WO2025070785A1 - 方向性電磁鋼板 - Google Patents

方向性電磁鋼板 Download PDF

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Publication number
WO2025070785A1
WO2025070785A1 PCT/JP2024/034809 JP2024034809W WO2025070785A1 WO 2025070785 A1 WO2025070785 A1 WO 2025070785A1 JP 2024034809 W JP2024034809 W JP 2024034809W WO 2025070785 A1 WO2025070785 A1 WO 2025070785A1
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Prior art keywords
magnetic domain
grain
steel sheet
electrical steel
oriented electrical
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English (en)
French (fr)
Japanese (ja)
Inventor
悠祐 川村
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Nippon Steel Corp
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Nippon Steel Corp
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Priority to KR1020257042875A priority Critical patent/KR20260013989A/ko
Priority to JP2025519940A priority patent/JPWO2025070785A1/ja
Priority to CN202480045423.7A priority patent/CN121511319A/zh
Publication of WO2025070785A1 publication Critical patent/WO2025070785A1/ja
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • C21D8/12—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/12—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials
    • H01F1/14—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys
    • H01F1/147—Alloys characterised by their composition
    • H01F1/14766—Fe-Si based alloys
    • H01F1/14775—Fe-Si based alloys in the form of sheets
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/12—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials
    • H01F1/14—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys
    • H01F1/16—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys in the form of sheets

Definitions

  • the present disclosure relates to grain-oriented electrical steel sheet. This application claims priority based on Japanese Patent Application No. 2023-165201, filed on September 27, 2023, the contents of which are incorporated herein by reference.
  • Grain-oriented electrical steel sheet is a steel sheet that contains 7% or less Si by mass and has a secondary recrystallized texture in which secondary recrystallized grains are concentrated in the ⁇ 110 ⁇ 001> orientation (Goss orientation). Grain-oriented electrical steel sheet is mainly used as the iron core of power transformers, and there is a growing need for reduced noise as well as reduced energy loss (iron loss).
  • This disclosure was made in consideration of the above problems, and aims to provide a grain-oriented electrical steel sheet that can achieve both low iron loss and low noise.
  • a grain-oriented electrical steel sheet is a grain-oriented electrical steel sheet having magnetic domain refinement treatment lines on a surface, in which the relationship between the sheet thickness t (mm) and the iron loss W17/50 (W/kg) satisfies W17/50 ⁇ 1.350t + 0.450, and where the peak-to-peak value of magnetostriction at a magnetic flux density of 1.7 T is denoted as ⁇ 1pp and the peak-to-peak value of magnetostriction at a magnetic flux density of 1.9 T is denoted as ⁇ 2pp, the relationship ⁇ 2pp/ ⁇ 1pp ⁇ 2.2 is satisfied.
  • the magnetic domain refinement treatment lines preferably represent thermal distortion.
  • the magnetic domain refinement treatment lines preferably represent grooves.
  • the maximum value of the tensile strength introduced by the thermal strain in the magnetic domain refinement treatment line is non-uniform for each measurement point of the tensile strength.
  • ⁇ 2 ( TSm ) > 5.0 is satisfied, TSm being the maximum value of the tensile strength in unit MPa introduced into the thermal strain, measured at each of a plurality of magnetic domain refinement points, which are the intersections of a plurality of imaginary lines set parallel to the rolling direction of the grain-oriented electrical steel sheet at intervals of 5 mm and the magnetic domain refinement treatment line, and ⁇ 2 ( TSm ) being the variance of TSm .
  • TS m( ⁇ 2) > TS m( ⁇ 2) is satisfied, where TS m( ⁇ 2) is the arithmetic average value of the maximum values of the tensile strength in unit MPa introduced into the thermal strain, measured at each of a plurality of magnetic domain refinement points, which are intersections between a plurality of imaginary lines set parallel to the rolling direction of the grain-oriented electrical steel sheet at intervals of 5 mm and the magnetic domain refinement treatment line, and where the magnetic domain refinement treatment line has a ⁇ angle of less than 2°, and TS m( ⁇ 2) is the arithmetic average value of the maximum values of the tensile strength in unit MPa introduced into the thermal strain, measured at each of the magnetic domain refinement points where the ⁇ angle is 2° or more.
  • a maximum value of the depth of the groove in the magnetic domain refinement treatment line is non-uniform for each measurement point of the groove.
  • ⁇ 2 ( Dm ) > 3.0 is satisfied, Dm being the maximum value of the groove depth in units of ⁇ m at magnetic domain refinement points which are intersections of the magnetic domain refinement treatment lines and a plurality of imaginary lines which are set in parallel along the rolling direction of the grain-oriented electrical steel sheet at intervals of 5 mm, and ⁇ 2 ( Dm ) being the variance of Dm .
  • Dm( ⁇ 2) > Dm ( ⁇ 2) is satisfied, where Dm( ⁇ 2) is the arithmetic average value of the maximum groove depth in unit ⁇ m measured at each of a plurality of magnetic domain refinement points, which are intersections between the magnetic domain refinement treatment line and a plurality of imaginary lines set in parallel along the rolling direction of the grain-oriented electrical steel sheet at intervals of 5 mm, and where the magnetic domain refinement treatment line has a ⁇ angle of less than 2°, and Dm ( ⁇ 2) is the arithmetic average value of the maximum groove depth in unit ⁇ m measured at each of the magnetic domain refinement points where the ⁇ angle is 2° or more.
  • 1 is a graph showing an example of the spatial distribution of magnetic domain width in a grain-oriented electrical steel sheet before magnetic domain refinement treatment.
  • 1 is a graph showing an example of the spatial distribution of magnetic domain width in a grain-oriented electrical steel sheet after magnetic domain refinement treatment.
  • 1C is a graph showing regions in which the magnetic domain width is subdivided by 50 ⁇ m or more before and after the magnetic domain subdivision process shown in FIGS. 1A and 1B.
  • 1 is a graph showing the relationship between the magnetic domain width before laser irradiation and the magnetic domain width after laser irradiation.
