Groove processing method of grain-oriented magnetic steel sheet, groove processing apparatus of grain-oriented magnetic steel sheet, grain-oriented magnetic steel sheet, wound core, and method for manufacturing wound core

Abstract

A method for slotting a directional electromagnetic steel sheet includes: a first irradiation step in which a first beam is irradiated onto the surface of the directional electromagnetic steel sheet under first irradiation conditions that enable the formation of a linear slot extending in a direction corresponding to the width direction of the directional electromagnetic steel sheet; and a second irradiation step in which a second beam is irradiated onto the surface of the directional electromagnetic steel sheet along the slot under second irradiation conditions different from the first irradiation conditions, wherein the directional electromagnetic steel sheet undergoes final annealing, and the second irradiation conditions are irradiation conditions corresponding to heat treatment conditions that enable the application of a predetermined heat treatment to a portion of the directional electromagnetic steel sheet within a specified range from the surface of the slot.

Description

Technical Field

[0001] This disclosure relates to a method for processing grooves in a directional electromagnetic steel sheet, an apparatus for processing grooves in a directional electromagnetic steel sheet, a directional electromagnetic steel sheet, a wound iron core, and a method for manufacturing the wound iron core. Background Technology

[0002] As an example of a manufacturing method for directional electromagnetic steel sheets, there is a method comprising the following steps: casting, hot rolling, annealing, cold rolling, decarburization annealing, annealing separation coating, final annealing, insulating film formation, groove formation, and re-insulating film formation. In the groove formation step, periodic grooves are formed on the directional electromagnetic steel sheet using a laser beam. In the re-insulating film formation step, a tension-imparting film is formed, thereby subdividing the magnetic domains of the directional electromagnetic steel sheet.

[0003] While the above manufacturing method requires two insulation coating processes—an insulation coating formation process and a second insulation coating formation process—it excels in improving the stability of iron loss and preventing the adhesion of molten material. However, when manufacturing the wound core of a transformer from a directional electromagnetic steel sheet produced by the above method, a problem arises where iron loss deteriorates during the stress-relief annealing process following the winding of the directional electromagnetic steel sheet. This problem is believed to arise because the strain generated around the groove during the laser beam forming process creates subgrain boundaries around the groove during the stress-relief annealing process.

[0004] Therefore, as a countermeasure to suppress iron loss degradation during the stress-relief annealing process, the following technologies have been proposed. For example, Japanese Patent No. 7031364 (Patent Document 1) discloses a method to suppress the formation of subgrain boundaries by performing a heat treatment on the steel plate at a temperature of 1000°C or higher and 1100°C or lower after the groove forming process. Additionally, Japanese Patent No. 6614398 (Patent Document 2) discloses a method to suppress the formation of subgrain boundaries by adjusting the cooling rate during the re-insulating coating forming process to make the KAM (Kernel Average Misorientation) value at the periphery of the groove 0.1 or higher and 3.0 or lower. Furthermore, International Publication No. 2022 / 045264 (Patent Document 3) discloses a method to suppress iron loss degradation by linearly irradiating the surface of the steel plate with a ring-shaped intensity distribution, where the periphery is lower than the center, along a direction intersecting the rolling direction during the groove forming process.

[0005] Furthermore, Japanese Patent Application Publication No. 2012-126995 (Patent Document 4) discloses a method in which, in the case of magnetic domain refinement treatment by irradiating the surface of a directional electromagnetic steel sheet after final annealing with an electron beam, thermal strain is introduced by irradiating the electron beam multiple times. Additionally, International Patent Publication No. 2024 / 111642 (Patent Document 5) discloses a method in which, in the groove forming process between the cold rolling process and the final annealing process, in the first stage, a laser beam is irradiated onto the surface of the steel sheet to form a groove, and a protrusion is formed on the side or bottom of the groove. Then, in the first stage, a laser beam is irradiated onto the same area as the area irradiated in the first stage, thereby making the average crystal orientation of the protrusion differ from the Goss orientation by 10 degrees or more. Summary of the Invention

[0006] The problem that the invention aims to solve In the method described in Patent Document 1, after the groove forming process, the entire steel plate needs to undergo additional heat treatment to suppress the formation of subgrain boundaries, thus reducing production efficiency. Furthermore, in the method described in Patent Document 2, the cooling rate needs to be adjusted to regulate the KAM value around the groove, further reducing production efficiency. Additionally, in the method described in Patent Document 3, it is difficult to control the application of a laser beam with a ring-shaped intensity distribution to the surface of the steel plate, resulting in reduced production stability. Moreover, in the methods described in Patent Documents 4 and 5, no countermeasures are taken to address the situation where subgrain boundaries are formed around the groove during the stress-relief annealing process due to strain generated around the groove during groove forming with a laser beam.

[0007] This disclosure provides a method for processing grooves in a directional electromagnetic steel plate, a device for processing grooves in a directional electromagnetic steel plate, a directional electromagnetic steel plate, a wound iron core, and a method for manufacturing a wound iron core. Even when manufacturing a wound iron core, the iron loss will not deteriorate, and production efficiency and production stability can be improved.

[0008] Methods for solving problems The first aspect of this disclosure is a method for processing grooves in a directional electromagnetic steel sheet. The method involves processing grooves on the surface of the directional electromagnetic steel sheet, comprising: a first irradiation step, in which a first beam is irradiated onto the surface of the directional electromagnetic steel sheet under first irradiation conditions that enable the formation of a linear groove extending in a direction corresponding to the width direction of the directional electromagnetic steel sheet; and a second irradiation step, in which a second beam is irradiated onto the surface of the directional electromagnetic steel sheet along the groove under second irradiation conditions different from the first irradiation conditions, wherein the directional electromagnetic steel sheet undergoes final annealing, and the second irradiation conditions are irradiation conditions corresponding to heat treatment conditions that allow a predetermined heat treatment to be applied to a portion of the directional electromagnetic steel sheet within a predetermined range from the surface of the groove.

[0009] Regarding the second aspect of this disclosure, in the groove processing method of the directional electromagnetic steel plate of the first aspect, the heat treatment conditions are heat treatment conditions that eliminate strain within the portion of the steel plate.

[0010] Regarding the third aspect of this disclosure, in the groove processing method of the directional electromagnetic steel plate of the first or second aspect, the power density of the second beam is lower than that of the first beam.

[0011] Regarding the fourth aspect of this disclosure, in the groove processing method of the directional electromagnetic steel plate in any of the first to third aspects, the center of the second beam corresponds to the center of the first beam.

[0012] Regarding the fifth aspect of this disclosure, in the method for processing grooves in a directional electromagnetic steel plate according to any of the first to fourth aspects, the first irradiation step uses a fiber laser device, and the second irradiation step uses a semiconductor laser device, which, compared with the fiber laser device, outputs a laser beam with a high absorption rate and a short wavelength from the steel plate.

[0013] Regarding the sixth aspect of this disclosure, in the method for processing the groove of the directional electromagnetic steel plate in any of the first to fifth aspects, the heat treatment conditions are: the temperature in the range from the opening edge of the groove, the side surface of the groove and the bottom surface of the groove to 10 μm is maintained at 1000°C or higher for 0.1 msec or more, and the temperature in the range is maintained below 1600°C.

[0014] Regarding the seventh aspect of this disclosure, in the method for processing the groove of the directional electromagnetic steel plate in any of the first to sixth aspects, the first irradiation step and the second irradiation step are performed when the directional electromagnetic steel plate is being transported.

