JP7804248B2 - Laser processing device and laser processing method - Google Patents

Description

This disclosure relates to a laser processing apparatus and a laser processing method.

The manufacturing process for grain-oriented electrical steel sheets mainly consists of hot rolling, cold rolling, primary recrystallization (decarburization) annealing, secondary recrystallization (finishing) annealing, flattening annealing, and coating. During this manufacturing process, a magnetic domain control technology has been put into practical use to reduce iron loss by applying linear thermal strain at regular intervals in a direction approximately perpendicular to the rolling direction (i.e., in the sheet width direction) to the surface of the grain-oriented electrical steel sheet after the coating process as the steel sheet is transported in the rolling direction (Patent Document 1). Another method for improving iron loss is to form grooves by laser irradiation (Patent Document 2).

Furthermore, a technology has been disclosed in which localized heating areas are formed by laser irradiation in a direction approximately parallel to the sheet width direction on an electrical steel sheet after cold rolling and before finish annealing, thereby generating grain boundaries in the area after finish annealing, thereby improving magnetic properties such as reducing iron loss and increasing magnetic flux density (Patent Document 3).

In these techniques, localized heat treatment is performed by irradiating a steel sheet surface transported in the rolling direction L at a transport speed VL with laser light focused in a thin linear, circular, or elliptical shape in the rolling direction L, while scanning the laser light in the sheet width direction C, which is approximately parallel to the rolling direction, at a speed _Vc . Here, if the laser power is P [W], the focused shape is an ellipse, the major axis diameter in the scanning direction is _Dc , and the minor axis diameter which is the focused diameter in the direction perpendicular to the scanning direction is Dl, then, as expressed by equations (1) and (2), the focused area, which is the product of Dc and _Dl , is S [ ^mm2 ], and the power density _Ip [W/ ^mm2 ] is _Ip = P/S. Since Ip represents the energy input per unit time, the higher Ip, the faster the heating rate.

Furthermore, to achieve certain effects by heating steel sheets, such as distortion, deep groove processing, and grain boundary formation, it is necessary to reach the required temperature, which means that even at a high Ip, a certain amount of irradiation time is required. In a method in which a laser is scanned across the sheet width, the irradiation time Tt at the point where the laser light passes is expressed as Tt = Dc/Vc, as shown in equation (3) below, where Vc is the scanning speed. To increase Tt, Dc must be increased or Vc must be decreased. Here, from a productivity perspective, decreasing Vc is disadvantageous, so to increase Tt, the focused beam diameter Dc in the scanning direction must be increased.

S=(π/4)・D _L・D _C [mm ² ] (1)
I _P = P/S = (4/π)・P/(D _L・D _C ) [W/mm ² ] (2)
T _t =D _C /V _C [sec] (3)

Therefore, in order to efficiently form a linear heating area by scanning laser light across the width of a steel plate moving in the rolling direction at high speed, it is desirable to focus the light in a line that is long in the scanning direction and narrow in the perpendicular direction.

As a method for scanning, in the sheet width direction, a laser beam having such a focused shape that is long in the sheet width direction, to form a thin heated region having a diameter equivalent to the minor axis diameter D _L of the elliptical (or linear) focused beam, Patent Document 1 describes a technique for calculating and setting an inclination angle, which is the angle between the scanning direction of the laser beam and the major axis of _{the focused beam shape, from the conveying speed V L of} the steel sheet and the scanning speed V C of the laser beam.

Patent No. 5135542 Patent No. 5234222 Patent No. 4782248

However, as in the method of Patent Document 1, in the case of a linear focusing shape in which the beam diameter D _C in the sheet width direction is extremely long compared to the minor axis diameter D _L of the elliptical (or linear) focusing, the angle must be set very precisely. In other words, if the angle setting is not precise enough, the width of the heated area in the effective rolling direction increases. As a result, there is a problem that I _p shown in equation (2) decreases and heating necessary for thermal distortion and the formation of grain boundaries cannot be performed. For example, when an elongated elliptical focusing shape with a minor axis diameter D _L = 0.1 mm and a beam diameter D _C in the sheet width direction = 50 mm is scanned parallel to the sheet width direction, the width of the heated area in the rolling direction should ideally be 0.1 mm, equal to the minor axis diameter D _L . However, if the actual setting angle is off by 0.1 degrees, the width of the heated area in the effective rolling direction L becomes approximately 0.2 mm, which is approximately twice the width of the target heated area, i.e., I _p is halved.

In consideration of the above problems, the present disclosure aims to provide a technology for laser processing the surface of a transported workpiece.

In order to solve the above problem, according to one aspect of the present disclosure, there is provided a laser processing device that irradiates laser light to process the surface of a workpiece, the laser processing device having an output device that outputs laser light, a focusing device that focuses the laser light into a predetermined focused shape, and a deflection device that moves the irradiation position of the focused laser light on the surface of the workpiece at a moving speed that is the same as the conveying speed of the workpiece being conveyed in a first direction by a conveying device.

In addition, in order to solve the above problem, according to another aspect of the present disclosure, there is provided a laser processing method for processing the surface of a workpiece by irradiating it with laser light, the laser processing method comprising: a focusing step for focusing the laser light on the workpiece while the workpiece is being transported in a first direction at a predetermined transport speed; and a moving step for moving the irradiation position of the focused laser light on the surface of the workpiece at a moving speed equal to the transport speed in the first direction.

According to the present invention, the focused shape of the laser light on the workpiece moves in the transport direction of the workpiece at a moving speed that is the same as the transport speed. Conventionally, the focused shape of the laser light moves in a direction approximately perpendicular to the transport direction, but the present invention provides a technology for laser processing the surface of a transported workpiece. Therefore, it is possible to stably perform thin or minute localized heating processing by irradiating the surface of a moving workpiece with laser, as typified by the magnetic domain control process of electromagnetic steel sheets, for example.