  • 1 is a block diagram showing a hardware configuration of an image acquisition device according to an embodiment of the present invention.
  • FIG. 2 is a block diagram showing a hardware configuration of the analysis device according to the present embodiment.
  • FIG. 1 is a schematic diagram showing a configuration of a laser irradiation device according to an embodiment of the present invention.
  • 1 is a flowchart showing a method for manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention.
  • FIG. 2 is a schematic diagram showing magnetic domain refinement treatment lines that represent locations on a grain-oriented electrical steel sheet where magnetic domain refinement treatment has been selectively performed.
  • 1 is a graph showing the relationship between sheet thickness and core loss of a grain-oriented electrical steel sheet that has been selectively subjected to magnetic domain refinement processing.
  • 1 is a graph showing magnetostriction waveforms when a grain-oriented electrical steel sheet that has been selectively irradiated with a laser and a grain-oriented electrical steel sheet that has been uniformly irradiated with a laser over the entire surface are subjected to AC excitation up to ⁇ 1.7 T.
  • 1 is a graph showing magnetostriction waveforms when a grain-oriented electrical steel sheet that has been selectively irradiated with a laser and a grain-oriented electrical steel sheet that has been uniformly irradiated with a laser over the entire surface are subjected to AC excitation up to ⁇ 1.9 T.
  • 1 is a graph showing data on the ratio ( ⁇ 2pp/ ⁇ 1pp) of the peak-to-peak magnetostriction value ⁇ 2pp at a magnetic flux density of 1.9 T to the peak-to-peak magnetostriction value ⁇ 1pp at a magnetic flux density of 1.7 T for a plurality of grain-oriented electrical steel sheets selectively irradiated with a laser and a plurality of grain-oriented electrical steel sheets uniformly irradiated with a laser over the entire surface.
  • 1 is a graph showing a schematic relationship between the magnetic domain width and the magnetic domain control saturation strength.
  • 1 is a graph showing a schematic relationship between the magnitude of the ⁇ angle and the magnetic domain control saturation strength.
  • FIG. 2 is a cross-sectional schematic diagram of a grain-oriented electrical steel sheet in which magnetic domain refinement treatment lines are thermal distortion.
  • FIG. 2 is a schematic cross-sectional view of a grain-oriented electrical steel sheet in which the magnetic domain refinement treatment lines are grooves.
  • FIG. 13 is a schematic plan view illustrating a method for measuring the magnetic domain control strength at the intersection of a magnetic domain subdivision treatment line and a virtual line when the magnetic domain subdivision treatment line is a thermal distortion.
  • FIG. 13 is a schematic plan view illustrating a method for measuring the magnetic domain control strength at the intersection of a magnetic domain subdivision treatment line and a virtual line when the magnetic domain subdivision treatment line is a groove.
  • Figure 1A shows the spatial distribution of the width of the 180° magnetic domains (hereinafter simply referred to as "magnetic domain width") of a grain-oriented electrical steel sheet before magnetic domain refinement treatment.
  • Figure 1B shows the spatial distribution of the magnetic domain width after magnetic domain refinement treatment has been applied to the surface of the grain-oriented electrical steel sheet of Figure 1A.
  • the magnetic domain refinement treatment here was performed by irradiating a continuous wave laser along a magnetic domain control treatment line that is approximately perpendicular to the rolling direction (RD).
  • a 180° magnetic domain refers to a magnetic domain whose magnetization direction is the ⁇ 100> crystal orientation and is sandwiched between two 180° magnetic domain walls that are nearly parallel to the rolling direction.
  • the "width" of a 180° magnetic domain refers to the distance between adjacent magnetic domain walls (magnetic domain wall spacing).
  • the spatial distribution of the magnetic domain width shown in Figures 1A and 1B was derived from the magnetic domain image of the grain-oriented electrical steel sheet using a two-dimensional Fourier transform (see JP 2021-169655 A and JP 2021-169979 A).
  • Figure 1C shows the areas where the magnetic domain width has been subdivided by 50 ⁇ m or more before and after the magnetic domain subdivision process shown in Figures 1A and 1B, and visualizes the values of the original magnetic domain width at which subdivision occurred.
  • magnetic domain control is performed so that magnetic domain refinement processing is performed only in areas of the grain-oriented electromagnetic steel sheet where the original magnetic domain width is relatively wide (e.g., areas of 500 ⁇ m or more).
  • 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 process.
  • the magnetic domain control strength is the amount of thermal distortion when the magnetic domain control method is thermal distortion, and is the groove depth when the magnetic domain control method is grooves.
  • the magnetic domain control saturation strength is not uniform in grain-oriented electrical steel sheets.
  • the magnetic domain control saturation strength is the magnetic domain control strength at which the effect of the magnetic domain subdivision process is substantially saturated.
  • 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.
  • the magnetic domain control strength exceeds the magnetic domain control saturation strength, increasing the magnetic domain control strength does not have much effect on reducing iron loss.
  • 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 to set the magnetic domain control strength within a range that does not exceed the magnetic domain control saturation strength.
  • the magnetic domain control saturation strength has a strong correlation with the ⁇ angle.
  • the ⁇ angle is the deviation angle from the Goss orientation of the crystal grains around the axis perpendicular to the rolling direction (TD). Where the ⁇ angle is small, the magnetic domain control saturation strength is large.
  • the optimal magnetic domain control strength depending on the magnetic domain width or ⁇ angle. Specifically, it is preferable to perform magnetic domain subdivision processing with high magnetic domain control strength in areas where the magnetic domain width is large and the ⁇ angle is small, and to perform magnetic domain subdivision processing with low magnetic domain control strength in areas where the magnetic domain width is small and the ⁇ angle is large. Also, as mentioned above, magnetic domain subdivision processing is not performed in areas where the original magnetic domain width is smaller than a predetermined value.
  • FIG. 11 shows a graph that illustrates a method for determining the magnetic domain control strength based on the magnetic domain width.
  • the vertical axis of FIG. 11 is the magnetic domain control strength
  • the horizontal axis is the magnetic domain width.