[0015] The eighth aspect of this disclosure is a groove processing apparatus for a directional electromagnetic steel sheet, which grooves the surface of the directional electromagnetic steel sheet. The groove processing apparatus comprises: a first irradiation unit that irradiates the surface of the directional electromagnetic steel sheet with a first beam under a first irradiation condition that enables the formation of a linear groove extending in a direction corresponding to the width direction of the directional electromagnetic steel sheet; and a second irradiation unit that irradiates the surface of the directional electromagnetic steel sheet with a second beam along the groove under a second irradiation condition different from the first irradiation condition, wherein the directional electromagnetic steel sheet has undergone final annealing, and the second irradiation condition is an irradiation condition corresponding to a heat treatment condition that enables the application of a predetermined heat treatment to a portion of the directional electromagnetic steel sheet within a predetermined range from the surface of the groove.

[0016] Regarding the ninth aspect of this disclosure, in the groove processing apparatus for the directional electromagnetic steel plate of the eighth aspect, the heat treatment conditions are heat treatment conditions that eliminate strain within the portion of the steel plate.

[0017] Regarding the tenth aspect of this disclosure, in the groove processing apparatus for the directional electromagnetic steel plate of the eighth or ninth aspect, the first irradiation unit and the second irradiation unit operate when the directional electromagnetic steel plate is being transported.

[0018] Regarding the eleventh aspect of this disclosure, in the groove processing apparatus for the directional electromagnetic steel plate of any one of the eighth to tenth aspects, the distance between the first irradiation part and the second irradiation part is set to a length that is a natural multiple of the spacing of the grooves.

[0019] The twelfth aspect of this disclosure is a directional electromagnetic steel sheet having linear grooves, and a coating covering a portion of the steel sheet extending from a predetermined distance from the grooves having a modified portion.

[0020] Regarding the thirteenth aspect of this disclosure, in the directional electromagnetic steel plate of the twelfth aspect, the KAM value of the steel plate portion within a specified range from the surface of the groove is 0.1 or more and 3.0 or less.

[0021] The fourteenth aspect of this disclosure is a wound iron core formed from a directional electromagnetic steel plate having linear grooves, and a coating covering a portion of the steel plate extending from a predetermined distance from the grooves having a modified portion.

[0022] The fifteenth aspect of this disclosure is a method for manufacturing a wound iron core, comprising: a directional electromagnetic steel sheet manufacturing step, manufacturing a directional electromagnetic steel sheet; a wound iron core forming step, forming a wound iron core from the directional electromagnetic steel sheet; and a stress-relief annealing step, performing stress-relief annealing treatment on the wound iron core. The directional electromagnetic steel sheet manufacturing step includes a groove processing step for processing grooves on the surface of the directional electromagnetic steel sheet. The groove processing step includes: a first irradiation step, under first irradiation conditions forming a linear groove extending in a direction corresponding to the width direction of the directional electromagnetic steel sheet, irradiating the surface of the directional electromagnetic steel sheet with a first beam; and a second irradiation step, along the groove, under second irradiation conditions different from the first irradiation conditions, irradiating the surface of the directional electromagnetic steel sheet with a second beam, wherein the directional electromagnetic steel sheet undergoes final annealing, and the second irradiation conditions are irradiation conditions corresponding to heat treatment conditions that can apply a predetermined heat treatment to a portion of the directional electromagnetic steel sheet within a predetermined range from the surface of the groove.

[0023] Invention Effects According to this disclosure, a method for processing grooves in a directional electromagnetic steel plate, a device for processing grooves in a directional electromagnetic steel plate, a directional electromagnetic steel plate, a wound iron core, and a method for manufacturing a wound iron core are provided. Even when manufacturing a wound iron core, the iron loss will not deteriorate, and production efficiency and production stability can be improved. Attached Figure Description

[0024] Figure 1 These are two-view drawings illustrating an embodiment of the groove processing apparatus and an example of a steel plate as the object of processing according to the present disclosure.

[0025] Figure 2 This is a cross-sectional view showing an example of a region on the surface of a steel plate that is irradiated by a second laser beam.

[0026] Figure 3 This is a diagram illustrating the first example of a manufacturing method for directional electromagnetic steel sheets.

[0027] Figure 4 This is a second example of a method for manufacturing directional electromagnetic steel sheets.

[0028] Figure 5 This is a graph showing the results obtained by comparing the iron loss improvement rate between the example and the comparative example of this disclosure.

[0029] Figure 6 This is a schematic diagram of the cross-section of the periphery of the groove of the wound core after the stress-relief annealing process in the examples and comparative examples of this disclosure.

[0030] Figure 7 This is a diagram illustrating an example of a method for manufacturing a wound iron core according to one embodiment of the present disclosure.

[0031] Figure 8 This is a diagram illustrating an example of the temperature distribution along the width of a steel plate obtained through heat transfer calculations.

[0032] Figure 9 This is a diagram showing an example of the temperature distribution along the thickness of a steel plate calculated using heat transfer methods.

[0033] Figure 10 This is a diagram illustrating an example of irradiation conditions for a second laser beam that satisfy the heat treatment conditions obtained from heat transfer calculations.

[0034] Figure 11 This is a cross-sectional view showing a first example of the cross-sectional structure of a directional electromagnetic steel plate according to an embodiment of the present disclosure.

[0035] Figure 12 This is a cross-sectional view showing a first example of the cross-sectional structure of a directional electromagnetic steel plate according to an embodiment of the present disclosure.

[0036] Figure 13This is a cross-sectional view showing an example of the cross-sectional structure of a comparative example of a directional electromagnetic steel sheet. Detailed Implementation

[0037] Hereinafter, one embodiment of the present disclosure will be described.

[0038] Figure 1 This section illustrates an example of a groove processing apparatus 10 and a steel plate 30 as the processing target, according to one embodiment of the present disclosure. The groove processing apparatus 10 is a device described below: In the groove forming process of a method for manufacturing directional electromagnetic steel sheets, for the purpose of magnetic domain control (i.e., magnetic domain refinement), a plurality of grooves 32 extending in directions intersecting the conveying direction are formed at predetermined intervals along the conveying direction on the surface of the steel plate 30, which is being conveyed along the conveying direction indicated by arrow X. The conveying direction is a direction substantially parallel to the long side direction (i.e., the rolling direction) of the steel plate 30. The groove processing apparatus 10 includes a first laser beam irradiation unit 12, a second laser beam irradiation unit 14, and a control unit 16.

[0039] The first laser beam irradiation unit 12 and the second laser beam irradiation unit 14 output laser beams under the control of the control unit 16. Specifically, the first laser beam irradiation unit 12 outputs a first laser beam L1, and the second laser beam irradiation unit 14 outputs a second laser beam L2. The first laser beam irradiation unit 12 is an example of a "first irradiation unit" in this disclosure, and the second laser beam irradiation unit 14 is an example of a "second irradiation unit" in this disclosure. Furthermore, the first laser beam L1 is an example of a "first beam" in this disclosure, and the second laser beam L2 is an example of a "second beam" in this disclosure.

[0040] Under first irradiation conditions, the first laser beam irradiation section 12 irradiates the surface of the steel plate 30 with a first laser beam L1, which forms a linear groove 32 extending in a direction corresponding to the width direction of the steel plate 30 (a predetermined first direction). Here, the steel plate 30 is a directional electromagnetic steel plate that has undergone final annealing, for example, equivalent to an insulating coating formation process (see [reference]). Figure 3 The directional electromagnetic steel sheet after the final annealing process (refer to...) Figure 4The directional electromagnetic steel plate after ( ). Furthermore, the direction corresponding to the width direction of the steel plate 30 refers to a direction that is approximately parallel to the width direction. Additionally, a direction approximately parallel to the width direction is a direction intersecting the conveying direction, meaning a direction that intersects the width direction of the steel plate 30 at a specified angle. For example, the specified angle refers to an angle within ±30 degrees relative to the width direction (i.e., -30° ≤ specified angle ≤ +30°). The depth of the groove 32 is, for example, 10 μm to 30 μm. Here, if the steel plate 30 has a coating (e.g., glass coating or insulating coating), the depth of the groove 32 refers to the depth including the coating. Furthermore, the steel plate 30 mentioned in this specification, if it does not have a glass coating, insulating coating, or other coating, refers only to the steel plate portion 30A (see reference ). Figure 2 If a coating is present, it includes the steel plate portion 30A and the coating. The steel plate portion 30A has a specified thickness, and the coating is disposed on the surface of at least one side (at least one side of the two sides in the thickness direction) of the steel plate portion 30A. Additionally, for simplicity, Figure 2 This indicates that the steel plate 30 is not coated.