FIG. 1 is a schematic diagram of an example of a laser processing apparatus according to an embodiment of the present invention, viewed from the Z direction (vertical direction). FIG. 2 is a schematic view of an example of a laser processing apparatus according to an embodiment of the present invention, viewed from the arrow C direction. FIG. 3 is a schematic view of an example of a laser processing device according to an embodiment of the present invention, viewed from the arrow L direction. FIG. 4 is a schematic diagram of a heating region according to an embodiment of the present invention. FIG. 5 is a schematic diagram showing an example of a laser processing apparatus according to an embodiment of the present invention. FIG. 6 is a schematic diagram showing an example of a laser beam deflected by a polygon mirror according to an embodiment of the present invention. FIG. 7 is a schematic view of another example of a laser processing device according to an embodiment of the present invention, viewed from the arrow C direction. FIG. 8 is a schematic view of another example of a laser processing device according to an embodiment of the present invention, viewed from the arrow C direction. FIG. 9 is a schematic diagram showing another example of laser light deflected by a polygon mirror according to an embodiment of the present invention. FIG. 10 is a schematic view of another example of a laser processing device according to an embodiment of the present invention, viewed from the arrow C direction. FIG. 11 is a flow chart showing a laser processing method according to an embodiment of the present invention. FIG. 12 is a diagram illustrating laser illumination parameters and polygon mirror parameters for various embodiments of the present disclosure. FIG. 13 is a schematic view of another example of a laser processing apparatus according to an embodiment of the present invention, viewed from the arrow C direction. FIG. 14 is a schematic view of another example of a laser processing device according to an embodiment of the present invention, viewed from the arrow C direction. FIG. 15 is a schematic view of another example of a laser processing apparatus according to an embodiment of the present invention, viewed from the arrow C direction. FIG. 16 is a schematic diagram of an example of an optical path switching device according to an embodiment of the present invention. FIG. 17 is a schematic view of another example of a laser processing device according to an embodiment of the present invention, viewed from the arrow C direction. FIG. 18 is a schematic view of another example of a laser processing device according to an embodiment of the present invention, viewed from the arrow C direction. FIG. 19 is a schematic view of another example of a laser processing apparatus according to an embodiment of the present invention, viewed from the arrow C direction. FIG. 20 is a schematic diagram showing two or more laser processing devices according to an embodiment of the present invention arranged in the plate width direction. FIG. 21 is a schematic diagram showing another example of a laser processing device according to an embodiment of the present invention. FIG. 22 is a schematic diagram of another example of a heating region according to an embodiment of the present invention.

Embodiments of the present invention will be described below with reference to the drawings. In the following embodiments, the case of introducing thermal strain to control the magnetic domains of grain-oriented electrical steel sheets will be described as an example. Note that the present invention can also be applied to other cases where the purpose is different, such as thermal processing of a small area by irradiating a transported workpiece with a laser, such as melting to excavate a groove or drilling a hole to penetrate that area. Melting and drilling are achieved by adjusting at least one of the energy density and irradiation time in the thermal processing. Note that in this specification and drawings, components having substantially the same functional configuration will be assigned the same reference numerals, and redundant explanations will be omitted.

[Laser processing equipment]
1 to 3 show a laser processing apparatus 100 according to an embodiment of the present invention. FIG. 1 is a view of the laser processing apparatus 100 viewed from above in the vertical direction, and FIG. 2 is a view of the laser processing apparatus 100 viewed from the sheet width direction C. FIG. 3 is a view of the laser processing apparatus 100 viewed from the conveyance direction L of the grain-oriented electrical steel sheet 10. The laser processing apparatus 100 according to an embodiment of the present invention thermally processes the surface of the grain-oriented electrical steel sheet 10 to form linear grooves or linear thermal strains extending in an extension direction of the grain-oriented electrical steel sheet 10, which is a direction substantially parallel to the sheet width direction C. As shown in the figures, the laser processing apparatus 100 includes a conveyance device 110, an output device 120, a focusing device 130, and a polygon mirror 140. Note that in the following examples, the laser processing apparatus 100 processes the surface of a grain-oriented electrical steel sheet 10, but the laser processing apparatus 100 according to the present disclosure is not necessarily limited to this and may process any other workpiece.

The conveying device 110 conveys the grain-oriented electrical steel sheet 10 at a predetermined conveying speed _VL in a conveying direction L perpendicular to the sheet width direction C. For example, the conveying device 110 includes a plurality of rollers for moving the grain-oriented electrical steel sheet 10 in the conveying direction L, and by rotating the rollers in the conveying direction L, the grain-oriented electrical steel sheet 10 placed on the rollers is moved in the conveying direction L at a predetermined conveying speed _VL . The conveying direction L is the same as the rolling direction of the rolled steel sheet. The sheet width direction C is a direction perpendicular to the rolling direction of the steel sheet.

The output device 120 is a device that outputs laser light 20. Specifically, it may be a fiber laser, YAG laser, _CO2 laser, etc., and the type of laser is not particularly important as long as it is used for processing. The output laser light 20 propagates toward the focusing device 130 and the polygon mirror 140.

The focusing device 130 is provided as a single or multiple components on the optical path from the output device 120 to the grain-oriented electromagnetic steel sheet 10, and focuses the input laser beam 20 into a predetermined focused shape before outputting it. Specifically, the focusing device 130 focuses the laser beam 20 on the surface of the grain-oriented electromagnetic steel sheet 10 into a shape that is long in one direction and short in another direction perpendicular to the first direction, such as the approximately linear elliptical shape shown in FIG. 4. The predetermined focused shape is formed so that the extension direction of the linear groove or linear thermal distortion to be formed coincides with the first direction. For example, the extension direction of the groove or linear thermal distortion is aligned with the first direction by rotating the focusing device 130 relative to the laser optical axis E. In order to reduce iron loss, the linear grooves or linear strains are set to extend in a direction perpendicular to the conveyance direction (sheet width direction C) in a plane parallel to the steel sheet surface, or in a direction within 45 degrees (0 degrees≦approximately parallel≦45 degrees) from the sheet width direction C. For grain-oriented electrical steel sheet 10, the extension direction of the linear grooves or linear strains may be 0 degrees or more and 10 degrees or less with respect to the sheet width direction C.

The focused beam shape can be adjusted using the focusing device 130. That is, the focusing device 130 may form the laser beam 20 in a focused beam shape that is short in a first direction and long in a second direction perpendicular to the first direction. For example, in the example shown in FIGS. 1 and 2 , the focusing device 130 includes a lens 131 that adjusts a width-direction focused beam diameter D _C (i.e., the length of the diameter passing through the intersection of the major axis and minor axis and parallel to the conveying direction L) that is the focused beam diameter in the width direction C of the grain-oriented electrical steel sheet 10, and a lens 132 that adjusts a minor axis diameter D _L of the focused beam in the conveying direction L of the grain-oriented electrical steel sheet 10. Furthermore, as shown in FIG. 4 , the focused beam shape of the laser beam 20 is adjusted to be an oblong ellipse such that D _L < D _C. Specifically, to set the sheet width direction focused diameter _Dc to a desired length, a concave lens may be used as the lens 131 to expand the diameter of the laser beam 20, and Dc may be set to a desired value by adjusting the distance between the lens 131 and the steel sheet. Regarding the minor axis diameter _DL of the elliptical focused beam, a convex lens may be used as the lens 132, and the position of the lens 132 may be adjusted so that the focal position of the lens 132 coincides with the steel sheet surface, thereby setting the minor axis diameter _DL to a desired value. Here, FIG. 5 is a schematic diagram of the laser beam 20 deflected by the polygon mirror 140 according to an embodiment of the present invention. More specifically, FIG. 5 shows a schematic diagram of the laser beam 20 deflected by the polygon mirror 140 according to an embodiment of the present invention. Note that FIG. 4 is an enlarged view of a portion of the electromagnetic steel sheet shown in B of FIG. 5, viewed vertically from above.

