stress in any direction is 40 MPa or more is found. However, as will be described later, σ(TS ｍ )２ , T.S. ｍ（β＜２） , or TS ｍ（β≧２） When determining the tensile stress, do not stop the measurement and determine the tensile stress at each measurement point.

[0161] (Method for Measuring Groove Depth and Width) The depth and width of the groove can be measured by identifying the surface shape of the sample using a known three-dimensional measuring machine. If the grain-oriented electrical steel sheet 1 has an insulating coating, the insulating coating is removed using the procedure described above before three-dimensional measurement of the sample surface is performed.

[0162] The effects of one embodiment of the present disclosure will be explained in more detail using examples. However, the conditions in the examples are merely examples of conditions adopted to confirm the feasibility and effects of the present disclosure. The present disclosure is not limited to this example of conditions. Various conditions may be adopted in the present disclosure as long as they do not deviate from the gist of the present disclosure and the object of the present disclosure is achieved.

[0163] Example 1 Grain-oriented electrical steel sheets of the same lot with a sheet thickness of 0.20 mm were used as base sheets. The base sheets were subjected to magnetic domain control treatment under various conditions shown in Table 1. For steel sheets Nos. 1 to 13 obtained by each treatment, the number of VLs (virtual lines) with a standard deviation of 1.25 mm or more is shown in column A of Table 1, and further, for the VLs shown in column A, |β Ｌ The number of VLs that satisfy the relationship |≧1.5° is shown in column B of Table 1. In column C of Table 1, the number of VLs that satisfy the relationship |≧1.5° is shown in column B of Table 1. Ｌ / D Ｓ Column D of Table 1 shows the number of VLs that satisfy the relationship of 0.5°<|β Ｌ |-|β Ｓ The number of VLs that satisfy the relationship of | is shown. Ｌ |, |β Ｓ The measurement of | was performed according to the procedure described above. A rectangular sample with both sides 100 mm long was cut out from a three-phase transformer core for measuring noise and iron loss, as described below, and subjected to the measurement. A rectangular evaluation area was set in this rectangular sample, with the side parallel to the rolling direction RD being 50 mm long and the side parallel to the direction transverse to the rolling direction TD being 100 mm long, and virtual lines VL, parallel to the direction transverse to the rolling direction TD and 100 mm long, were set at 5 mm intervals within the evaluation area. There were nine virtual lines VL.

[0164] Samples No. 1 to 10 shown in Table 1 are samples in which linear magnetic domain control treatment lines were formed in regions with wide magnetic domain widths. Sample No. 11 is a sample in which linear magnetic domain control treatment lines were formed across the entire width. Sample No. 12 is a sample in which regularly broken magnetic domain control treatment lines were formed. Sample No. 13 is a sample in which random broken magnetic domain control treatment lines were formed. Sample No. 14 is a sample in which linear magnetic domain control treatment lines, including curves, were formed in regions with wide magnetic domain widths. Sample No. 15 is a sample in which magnetic domain control treatment lines were formed at 4 mm intervals only in regions within ±4 mm in the rolling direction RD from the center of each crystal grain in the rolling direction. The radius of curvature of the steel sheet at the position where the crystal grain was located during final annealing was 250 mm.

[0165] The samples described as thermally strained in Table 1 were measured at 4 mm intervals with an average irradiation energy density of 1.5 mJ / mm ２ The sample marked with "groove" in Table 1 had a groove (depth: 15 μm, width: 20 μm) formed and was subjected to magnetic domain control. The "mixed" condition in Table 1 refers to the magnetic domain control treatment conditions under which magnetic domain control was performed so that the total length of the thermal distortion and the groove was 1:1.

[0166] Next, the noise and iron loss of the grain-oriented electrical steel sheets that had undergone the magnetic domain control treatment were measured, and the measurement results are shown in Table 2. The noise and iron loss were measured as follows. First, 205 grain-oriented electrical steel sheets with a thickness of 0.20 mm were stacked to produce a three-phase transformer core. The widths of the legs and yoke of the three-phase transformer core were both 150 mm. The height and width of the outer shape 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 a frequency of 50 Hz and an excitation magnetic flux density of 1.8 T.