  • the solid line graph in FIG. 11 is the magnetic domain control saturation strength. In areas where the magnetic domain width is small, the effect of magnetic domain control cannot be obtained, so the magnetic domain control saturation strength is 0. In areas where the magnetic domain width exceeds 500 ⁇ m, the effect of magnetic domain control can be obtained. And in areas where the magnetic domain width exceeds 500 ⁇ m, the magnetic domain control saturation strength increases as the magnetic domain width increases. And in areas where the magnetic domain width exceeds approximately 1200 ⁇ m, the magnetic domain control saturation strength is approximately constant.
  • Figure 12 shows a graph that illustrates a method for determining the magnetic domain control strength based on the ⁇ angle.
  • the vertical axis of Figure 12 is the magnetic domain control strength, and the horizontal axis is the magnitude of the ⁇ angle.
  • the solid line graph in Figure 12 is the magnetic domain control saturation strength. In areas where the ⁇ angle is large, the effect of magnetic domain control cannot be obtained, so the magnetic domain control saturation strength is 0. In areas where the ⁇ angle is below a predetermined value, the effect of magnetic domain control can be obtained. For example, when the ⁇ angle is 2.0° or less, it is estimated that the effect of magnetic domain control can be obtained. And in areas where the ⁇ angle is below a predetermined value, the larger the ⁇ angle, the greater the magnetic domain control saturation strength. And in areas where the ⁇ angle is even smaller, the magnetic domain control saturation strength is approximately constant.
  • 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 11. Or, it is most preferable that the relationship between the ⁇ angle at the location where magnetic domain control is performed and the magnetic domain control strength is on the solid line graph in Figure 12.
  • the magnetic domain control saturation strength can be used as a target value for the magnetic domain control strength.
  • the magnetic domain control strength is the minimum strength at which the magnetic domain control effect is manifested.
  • the magnetic domain control strength is equal to or greater than the minimum magnetic domain control strength.
  • the magnetic domain control strength may vary slightly from the target value of the magnetic domain control saturation strength.
  • the region that is equal to or greater than the magnetic domain control minimum strength and that is within a certain range of the graph of the magnetic domain control saturation strength is referred to as the target range of the magnetic domain control strength. It is preferable that the magnetic domain control strength and the magnetic domain width of the magnetic domain control target portion are within the shaded region surrounded by dashed lines in Figs. 11 and 12.
  • the ⁇ angle in grain-oriented electrical steel sheets is measured using the side reflection Laue method.
  • the side reflection Laue method is widely known as a method for measuring crystal orientation.
  • FIG. 3 shows the hardware configuration of an image acquisition device 30 that acquires magnetic domain images of grain-oriented electromagnetic steel sheets.
  • the image acquisition device 30 includes a light source unit 31, a magneto-optical (MO) sensor 33, an image sensor 35, and a signal processing unit 37.
  • MO magneto-optical
  • the light source unit 31 has a light source consisting of a light emitting diode (LED) and irradiates the MO sensor 33 with light with a uniform polarization plane.
  • LED light emitting diode
  • the MO sensor 33 is a device for measuring the magnetic domain structure of a magnetic material, and has an observation surface on which the magnetic material sample to be measured is placed. Light irradiated from the light source unit 31 passes through the inside of the MO sensor 33 and is reflected by the reflective layer, and the reflected light passes through the inside of the MO sensor 33 again and is output to the outside of the MO sensor 33.
  • a grain-oriented electromagnetic steel sheet is placed on the observation surface of the MO sensor 33 as the magnetic material sample, a leakage magnetic field corresponding to the direction of spontaneous magnetization of the grain-oriented electromagnetic steel sheet is generated inside the MO sensor 33, and this leakage magnetic field rotates the polarization plane of the reflected light.
  • the image sensor 35 is a complementary metal-oxide-semiconductor (CMOS) image sensor that forms an image of the reflected light from the MO sensor 33 on its light receiving surface, photoelectrically converts it, and outputs the analog signal after photoelectric conversion to the signal processing unit 37.
  • CMOS complementary metal-oxide-semiconductor
  • the signal processing unit 37 has an amplifier, an AD converter, a digital signal processor (DSP), etc.
  • the analog signal output from the image sensor 35 is amplified by the amplifier and converted into a digital signal by the AD converter. This digital signal is subjected to a predetermined digital processing by the DSP to generate an image signal.
  • the image signal generated by the signal processing unit 37 is output to the analysis device 40 (see Figure 4) via a cable or wireless communication.
  • FIG. 4 shows the hardware configuration of an analysis device 40 that analyzes the magnetic domain structure of grain-oriented electromagnetic steel sheets.
  • the analysis device 40 is a computer device such as a personal computer (PC), and includes a calculation unit 41, a memory 43, a display unit 45, an input unit 47, and a communication I/F 49.
  • PC personal computer
  • the calculation unit 41 has a Central Processing Unit (CPU) and, according to a program stored in the memory 43, analyzes the magnetic domain structure from the magnetic domain image of the directional electromagnetic steel sheet and determines the locations to which the magnetic domain subdivision process is applied (see Figure 6 described below).
  • CPU Central Processing Unit
  • Memory 43 has a Read Only Memory (ROM) and a Random Access Memory (RAM).
  • the ROM stores programs executed by the CPU of the calculation unit 41 and data required when these programs are executed.
  • the programs and data stored in the ROM are loaded into the RAM and executed.
  • the memory 43 may include a magnetic memory such as a hard disk drive (HDD) or an optical memory such as an optical disk.
  • the programs and data may be stored in a computer-readable recording medium that is detachable from the analysis device 40.
  • the programs executed by the calculation unit 41 may be received from an external device via the communication I/F 49.
  • the display unit 45 has a display such as a liquid crystal display (LCD), a plasma display, or an organic electroluminescence (EL) display, and displays an image based on the image signal output from the image acquisition device 30, and also displays the analysis results of the magnetic domain structure by the calculation unit 41.
  • LCD liquid crystal display
  • EL organic electroluminescence
  • 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.