The polygon mirror 140 has multiple reflecting surfaces and is rotatable about a rotation axis that is parallel to the steel sheet surface and perpendicular to the conveyance direction of the workpiece, specifically, the grain-oriented electrical steel sheet 10 in this embodiment. The polygon mirror 140 may also rotate at a rotation speed corresponding to the movement speed of the irradiation position. The rotation axis is rotatably supported by a support device (not shown) so that it rotates in a direction that deflects the laser beam 20 incident from one direction by reflection on each reflecting surface of the polygon mirror 140 and moves it in the conveyance direction L. That is, as each reflecting surface rotates around the rotation axis RX, the angle of incidence of the laser beam 20 sequentially changes within each reflecting surface, thereby moving the irradiation position of the laser beam 20 on the surface of the grain-oriented electrical steel sheet 10 in the same direction and at the same speed as the conveyance direction L at a movement speed V _C that corresponds to the rotation speed. When changing to the next reflecting surface, the angle of incidence returns to the original, and the irradiation position returns upstream in the conveyance direction L. This is repeated as many times as the number of reflecting surfaces during one rotation of the polygon mirror 140.

The irradiation interval P _L will be explained in detail below with reference to Fig. 6. Fig. 6 is a schematic diagram showing the laser light 20 reflected and deflected by the polygon mirror and the irradiation interval P _L in the conveying direction. Fig. 6 is an enlarged view of the portion shown in A in Fig. 2. Focusing on one surface of the polygon mirror 140, consider a case where the laser light 20 is reflected by the surface. When the polygon mirror 140 is viewed from the sheet width direction C, the boundary between the surface and a surface located ahead of the surface in the rotation direction is defined as vertex A', and the boundary between the surface and a surface located behind the surface in the rotation direction is defined as vertex B'. When the laser beam 20 is reflected by the vertex A', the position on the steel sheet where the reflected laser beam 20 is irradiated is defined as irradiation position I, and when the laser beam 20 is reflected by the vertex B', the position on the steel sheet where the reflected laser beam 20 is irradiated is defined as irradiation position II. As the polygon mirror 140 rotates, the reflection point R where the laser beam 20 is reflected moves from the vertex A' to the vertex B' of the polygon mirror 140, so that the laser beam 20 moves from irradiation position I on the surface of the grain-oriented electrical steel sheet 10 to irradiation position II on the surface of the grain-oriented electrical steel sheet 10. Immediately after the laser beam 20 is irradiated at the vertex A' on the (next) face behind the given face in the rotation direction, the reflected laser beam 20 is again irradiated at irradiation position I, and this operation is repeated. If the moving distance from irradiation position I to irradiation position II on the surface of the grain-oriented electrical steel sheet 10 is defined as the laser irradiation interval _PL , then as the polygon mirror 140 rotates, thermally processed areas are formed by laser irradiation at intervals of _PL in the conveying direction of the steel sheet.

Here, if the number of faces of the polygon mirror is N _p and the central angle of each mirror face is θ _P , the following relationship holds:
θ _P =360/N _p (4)
Here, θ _P corresponds to ½ of the deflection angle of _{the laser light 20 reflected by the polygon mirror, so if the distance of the perpendicular line from the reflection point R of the polygon mirror to the steel sheet surface is h, then P L is} given by equation (5).
P _L =2・h・tanθ _P (5)

Furthermore, in the present invention, the moving speed V C of the irradiation point of the laser beam 20 by the polygon mirror 140 (for example, a specific position such as the center position between the start and end points of the laser beam irradiation positions resulting from the deflection of the laser beam 20 due to a change in the reflection angle of one mirror as the polygon mirror 140 rotates ₎ on the grain-oriented electrical steel sheet 10 is made the same as the conveying speed V _L of the grain-oriented electrical steel sheet 10 by the conveying device 110. This causes the focused shape of the laser beam 20 to progress in the conveying direction L so as to follow the same region on the grain-oriented electrical steel sheet 10 being conveyed, making it possible to continuously irradiate the same region on the surface of the grain-oriented electrical steel sheet 10 with the laser beam 20.

For example, when the reflection direction is deflected by rotating the polygon mirror 140 and the irradiation point of the laser beam 20 is moved by _PL , the distance between the reflection point R of the polygon mirror 140 and the grain-oriented electrical steel sheet 10 changes from he at the start point of the movement (irradiation position I) to h at the center point O of the movement, and then changes to he at the end point (irradiation position II). Therefore, even if the rotation speed of the polygon mirror 140 is constant, the movement speed of the irradiation point on the steel sheet changes slightly. Specifically, if the speed at the center point O of the movement is V _C , the speeds V _Ce at the start and end points of the movement are as follows:
V _Ce = (he/h)・V _C (6)

That is, the speed of movement of the irradiation shape due to the rotation of one of the reflecting surfaces of the polygon mirror 140 slows down from the start point to the center point O and increases from the center point O to the end point. In the present invention, for example, as described above, the rotation of the polygon mirror 140 causes the deflection of the laser beam 20 due to a change in the reflection angle of one mirror, and the movement speed _Vc is defined as the movement speed at the center point O between the start point and the end point of the laser beam irradiation position (hereinafter, also referred to as the irradiation position). Therefore, within the time that the laser beam 20 is reflected by one of the reflecting surfaces of the polygon mirror 140, the speed changes between the start point of movement, the center point O of irradiation, and the end point of movement. Therefore, if the conveying speed _VL of the grain-oriented electrical steel sheet 10 is constant, a discrepancy occurs between the conveying speed L of the grain-oriented electrical steel sheet 10 and the moving speed of the irradiation position during the movement of the irradiation point. As a result, the effective focused beam shape on the grain-oriented electrical steel sheet 10 changes, that is, the power density changes. It is preferable that the moving speed and the transport speed are perfectly matched, but a certain degree of change in power density caused by such a speed difference is acceptable depending on the processing purpose. For example, if the change in power density is within about 10%, it will not affect the purpose of thermal distortion or groove processing.

For example, in Example 1 described later, when the number of polygon faces N _p = 38 and the distance h between the reflection point and the steel plate = 30 mm, he = 30.41 mm, the speed difference between the start point and the center point of movement is approximately 1%, and the difference in the effective light-collecting shape between the center point of movement and the start point and end point is also equivalent, so that the effect on processing is within a negligible range.

