Laser processing methods and laser processing equipment

Abstract

One laser processing method of the present invention is a method of imparting compressive residual stress to an object by irradiating a target area in the surface of an object with a laser. The laser processing method includes: a first step, extending the irradiated area of ​​the laser towards a first side in the target area; and a second step, extending the irradiated area of ​​the laser towards a second side different from the first side in the target area.

Description

Technical Field

[0001] This disclosure relates to laser processing methods and laser processing apparatus. Background Technology

[0002] Laser processing methods are known to impart compressive residual stress to an object by irradiating a material layer with a laser. In the laser processing method described in Patent Document 1, an absorbing material layer is formed such that the thickness of the absorbing material layer is a predetermined thickness in order to impart uniform compressive residual stress to the object.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 8-112681 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] However, as described in the laser processing method in Patent Document 1, it is difficult to impart uniform compressive residual stress to the object along the object area of ​​the object surface by simply forming the absorbent material layer in such a way that the thickness of the absorbent material layer is a predetermined thickness.

[0008] The purpose of this disclosure is to provide a laser processing method and laser processing apparatus capable of suppressing non-uniform compressive residual stress imposed on an object by an object region along the surface of an object.

[0009] Methods for solving problems

[0010] One aspect of the laser processing method disclosed herein is a laser processing method that imparts compressive residual stress to an object by irradiating a laser into an object region on the surface of an object, comprising: a first step, in the object region, extending the irradiated area of ​​the laser toward a first side; and a second step, in the object region, extending the irradiated area of ​​the laser toward a second side different from the first side.

[0011] In this laser processing method, in the first step, the irradiated area of ​​the laser is extended towards a first side, and in the second step, the irradiated area of ​​the laser is extended towards a second side different from the first side. As a result, the compressive residual stress imposed on the object by the first step decreases towards the first side, and the compressive residual stress imposed on the object by the second step decreases towards the second side different from the first side. Therefore, for example, compared to the case where the irradiated area of ​​the laser is extended towards the first side in the first step and then towards the first side in the second step, the non-uniformity of the compressive residual stress imposed on the object by the first and second steps is suppressed. Therefore, according to this laser processing method, it is possible to suppress the non-uniformity of the compressive residual stress imposed on the object along the object region in the surface of the object.

[0012] In the laser processing method of one aspect of this disclosure, the first side and the second side can be sides opposite to each other in a first direction. This allows for more reliable suppression of uneven compressive residual stress imparted to the workpiece through the first and second steps.

[0013] In one aspect of the laser processing method disclosed herein, the laser-irradiated area can be expanded toward the first side by performing a first process sequentially from the second side to the first side, in which the laser irradiation spot is moved along multiple lines extending in a second direction perpendicular to the first direction and arranged in the first direction. In a second step, the laser-irradiated area is expanded toward the second side by performing a second process sequentially from the first side to the second side, in which the laser irradiation spot is moved along multiple lines extending in the second direction and arranged in the first direction. Therefore, the laser-irradiated area can be reliably and easily expanded toward the first side in the first step, and the laser-irradiated area can be reliably and easily expanded toward a second side different from the first side in the second step.

[0014] In one aspect of the laser processing method disclosed herein, the method may include: in a first step, as a first process, alternately performing a process of moving the laser irradiation spot from one side to the other in a second direction and a process of moving the laser irradiation spot from the other side to one side in the second direction; and in a second step, as a second process, alternately performing a process of moving the laser irradiation spot from one side to the other in the second direction and a process of moving the laser irradiation spot from the other side to one side in the second direction. Therefore, in the first step, the irradiated area of ​​the laser can be efficiently extended toward the first side, and in the second step, the irradiated area of ​​the laser can be efficiently extended toward a second side different from the first side.

[0015] The laser processing method of this disclosure may further include: a third step, extending the irradiated area of ​​the laser towards a third side in the object region; and a fourth step, extending the irradiated area of ​​the laser towards a fourth side different from the third side in the object region, wherein the third side and the fourth side are opposite to each other in a second direction perpendicular to the first direction. This allows for more reliable suppression of non-uniform compressive residual stress imparted to the object along the object region on the surface of the object.

[0016] In one aspect of the laser processing method disclosed herein, the laser-irradiated area may be expanded toward the third side by performing a third process sequentially from the fourth side to the third side, in which the laser irradiation spot is moved along multiple lines extending in the first direction and arranged in the second direction, respectively; and in the fourth step, the laser-irradiated area is expanded toward the fourth side by performing a fourth process sequentially from the third side to the fourth side, in which the laser irradiation spot is moved along multiple lines extending in the first direction and arranged in the second direction, respectively. Therefore, the laser-irradiated area can be reliably and easily expanded toward the third side in the third step, and the laser-irradiated area can be reliably and easily expanded toward a fourth side different from the third side in the fourth step.