  • LAN Local Area Network
  • WAN Wide Area Network
  • calculation unit 41 instead of general-purpose hardware such as a CPU, an application specific integrated circuit (ASIC) or a field programmable gate array (FGA) specialized for analyzing the magnetic domain structure may be used.
  • ASIC application specific integrated circuit
  • FGA field programmable gate array
  • dedicated hardware such as a PGA may be employed.
  • FIGS. 3 and 4 show a case where the image acquisition device 30 and the analysis device 40 are separate devices, a system in which the image acquisition device 30 and the analysis device 40 are integrated may also be adopted.
  • FIG. 5 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 plate threading device 515.
  • the threading device 515 threads the grain-oriented electromagnetic steel sheet 50 in the rolling direction (RD).
  • the polygon mirror 501 has, for example, a regular polygonal prism shape, and a number of plane mirrors are provided on each of the multiple side surfaces that make up the regular polygonal prism.
  • a laser beam LB is incident on the plane mirror of the polygon mirror 501 in one direction (horizontal direction) from the light source device 503 via the collimator 505, and is reflected by the plane mirror.
  • the polygon mirror 501 can be rotated around the 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, and the reflection direction of the laser beam LB changes sequentially, allowing scanning along the magnetic domain control processing lines 52 of the grain-oriented electromagnetic steel sheet 50.
  • the magnetic domain control processing lines 52 are multiple parallel straight lines or curves that are arranged at equal intervals in the rolling direction (RD) and make an angle of 0° to 45° with respect to the direction perpendicular to the rolling (TD) on the surface of the grain-oriented electromagnetic steel sheet 50.
  • the interval P between adjacent magnetic domain control processing lines 52 represents the irradiation pitch.
  • the light source device 503 outputs a laser beam LB in a predetermined irradiation method (e.g., continuous irradiation method or pulse irradiation method) under the control of the control unit 513.
  • a predetermined irradiation method e.g., continuous irradiation method or pulse irradiation method
  • the focusing lens 507 is provided in the optical path of the laser beam LB reflected from the polygon mirror 501, and constitutes a focusing optical system with a predetermined focal length.
  • the laser beam LB reflected from the polygon mirror 501 is focused on the surface of the grain-oriented electromagnetic steel sheet 50 via the focusing lens 507, forming grooves along the magnetic domain control processing lines 52 on the surface of the grain-oriented electromagnetic steel sheet 50, or introducing thermal distortion.
  • the motor 509 is connected to the polygon mirror 501 and drives the polygon mirror 501 to rotate under the control of the control unit 513.
  • the sensor 511 is connected to the drive shaft of the motor 509, detects the rotation angle of the polygon mirror 501 rotated by the motor 509, and outputs a signal indicating the detected rotation angle (hereinafter referred to as the rotation angle signal) to the control unit 513.
  • the control unit 513 is made up of a processor and is connected to the light source device 503, the motor 509, the sensor 511, and the plate threading device 515.
  • the control unit 513 receives a speed signal from the plate threading device 515 and outputs a signal to the motor 509 to instruct the motor 509 to rotate the polygon mirror 501.
  • the control unit 513 also controls the power of the laser beam LB output by the light source device 503 to be turned on and off based on a magnetic domain subdivision signal indicating the location of the magnetic domain control processing line 52 where the magnetic domain subdivision processing is applied, and the rotation angle signal output from the sensor 511.
  • the magnetic domain subdivision signal is input from the analysis device 40 to the laser irradiation device 500.
  • the magnetic domain subdivision signal may also be input to the laser irradiation device 500 by an operator.
  • the image acquisition device 30 acquires a magnetic domain image of the grain-oriented electromagnetic steel sheet 50 (step S62).
  • the calculation unit 41 of the analysis device 40 derives the spatial distribution of the width of the 180° magnetic domain (magnetic domain width) from the magnetic domain image using a line segment method or a two-dimensional Fourier transform. Methods for deriving the spatial distribution of the magnetic domain width using a two-dimensional Fourier transform are disclosed in JP 2021-169655 A and JP 2021-169979 A.
  • the calculation unit 41 determines, among the magnetic domain control processing lines 52 of the grain-oriented electromagnetic steel sheet 50, the locations where the magnetic domain width is equal to or greater than a predetermined value (e.g., 500 ⁇ m or greater) as the locations to which the magnetic domain refinement processing is applied (step S64).
  • a predetermined value e.g. 500 ⁇ m or greater
  • step S64 the operator may visually observe the magnetic domain image displayed on the display unit 45 of the analysis device 40 to determine the location to which the magnetic domain subdivision process is to be applied, and a magnetic domain subdivision signal representing the determined location may be input to the laser irradiation device 500.
  • the magnetic domain refinement process is performed on the locations of the magnetic domain control processing line 52 of the grain-oriented electromagnetic steel sheet 50 determined in step S64 (step S66).
  • the control unit 513 of the laser irradiation device 500 controls the power of the laser beam LB to be turned on for the locations of the magnetic domain control processing line 52 where the magnetic domain refinement process is to be performed, and to be turned off for the other locations. This causes thermal distortion or grooves to be formed in the locations where the magnetic domain refinement process was performed.
  • the magnetic domain subdivision process of step S66 may be performed by irradiating a laser beam LB by the laser irradiation device 500 as described above, or other means such as irradiating an electron beam may be used.
  • FIG. 7 the areas of the magnetic domain control process line 52 (dashed line) where the magnetic domain subdivision process has been selectively (partially) applied are shown as magnetic domain subdivision process lines 54 (thick solid lines).
  • Figure 8 shows the results of measuring the iron loss W17/50 (W/kg) for grain-oriented electrical steel sheets 50 of various thicknesses t (mm) that have been selectively subjected to magnetic domain refinement.
  • Figure 9A shows the results of measuring the magnetostriction ⁇ versus magnetic flux density B when the grain-oriented electromagnetic steel sheet 50a selectively irradiated with a laser and the grain-oriented electromagnetic steel sheet 50b uniformly irradiated with a laser are subjected to AC excitation up to ⁇ 1.7 T.