6 , when the movement of the laser beam 20 is viewed from the sheet width direction C, the focus of the laser beam 20 is formed on an arc shown by the dotted line, centered on the reflection point R of the polygon mirror 140. Therefore, if h is set so that the focus is formed at the center point O of the movement, strictly speaking, the focused shape at irradiation positions I and II will differ from the shape at the focus. However, by shortening the distance h between the reflection point R of the polygon mirror 140 and the grain-oriented electrical steel sheet 10 or by appropriately setting the configuration and focal length of the focusing device 130, for example, it is possible to keep the deviation of the focused shape within a relatively negligible range. Furthermore, setting h to a short value also leads to a reduction in the deviation of _Vc and _Vce described above.

In order to prevent such changes in the focused shape on the steel sheet plane and changes in the moving speed V _C , an Fθ lens 133 can be used as one component of the output device 120 between the reflection point R of the polygon mirror 140 and the grain-oriented electrical steel sheet 10, as shown in Figure 7, so that the focus is formed along the steel sheet surface regardless of the moving position and the moving speed can be made constant. Note that the focusing device 130 may include one or more convex or concave lenses 134 between the polygon mirror 140 and the output device 120 in addition to the Fθ lens 133, for adjusting the laser focused shape.

Therefore, in the present invention, the same region is continuously irradiated with the laser beam 20 while it moves _at the conveying direction irradiation interval _PL on the surface of the grain-oriented electrical steel sheet 10. As a result, the region (hereinafter referred to as the heated region) that is continuously irradiated with the laser beam 20 for the time required for the laser beam 20 to travel at the conveying direction irradiation interval PL forms a linear or dot-series groove or linear distortion having the length of the major axis of the focused shape. The repeated movement of the laser beam 20 by each reflecting surface of the polygon mirror 140 switches instantaneously from irradiation position II to irradiation position I, so the interval at which the linear groove or linear distortion is formed can be considered to be equal to the irradiation interval _PL in the conveying direction L.

Here, the heating area refers to the area irradiated with the focused shape of the laser light 20 on the surface of the directional electrical steel sheet 10.

As shown in FIG. 5 , the polygon mirror 140 has a polygonal cross section depending on the number of faces, with the center of this cross section being the rotation axis RX. The direction of rotation is the same as the conveyance direction L of the grain-oriented electrical steel sheet 10, in which the deflection direction of the reflected laser light due to rotation is the same as the conveyance direction _L of the grain-oriented electrical steel sheet 10. The rotational speed _Vθ [degrees/sec] of the polygon mirror 140 is controlled so that the moving speed _VC at the center point O of the moving distance P _L of the laser light 20 moved by the polygon mirror 140 matches the conveyance speed VL of the grain-oriented electrical steel sheet 10 (see FIG. 6 ). With respect to this conveyance speed _VL , a rotational speed signal of the motor driving the rollers of the conveyance device 100 is input to a control device (not shown) of the rotary motor of the polygon mirror 140, thereby controlling (e.g., feedback control) the motor rotational speed V _rpm of the rotary motor of the polygon mirror 140. Note that the rotational speed of the motor and the rotational speed of the polygon mirror 140 do not necessarily need to match, and a rotation speed conversion gear may be inserted between the motor and the polygon mirror 140. In this case, the gear ratio may be appropriately set to set the rotation speed of the polygon mirror 140 so that the moving speed V _C of the irradiation position of the laser light matches the moving speed V _L of the workpiece.

In this way, according to the present embodiment, the focused shape formed on the surface of the grain-oriented electrical steel sheet 10 by using the focusing device 130 is maintained substantially constant, while the irradiation position moves in the conveying direction L in accordance with the conveyance of the grain-oriented electrical steel sheet 10. As a result, the power density _IP can be maintained at a desired value during the irradiation time _Tt , while irradiating the irradiation position of the grain-oriented electrical steel sheet 10. In this way, by moving the focused shape of the laser beam 20 having the major axis in the conveying direction L so as to follow the same region on the steel sheet being conveyed, fine adjustment of the inclination angle, which is required in the conventional case of movement substantially parallel to the sheet width direction C, is no longer necessary, and appropriate laser irradiation of the workpiece can be performed.

When the present invention is applied to the production of grain-oriented electrical steel sheet 10, the laser irradiation parameters and the design parameters of the polygon mirror 140 can be set by the following procedure. Important parameters for properly forming linear grooves or linear distortions in grain-oriented electrical steel sheet 10 are power density I _p , irradiation time T _t , and conveyance direction irradiation interval P _L . In a production line for grain-oriented electrical steel sheet 10, the conveyance speed V _L of grain-oriented electrical steel sheet 10 is set to a predetermined speed. Furthermore, the conveyance direction irradiation interval P _L of the grooves or distortions is preferably approximately 3 to 10 mm, and the width of the grooves or distortions in the rolling direction is preferably narrow, so these parameters should be determined in advance. Therefore, the conveyance speed V _L, the conveyance direction irradiation interval P _L , and the ellipse focusing minor axis diameter D _L are set to given fixed parameters.

Step 1: Laser Irradiation Parameters The irradiation time _Tt , which is an important parameter for providing grooves or distortion to the grain-oriented electrical steel sheet 10, is set by the following equation (7).
T _t =P _L /V _L [msec] (7)

Step 2: Polygon Mirror Design Parameters The central angle θ _P of each facet of the polygon mirror 140 is determined by the following equation (8).
θ _P = tan ⁻¹ (P _L /(2・h)) [degrees] (8)
Here, h is the distance from the reflection point R of the polygon mirror 140 to the vertically downward surface of the grain-oriented electrical steel sheet 10. Furthermore, h may be finely adjusted so that the number of faces _{N_P} of the polygon mirror 140 is an integer.
The rotational angular velocity V _θ of the polygon mirror 140 is determined by the following equation (9).
V _θ = θ _P /(T _t /1000) [degrees/sec] (9)
The motor rotation speed V _rpm of the polygon mirror 140 is determined by the following equation (10).
V _rpm = (V _θ /360)・60[rpm] (10)
The number of faces N _P of the polygon mirror 140 is determined by the following equation (11).
N _P =360/θ _P (11)

The main parameter names, symbols and units used in this specification are summarized in the table below.