[0167] To measure the noise, microphones were placed at equal intervals around eight locations around the transformer incorporating the three-phase transformer core. The distance between the transformer and the microphones was 30 cm. The noise measurement results from these microphones were A-weighted corrected and averaged to obtain values, which are shown in Table 3 as the noise evaluation results (unit: dBA) of the grain-oriented electrical steel sheets. Examples with a noise evaluation result of 43.50 dBA or less were determined to be examples in which low noise was achieved. In Table 2, noise evaluation results that were determined to be unacceptable are underlined.

[0168] The iron loss was determined by measuring the voltage and current on the primary and secondary sides with a power analyzer when excitation was performed at a frequency of 50 Hz and an excitation magnetic flux density of 1.8 T, as described above. The determined iron loss is shown in Table 3 as the iron loss evaluation results (unit: W / kg) of the grain-oriented electrical steel sheet. Examples with an iron loss evaluation result of 1.270 W / kg or less were determined to be examples in which low iron loss was achieved.

[0169]

[0170]

[0171] In the samples Nos. 1 to 3 and 14 shown in Table 2, the standard deviation of the intervals between the magnetic domain control points, which are the intersections of the imaginary lines and the magnetic domain control processing lines, is 1.25 mm or more, and the average value of the absolute value of the β angle |β Ｌ The samples were those in which the angle | was 1.5° or more. In contrast, sample No. 11 was subjected to magnetic domain control treatment over the entire width, so its iron loss was good but its noise characteristics were poor. Sample No. 12 was subjected to magnetic domain control treatment in the dashed line pattern, so its noise was improved compared to sample No. 11, but both its iron loss and noise characteristics were unacceptable. Sample No. 13 was subjected to random magnetic domain control treatment in the dashed line pattern, so its noise was further improved compared to sample No. 12, but its iron loss characteristics were unacceptable. Sample No. 15 was subjected to magnetic domain control treatment only in the central region of each crystal grain in the rolling direction, so its noise was within the acceptable range but its iron loss characteristics were unacceptable.

[0172] Samples No. 4 and No. 5 satisfy the conditions met by samples No. 1 to No. 3 described above, and in addition, among a plurality of virtual lines spaced 5 mm apart, the standard deviation of the spacing between magnetic domain control points is 1.25 mm or more in each of two or more virtual lines, and the average value of the absolute value of the β angle |β Ｌ The iron loss of samples No. 4 and No. 5 was better than that of samples No. 1 and No. 2, and in terms of noise, it was possible to obtain excellent characteristics equivalent to those of samples No. 1 and No. 2. Sample No. 6 not only satisfied the conditions that samples No. 1 to No. 3 mentioned above met, but also had D Ｌ / D Ｓ The iron loss of sample No. 6 is equivalent to the best characteristics among the iron loss of samples No. 1 to 3, and the noise of sample No. 6 is equivalent to the best characteristics among the noise of samples No. 1 to 3. Sample No. 6 can be evaluated as having superior characteristics in both iron loss and noise. Sample No. 7 not only fulfills the conditions fulfilled by samples No. 4 and 5, but also has D Ｌ / D Ｓ The iron loss and noise of sample No. 7 were superior to those of samples Nos. 1 to 3.

[0173] Sample No. 8 satisfied the conditions satisfied by samples No. 1 to 3, and also satisfied the condition of 0.5°≦|β Ｌ |-|β Ｓ | relationship. The iron loss and noise of sample No. 8 were even better than those of samples No. 1 to 3. Sample No. 9 was a sample that met both the conditions met by samples No. 6 and No. 8. The iron loss and noise of sample No. 9 were even better than those of samples No. 1 to 3. Sample No. 10 was a sample that met all the conditions met by samples No. 7 and 8. The iron loss and noise of sample No. 10 were even better than those of samples No. 7 to 9.

[0174] (Example 2) Grain-oriented electrical steel sheets of the same lot with a sheet thickness of 0.20 mm were used as base sheets. The base sheets were subjected to magnetic domain control treatment under various conditions shown in Table 3. For steel sheets Nos. 16 to 23 obtained by each treatment, the number of VLs (virtual lines) with a standard deviation of 1.25 mm or more is shown in column A of Table 1, and further, for the VLs shown in column A, |β Ｌ The number of VLs that satisfy the relationship |≧1.5° is shown in column B of Table 1. In column C of Table 1, the number of VLs that satisfy the relationship |≧1.5° is shown in column B of Table 1. Ｌ / D Ｓ Column D of Table 1 shows the number of VLs that satisfy the relationship of 0.5°<|β Ｌ |-|β Ｓ The number of VLs that satisfy the relationship of | is shown. Ｌ |, |β Ｓ The measurement of | was performed according to the procedure described above. A rectangular sample with both sides 100 mm long was cut out from a three-phase transformer core for measuring noise and iron loss, as described below, and subjected to the measurement. A rectangular evaluation area was set in this rectangular sample, with the side parallel to the rolling direction RD being 50 mm long and the side parallel to the direction transverse to the rolling direction TD being 100 mm long, and virtual lines VL, parallel to the direction transverse to the rolling direction TD and 100 mm long, were set at 5 mm intervals within the evaluation area. There were nine virtual lines VL.