  • Figure 9B shows the results of measuring the magnetostriction ⁇ versus magnetic flux density B when the grain-oriented electromagnetic steel sheet 50a and the grain-oriented electromagnetic steel sheet 50b are subjected to AC excitation up to ⁇ 1.9 T.
  • the magnetostriction is a value measured using a method specified in IEC 60404-17:2021.
  • "uniform laser irradiation over the entire surface” means that the entire magnetic domain control processing line 52 is uniformly irradiated with the laser.
  • the directional electromagnetic steel sheet 50a is selectively laser-irradiated, and therefore has a smaller amount of closure domains than the directional electromagnetic steel sheet 50b that is fully laser-irradiated, and therefore the amount of closure domains that disappear when the sample is excited by applying a high magnetic field is similarly smaller.
  • the peak-to-peak value of magnetostriction when AC excited to ⁇ 1.7 T will be denoted as ⁇ 1pp
  • the peak-to-peak value of magnetostriction when AC excited to ⁇ 1.9 T will be denoted as ⁇ 2pp.
  • Figure 10 shows the results of calculating the ratio of ⁇ 2pp to ⁇ 1pp ( ⁇ 2pp/ ⁇ 1pp) for 40 samples of grain-oriented electromagnetic steel sheets 50a that were selectively irradiated with a laser and for 40 samples of grain-oriented electromagnetic steel sheets 50b that were fully irradiated with a laser.
  • the horizontal axis in Figure 10 shows the sample number, with sample numbers 1 to 40 corresponding to grain-oriented electromagnetic steel sheets 50a and sample numbers 41 to 80 corresponding to grain-oriented electromagnetic steel sheets 50b.
  • the ⁇ 2pp/ ⁇ 1pp value of grain-oriented electromagnetic steel sheet 50a is significantly smaller than that of grain-oriented electromagnetic steel sheet 50b, and a reduction in the peak-to-peak value of magnetostriction at 1.9 T can be confirmed.
  • ⁇ 2pp/ ⁇ 1pp for grain-oriented electromagnetic steel sheet 50a is less than 2.2
  • ⁇ 2pp/ ⁇ 1pp for grain-oriented electromagnetic steel sheet 50b is 2.2 or greater.
  • the grain-oriented electromagnetic steel sheet that has been selectively subjected to magnetic domain refinement processing satisfies ⁇ 2pp/ ⁇ 1pp ⁇ 2.2.
  • the grain-oriented electrical steel sheet that has been selectively subjected to magnetic domain refinement has a relationship between sheet thickness t (mm) and iron loss W17/50 (W/kg) that satisfies W17/50 ⁇ 1.350t + 0.450, and the peak-to-peak magnetostriction ratio satisfies ⁇ 2pp/ ⁇ 1pp ⁇ 2.2.
  • the magnetic domain control strength in the magnetic domain refinement processing line 54 is preferably made non-uniform.
  • the magnetic domain control strength is the maximum value of the tensile strength introduced into the thermal distortion 541 when the magnetic domain control means is the thermal distortion 541, and is the maximum value of the depth of the groove 542 when the magnetic domain control means is the groove 542.
  • the "maximum value of tensile strength introduced into thermal strain 541" is the maximum value of tensile strength measured at any one measurement cross section. It should be noted here that the magnitude and direction of the tensile strength vary in one measurement cross section, and therefore one "maximum value of tensile strength introduced into thermal strain 541" is specified for one measurement cross section. As shown diagrammatically in FIG. 13, thermal strain 541 has a certain degree of spread in the cross section. The tensile strength is greatest at the site directly irradiated with the laser, and is small at sites away from that site. In other words, the measured value of tensile strength differs for each measurement site and measurement direction in the cross section. According to the tensile strength measurement method described below, the distribution and maximum value of tensile strength in the cross section can be derived.
  • the maximum value of the tensile strength introduced into the thermal strain 541 is a constant value throughout the entire magnetic domain refinement processing line 54.
  • the maximum value of the tensile strength introduced into the thermal strain in the magnetic domain refinement processing line is non-uniform for each tensile strength measurement point.
  • the maximum value of the tensile strength introduced into the thermal strain may be referred to simply as "tensile strength.”
  • the “maximum depth of groove 542" is the maximum depth of groove 542 at any one measurement point, measured by the method described below. As shown diagrammatically in FIG. 14, the depth of groove 542 is also not uniform at one measurement point. In general, the closer to the edge of the groove, the smaller the groove depth is. Therefore, one "maximum depth of groove 542" is identified for one measurement cross section.
  • the maximum depth of the groove 542 is a constant value throughout the magnetic domain refinement processing line 54.
  • the maximum depth of the groove 542 on the magnetic domain refinement processing line is non-uniform for each measurement point of the groove depth.
  • the maximum depth of the groove 542 may be simply referred to as the "groove depth.”
  • the magnetic domain control saturation strength is high at locations where the ⁇ angle is small. It is preferable to perform magnetic domain refinement processing with high magnetic domain control strength at locations where the ⁇ angle is small, and to perform magnetic domain refinement processing with low magnetic domain control strength at locations where the ⁇ angle is large. In this way, in a grain-oriented electromagnetic steel sheet that has been subjected to a magnetic domain refinement processing that selects the optimal magnetic domain control strength according to the size of the ⁇ angle, the magnetic domain control strength in the magnetic domain refinement processing line 54 becomes non-uniform. In a magnetic domain refinement processing line provided at a location where the ⁇ angle is large, the groove is shallow or the tensile strength introduced by thermal distortion is small.
  • the groove is deep or the tensile strength introduced by thermal distortion is large.
  • the iron loss of the grain-oriented electromagnetic steel sheet after magnetic domain control is further reduced.
  • the increase in hysteresis loss and the deterioration of noise characteristics of the grain-oriented electromagnetic steel sheet after magnetic domain control are further suppressed.
  • the grain-oriented electrical steel sheet satisfies ⁇ 2 ( TSm )>5.0, where TSm is the maximum value of the tensile strength in unit MPa introduced by the thermal strain, measured at each of a plurality of magnetic domain refinement points, which are the intersections of a plurality of imaginary lines set in parallel at intervals of 5 mm along the rolling direction of the grain-oriented electrical steel sheet and the magnetic domain refinement lines.