[0041] The second laser beam irradiation unit 14 irradiates the surface of the steel plate 30 with a second laser beam L2 along the groove 32 under a second irradiation condition different from the first irradiation condition. The second laser beam irradiation unit 14 irradiates the second laser beam L2 in such a way that the irradiated area of ​​the irradiated second laser beam L2 overlaps with at least a portion of the surface of the groove 32. The second laser beam irradiation unit 14 irradiates the surface of the steel plate 30 with the second laser beam L2 along the scanning path of the first laser beam irradiation unit 12 on the steel plate 30. Here, the second irradiation condition corresponds to the heat treatment condition that allows a predetermined heat treatment to be applied to the steel plate portion 30A within a defined range from the surface of the groove 32. The heat treatment condition is a heat treatment condition that eliminates strain within the steel plate portion 30A surrounding the groove 32 generated during the formation of the groove 32. The heat treatment condition is a condition in which the steel plate 30 is heated to a temperature above the temperature required for heat treatment within a range where the steel plate 30 has not melted. The elimination of strain includes not only complete elimination of strain but also the degree to which strain is suppressed to the point that subgrain boundaries generated during the stress-relief annealing process will not become a problem.

[0042] The heat treatment conditions are, for example, as follows: the temperature in a range of 10 μm from the opening edge of the groove 32, the side surface of the groove 32, and the bottom surface of the groove 32 is maintained at 1000°C or higher for at least 0.1 ms, and the temperature in the aforementioned range is maintained at 1600°C or lower, as will be described later. The range of 10 μm from the opening edge of the groove 32, the side surface of the groove 32, and the bottom surface of the groove 32 is an example of the specified range to which the aforementioned heat treatment is to be applied. The range from the opening edge of the groove 32 to 10 μm refers to the range on one side of the groove 32 in the width direction. The second irradiation conditions may not be equal to the heat treatment conditions, or they may be set based on the heat treatment conditions. Furthermore, the second irradiation conditions may also be set based on heat transfer calculations or experiments, etc.

[0043] Here, use Figure 1 The scanning paths of the first laser beam irradiation unit 12 and the second laser beam irradiation unit 14 will be explained below. The first laser beam irradiation unit 12 irradiates the surface of the steel plate 30 with the first laser beam L1 while moving in the direction indicated by arrow Y1. The second laser beam irradiation unit 14 irradiates the surface of the steel plate 30 with the second laser beam L2 while moving in the direction indicated by arrow Y2. That is, the second laser beam irradiation unit 14 irradiates the surface of the steel plate 30 with the second laser beam L2 along the path (arrow Y1) from the first laser beam irradiation unit 12 irradiating the first laser beam L1 onto the surface of the steel plate 30. The moving directions of the first laser beam L1 and the second laser beam L2 are the same, and are approximately parallel to the width direction of the steel plate 30.

[0044] The first laser beam irradiation unit 12 includes a first laser source serving as a laser source for outputting a first laser beam L1, and a first moving mechanism serving as a moving mechanism for moving the first laser beam L1. The first moving mechanism includes, for example, a polygon mirror and a motor for rotating the polygon mirror. Similarly, the second laser beam irradiation unit 14 includes a second laser source serving as a laser source for outputting a second laser beam L2, and a second moving mechanism serving as a moving mechanism for moving the second laser beam L2. The second moving mechanism includes, for example, a polygon mirror and a motor for rotating the polygon mirror. Furthermore, the groove processing apparatus 10 may include a polygon mirror and a motor shared by the first laser beam irradiation unit 12 and the second laser beam irradiation unit 14, and may also include different polygon mirrors and motors as moving mechanisms for moving the first laser beam L1 and the second laser beam L2. Additionally, when the first laser beam irradiation unit 12 and the second laser beam irradiation unit 14 each include a polygon mirror and a motor, the moving speeds of the first laser beam L1 and the second laser beam L2 may be the same or different. Furthermore, at least one of the first laser beam irradiation unit 12 and the second laser beam irradiation unit 14 may also have a structure other than a multifaceted mirror (e.g., a galvano mirror).

[0045] Furthermore, the first laser beam irradiation unit 12 and the second laser beam irradiation unit 14 preferably irradiate the first laser beam L1 and the second laser beam L2 during the conveying of the steel plate 30, but they can also irradiate the first laser beam L1 and the second laser beam L2 when the steel plate 30 is stopped. Additionally, the first laser beam irradiation unit 12 and the second laser beam irradiation unit 14 can irradiate the first laser beam L1 and the second laser beam L2 in the same direction, or they can irradiate the first laser beam L1 and the second laser beam L2 in different directions. Furthermore, the second laser beam irradiation unit 14 preferably irradiates the second laser beam L2 continuously along the scanning path of the first laser beam irradiation unit 12 on the steel plate 30, but it can also irradiate a slot 32 intermittently along the length of the slot 32, or selectively (e.g., every other slot) irradiate multiple slots 32.

[0046] The first laser beam irradiation unit 12 is positioned upstream of the second laser beam irradiation unit 14 in the conveying direction. The groove processing apparatus 10 forms a linear groove 32 extending in a direction substantially parallel to the width direction by irradiating the surface of the steel plate 30 with a first laser beam L1 from the first laser beam irradiation unit 12. The second laser beam L2 is irradiated from the second laser beam irradiation unit 14 in a manner that traces (tracks) the groove 32, thereby applying heat treatment to the steel plate portion 30A surrounding the groove 32. Hereinafter, the irradiation area of ​​the first laser beam L1 focused on the surface of the steel plate 30 is referred to as the "first focusing point S1", and the irradiation area of ​​the second laser beam L2 focused on the surface of the steel plate 30 is referred to as the "second focusing point S2". In addition, the area irradiated by the second laser beam L2 is referred to as the "second laser beam irradiation area 34", and the area that has undergone heat treatment by irradiating the second laser beam L2 from the second laser beam irradiation unit 14 under the second irradiation conditions corresponding to the above-described heat treatment conditions is referred to as the "heat treatment area 36".

[0047] To ensure that the irradiation areas of the first laser beam irradiation unit 12 and the second laser beam irradiation unit 14 overlap, it is preferable that the distance between the first laser beam irradiation unit 12 and the second laser beam irradiation unit 14 is set to a length that is a natural multiple of the spacing between the slots 32. The distance between the first laser beam irradiation unit 12 and the second laser beam irradiation unit 14 is defined by the distance between the centers of the first laser beam L1 and the second laser beam L2. When the distance between the first laser beam irradiation unit 12 and the second laser beam irradiation unit 14 is set to a length that is a natural multiple of the spacing between the slots 32, the structure of the slot processing apparatus 10 can be simplified compared to cases where the distance is set to a length other than a natural multiple of the spacing between the slots 32. When the first laser beam irradiation unit 12 and the second laser beam irradiation unit 14 share a polygon mirror, the distance between the first laser beam irradiation unit 12 and the second laser beam irradiation unit 14 is set to a length that is a natural multiple of the spacing between the slots 32, relative to the width of the polygon mirror having a rotation axis approximately parallel to the transport direction.

[0048] For example, in the first laser source serving as the laser source of the first laser beam irradiation section 12, a fiber laser device with high focusing characteristics can be used as the laser beam irradiation device suitable for forming the groove 32. Furthermore, in the second laser source serving as the laser source of the second laser beam irradiation section 14, a semiconductor laser device that can output laser light with a higher absorptivity and shorter wavelength than a fiber laser device can be used as the laser beam irradiation device suitable for heat treatment around the groove 32.