[0175] Samples No. 16 to No. 22 shown in Table 3 are samples in which linear magnetic domain control processing lines are formed in areas with wide magnetic domain widths. Sample No. 23 is a sample in which linear magnetic domain control processing lines including curves are formed in areas with wide magnetic domain widths.

[0176] The samples described as thermally strained in Table 3 were measured at 4 mm intervals with an average irradiation energy density of 1.5 mJ / mm ２ The sample marked with "groove" in Table 3 had a groove (depth: 15 μm, width: 20 μm) formed and was subjected to magnetic domain control. The "mixed" condition in Table 3 refers to the magnetic domain control treatment conditions under which magnetic domain control was performed so that the total length of the thermal distortion and the groove was 1:1.

[0177] The noise and core loss of the grain-oriented electrical steel sheets that had been subjected to the magnetic domain control treatment were measured in the same manner as in Example 1, and the measurement results are shown in Table 4.

[0178]

[0179]

[0180] As can be seen from Tables 3 and 4, at least one of the virtual lines D Ｌ / D Ｓ In these examples where the value is 4 or more, even better characteristics were obtained in terms of iron loss and noise compared to Example 1.

[0181] (Example 3) Grain-oriented electrical steel sheets of the same lot with a sheet thickness of 0.20 mm were used as base sheets. The base sheets were subjected to magnetic domain control treatment under various conditions shown in Table 5. For steel sheets Nos. 24 to 61 obtained by each treatment, the number of VLs (virtual lines) with a standard deviation of 1.25 mm or more is shown in column A of Table 1, and for the VLs shown in column A, the number of VLs with a standard deviation of 1.25 mm or more is shown in column A. Ｌ The number of VLs that satisfy the relationship |≧1.5° is shown in column B of Table 1. In column C of Table 1, the number of VLs that satisfy the relationship |≧1.5° is shown in column B of Table 1. Ｌ / D Ｓ In column D of Table 1, the number of VLs that satisfy the relationship 4≦D Ｌ / D Ｓ Column E shows the number of VLs that satisfy the relationship of 0.5°<|β Ｌ |-|β Ｓ Column F shows the number of VLs that satisfy the relationship of 0.5°<|β Ｌ |-|β Ｓ The number of VLs that satisfy the relationship of | is shown. Ｌ |, |β ＳThe measurement of | was performed according to the procedure described above. A rectangular sample with both sides 100 mm long was cut out from a three-phase transformer core for measuring noise and iron loss, as described below, and subjected to the measurement. A rectangular evaluation area was set in this rectangular sample, with the side parallel to the rolling direction RD being 50 mm long and the side parallel to the direction transverse to the rolling direction TD being 100 mm long, and virtual lines VL, parallel to the direction transverse to the rolling direction TD and 100 mm long, were set at 5 mm intervals within the evaluation area. There were nine virtual lines VL.

[0182] Samples No. 24 to No. 61 shown in Table 5 are samples in which linear magnetic domain control treatment lines were formed in the region with a wide magnetic domain width. The samples listed as thermally distorted in Table 5 were samples in which linear magnetic domain control treatment lines were formed at 4 mm intervals with an average irradiation energy density of 0.5 mJ / mm ２ ~4.0 mJ / mm ２ The samples shown in Table 5 with the description "groove" have grooves (depth: 15 μm to 41 μm, width: 20 μm) formed therein to control the magnetic domains.

[0183] The noise and core loss of the grain-oriented electrical steel sheets that had been subjected to the magnetic domain control treatment were measured in the same manner as in Example 1, and the measurement results are shown in Table 6.

[0184]

[0185]

[0186] As can be seen from Tables 5 and 6, σ(TS ｍ ) ２ >5.0, TS ｍ（β＜２） >TS ｍ（β≧２） , σ(D ｍ ) ２ >3.0, and / or D ｍ（β＜２） >D ｍ（β≧２） In these examples that satisfied the above condition, even more excellent characteristics were obtained in terms of iron loss and noise compared to the example of Example 1.