Here, an example of adjusting the conveying direction irradiation interval _PL while maintaining the conveying speed _VL constant is shown. FIG. 8 is a schematic diagram of the laser beam 20 deflected by the polygon mirror 140 according to an embodiment of the present invention, as viewed from the sheet width direction C. FIG. 9 is an enlarged view of portion A in FIG. 8, showing the laser beam 20 represented by its optical axis E. This is a schematic diagram of the conveying direction irradiation interval _PL according to an embodiment of the present invention. When changing the conveying direction irradiation interval _PL without changing the conveying speed _VL , the laser power P of the output device 120, the distance h between the reflection point R of the polygon mirror 140 and the grain-oriented electrical steel sheet 10, and the motor rotation speed V _rpm of the polygon mirror 140 are changed. First, when the conveying direction irradiation interval _PL is multiplied by n, as shown in FIG. 9, by multiplying the distance h by n (where n is any number greater than 0) to h', it is possible to make the physical distance of the conveying direction irradiation interval _PL n times _PL '. 8 , when the distance h is multiplied by n, the position of the focusing device 130 is appropriately adjusted in accordance with the movement of the polygon mirror 140 so as to maintain a constant distance from the focusing device 130 to the grain-oriented electromagnetic steel sheet 10 and prevent focus shift. The focusing device 130 is configured, for example, with a concave lens 131 and a convex lens 132 to focus the laser beam 20 linearly, and the distance between these lenses is maintained. The distance between the focusing device 130 and the grain-oriented electromagnetic steel sheet 10 is, for example, the distance along the optical axis E from the convex lens 132 to the grain-oriented electromagnetic steel sheet 10, and the position of the focusing device 130 is moved so as to maintain this distance when the polygon mirror 140 is moved. Furthermore, when the irradiation interval P _L in the transport direction L is multiplied by n, the time during which the heating region is continuously irradiated (laser irradiation time T _t ) is multiplied by n. However, the laser power P is set to 1/n in order to maintain a constant power density I _p irradiated to the grain-oriented electromagnetic steel sheet 10. Furthermore, when the distance h is multiplied by n, the moving speed V _C of the laser beam 20 becomes n times larger, and therefore, by multiplying the motor rotation speed V _rpm by 1/n, the moving speed V _C of the laser beam 20 becomes constant with the conveying speed V _L. By setting it as described above, it is possible to change the irradiation interval P _L in the conveying direction L by n times while maintaining the conveying speed V _L constant, without changing the local heat treatment conditions. By adjusting the irradiation interval P _L in the conveying direction L in this way, it is also possible to control the magnetic domain control characteristics of the grain-oriented electrical steel sheet, and applications such as changing P _L to match the magnetic properties before magnetic domain control are possible.

The magnetic domain control characteristics herein refer to a rate of change or the like that indicates the degree of change in magnetic properties (e.g., iron loss, magnetostriction, magnetic flux density, etc.) that change as a result of magnetic domain control. The change in magnetic properties depends on the irradiation interval P _L in the conveyance direction L, the magnitude of each thermal distortion, the depth of the groove, etc. In other words, the deflection device 150 such as the polygon mirror 140 has a function of adjusting the irradiation interval P _L in the conveyance direction L, and by adjusting the irradiation interval P _L in the conveyance direction L, the iron loss, magnetostriction, magnetic flux density, etc. of the grain-oriented electrical steel sheet 10 may be changed.

10 , a laser irradiation device 100 may include one transport device 110, two output devices 120, two focusing devices 130, and one polygon mirror 140 (deflection device 150), and two laser beams 20 may be incident on the polygon mirror 140 from opposite directions. As shown in the figure, the two output devices 120 irradiate the laser beams 20 toward the corresponding focusing devices 130. In this case, the interval G between the two laser beams 20 in the movement direction of each irradiation position can be set to satisfy the following formula (12).
G=(m+1/2)・P _L (12)
Here, m is an integer greater than or equal to 1. Specifically, a method for setting G so as to satisfy equation (12) involves appropriately adjusting the diameter of the polygon mirror 140. According to the embodiment shown in FIG. 10 , the irradiation interval in the transport direction L of each output device 120 can be set to 2×P _L. From equation (8), the central angle θ _P of each face of the polygon mirror 140 doubles, and the number of faces N _P of the polygon mirror 140 can be reduced by half, resulting in an advantage of reducing the manufacturing cost of the polygon mirror 140. Furthermore, since the distance h between the polygon mirror reflection point R and the grain-oriented electromagnetic steel sheet 10 also increases, it is possible to prevent molten material, etc., scattering from the processed portion from adhering to the polygon mirror 140, for example, in the case of groove machining.

[Laser processing method]
Next, a laser processing method according to an embodiment of the present invention will be described using Fig. 11 as an example in which the object to be processed is a grain-oriented electrical steel sheet 10. Fig. 11 is a diagram showing the laser processing method according to an embodiment of the present invention. In the laser processing method shown in Fig. 11, a laser processing apparatus 100 irradiates the surface of the grain-oriented electrical steel sheet 10 with laser light 20 having the above-mentioned elliptically focused shape, thereby forming linear grooves or linear distortions extending in a direction approximately parallel to the sheet width direction C of the grain-oriented electrical steel sheet 10.

As shown in Figure 11, the laser processing method includes a focusing step (S103) and a moving step (S104). In the embodiment shown in Figure 11, the laser processing method further includes a preparation step (S101) and a transport step (S102).

In step S101, the laser processing device 100 is adjusted. Specifically, using a focusing device 130 provided on the optical path from the output device 120 to the grain-oriented electromagnetic steel sheet 10, the focused shape of the laser light 20 on the surface of the grain-oriented electromagnetic steel sheet 10 is adjusted to a substantially linear elliptical shape that is long in one direction and short in another direction perpendicular to that one direction, and one direction of the substantially linear elliptical shape is aligned with a direction substantially parallel to the sheet width direction C.

In order to reduce iron loss, the linear grooves or linear strains are set to extend in a direction approximately perpendicular to the rolling direction (a direction approximately parallel to the plate width direction C). Therefore, the one direction is parallel to the direction in which the linear grooves or linear strains extend.

In step S102, the laser processing apparatus 100 uses the conveying device 110 to convey the grain-oriented electrical steel sheet 10 as the workpiece in a conveying direction L perpendicular to the sheet width direction C at a predetermined conveying speed _VL .

In step S103, the laser processing apparatus 100 focuses the laser beam 20 output from the output device 120 onto the grain-oriented electrical steel sheet 10, which is being transported in the transport direction _L at a predetermined transport speed _VL .

In step S104, the laser processing apparatus 100 moves the focused laser beam 20 to the irradiation position on the surface of the grain-oriented electrical steel sheet 10 at a moving speed V _C that is the same as the conveying speed V _L in the conveying direction L. Specifically, the laser processing apparatus 100 uses the deflection device 150 (the polygon mirror 140 in this embodiment) to reflect the laser beam 20, thereby irradiating the laser beam 20 toward the surface of the grain-oriented electrical steel sheet 10, and rotates the deflection device 150 about a rotation axis parallel to the sheet width direction C to change the traveling direction of the laser beam 20, thereby moving the irradiation position of the laser beam 20 on the surface of the grain-oriented electrical steel sheet 10 at a predetermined moving speed V _C in the conveying direction L. Here, the laser processing apparatus 100 matches the conveying speed V _L of the conveying device 110 with the moving speed V _C of the laser beam 20 from the polygon mirror 140. Specifically, the motor rotation speed V _rpm of the rotary motor of the polygon mirror 140 is controlled so that the moving speed V _C of the laser beam 20 coincides with the conveying speed V _L of the grain-oriented electrical steel sheet 10 .