[0049] Figure 2 An example of a second laser beam irradiation region 34 on the surface of the steel plate 30, irradiated by the second laser beam L2, is shown. The groove 32 has a side surface 32B connected to an opening edge 32A that forms the boundary between the surface of the steel plate 30 and the groove 32 (recess), and a bottom surface 32C connected to the side surface 32B. The side surface 32B is connected to the surface of the steel plate 30 (region 32A1) via the opening edge 32A. That is, the surface of the groove 32 includes the side surface 32B and the bottom surface 32C. More specifically, the second laser beam irradiation region 34 is a region that includes the region 32A1 adjacent to the opening edge 32A, the side surface 32B of the groove 32, and the bottom surface 32C of the groove 32. In other words, the second laser beam irradiation region 34 overlaps with the groove 32 and has a longer width on both sides in the transport direction compared to the groove 32.

[0050] However, typically, when a laser beam is irradiated onto the surface of the steel plate 30 to form a groove 32, strain will occur around the groove 32 during the formation of the groove 32. Figure 2An example of a strain-generating region (hereinafter referred to as "strain generation region 38") in the periphery of the groove 32 is shown. In the case of manufacturing the wound core of a transformer from directional electromagnetic steel sheets, there is a problem of iron loss deterioration during the stress-relief annealing process performed after the directional electromagnetic steel sheets are wound and formed. This problem is believed to arise because the strain generated in the strain generation region 38 when the groove 32 is formed using a laser beam causes subgrain boundaries to form around the groove 32 during the stress-relief annealing process.

[0051] Therefore, in addition to a first laser beam irradiation unit 12 that irradiates a first laser beam L1 for forming the groove 32, the groove processing apparatus 10 also includes a second laser beam irradiation unit 14 that irradiates a second laser beam L2 for heat treatment (i.e., high-temperature stress-relieving annealing heat treatment) of the strain-generating region 38 to eliminate strain. That is, the groove processing apparatus 10 is configured to irradiate the surface of the steel plate 30 with a first laser beam L1 as the main beam for forming the groove 32 and a second laser beam L2 as the auxiliary beam for heat treatment of the strain-generating region 38.

[0052] By irradiating the strain-generating region 38 with a second laser beam L2 under specified conditions, the strain generated in the strain-generating region 38 can be eliminated. By eliminating the strain generated in the strain-generating region 38, the formation of subgrain boundaries around the groove 32 during the stress-relieving annealing process after the winding and forming of the directional electromagnetic steel sheet can be suppressed. In order to eliminate the strain generated around the groove 32, the heat-treated region 36 subjected to heat treatment by irradiating the second laser beam L2 preferably includes the strain-generating region 38.

[0053] The heat treatment conditions for the strain-generating region 38 can be set by adjusting the power density and energy density of the second laser beam L2. Here, power density refers to the power input per unit area from the second laser beam irradiation section 14 onto the surface of the steel plate 30, and is the value obtained by dividing the output power of the second laser beam L2 by the area of ​​the second focusing point S2, with units of W / mm². Energy density is the heat input per unit time, and is the value obtained by multiplying the power density by the irradiation time, with units of J / mm². Irradiation time is the value obtained by dividing the beam diameter in the plate width direction by the moving speed. In other words, the second irradiation conditions of the second laser beam irradiation section 14 can be set by adjusting the output power of the second laser beam L2, the irradiation time, and the area of ​​the second focusing point S2.

[0054] The second laser beam irradiation unit 14 irradiates the area 38 surrounding the groove 32 to perform heat treatment. Meanwhile, the first laser beam irradiation unit 12 irradiates the area to form the groove 32. Therefore, the second laser beam irradiation unit 14 irradiates at a lower power density than the first laser beam irradiation unit 12 requires to form the groove. That is, the power density of the second laser beam L2 is lower than the power density of the first laser beam L1.

[0055] For example, even if the output power of the first laser beam L1 is the same as the output power of the second laser beam L2, in order to irradiate with a lower power density than the first laser beam irradiation unit 12, the second laser beam irradiation unit 14 can be adjusted by setting the area of ​​the second focusing point S2 to be larger than the area of ​​the first focusing point S1. Furthermore, as mentioned above, energy density is the value obtained by multiplying power density by irradiation time; therefore, to obtain the desired energy density, the power density can be reduced by extending the irradiation time. Therefore, the second laser beam irradiation unit 14 can also set the shape of the second focusing point S2 to have a long axis, and set the scanning direction of the second laser beam L2 to be the same as the long axis direction of the second focusing point S2, thereby increasing the irradiation time. That is, the length of the steel plate 30 of the second focusing point S2 in the width direction can also be set to be longer than that of the first focusing point S1.

[0056] Furthermore, the length of the heat-treated region 36, which is subjected to heat treatment by irradiation with the second laser beam L2, in the conveying direction of the steel plate 30 (the direction perpendicular to the plate width direction) is preferably the same as or greater than the strain-generating region 38, which includes the region containing the strain generated when the groove 32 is formed. Therefore, the length of the second focusing point S2 in the conveying direction of the steel plate 30 is preferably set to be longer than that of the first focusing point S1.

[0057] Furthermore, to eliminate the strain generated around the periphery of the groove 32, it is preferable that the beam diameter of the second laser beam L2 irradiating the periphery of the groove 32 is larger than the beam diameter of the first laser beam L1 forming the groove 32. Therefore, the second laser beam irradiation section 14 irradiates the second laser beam L2, which has a larger beam diameter than the first laser beam L1 irradiated by the first laser beam irradiation section 12. For example, the beam diameter of the first laser beam L1 is defined by the length of the first focusing point S1 in the width direction of the steel plate 30, and the beam diameter of the second laser beam L2 is defined by the length of the second focusing point S2 in the width direction of the steel plate 30.

[0058] Around the periphery of the groove 32, since strain is generated approximately around the center of the first laser beam L1 during the formation of the groove 32, it is preferable that the center of the second laser beam L2, used to eliminate the strain, corresponds to the center of the first laser beam L1. That is, it is preferable that the second laser beam irradiation section 14 irradiates the second laser beam L2 in such a manner that the center of the second laser beam L2 is approximately aligned with the center of the first laser beam L1. Thus, the second laser beam L2 irradiates symmetrically in the width direction relative to the center of the groove 32, making it easy to cover the entire strain-generating region 38 through the irradiation area 34 of the second laser beam L2. However, as long as the strain generated around the groove 32 can be eliminated, the center of the second laser beam L2 can also deviate from the center of the first laser beam L1. For example, the center of the second laser beam L2 can deviate from the center of the first laser beam L1 within a range converging within the width of the groove 32.

[0059] Furthermore, in the groove forming process, as long as the strain generated around the groove 32 can be eliminated, the distance between the first laser beam irradiation section 12 and the second laser beam irradiation section 14 (i.e., the length of a natural multiple of the spacing of the groove 32) can also be set to any length.

[0060] This concludes the explanation of the irradiation conditions of the second laser beam irradiation unit 14 when compared with the irradiation conditions of the first laser beam unit 12. Detailed heat treatment conditions will be explained together with the heat transfer calculations described later.

[0061] return Figure 1 The control unit 16 is a device that controls the first laser beam irradiation unit 12 and the second laser beam irradiation unit 14. The control unit 16 is, for example, a computer equipped with a processor such as a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), and memory.

[0062] As a functional structure, the control unit 16 includes a first control unit 18 and a second control unit 20. The first control unit 18 and the second control unit 20 are implemented, for example, by a processor executing a program stored in ROM or memory. Alternatively, the control unit 16 may replace the processor or incorporate electronic circuitry such as a PLD (Programmable Logic Device) or an ASIC (Application Specific Integrated Circuit) based on the processor. Furthermore, part or all of the first control unit 18 and the second control unit 20 may also be implemented using electronic circuitry such as a PLD or an ASIC.