[0187] According to the present disclosure, it is possible to provide a grain-oriented electrical steel sheet that can achieve both low iron loss and low noise, and a method for manufacturing the same, which has high industrial applicability.

[0188] RD Rolling direction TD Direction perpendicular to rolling ND Normal direction to rolling surface VL Virtual line VP Magnetic domain control point D Ｌ Maximum distance between magnetic domain control points D Ｓ Minimum spacing between magnetic domain control points P βＬ　 The midpoint of the two magnetic domain control points with the maximum spacing P βＳ　 REFERENCE SIGNS LIST X: Midpoint between two magnetic domain control points with a minimum distance X: Area where no magnetic domain control processing line is provided 1: Grain-oriented electrical steel sheet 2: Original sheet 11: Magnetic domain control processing line 21: Magnetic domain control processing area 22: Non-magnetic domain control processing area 30: Image acquisition device 31: Light source unit 33: MO sensor 35: Image sensor 37: Signal processing unit 40: Analysis device 41: Calculation unit 43: Memory 45: Display unit 47: Input unit 49: Communication I / F 500: Laser irradiation device 501: Polygon mirror 503: Light source device 505: Collimator 507: Condenser lens 509: Motor 511: Sensor 513: Control unit 515: Strip threading device

Claims

1. A grain-oriented electrical steel sheet having a plurality of magnetic domain control processing lines on a surface thereof, wherein a rectangular evaluation area is set in the grain-oriented electrical steel sheet, the length of a side parallel to the rolling direction of the grain-oriented electrical steel sheet being 50 mm, and the length of a side parallel to the direction perpendicular to the rolling direction of the grain-oriented electrical steel sheet being 100 mm, and further, virtual lines parallel to the direction perpendicular to the rolling direction and having a length of 100 mm are set inside the evaluation area at intervals of 5 mm in a direction parallel to the rolling direction, wherein: in at least one of the virtual lines, the standard deviation of the intervals between the magnetic domain control points, which are the intersections of the virtual line and the magnetic domain control processing lines, is 1.25 mm or more, and the intervals are equal to or smaller than a maximum value D Ｌ The average value of the absolute value of the β angle measured between the two magnetic domain control points |β Ｌ | is 1.5° or more.

2. In each of the two or more virtual lines, the standard deviation of the intervals between the magnetic domain control points is 1.25 mm or more, and the intervals are equal to or smaller than the maximum value D Ｌ The average value |β of the absolute values ​​of the β angles measured between the two magnetic domain control points Ｌ The grain-oriented electrical steel sheet according to claim 1, wherein | is 1.5° or more.

3. The maximum distance D between the magnetic domain control points Ｌ and the minimum value D of the interval between the magnetic domain control points. Ｓ Compared to D Ｌ / D Ｓ The grain-oriented electrical steel sheet according to claim 1 or 2, wherein R is 2 or more.

4. D Ｌ / D Ｓ The grain-oriented electrical steel sheet according to claim 3 , wherein the grain size is 4 or more.

5. Said|β Ｌ | and the interval is the minimum value D Ｓ The average value of the absolute value of the β angle measured between the two magnetic domain control points |β Ｓ The grain-oriented electrical steel sheet according to claim 3 or 4, wherein | and satisfy the following formula: 0.5°≦|β. Ｌ |-|β Ｓ | 6. The grain-oriented electrical steel sheet according to any one of claims 1 to 5, wherein the magnetic domain control treatment line is a thermal strain.

7. The grain-oriented electrical steel sheet according to claim 6, characterized in that the maximum value of the tensile stress introduced into the thermal strain in the magnetic domain control treatment wire is non-uniform for each measurement point of the tensile stress.

8. A rectangular evaluation area is set on the surface, with the length of the side parallel to the rolling direction being 50 mm and the length of the side parallel to the direction perpendicular to the rolling direction of the grain-oriented electrical steel sheet being 100 mm, and further, virtual lines parallel to the direction perpendicular to the rolling direction and having a length of 100 mm are set inside the evaluation area at 5 mm intervals in a direction parallel to the rolling direction, each of a plurality of intersections between the virtual lines and the plurality of magnetic domain control treatment lines is defined as a magnetic domain control point, and the maximum value of the tensile stress in unit MPa measured at each of the magnetic domain control points is defined as TS ｍ , the TS ｍ The variance of σ(TS ｍ ) ２ Then, σ(TS ｍ ) ２ The grain-oriented electrical steel sheet according to claim 7, wherein the grain-oriented electrical steel sheet satisfies a tensile strength of 0.01 to 0.01%.