As described above, the laser processing apparatus 100 and laser processing method according to the present invention can stably form thin linear heated regions on the surface of the grain-oriented electrical steel sheet 10 regardless of the length in the major axis direction of the focused shape of the laser beam 20, and can arbitrarily set the interval in the conveyance direction L of the linear grooves or linear distortions (irradiation interval P _L in the conveyance direction L) while maintaining a constant conveyance speed V _L of the grain-oriented electrical steel sheet 10. In other words, the deflection device 150 may be provided with a function to adjust the irradiation interval in the conveyance direction L.

Although the above example shows the installation of one laser processing device 100, it is also possible to install multiple devices in the plate width direction C according to the plate width, and form linear grooves or linear distortions along the entire plate width direction. Furthermore, the present invention also allows two output devices 120 to be installed with polygon mirrors 140 facing each other, and two laser beams 20 to be moved by the polygon mirrors 140.

For Examples 1 to 3 described below, when the laser irradiation parameters and polygon mirror design parameters were set to the parameter values shown in Figure 12, the magnetic characteristics shown in Figure 12 were obtained. Note that, where Vθ [degrees/sec] is the rotational speed of the polygon mirror 140 and Vrpm [rpm] is the motor rotational speed of the rotary motor, Vrpm = Vθ/360 x 60.

[Example 1]
In the laser processing apparatus and laser processing method disclosed herein, linear heating was performed on grain-oriented electrical steel sheet 10 having a sheet width of 100 mm, which was continuously fed at a conveying speed V _L =0.5 m/sec, in the conveying direction (rolling direction) at intervals _PL =10 mm. The laser irradiation parameters were as follows: a continuous wave fiber laser with a wavelength of 1.06 μm and a laser power of 5000 W was used as output device 120, a combined cylindrical convex lens and cylindrical concave lens was used as focusing device 130, and the conveying direction width _DL =0.2 mm, the sheet width direction focused diameter _DC =106.2 mm, the power density _IP =300 W/mm2, and the irradiation time _Tt =20 msec.

Next, with regard to the polygon mirror design parameters, to select the face central angle _θP of polygon mirror 140 in equation (8) so that the number of faces N _P of polygon mirror 140 is an integer, the vertical distance between the reflection point of polygon mirror 140 and grain-oriented electrical steel sheet 10 was set to h = 30 [mm], the face central angle of polygon mirror 140 was set to θ _P = 9.5 [degrees], and the number of faces was determined to be N _P = 38. From equations (9) and (10), the motor rotation speed V _rpm of polygon mirror 140 was set to V _rpm = 78.9 [rpm]. After determining the number of faces of polygon mirror 140 as described above, V _c and V _L were made to match by fine-tuning h and V _rpm .

The grain-oriented electrical steel sheets 10 were subjected to continuous laser irradiation under the above conditions, and then decarburization annealing, finish annealing, flattening annealing, and coating processes. Thirty grain-oriented electrical steel sheets 10, each measuring 300 mm in the conveying direction and 60 mm in the sheet width direction, were sampled and their magnetic properties were evaluated. The magnetic properties were measured by measuring the iron loss W _17/50 in an alternating magnetic field with a magnetic flux density of 1.7 T and a frequency of 50 Hz, and the magnetic flux density B ₈ generated in a magnetic field of 0.8 A/m. The smaller the iron loss W _17/50 and the higher the magnetic flux density B ₈ , the better the magnetic properties. Since there is a trade-off between reducing iron loss and improving magnetic flux density through thermal processing, in the grain-oriented electrical steel sheet 10 of Example 1, the magnetic flux density B ₈ decreased by 0.02 T compared to the non-laser-irradiated portion, but the iron loss W _17/50 was 0.753 W/kg, meaning that the iron loss was reduced by approximately 10%. Therefore, according to the first embodiment, it is possible to provide a material suitable for a transformer in which iron loss is important.

[Example 2]
In Example 2, based on the embodiment described above with reference to Figures 8 and 9, the conveying speed VL of the grain-oriented electrical steel sheet 10 was kept constant, but the conveying direction irradiation interval P _L in the conveying direction of the linear heating region was increased from 10 mm to 15 mm. Based on the 1.5-fold increase in the conveying direction irradiation _{interval P L ,} the laser power P was set to 1/1.5, the distance h between the reflecting surface of the polygon mirror 140 and the grain-oriented electrical steel sheet 10 was set to 1.5, and the motor rotation speed V _rpm of the polygon mirror 140 was set to 1/1.5. Furthermore, in response to the change in the distance h, the position of the focusing device 130 was appropriately adjusted to maintain a constant distance between the focusing device 130 and the grain-oriented electrical steel sheet 10, i.e., to maintain a constant focused beam shape. When the magnetic properties were measured, the iron loss W _17/50 increased slightly, but the magnetic flux density B ₈ increased. Therefore, according to the second embodiment, it is possible to provide a material suitable for a transformer that places importance on the magnetic flux density _B8 .

[Example 3]
In Example 3, as in the embodiment described above with reference to FIG. 10 , two output devices 120 were installed facing each other on the upstream and downstream sides of the conveyance direction L, and two laser beams 20 were moved by a single polygon mirror 140. The conveyance direction irradiation interval P _L between the linear heating areas formed by each laser beam 20 in the conveyance direction L was set to 20 mm, and the interval G between the irradiation points of each laser beam 20 was set to 110 mm, so that the laser beam 20 was irradiated between the linear heating areas formed by the output devices 120. The laser power P was 5000 W, the sheet width direction focused diameter D _C was doubled, and the power density I _p was halved. In addition, the conveyance direction irradiation interval P _L was set to 20 mm and the irradiation time T _t was doubled to 40 msec, so that the reduction in power density was offset and the input energy to the irradiation section was kept the same. With such a laser processing apparatus 100, the number of faces N _P of the polygon mirror 140 can be halved, thereby reducing the manufacturing cost of the polygon mirror 140. As a result of measuring the magnetic properties, since the transport direction irradiation interval P _L and other conditions were the same as in Example 1, similar magnetic properties were also obtained.

In the above-described embodiment, the laser processing apparatus 100 irradiates the surface of the workpiece 10 with laser light 20 using a polygon mirror 140, but the laser processing apparatus 100 according to the present disclosure is not necessarily limited to this and may utilize a deflection device 150 such as another type of lens. One variation is a method in which a galvanometer mirror 151 is used in the deflection device 150 shown in FIG. 13. The laser processing apparatus 100 according to this variation is composed of an output device 120, a focusing device 130, a deflection device 150 using a galvanometer mirror 151, and a synchronization device 160.