[0063] The first control unit 18 controls the first laser beam irradiation unit 12 to irradiate the surface of the steel plate 30 with the first laser beam L1, so as to form a groove 32 on the surface of the steel plate 30. The first control unit 18 calculates, for example, based on a signal from a speed sensor that detects the conveying speed of the steel plate 30, the moving speed of the first laser beam L1 corresponding to the conveying speed of the steel plate 30, and controls the first laser beam irradiation unit 12 (e.g., a motor that rotates a polygon mirror) to move the first laser beam L1 at the calculated moving speed. The moving speed of the first laser beam L1 refers to, for example,... Figure 1 The second control unit 20 controls the second laser beam irradiation unit 14 as follows: under irradiation conditions corresponding to heat treatment conditions that eliminate strain generated in strain generation region 38 during groove formation 32, the second laser beam L2 is irradiated along the scanning path of the first laser beam irradiation unit 12 that forms the groove 32. The second control unit 20 calculates, for example, based on a signal from a speed sensor detecting the conveying speed of the steel plate 30, the moving speed of the second laser beam L2 corresponding to the conveying speed of the steel plate 30, and controls the second laser beam irradiation unit 14 (e.g., a motor that rotates the polygon mirror) to move the second laser beam L2 at the calculated moving speed. The moving speed of the second laser beam L2 refers to, for example, the... Figure 1 The speed of movement in the direction of arrow Y2.

[0064] Figure 3 The first example of a method for manufacturing directional electromagnetic steel sheets is shown. Figure 3 The manufacturing method shown includes casting, hot rolling, annealing, cold rolling, decarburization annealing, annealing separation coating, final annealing, insulating film formation, groove formation, and re-insulating film formation.

[0065] The casting process is the process of manufacturing slabs using continuous casting. The hot rolling process is the process of hot-rolling slabs heated to a specified temperature (e.g., 1100℃~1400℃) to obtain hot-rolled steel sheets. The annealing process is the process of annealing hot-rolled steel sheets immediately or within a short period to obtain annealed steel sheets. The cold rolling process is the process of cold-rolling annealed steel sheets once or multiple times (e.g., more than twice) via intermediate annealing to obtain cold-rolled steel sheets. The decarburizing annealing process is the process of decarburizing cold-rolled steel sheets to obtain decarburized annealed steel sheets that have undergone one recrystallization.

[0066] The annealing separation coating process involves coating the decarburized annealed steel sheet with an annealing separating agent. The final annealing process involves subjecting the decarburized annealed steel sheet coated with the annealing separating agent to final annealing, resulting in secondary recrystallization and obtaining a finished annealed steel sheet. Here, a finished annealed steel sheet refers to a steel sheet that has undergone final annealing of a decarburized annealed steel sheet coated with an annealing separating agent, resulting in secondary recrystallization. The insulating film formation process involves coating the surface of the finished annealed steel sheet with a coating solution and sintering it to form an insulating film on the surface of the finished annealed steel sheet. Figure 1 The steel plate 30 shown is equivalent to a finished annealed steel plate.

[0067] The groove forming process is as follows: For the purpose of magnetic domain control, along arrow X (refer to...) Figure 1 The surface of the finished annealed steel sheet, conveyed in the conveying direction shown, is formed with a plurality of grooves 32 extending in a direction intersecting the conveying direction at predetermined intervals. The groove forming process includes a first laser beam irradiation process and a second laser beam irradiation process. The first laser beam irradiation process is a process in which a first laser beam L1 is irradiated onto the surface of the finished annealed steel sheet from the first laser beam irradiation unit 12 to form grooves 32 on the surface of the finished annealed steel sheet. The second laser beam irradiation process is as follows: after the first laser beam irradiation process, a second laser beam L2 is irradiated from the second laser beam irradiation unit 14 along the grooves 32 in the surface of the finished annealed steel sheet under second irradiation conditions corresponding to the heat treatment conditions that eliminate the strain generated in the strain generation region 38 when forming the grooves 32.

[0068] Both the first laser beam irradiation process and the second laser beam irradiation process are performed while the steel plate 30 is being conveyed. That is, both the first laser beam irradiation unit 12 and the second laser beam irradiation unit 14 operate while the steel plate 30 is being conveyed, respectively irradiating the surface of the steel plate 30 with the first laser beam L1 and the second laser beam L2. The first laser beam irradiation process is an example of the "first irradiation process" in this disclosure, and the second laser beam irradiation process is an example of the "second irradiation process" in this disclosure.

[0069] The process of forming a second insulating film involves applying a coating solution to the surface of the annealed steel plate with grooves 32 and then sintering it to form an insulating film on the surface of the annealed steel plate again.

[0070] Figure 4 The image shows a second example of a method for manufacturing directional electromagnetic steel sheets. Figure 4 In the manufacturing method shown, relative to Figure 3 The manufacturing method shown omits the insulating film forming process prior to the trench forming process, and instead performs the insulating film forming process after the trench forming process. That is, in Figure 4 In the manufacturing method shown, a groove forming process is performed on the annealed steel sheet before an insulating coating is formed on its surface. Figure 1 The steel plate 30 shown is equivalent to a finished annealed steel plate.

[0071] Thus, the groove machining method of the groove machining apparatus 10 of this embodiment can be applied to Figure 3 and Figure 4 Any step in the groove forming process of the manufacturing method of the directional electromagnetic steel sheet shown.

[0072] Figure 7 This describes an example of a method for manufacturing a wound iron core according to an embodiment of the present disclosure. The method includes a directional electromagnetic steel sheet manufacturing step, a wound iron core forming step, and a stress-relief annealing step. The directional electromagnetic steel sheet manufacturing step is the process of manufacturing the aforementioned steel sheet 30, and includes a groove machining step of machining grooves on the surface of the steel sheet 30 after final annealing. As described above, the groove machining step includes a first laser beam irradiation step and a second laser beam irradiation step. As described above, the steel sheet 30 has linear grooves 32 extending in a direction corresponding to the width direction, and heat treatment regions 36 formed along the grooves 32. The wound iron core forming step is the process of forming a wound iron core 50 from the steel sheet 30. Specifically, the steel sheet 30 is wound into a coil, and cut at a stage where it is wound to a desired size, thereby forming the wound iron core 50. The stress-relief annealing step is a process of performing stress-relief annealing treatment on the wound iron core 50 to eliminate the strain generated in the wound iron core 50 during its formation. Stress-relieving annealing is a process of heating the wound core 50 at a temperature that can eliminate the strain generated in the wound core 50 during its formation.

[0073] Next, experimental examples will be described. In this experimental example, steel plates of the present disclosure example and steel plates of the comparative example were prepared. Specifically, as the steel plate of the present disclosure example, a steel plate was prepared in which, in the groove forming process, a groove 32 was formed by irradiating the surface of the steel plate with a first laser beam L1 from the first laser beam irradiation unit 12, and the periphery of the groove 32 (i.e., the strain generation region 38) was heat-treated by irradiating the surface of the steel plate with a second laser beam L2 from the second laser beam irradiation unit 14 in a manner that traces the groove 32. In addition, as the steel plate of the comparative example, a steel plate was prepared in which, in the groove forming process, a groove 32 was formed by irradiating the surface of the steel plate with a first laser beam L1 from the first laser beam irradiation unit 12, and the irradiation of the second laser beam L2 from the second laser beam irradiation unit 14 was omitted.

[0074] The test samples used in the examples and comparative examples of this disclosure are common to both. Figure 3 The first example shown is manufactured using the method for producing directional electromagnetic steel sheets. Details are shown below.