  • ⁇ 2 ( TSm ) is the variance of TSm .
  • the magnetic domain control strength is changed based on the magnetic domain width or the ⁇ 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.
  • Fig. 15 An example of a method for measuring TS m and ⁇ 2 (TS m ) is shown in Fig. 15.
  • the dashed lines in Fig. 15 are multiple imaginary lines VL set at 5 mm intervals in parallel along the rolling direction RD of the grain-oriented electrical steel sheet.
  • the X and O marks in Fig. 15 are intersections between the imaginary lines VL and thermal strain 541, which is the magnetic domain refinement treatment line. Note that the ⁇ angle at the location marked with the X mark is 2° or more, and the ⁇ angle at the location marked with the O mark is less than 2°. However, it is not necessary to take the ⁇ angle at the intersection into consideration when calculating ⁇ 2 (TS m ).
  • the rolling direction RD of the grain-oriented electromagnetic steel sheet is identified.
  • the rolling direction RD can be easily identified based on the roll marks on the surface of the grain-oriented electromagnetic steel sheet, the extension direction of the crystal grains, and the extension direction of the magnetic domains in the magnetic domain image.
  • imaginary lines VL are set parallel to the rolling direction RD of the grain-oriented electromagnetic steel sheet at intervals of 5 mm.
  • the intersections of the imaginary lines VL and the thermal distortion 541, which is the magnetic domain refinement processing line, are identified. If the thermal distortion 541 cannot be seen with the naked eye, the thermal distortion 541 is identified based on the magnetic domain image.
  • the shape of the measurement area is preferably a rectangle whose size along the rolling direction RD is 100 mm or more and whose size along the rolling perpendicular direction TD is 100 mm or more.
  • One side of the rectangle is preferably parallel to the rolling direction RD.
  • TS m is measured at all intersections in the measurement area, and the variance ⁇ 2 (TS m ) of TS m is calculated.
  • the tensile strength TS m introduced 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. 307-313.
  • the thermal strain 541 which is the magnetic domain control processing line
  • the grain-oriented electrical steel sheet 1 is cut through the magnetic domain control processing line and perpendicular to the magnetic domain control processing line. This cut surface is used as the measurement surface.
  • the cross section of the magnetic domain control processing line included in the measurement surface is analyzed by the EBSD Wilkinson method and the Cross Court manufactured by BLG Vantage, and the tensile strength component in any direction is extracted and its magnitude is measured.
  • the tensile strength components in the normal direction of the rolling surface, the direction parallel to the magnetic domain control processing line, and the direction perpendicular to the normal direction of the rolling surface and the magnetic domain control processing line can be extracted.
  • the variance ⁇ 2 (TS M ) of the maximum tensile strength values TS M determined at each of the multiple measurement points 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.”
  • the grain-oriented electrical steel sheet satisfies TS m ( ⁇ 2) > TS m ( ⁇ 2) .
  • TS m ( ⁇ 2) is the arithmetic mean value of the maximum tensile strength in unit MPa introduced by the thermal strain, measured at each of a plurality of magnetic domain refinement points, which are the intersections of a plurality of imaginary lines set at 5 mm intervals in parallel along the rolling direction of the grain-oriented electrical steel sheet and the magnetic domain refinement line, and where the ⁇ angle is less than 2°.
  • TS m ( ⁇ 2) is the arithmetic mean value of the maximum tensile strength in unit MPa introduced by the thermal strain, measured at each of the magnetic domain refinement points with a ⁇ angle of 2° or more.
  • Fig. 15 An example of a method for measuring TS m ( ⁇ 2) and TS m ( ⁇ 2) is shown in Fig. 15.
  • the marks X and O in Fig. 15 are the intersections of the imaginary line VL and the thermal distortion 541, which is the magnetic domain refining treatment line.
  • the ⁇ angle at the location marked with the mark X is 2° or more, and the ⁇ angle at the location marked with the mark O is less than 2°.
  • the intersections with a ⁇ angle of 2° or more and the intersections with a ⁇ angle of less than 2° are identified.
  • the maximum tensile strength TS m is identified at each of all intersections with a ⁇ angle of 2° or more, and the arithmetic average value of these values is calculated. This value is considered to be TS m ( ⁇ 2) .
  • the maximum tensile strength TS m is identified at each of all intersections with a ⁇ angle of less than 2°, and the arithmetic average value of these values is calculated. This value is considered to be TS m ( ⁇ 2) .
  • the method for measuring the maximum tensile strength TS m introduced into the thermal strain 541 at the intersection is as described above.
  • the grain-oriented electrical steel sheet preferably satisfies ⁇ 2 ( Dm )>3.0.
  • Dm is the depth of the grooves 542 in ⁇ m at the domain refinement points, which are the intersections of the domain refinement treatment lines and multiple imaginary lines set in parallel at intervals of 5 mm along the rolling direction of the grain-oriented electrical steel sheet.
  • ⁇ 2 ( Dm ) is the variance of Dm .
  • the magnetic domain control strength is changed based on the magnetic domain width or the ⁇ 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.
  • FIG. 16 An example of a method for measuring Dm and ⁇ 2 ( Dm ) is shown in Figure 16.
  • the dashed lines in Figure 16 are multiple imaginary lines VL set at 5 mm intervals in parallel along the rolling direction RD of the grain-oriented electrical steel sheet.
  • the X and O marks in Figure 16 are intersections between the imaginary lines VL and the grooves 542, which are magnetic domain refinement processing lines. Note that the ⁇ angle at the location marked with the X mark is 2° or more, and the ⁇ angle at the location marked with the O mark is less than 2°. However, it is not necessary to take the ⁇ angle at the intersection into consideration when calculating ⁇ 2 ( Dm ).
  • the rolling direction of the grain-oriented electrical steel sheet is identified.
  • imaginary lines VL are set parallel to the rolling direction RD of the grain-oriented electrical steel sheet at intervals of 5 mm.