In the laser processing apparatus 100, the galvanometer mirror 151 is substantially parallel to the surface of the workpiece 10 and has a rotation axis RY perpendicular to the conveyance direction L, and the laser processing apparatus 100 includes a mechanism for repeatedly rotating the galvanometer mirror 151 forward and backward around the rotation axis RY. The galvanometer mirror 151 changes its reflection angle in accordance with the moving speed of the irradiation position, so that when the galvanometer mirror 151 rotates forward, the reflected deflection direction of the laser beam 20 coincides with the conveyance direction L of the workpiece 10, and when the galvanometer mirror 151 rotates backward, the reflected deflection direction of the laser beam 20 is opposite to the conveyance direction L. The synchronizer 160 adjusts the rotation speed so that when the laser beam is reflected by the forward-rotating galvanometer mirror 151, the moving speed of the laser irradiation position on the workpiece 10 coincides with the conveyance speed _VL of the workpiece 10, and generates a signal for controlling (ON/OFF) the output of the laser beam 20 from the output device 120. Similar to the polygon mirror 140 described above, the galvanometer mirror 151 also decelerates from the start point of its forward rotation towards the center of its movement distance and then accelerates from the center towards the end point, but generates a signal to stop the laser output during the deceleration period and during the period when the galvanometer mirror 151 is rotating in the reverse direction. By repeating these steps, the laser irradiation position is matched with the transport speed of the workpiece 10, and heated areas that roughly match the focused shape are formed at regular intervals in the transport direction.

Note that, as with the example of the laser processing device 100 using the polygon mirror 140, deviations in the movement speed and transport speed of the laser focusing position at the start point, center point, and end point, as well as changes in the focused light shape due to changes in the distance between the reflection point R of the galvanometer mirror 151 and the workpiece 10, occur. However, these deviations can be adjusted to a range that does not affect the processing phenomenon by adjusting the position of the galvanometer mirror 151 and the design of the focusing device 130. An fθ lens 133 as shown in Figure 7 may also be used. Furthermore, the deflection device 150 is not limited to the above-mentioned galvanometer mirror 151, and may include any type of deflection mirror that moves the irradiation position in forward and reverse directions relative to the transport direction L.

Figures 14 and 15 show another embodiment of the laser processing apparatus 100 using the deflection device 150 of Figure 13. The laser processing apparatus 100 according to this embodiment is composed of one output device 120, two sets of laser processing devices _180-1 , _{180-2 each} consisting of a combination of deflection devices _150-1 , _150-2 using galvanometer mirrors _151-1 , _151-2 and focusing devices _130-1 , _130-2 , a laser beam guiding device 171 for guiding laser light 20 to each of the laser processing devices _180-1 , _180-2 , an optical path switching device 170 for switching the laser output to each of the laser beam guiding devices 171, the two deflection devices _150-1 , _150-2 , the optical path switching device 170, and a synchronization device 160 for controlling the operation of the output device 120. For example, in the laser processing apparatus 100, when the reflection deflection direction of the laser beam 20 by the galvanometer mirror _151-1 of one laser processing device _180-1 rotates forward, is the same as the conveying direction L of the workpiece 10, and the moving speed of the laser focusing position is the same as the conveying speed of the workpiece 10, the laser beam 20 is guided to that laser processing device 180 by the optical path switching device 170. Meanwhile, the galvanometer mirror _151-2 of the other laser processing device _180-2 rotates in the reverse direction. At the timing when the rotation directions of the two devices switch, the optical path switching device 170 controls so that the laser beam 20 is guided to the other device. In other words, the laser beam 20 is guided to that laser processing device _180-1 only while the galvanometer mirror 151-1 is rotating forward, and during that time the other galvanometer mirror _151-2 rotates in the reverse direction. By repeating this process alternately, the timing for stopping the laser output, which is required when there is only one laser processing device 180 as shown in FIG. 15, becomes unnecessary, and production efficiency can be improved.

The optical path switching device 170 may be, for example, a rotating reflecting mirror 170 with slits 171 that transmit the laser light 20, spaced at regular intervals around its circumference, as shown in Figure 16. The optical path is switched by the laser light being reflected on the reflecting surface of the rotating reflecting mirror 170 and passing through the slits. In other words, the synchronization device 160 synchronizes the timing of the laser output from the output device 120 with the reflection angle of the galvanometer mirror 151. The switching timing is controlled by the synchronization device 160, which controls the rotation of the motor of the rotating reflecting mirror 170. Alternatively, any method that can divide the propagation direction of one laser light 20 in time, such as switching the reflection direction of the laser light 20, may be used.

FIG. 17 is a diagram showing a laser processing apparatus 100 using a reciprocating laser irradiation device 190. There is a method using the reciprocating laser irradiation device 190 shown in FIG. 17. The laser processing apparatus 100 according to this embodiment includes an output device 120, a reciprocating laser irradiation device 190, a synchronization device 160, and a drive mechanism 194. The reciprocating laser irradiation device 190 includes a focusing device 130 composed of lenses 191 and 192, and a reflecting mirror 193 as a deflection device 150. The drive mechanism 194 moves the reciprocating laser irradiation device 190 back and forth in the conveying direction L parallel to the surface of the workpiece 10 while keeping the relative positional relationship between the lenses 191 and 192 and the reflecting mirror 193 fixed. The reciprocating laser irradiation device 190 itself moves in the conveying direction L of the workpiece 10 at a conveying speed _VL , and the irradiation position on the surface of the workpiece 10 moves in the conveying direction L at a moving speed _Vc that is the same as the conveying speed VL.

The synchronizer 160 synchronizes the driving of the reciprocating laser irradiation device 190 with the output and stop of the output device 120, outputting laser light from the output device 120 when the reciprocating laser irradiation device 190 moves in the same direction and at the same speed as the conveying direction L of the workpiece 10, and stopping the output from the output device 120 when the reflecting mirror 193 serving as the deflection device 150 moves in the opposite direction to the conveying direction L of the workpiece 10. By repeating these steps, the irradiation position is made to coincide with the conveying speed _VL of the grain-oriented electrical steel sheet 10, and heated areas that substantially coincide with the focused shape are formed at regular intervals in the conveying direction L. The position and orientation of the reflecting mirror 193 are set so as to reflect the laser light 20 focused by the lenses 191 and 192 serving as the focusing device 130 to a predetermined irradiation position on the surface of the workpiece 10, as shown in FIG.