[0075] Test sample: Steel plate after the insulating coating process; magnetic flux density B8 = 1.91T; iron loss W17 / 50 = 0.9W / kg Regarding the irradiation conditions of the first laser beam L1, the following conditions are common to both the present disclosure example and the comparative example.

[0076] Output power: 1000W; Moving speed in the width direction of the plate: 30m / s; Irradiation spacing in the conveying direction: 3mm; Beam diameter: 0.05mm (conveying direction) × 0.1mm (plate width direction); Groove depth: 20μm; Groove width: 50μm Regarding the irradiation conditions of the second laser beam L2 (only in this disclosure example), the following conditions are set.

[0077] Output power: 2000W, moving speed in the width direction of the board: 30m / s, irradiation spacing in the conveying direction: 3mm, beam diameter: 0.15mm (conveying direction) × 15mm (board width direction) In addition, in this experimental example, a steel plate before the groove forming process (i.e., a finished annealed steel plate without grooves) was prepared as the reference example steel plate. The above-described test sample was used in the reference example steel plate. Then, for the steel plate of the present disclosure example and the steel plate of the comparative example, the iron loss improvement rate relative to the reference example steel plate was compared after the second insulating coating process.

[0078] Furthermore, in this experimental example, the wound core of the present disclosure example and the wound core of the comparative example were both transformer wound cores manufactured from steel plates after the slot forming process. Additionally, the wound core of the reference example was a transformer wound core manufactured from steel plates before the slot forming process. Furthermore, the iron loss improvement rate after the stress-relief annealing process was compared between the wound core of the present disclosure example and the wound core of the comparative example, relative to the wound core of the reference example.

[0079] Furthermore, in this experimental example, each wound core was set as a single-phase wound core of 20kVA. Additionally, in the stress-relief annealing process, stress-relief annealing was performed at 800°C for 3 hours in a 100% nitrogen atmosphere. Then, a primary winding (excitation winding) and a secondary winding (detection coil) were wound on each wound core, and the iron loss of each wound core was measured using a power meter.

[0080] Figure 5The following is an example of the results obtained by comparing the iron loss improvement rate [%) between the examples of this disclosure and the comparative examples. Bar chart G1 represents the iron loss improvement rate of the steel sheet of the present disclosure relative to the steel sheet of the reference example. Bar chart G2 represents the iron loss improvement rate of the wound core of the present disclosure after the stress-relief annealing process relative to the wound core of the reference example. Bar chart G3 represents the iron loss improvement rate of the steel sheet of the comparative example relative to the steel sheet of the reference example. Bar chart G4 represents the iron loss improvement rate of the wound core of the comparative example after the stress-relief annealing process relative to the wound core of the reference example.

[0081] In this experimental example, when comparing the steel plate of the present disclosure example with the steel plate of the comparative example, there was no difference in the iron loss improvement rate after the groove forming process. However, when comparing the wound iron core of the present disclosure example with the wound iron core of the comparative example, the result was that the iron loss improvement rate of the wound iron core of the present disclosure example after the stress relief annealing process was more than 3% better than that of the wound iron core of the comparative example.

[0082] Figure 6 This is a schematic diagram showing the cross-section of the periphery of the comparative groove 32 of the wound core after the stress-relief annealing process in the examples and comparative examples of this disclosure. Figure 6 (A) represents a comparative example. Figure 6 (B) indicates an example of this disclosure. For example... Figure 6 As shown in (A), in the wound core of the comparative example, subgrain boundaries are generated around slot 32, such as... Figure 6 As shown in (B), in the wound core of this disclosure, no subgrain boundaries are generated around the groove 32.

[0083] Thus, this experimental example confirms that if the strain-generating region 38 is not heat-treated, subgrain boundaries will be generated around the groove 32 during the stress-relieving annealing process. If subgrain boundaries are generated around the groove 32, iron loss will deteriorate during the stress-relieving annealing process.

[0084] Furthermore, according to this experimental example, the region where subgrain boundaries are generated extends from the opening edge 32A, the side surface 32B, and the bottom surface 32C of the groove 32 to a range of 5-10 μm. It is assumed that the region where subgrain boundaries are generated is approximately the same as the strain generation region 38 described above. Therefore, in order to suppress the generation of subgrain boundaries around the groove 32, as an example of a defined range from the surface of the groove 32, it is considered that heat treatment (i.e., high-temperature stress-relieving annealing heat treatment) is performed on the range from the opening edge 32A, the side surface 32B, and the bottom surface 32C of the groove 32 to at least 10 μm using the second laser beam L2 to eliminate the strain present in this range. That is, it is understood that the heat treatment region 36 only needs to be set to a range from the opening edge 32A, the side surface 32B, and the bottom surface 32C of the groove 32 to at least 10 μm.

[0085] Furthermore, the irradiation conditions of the second laser beam L2 in this experimental example are merely one example; any irradiation conditions other than those described above can be used as long as they meet the irradiation conditions corresponding to the heat treatment conditions for eliminating strain. Here, we aim to define the specified conditions for heat treatment of the area from the opening edge 32A, the side surface 32B, and the bottom surface 32C of the groove 32 to 10 μm by heating temperature. However, in this experimental example, it is difficult to directly measure the temperature of the area from the opening edge 32A, the side surface 32B, and the bottom surface 32C of the groove 32 to 10 μm. Therefore, heat transfer calculations are used to define the specified conditions for heat treatment of the area from the opening edge 32A, the side surface 32B, and the bottom surface 32C of the groove 32 to 10 μm.

[0086] In the heat transfer calculation, the irradiation conditions of the second laser beam L2 are set to the same conditions as those in the present disclosure example, which can suppress the degradation of iron loss. Specifically, the irradiation conditions of the second laser beam L2 are set to the following conditions.

[0087] Output power: 2000W, moving speed in the width direction of the board: 30m / s, irradiation spacing in the conveying direction: 3mm, beam diameter: 0.15mm (conveying direction) × 15mm (board width direction) In addition, in the heat transfer calculation, the laser beam absorptivity of steel plate 30 is set to 60%.

[0088] Figure 8 This illustrates an example of how heat transfer calculations were performed to determine the temperature distribution along the width of the steel plate 30, using an arbitrary point on its surface as a reference. Figure 8 In the diagram, the horizontal axis represents the time [msec] based on the instant the second laser beam L2 passes through any point; specifically, it represents the elapsed time when the time it takes for the center of the second focusing point S2 in the conveying direction to coincide with any point is set to 0.00 seconds. The vertical axis represents the position [mm] of the steel plate 30 in the width direction when the position on the optical axis of the second laser beam L2 is set to 0 mm. For example... Figure 8 As shown, under the aforementioned irradiation conditions of the second laser beam L2 (i.e., irradiation conditions capable of suppressing the deterioration of iron loss), the calculated result was that the surface temperature of the steel plate 30 on the optical axis of the second laser beam L2 was below the melting temperature of the steel plate 30, i.e., 1600°C. If the surface temperature of the steel plate 30 exceeds 1600°C, the surface of the steel plate 30 will melt; therefore, it is considered that the surface temperature of the steel plate 30 needs to be below 1600°C.

[0089] Furthermore, the range in the conveying direction where the surface temperature of the steel plate 30 is above 1000°C is ±40μm (total 80μm) from the position on the optical axis of the second laser beam L2. This is a calculation result that is wider than the total 70μm (equivalent to the length of the strain generation region 38 in the conveying direction) obtained by adding 10μm to each side of the groove 32 with a groove width of 50μm. That is, the calculation result shows that the range in the conveying direction where the surface temperature of the steel plate 30 is above 1000°C includes a range from the opening edge 32A of the groove 32 to 10μm.