  • the intersections of the imaginary lines VL and the magnetic domain refinement processing lines are identified. If the magnetic domain refinement processing lines are grooves 542, they are easy to see with the naked eye.
  • the shape of the measurement area is preferably a rectangle whose size along the rolling direction RD is 100 mm or more and whose size along the rolling perpendicular direction TD is 100 mm or more.
  • One side of the rectangle is preferably parallel to the rolling direction RD.
  • the method for measuring the maximum value D m of the groove depth is as follows. The measurement is performed using a white interference microscope Control GT-I manufactured by Bruker. The lens used is an objective 5x (numerical aperture 0.12, optical resolution 2.2 ⁇ m) with an internal 1x, a white LED as the light source, and a monochrome CCD (1200 ⁇ 1000 pixels) as the camera.
  • the pixel size is 1.37 ⁇ m, and after performing tilt correction by fitting to a least squares plane using analysis software Vision64 Map Premium 9.2, a Gaussian filter with a cutoff value of 2.5 mm is used to remove the waviness of long wavelengths and perform analysis. Note that the pixel size may be resampled to 10 ⁇ m as necessary during analysis. Also, any part that is clearly determined to be an abnormal point may be excluded from the analysis, and the type of lens, 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 performed.
  • the grain-oriented electrical steel sheet satisfies Dm ( ⁇ 2) > Dm ( ⁇ 2) .
  • Dm( ⁇ 2) is the arithmetic mean value of the maximum groove depth in ⁇ m measured at each of a plurality of magnetic domain refinement points, which are the intersections of a plurality of imaginary lines VL and magnetic domain refinement lines set in parallel at intervals of 5 mm along the rolling direction of the grain-oriented electrical steel sheet, and where the ⁇ angle is less than 2°.
  • Dm( ⁇ 2) is the arithmetic mean value of the maximum groove depth in ⁇ m measured at each of a plurality of magnetic domain refinement points, which are the intersections of a plurality of imaginary lines VL and magnetic domain refinement lines set in parallel at intervals of 5 mm along the rolling direction of the grain-oriented electrical steel sheet.
  • the magnetic domain control strength is high where the ⁇ angle is small, and low where the ⁇ angle is large. Therefore, the iron loss of the grain-oriented electrical steel sheet after magnetic domain control is further reduced. At the same time, 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.
  • Fig. 16 An example of a method for measuring TS m ( ⁇ 2) and TS m ( ⁇ 2) is shown in Fig. 16.
  • the marks X and O in Fig. 16 are the intersections of the imaginary line VL and the groove 542, which is the magnetic domain refining processing line.
  • the ⁇ angle at the location marked with the mark X is 2° or more, and the ⁇ angle at the location marked with the mark O is less than 2°.
  • the ⁇ angle at the intersection is measured to identify the intersections with a ⁇ angle of 2° or more and the intersections with a ⁇ angle of less than 2°.
  • the arithmetic average value of Dm at all intersections with a ⁇ angle of 2° or more is calculated and this is regarded as Dm ( ⁇ 2) .
  • the arithmetic average value of Dm at all intersections with a ⁇ angle of less than 2° is calculated and this is regarded as Dm ( ⁇ 2) .
  • the method for measuring the maximum groove depth Dm at the intersection is as described above.
  • magnetic domain refinement processing lines were provided according to the method in accordance with the flowchart shown in Figure 6.
  • an image acquisition device was used to acquire a magnetic domain image of the grain-oriented electrical steel sheet.
  • the computation unit of the analysis device used the line segment method or two-dimensional Fourier transform to derive the spatial distribution of the width of the 180° magnetic domain (magnetic domain width) from the magnetic domain image.
  • the locations where the magnetic domain width was 500 ⁇ m or more were determined as the locations to which the magnetic domain refinement processing was applied.
  • the magnetic domain control strength was set under the various conditions shown in Tables 1 and 2.
  • the SST iron loss W17/50 and ⁇ 2pp/ ⁇ 1pp of the various grain-oriented electrical steel sheets No. A1 to A5 and No. B1 to B5 thus obtained were measured.
  • the SST iron loss W17/50 is a value measured using a 100 mm wide single sheet testing machine specified in JIS C 2556:2015.
  • ⁇ 1pp is a value measured using a method specified in IEC 60404-17:2021, and as described above, is the peak-to-peak value of magnetostriction in the measurement results of magnetostriction ⁇ versus magnetic flux density B when grain-oriented electrical steel sheets are excited with AC up to ⁇ 1.7 T.
  • ⁇ 2pp is a value measured using a similar method, and as described above, is the peak-to-peak value of magnetostriction in the measurement results of magnetostriction ⁇ versus magnetic flux density B when grain-oriented electrical steel sheets are excited with AC up to ⁇ 1.9 T.
  • the noise and transformer iron loss W16/50 of Nos. A1-A5 and B1-B5 were also evaluated.
  • the method for evaluating the noise and transformer iron loss W16/50 was as follows. First, a three-phase transformer core was made by laminating 180 grain-oriented electromagnetic steel sheets with a thickness of 0.23 mm. The widths of the legs and yoke of the three-phase transformer core were both 150 mm. The external height and width of the three-phase transformer core were both 750 mm. The noise and iron loss of these three-phase transformer cores were measured. The measurement conditions were a frequency of 50 Hz and an excitation magnetic flux density of 1.6 T.
  • noise evaluation results (unit: dBA) for the grain-oriented electrical steel sheet. Examples with a noise evaluation result of 25.5 dBA or less were determined to be examples in which low noise had been achieved.
  • the iron loss of the three-phase transformer was determined by using a power analyzer to measure the voltage and current on the primary and secondary sides when excitation was performed at a frequency of 50 Hz and an excitation flux density of 1.6 T as described above.
  • the determined iron loss is shown in Table 2 as the iron loss evaluation results (units: W/kg) of the three-phase transformer. Examples where the evaluation result of the transformer iron loss W16/50 was 0.770 W/kg or less were determined to be examples where low iron loss had been achieved.
  • No. A1 met the requirements of W17/50 ⁇ 1.350t+0.450 and ⁇ 2pp/ ⁇ 1pp ⁇ 2.2, and therefore showed better iron loss and noise evaluation results than conventional grain-oriented electrical steel sheets.