9. The arithmetic average value of the maximum value of the tensile stress in unit MPa introduced into the thermal strain, which is measured at each of the magnetic domain control points having a β angle of less than 2°, is defined as TS. ｍ（β＜２） The arithmetic mean value of the maximum value of the tensile stress in unit MPa introduced into the thermal strain, which is measured at each of the magnetic domain control points having the β angle of 2° or more among the magnetic domain control points, is defined as TS ｍ（β≧２） When this is done, TS ｍ（β＜２） >T.S. ｍ（β≧２） The grain-oriented electrical steel sheet according to claim 7 or 8, wherein the following is satisfied:

10. The grain-oriented electrical steel sheet according to any one of claims 1 to 5, wherein the magnetic domain control treatment lines are grooves.

11. The grain-oriented electrical steel sheet according to claim 10, characterized in that the maximum value of the groove depth in the magnetic domain control treatment line is non-uniform for each measurement point of the groove depth.

12. A rectangular evaluation area is set on the surface, with the length of the side parallel to the rolling direction being 50 mm and the length of the side parallel to the rolling transverse direction of the grain-oriented electrical steel sheet being 100 mm, and further, virtual lines parallel to the rolling transverse direction and 100 mm long are set inside the evaluation area at 5 mm intervals in a direction parallel to the rolling direction, each of a plurality of intersections between the virtual lines and the plurality of magnetic domain control processing lines is set as a magnetic domain control point, and the maximum value of the groove depth in units of μm measured at each of the magnetic domain control points is defined as D ｍ , the D ｍ The variance of σ(D ｍ ) ２ Then, σ(D ｍ ) ２ The grain-oriented electrical steel sheet according to claim 11, wherein the grain-oriented electrical steel sheet satisfies a tensile strength of 0.01 to 0.01%.

13. The arithmetic average value of the maximum value of the groove depth in unit μm measured at each of the magnetic domain control points having a β angle of less than 2° among the magnetic domain control points is defined as D ｍ（β＜２） The arithmetic mean value of the maximum value of the groove depth in unit μm measured at each of the magnetic domain control points where the β angle is 2° or more is defined as D ｍ（β≧２） When this is done, D ｍ（β＜２） >D ｍ（β≧２） The grain-oriented electrical steel sheet according to claim 11 or 12, wherein 14. A method for manufacturing grain-oriented electromagnetic steel sheet, comprising the steps of: acquiring a magnetic domain image of an original sheet of grain-oriented electromagnetic steel sheet; determining a magnetic domain control treatment area based on the distribution of magnetic domain widths in the magnetic domain image; and applying magnetic domain control treatment to the magnetic domain control treatment area determined based on the distribution of magnetic domain widths, wherein a rectangular evaluation area is set in the grain-oriented electromagnetic steel sheet, the length of a side parallel to the rolling direction of the grain-oriented electromagnetic steel sheet being 50 mm and the length of a side parallel to the direction perpendicular to the rolling of the grain-oriented electromagnetic steel sheet being 100 mm, and further, when virtual lines parallel to the direction perpendicular to the rolling and having a length of 100 mm are set within the evaluation area at intervals of 5 mm in a direction parallel to the rolling direction, the standard deviation of the intervals along the virtual line at the intersections of the virtual line and the magnetic domain control treatment line formed by the magnetic domain control treatment for at least one of the virtual lines is 1.25 mm or more.

15. The method for producing grain-oriented electrical steel sheet according to claim 14, wherein in the step of determining the magnetic domain control treatment region, a region in which the magnetic domain width is equal to or greater than a predetermined value is determined to be the magnetic domain control treatment region.

16. A method for producing grain-oriented electrical steel sheet according to claim 14 or 15, wherein in the step of acquiring the magnetic domain image, a distribution of the magnetic domain widths is derived from the magnetic domain image using a two-dimensional Fourier transform.

17. A method for producing a grain-oriented electrical steel sheet according to any one of claims 14 to 16, wherein in the step of applying the magnetic domain control treatment, the magnetic domain control treatment is applied by irradiation with a laser or an electron beam.

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