[0090] Figure 9 This illustrates an example of how heat transfer calculations were used to determine the temperature distribution along the thickness of steel plate 30. Figure 9 In the diagram, the horizontal axis represents the time [msec] at the instant the second laser beam L2 passes through any point, and the vertical axis represents the position [μm] of the steel plate 30 in the thickness direction when the surface thickness of the steel plate 30 is set to 0 μm. For example... Figure 9 As shown, under the aforementioned irradiation conditions of the second laser beam L2 (i.e., irradiation conditions capable of suppressing iron loss degradation), for example, a calculation result was obtained where the temperature in the thickness direction, from the surface of the steel plate 30 to 10 μm, is at least 1000°C for 0.1 ms. Therefore, in order to suppress iron loss degradation, it is considered sufficient that the temperature in the range from the opening edge 32A of the groove 32, the side surface 32B of the groove 32, and the bottom surface 32C of the groove 32 to 10 μm is maintained at 1000°C or higher for at least 0.1 ms.

[0091] Based on the above heat transfer calculations, the following results were obtained: In the second laser beam irradiation process of irradiating the second laser beam L2, the second laser beam L2 can be irradiated along the groove 32 if the temperature of the area from the opening edge 32A of the groove 32, the side surface 32B of the groove 32, and the bottom surface 32C of the groove 32 to a range of 10 μm (heat treatment area 36) is maintained at 1000°C or higher for at least 0.1 msec, and the temperature of area 34 is maintained at 1600°C or lower.

[0092] Figure 10 An example of the irradiation conditions of the second laser beam L2 is shown, which satisfy the heat treatment conditions obtained from heat transfer calculations (i.e., the conditions that can suppress the deterioration of iron loss). Figure 10 The example shown is an example of the irradiation conditions of the second laser beam L2 when performing heat transfer calculations based on the following conditions.

[0093] The beam diameter of the second laser beam L2 in the delivery direction is 0.15 mm; the moving speed of the second laser beam L2 in the plate width direction is 30 m / s; and the laser beam absorption rate of the steel plate 30 is 60%. exist Figure 10In the diagram, the horizontal axis represents the output power [W] of the second laser beam L2, and the vertical axis represents the beam diameter [mm] of the second laser beam L2 along the width of the plate. Figure 10 In the text, "the range that meets the heat treatment conditions" refers to the irradiation conditions of the second laser beam L2 when the temperature in the range from the opening edge 32A of the groove 32, the side surface 32B of the groove 32, and the bottom surface 32C of the groove 32 to 10 μm is maintained at 1000°C or higher for more than 0.1 msec and the temperature in the region 34 is maintained at 1600°C or lower.

[0094] On the other hand, Figure 10 In this context, "the range that does not meet the first heat treatment conditions" refers to the irradiation conditions of the second laser beam L2 when the temperature in the range from the opening edge 32A of the groove 32, the side surface 32B of the groove 32, and the bottom surface 32C of the groove 32 to 10 μm is maintained at 1000°C or higher for more than 0.1 msec. Furthermore, in Figure 10 In the text, "the range that does not meet the second heat treatment conditions" refers to the irradiation conditions of the second laser beam L2 when the second heat treatment condition of maintaining the temperature of region 34 below 1600°C is not met.

[0095] If Figure 10 The range of conditions that satisfy heat treatment, as shown, is expressed by the following formula.

[0096] 0.0105×P-6.5≤dc≤0.0155×P-12.0 Where P is the output power of the second laser beam L2 [W], and dc is the beam diameter [mm] in the plate width direction.

[0097] For example, in Figure 10 In the range of conditions for heat treatment shown, if the irradiation conditions of the second laser beam L2 are set and the second laser beam L2 is irradiated, the KAM value of the periphery of the groove 32 can be made to be 0.1 or higher and 3.0 or lower. This suppresses the formation of subgrain boundaries and thus suppresses iron loss degradation. Furthermore, while etching can achieve a KAM value of 0, it is theoretically impossible to achieve a KAM value below 0.1 when irradiated with a laser beam.

[0098] Figure 11 The diagram shows a first example of the cross-sectional structure of a directional electromagnetic steel plate according to an embodiment of the present disclosure. Figure 11 The steel plate 30 shown is through Figure 3 This is a first example of a method for manufacturing a directional electromagnetic steel sheet. The steel sheet 30 includes a glass coating 40, an insulating coating 42 formed based on an insulating coating forming process, and a secondary insulating coating 44 formed based on a secondary insulating coating forming process. Figure 11In the example shown in (A), a modified portion 42A is generated in a portion of the insulating coating 42 (i.e., the portion irradiated by the second laser beam L2). Figure 11 In the example shown in (B), the altered portion 42B is a region in the insulating film 42 that has become thinner or damaged (i.e., the portion irradiated by the second laser beam L2). Furthermore, in Figure 11 In the example shown in (A), the altered portion 42A remains on the insulating film 42, but it is also possible for the altered portion 42A to be formed on both the insulating film 42 and the glass film 40. That is, the altered portion 42A is generated only in the insulating film 42, but it is also possible for the altered portion 42A to be present in at least a portion of the region where the altered portion 42A is generated, in both the insulating film 42 and the insulating film 40. Figure 11 The same applies to the altered part 42B shown in (B).

[0099] Figure 12 The diagram shows a second example of the cross-sectional structure of a directional electromagnetic steel plate according to an embodiment of the present disclosure. Figure 12 The steel plate 30 shown is through Figure 4 This is a second example of the manufacturing method for the directional electromagnetic steel sheet shown. The steel sheet 30 has a glass coating 40 and an insulating coating 46 formed by an insulating coating forming process performed after the groove forming process. Figure 12 In the example shown in (A), a modified portion 40A is generated in a portion of the glass coating 40 (i.e., the portion irradiated by the second laser beam L2). Figure 12 In the example shown in (B), the deteriorated portion 40B is a region in the glass coating 40 that has become thinner or damaged (i.e., the portion that has been irradiated by the second laser beam L2).

[0100] Figure 13 The image shows an example of the cross-sectional structure of a directional electromagnetic steel sheet used in a comparative example. Figure 13 The steel plate 130 shown in (A) is obtained by means of relative to Figure 3 The first example of the manufacturing method of the directional electromagnetic steel sheet shown is a manufacturing method that omits the second laser beam irradiation process. Figure 13 The steel plate 130 shown in (A) has a glass coating 40, an insulating coating 42 based on the insulating coating forming process, and a re-insulating coating 44 based on the re-insulating coating forming process, which is consistent with the fact that... Figure 11 The steel plate 30 shown is the same as, and Figure 11 The difference in the steel plate 30 shown is that it does not have the characteristic of producing altered portions 42A or 42B in a portion of the insulating coating 42. That is, in Figure 13 The steel plate 130 of the comparative example shown in (A) does not have the altered portion 42A or 42B, but... Figure 11In the example shown, there are altered portions 42A or 42B in the coating covering the surface of the steel plate portion 30A within a specified range from the groove 32 (more specifically, the opening edge 32A of the groove 32).

[0101] Figure 13 The steel plate 130 shown in (B) is through relative to Figure 4 The second example of the manufacturing method for the directional electromagnetic steel sheet shown omits the manufacturing method of the second laser beam irradiation step. Figure 13 The steel plate 130 shown in (B) has a glass coating 40 and an insulating coating 46 based on an insulating coating forming process performed after the groove forming process, which is consistent with the fact that... Figure 12 The steel plate 30 shown is the same as, and Figure 12 The difference in the steel plate 30 shown is that it does not have the characteristic of producing altered portions 40A or 40B in a portion of the glass coating 40. That is, in Figure 13 The steel plate 130 of the comparative example shown in (B) does not have the altered portion 40A or 40B, but... Figure 12 In the example shown, there are altered portions 40A or 40B in the coating covering the surface of the steel plate portion 30A within a specified range from the groove 32 (more specifically, the opening edge 32A of the groove 32).