  • No. A2 not only satisfied W17/50 ⁇ 1.350t+0.450 and ⁇ 2pp/ ⁇ 1pp ⁇ 2.2, but also the maximum value of the tensile strength introduced by the thermal strain in the magnetic domain refinement wire was non-uniform at each tensile strength measurement point.
  • the evaluation results of the iron loss and noise of No. A2 were even better than those of No. A1.
  • No. A3 satisfied W17/50 ⁇ 1.350t+0.450 and ⁇ 2pp/ ⁇ 1pp ⁇ 2.2, and also satisfied ⁇ 2 ( TSm )>5.0.
  • the evaluation results of iron loss and noise of No. A3 were even better than those of No. A1 and No. A2.
  • No. A4 satisfied W17/50 ⁇ 1.350t+0.450 and ⁇ 2pp/ ⁇ 1pp ⁇ 2.2, and also satisfied TSm ( ⁇ 2) >TSm ( ⁇ 2) .
  • the evaluation results of iron loss and noise of No. A4 were better than those of No. A1 and No. A2.
  • No. A5 satisfied W17/50 ⁇ 1.350t+0.450 and ⁇ 2pp/ ⁇ 1pp ⁇ 2.2, and also ⁇ 2 ( TSm )>5.0 and TSm ( ⁇ 2) >TSm ( ⁇ 2) .
  • the evaluation results of iron loss and noise of No. A5 were the best among Nos. A1 to A5.
  • No. B1 satisfied the requirements of W17/50 ⁇ 1.350t+0.450 and ⁇ 2pp/ ⁇ 1pp ⁇ 2.2, and therefore showed better iron loss and noise evaluation results than conventional grain-oriented electrical steel sheets.
  • No. B2 not only satisfied W17/50 ⁇ 1.350t+0.450 and ⁇ 2pp/ ⁇ 1pp ⁇ 2.2, but also had non-uniform maximum groove depths at each measurement point.
  • the iron loss and noise evaluation results for No. B2 were even better than those for No. B1.
  • No. B3 satisfied W17/50 ⁇ 1.350t+0.450 and ⁇ 2pp/ ⁇ 1pp ⁇ 2.2, and also satisfied ⁇ 2 ( Dm )>3.0.
  • the evaluation results of iron loss and noise of No. B3 were even better than those of No. B1 and No. B2.
  • No. B4 satisfied W17/50 ⁇ 1.350t+0.450 and ⁇ 2pp/ ⁇ 1pp ⁇ 2.2, and also Dm ( ⁇ 2) >Dm ( ⁇ 2) .
  • the evaluation results of iron loss and noise of No. B4 were better than those of No. B1 and No. B2.
  • No. B5 satisfied W17/50 ⁇ 1.350t+0.450 and ⁇ 2pp/ ⁇ 1pp ⁇ 2.2, as well as ⁇ 2 ( Dm )>3.0 and Dm ( ⁇ 2) >Dm ( ⁇ 2) .
  • the evaluation results of iron loss and noise of No. B5 were the best among Nos. B1 to B5.
  • No. C1 to No. C8 in Table 3 were manufactured by the following procedure. First, the distribution of secondary recrystallized grains in the grain-oriented electrical steel sheet in which secondary recrystallized grains were formed before the magnetic domain control treatment was identified. The distribution of secondary recrystallized grains was identified by photographing the above-mentioned magnetic domain image while the steel sheet was magnetized in the rolling direction and observing it. Then, in the examples of No. C1 to C4, magnetic domain refinement lines were formed by laser irradiation or groove formation only in the region within ⁇ 6 mm from the center of the rolling direction of the secondary recrystallized grains in the rolling direction RD. In the examples of No.
  • magnetic domain refinement lines were formed by laser irradiation or groove formation only in the region within ⁇ 10 mm from the center of the rolling direction of the secondary recrystallized grains in the rolling direction RD.
  • the domain refinement processing lines 54 were provided along the domain control processing lines 52 as shown in FIG. 7.
  • the domain control processing lines 52 extended in a direction substantially perpendicular to the rolling direction RD. Furthermore, multiple domain control processing lines 52 were provided repeatedly in the rolling direction. The spacing between the domain control processing lines 52 along the rolling direction was 4 mm. In Nos. C1 to C4, the number of domain control processing lines 52 was four. In Nos. C5 to C8, the number of domain control processing lines 52 was six.
  • the SST iron loss W17/50 and ⁇ 2pp/ ⁇ 1pp of No. C1 to C8 obtained by the above procedure were measured.
  • the measurement procedure was as described above.
  • SST iron loss W17/50 that does not satisfy W17/50 ⁇ 1.350t + 0.450 and ⁇ 2pp/ ⁇ 1pp that does not satisfy ⁇ 2pp/ ⁇ 1pp ⁇ 2.2 are underlined.
  • transformer iron loss W16/50 and noise of No. C1 to C8 were also measured using the above-mentioned procedure. Examples with a noise evaluation result of 25.5 dBA or less were judged to be examples in which low noise had been achieved. Additionally, examples with a transformer iron loss W16/50 evaluation result of 0.770 W/kg or less were judged to be examples in which low iron loss had been achieved. Noise evaluation results and iron loss evaluation results that were judged to be unsatisfactory are underlined.
  • Nos. C5 to C8 had a larger number of magnetic domain control processing lines, so iron loss was suppressed compared to Nos. C1 to C4. However, the transformer iron loss W16/50 of Nos. C5 to C8 was judged to be unacceptable. Furthermore, in Nos. C5 to C8, the magnetostrictive waveform in a high magnetic field (near 1.9 T) due to the closure magnetic domain became significantly larger, and ⁇ 2pp/ ⁇ 1pp ⁇ 2.2 was not met. The noise of Nos. C5 to C8 was judged to be unacceptable.
  • 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 50: Grain-oriented electromagnetic steel sheet 52: Magnetic domain control processing line 54: Magnetic domain refinement processing line 500: Laser irradiation device

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