Figures 18 and 19 show another embodiment of an apparatus using the reciprocating laser irradiation device 190 of Figure 17. The laser processing apparatus 100 according to this embodiment is composed of one output device 120, two reciprocating laser irradiation devices ₁₉₀₁ and ₁₉₀₂ , drive mechanisms ₁₉₄₁ and ₁₉₄₂ , a laser beam guide device 171 that guides the laser beam 20 to each of the reciprocating laser irradiation devices ₁₉₀₁ and ₁₉₀₂ , an optical path switching device 170 that switches the laser beam 20 to each of the laser beam guide devices 171, and a synchronization device 160 that controls the operation of the output device 120. The two reciprocating laser irradiation devices ₁₉₀₁ and ₁₉₀₂ operate differently from each other, and the laser beam 20 from the output device 120 is guided by the optical path switching device 170 to one of the reciprocating laser irradiation devices ₁₉₀₁ , which moves in the same direction as the conveying direction _L at a moving speed Vc that is the same as the conveying speed _VL . Meanwhile, the other reciprocating laser irradiating device _190-2 moves in the direction opposite to the conveying direction L without irradiating the work-piece 10 with the laser beam 20. At the timing when the movement directions of the two reciprocating laser irradiating devices _190-1 , _190-2 are switched, the optical path switching device 170 controls the laser beam 20 to be directed to the other device. The movement directions and timing of the reciprocating laser irradiating devices _190-1 , _190-2 are determined by controlling the drive mechanisms _194-1 , _194-2 using a synchronization signal from the synchronizer 160. In other words, the laser beam 20 is directed to one of the reciprocating laser irradiating devices _190-1 , _190-2 only when the laser beam 20 is moving in the same direction as the conveying direction L at the same speed. By alternately repeating this, the timing to stop the laser output from the output device 120, which is required when there is only one reciprocating laser irradiating device 190 as shown in FIG. 17, becomes unnecessary, and production efficiency can be improved. That is, the synchronization device 160 synchronizes the laser output timing from the output device 120 with the reciprocating movements of the reciprocating laser irradiation devices 190 ₁ and 190 _2. Note that the deflection device 150 is not limited to the above-described reflection mirror 193, and may include any type of mirror that reciprocates in the transport direction L to change the reflection direction.

In addition, in the present disclosure, the deflection device 150 may include multiple deflection devices 150 that form multiple laser beams 20 in the plate width direction C. When the major axis length of the linear focused shape is shorter than the width of the workpiece 10, for example, as shown in FIG. 20, multiple laser processing devices 100 already described may be arranged side by side in the width direction of the workpiece 10. In this case, multiple processing regions spaced apart from each other in the width direction of the workpiece 10 are formed. Note that the laser processing device 100 in FIG. 20 has polygon mirrors _140-1 to _140-4 as deflection devices 150, but the present invention is not limited to this embodiment. The deflection device 150 included in the laser processing device 100 may be any of the deflection devices 150 already described.

Furthermore, Figure 21 is a schematic diagram of another example of a laser processing apparatus 100 according to another embodiment of the present invention, and Figure 22 is a schematic diagram of another example of a heating region according to another embodiment of the present invention. As shown in Figure 22, the focusing shape of a single polygon mirror 140 may be a dotted array. Such a focusing shape can be achieved by adding, for example, a diffractive optical element 135 that utilizes the well-known diffraction phenomenon to one component of the focusing device 130, as shown in Figure 21.

The above describes in detail the embodiments of the present disclosure, but the present disclosure is not limited to the specific embodiments described above, and various modifications and variations are possible within the scope of the gist of the present disclosure as set forth in the claims. For example, the workpiece 10 according to the present disclosure is not limited to grain-oriented electromagnetic steel sheets. Specifically, the workpiece 10 according to the present disclosure may be other electromagnetic steel sheets, or any other steel sheet other than electromagnetic steel sheets.

Furthermore, the thermal processing according to the present disclosure is not limited to forming grooves on the surface of the workpiece 10 described above. For example, the workpiece 10 may be a general steel plate, and the thermal processing according to the present disclosure may be used to facilitate identification of positions, areas, etc. on the steel plate surface. As one specific example, the thermal processing according to the present disclosure may be used to facilitate visual identification of defects detected on the steel plate surface. For example, when a defect is detected on the steel plate surface, a hole may be drilled at that position to facilitate identification of the location of the detected defect. In this way, when illumination light is irradiated onto the steel plate surface, the illumination light passes through the hole, making it easy to identify the location of the detected defect.

The disclosures of the specification, drawings and abstract contained in the Japanese application for Patent Application No. 2024-017940, filed February 8, 2024, are incorporated herein by reference in their entirety.

10 Grain-oriented electromagnetic steel sheet 100 Laser processing device 110 Conveying device 120 Output device 130 Light collecting device 150 Deflection device

Claims (13)

A laser processing device that processes a surface of an object to be processed by irradiating it with laser light,
an output device that outputs laser light;
a focusing device that focuses the laser light into a predetermined focused shape;
a deflection device that moves an irradiation position of the focused laser light on the surface of the object at the same moving speed as a conveying speed of the object conveyed in a first direction by a conveying device;
and
The focusing device forms the laser beam in a focused shape that is short in the first direction and long in a second direction perpendicular to the first direction . The laser processing apparatus according to claim 1 , wherein the deflection device includes a plurality of deflection devices that form a plurality of the laser beams in the second direction. 2. The laser processing device according to claim 1 , wherein the deflection device includes a polygon mirror that rotates at a rotation speed corresponding to the movement speed of the irradiation position. The laser processing device of claim 1, wherein the deflection device includes a deflection mirror that moves the irradiation position in a forward direction and a reverse direction relative to the first direction. 5. The laser processing device according to claim 4 , wherein the deflection device includes a galvanometer mirror that changes a reflection angle in response to a moving speed of the irradiation position. 6. The laser processing device according to claim 5 , further comprising a synchronization device that synchronizes the timing of the laser output from said output device with the reflection angle of said galvanometer mirror. The laser processing apparatus according to claim 4 , wherein the deflection device includes a mirror that moves back and forth in the first direction to change the reflection direction. 8. The laser processing device according to claim 7 , further comprising a synchronization device that synchronizes the timing of laser output from said output device with the reciprocating movement of said mirror. 9. The laser processing device according to claim 1 , wherein the object is a grain-oriented electrical steel sheet. 9. The laser processing device according to claim 1 , wherein the deflection device has a function of adjusting an irradiation interval in the first direction. A laser processing method for processing a surface of an object to be processed by irradiating the surface with laser light, comprising:
a focusing step of focusing the laser light on the object being transported in a first direction at a predetermined transport speed;
a moving step of moving an irradiation position of the focused laser light on the surface of the object to be processed at a moving speed that is the same as a conveying speed in the first direction;
and
The laser processing method, wherein the focusing step focuses the light into a focused shape that is short in the first direction and long in a second direction perpendicular to the first direction . 12. The laser processing method according to claim 11 , wherein the moving step moves the focused shape using a polygon mirror that rotates at a rotation speed corresponding to the moving speed of the irradiation position. The laser processing method according to claim 11 , wherein the moving step moves the focused shape using a deflection mirror that moves the irradiation position in a forward direction and a reverse direction with respect to the first direction.