[0102] Thus, through Figure 3 The first example of the manufacturing method of the directional electromagnetic steel sheet shown Figure 4 The steel plate 30 produced by the second example of the manufacturing method of the directional electromagnetic steel plate shown has a different cross-sectional structure than the steel plate 130 of the comparative example produced by the manufacturing method that omits the second laser beam irradiation step.

[0103] As described in detail above, in this embodiment, during the groove forming process, the second laser beam L2 is irradiated from the second laser beam irradiation unit 14 along the groove 32 under irradiation conditions corresponding to the heat treatment conditions that eliminate the strain generated during the formation of the groove 32. This eliminates the strain generated around the groove 32 during its formation. Therefore, even when the wound core of a transformer is manufactured from directional electromagnetic steel sheet, the generation of subgrain boundaries around the groove 32 can be suppressed during the stress-relief annealing process performed after the directional electromagnetic steel sheet is wound, thus suppressing iron loss degradation.

[0104] Furthermore, since there is no need for additional heat treatment of the steel plate 30 after the tank forming process, and no need to adjust the cooling rate for adjusting the KAM value around the tank 32, production efficiency can be improved. Moreover, there is no need to control the height of the laser beam with a ring-shaped intensity distribution irradiating the surface of the steel plate 30, thus improving production stability.

[0105] Furthermore, in the above embodiment, a first laser beam L1 and a second laser beam L2 are used in the groove forming process, but an electron beam can also be used instead of at least one of the first laser beam L1 and the second laser beam L2. When a first electron beam irradiation unit that irradiates an electron beam is used instead of the first laser beam irradiation unit 12 that irradiates the first laser beam L1, the first electron beam irradiation unit is an example of the "first irradiation unit" in this disclosure. Similarly, when a second electron beam irradiation unit that irradiates an electron beam is used instead of the second laser beam irradiation unit 14 that irradiates the second laser beam L2, the second electron beam irradiation unit is an example of the "second irradiation unit" in this disclosure. As an electron beam irradiation unit, any irradiation device capable of irradiating an electron beam can be used; for example, it can be any type of structure such as thermionic emission type, electric field emission type, or Schottky type.

[0106] The above describes one embodiment of the present disclosure, but the present disclosure is not limited to the above. In addition to the above, various modifications can be made without departing from its spirit.

[0107] All documents, patent applications, and technical standards described in this specification are incorporated herein by reference to the extent that each document, patent application, and technical standard is specifically and separately described herein. Furthermore, the entire disclosure of Japanese Patent Application No. 2024-031639, filed on March 1, 2024, is incorporated herein by reference.

[0108] Explanation of reference numerals in the attached figures 10-groove machining device 12 First laser beam irradiation section 14 Second laser beam irradiation section 16 Control Department 18 First Control Department 20 Second Control Department 30 steel plate 30A steel plate section 32 slots 34 Second laser beam irradiation area 36 Heat treatment area 38. Strain generation region L1 First laser beam L2 Second Laser Beam

Claims

1. A method for machining grooves on the surface of a directional electromagnetic steel sheet, comprising machining grooves on the surface of the directional electromagnetic steel sheet. The method for processing the grooves in the directional electromagnetic steel plate includes: In the first irradiation step, under first irradiation conditions capable of forming a linear groove extending in a direction corresponding to the width direction of the directional electromagnetic steel plate, a first beam is irradiated onto the surface of the directional electromagnetic steel plate; and In the second irradiation process, a second beam is irradiated along the groove under second irradiation conditions different from the first irradiation conditions onto the surface of the directional electromagnetic steel plate. The directional electromagnetic steel sheet underwent final annealing. The second irradiation condition is an irradiation condition that corresponds to a heat treatment condition that can apply a predetermined heat treatment to a portion of the steel plate within a specified range from the surface of the groove in the directional electromagnetic steel plate.

2. The groove processing method for the directional electromagnetic steel plate as described in claim 1, The heat treatment conditions are those that eliminate strain within the steel plate portion.

3. The groove processing method for directional electromagnetic steel plates as described in claim 1 or 2, The power density of the second beam is lower than that of the first beam.

4. The method for processing grooves in a directional electromagnetic steel plate as described in any one of claims 1 to 3. The center of the second beam corresponds to the center of the first beam.

5. The method for processing the grooves in the directional electromagnetic steel plate as described in any one of claims 1 to 4. The first irradiation process uses a fiber laser device. The second irradiation process uses a semiconductor laser device, which, compared to the fiber laser device, outputs a laser beam with a high absorption rate and a short wavelength from the steel plate.

6. The method for processing grooves in a directional electromagnetic steel plate as described in any one of claims 1 to 5. The heat treatment conditions are as follows: the temperature in the range from the opening edge of the tank, the side surface of the tank and the bottom surface of the tank to 10 μm is 1000°C or higher for at least 0.1 msec, and the temperature in the range is maintained below 1600°C.

7. The method for processing grooves in a directional electromagnetic steel plate as described in any one of claims 1 to 6. The first irradiation process and the second irradiation process are performed when the directional electromagnetic steel plate is being transported.

8. A groove processing device for directional electromagnetic steel plates, used to groove the surface of directional electromagnetic steel plates. The slotting device for the directional electromagnetic steel plate includes: The first irradiation unit, under first irradiation conditions capable of forming a linear groove extending in a direction corresponding to the width direction of the directional electromagnetic steel plate, irradiates the surface of the directional electromagnetic steel plate with a first beam; and The second irradiation unit, along the groove, irradiates the surface of the directional electromagnetic steel plate with a second beam under second irradiation conditions different from the first irradiation conditions. The directional electromagnetic steel sheet underwent final annealing. The second irradiation condition is an irradiation condition that corresponds to a heat treatment condition that can apply a predetermined heat treatment to a portion of the steel plate within a specified range from the surface of the groove in the directional electromagnetic steel plate.

9. The groove processing apparatus for directional electromagnetic steel plates as described in claim 8. The heat treatment conditions are those that eliminate strain within the steel plate portion.

10. The slot processing apparatus for directional electromagnetic steel plates as described in claim 8 or 9. The first irradiation unit and the second irradiation unit operate when conveying the directional electromagnetic steel plate.

11. The slot processing apparatus for the directional electromagnetic steel plate as described in any one of claims 8 to 10, The distance between the first irradiation part and the second irradiation part is set to a length that is a natural multiple of the spacing of the slots.

12. A directional electromagnetic steel plate, It has linear grooves. The coating covering the portion of the steel plate extending from the groove has a deteriorated portion.

13. The directional electromagnetic steel plate as described in claim 12, The KAM value of the steel plate portion within a specified range from the surface of the groove is 0.1 or higher and 3.0 or lower.

14. A wound iron core formed of a directional electromagnetic steel sheet, The directional electromagnetic steel plate has linear grooves. The coating covering the portion of the steel plate extending from the groove has a deteriorated portion.

15. A method for manufacturing a wound iron core, have: The manufacturing process of directional electromagnetic steel sheets involves producing directional electromagnetic steel sheets. The process of forming a wound iron core involves forming a wound iron core from the directional electromagnetic steel plate; and The stress-relief annealing process involves subjecting the wound iron core to stress-relief annealing treatment. The manufacturing process of the directional electromagnetic steel plate includes a groove machining process for machining grooves on the surface of the directional electromagnetic steel plate. The groove processing step includes: In the first irradiation step, under the first irradiation condition of forming a linear groove extending in a direction corresponding to the width direction of the directional electromagnetic steel plate, a first beam is irradiated onto the surface of the directional electromagnetic steel plate; and In the second irradiation process, a second beam is irradiated along the groove under second irradiation conditions different from the first irradiation conditions onto the surface of the directional electromagnetic steel plate. The directional electromagnetic steel sheet underwent final annealing. The second irradiation condition is an irradiation condition that corresponds to a heat treatment condition that can apply a predetermined heat treatment to a portion of the steel plate within a specified range from the surface of the groove in the directional electromagnetic steel plate.

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