[0017] In one aspect of the laser processing method disclosed herein, the method may include: in a third step, as a third process, alternately performing a process of moving the laser irradiation spot from one side to the other in a first direction and a process of moving the laser irradiation spot from the other side of the first direction to one side; and in a fourth step, as a fourth process, alternately performing a process of moving the laser irradiation spot from one side to the other in the first direction and a process of moving the laser irradiation spot from the other side of the first direction to one side. Therefore, in the third step, the irradiated area of ​​the laser can be efficiently extended toward a third side, and in the fourth step, the irradiated area of ​​the laser can be efficiently extended toward a fourth side different from the third side.

[0018] A laser processing apparatus of this disclosure is a laser processing apparatus that imparts compressive residual stress to an object by irradiating a target region in the surface of an object with a laser, and includes: a support portion supporting the object; an irradiation portion irradiating the target region with a laser; and a control portion controlling the operation of at least one of the support portion and the irradiation portion, wherein the control portion controls the operation of at least one of the support portion and the irradiation portion such that the irradiated area of ​​the laser in the target region expands toward a first side, and controls the operation of at least one of the support portion and the irradiation portion such that the irradiated area of ​​the laser in the target region expands toward a second side different from the first side.

[0019] According to this laser processing apparatus, similar to the laser processing method described above, it is possible to suppress the unevenness of compressive residual stress imposed on the object along the object region in the surface of the object.

[0020] Invention Effects

[0021] According to this disclosure, a laser processing method and laser processing apparatus are provided that can suppress non-uniform compressive residual stress imposed on an object along the object region in the surface of the object. Attached Figure Description

[0022] Figure 1 This is a structural diagram of a laser processing apparatus according to one embodiment.

[0023] Figure 2 This is a top view of the object used to illustrate a laser processing method of one embodiment.

[0024] Figure 3 This is a top view of the object used to illustrate a laser processing method of one embodiment.

[0025] Figure 4 This is a top view of the object used to illustrate the laser processing methods of Comparative Example 1 and Comparative Example 2.

[0026] Figure 5 This is a top view of the object used to illustrate the laser processing methods of Comparative Examples 3 and 4.

[0027] Figure 6 It is an image showing the two-dimensional distribution of compressive residual stress imparted by the laser processing methods of Comparative Example 1 and Comparative Example 2.

[0028] Figure 7 It is an image showing the two-dimensional distribution of compressive residual stress imparted by the laser processing methods of Comparative Example 3 and Comparative Example 4.

[0029] Figure 8 This is an image showing the two-dimensional distribution of compressive residual stress imparted by the laser processing methods of Comparative Example 5 and Example 1.

[0030] Figure 9 It is an image showing the two-dimensional distribution of compressive residual stress imparted by the laser processing method of Example 2.

[0031] Figure 10 This is a graph showing the distribution of compressive residual stress imparted by the laser processing methods of Comparative Example 5, Example 1, and Example 2.

[0032] Figure 11 This is a table representing the numerical values ​​of compressive residual stress imparted by the laser processing methods of Comparative Example 5, Example 1, and Example 2.

[0033] Figure 12 This is a top view of the object used to illustrate the laser processing method of Modified Example 1.

[0034] Figure 13 This is a top view of the object used to illustrate the laser processing method of Modified Example 2. Detailed Implementation

[0035] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Furthermore, in the drawings, the same or equivalent parts are given the same symbols, and repeated descriptions are omitted.

[0036] [Laser processing equipment]

[0037] like Figure 1 As shown, the laser processing apparatus 1 includes a support unit 2, an irradiation unit 3, and a control unit 4. The laser processing apparatus 1 is a device that imparts compressive residual stress to the object 10 by irradiating a laser L into the object region 11 in the surface 10a of the object 10, along the object region 11. That is, the laser processing apparatus 1 is a device for performing laser shot peening on the object region 11 in the surface 10a of the object 10. In the following description, the three mutually orthogonal directions are referred to as the X direction, Y direction, and Z direction. In this embodiment, the Z direction is a first horizontal direction, the X direction is a second horizontal direction perpendicular to the first horizontal direction, and the Y direction is a vertical direction.

[0038] The support portion 2 supports the object 10 in a manner orthogonal to the Z direction, with the surface 10a of the object 10 perpendicular to the Z direction. The support portion 2 may include, for example, a clamp for holding the object 10, a robotic arm, etc. The object 10 may be, for example, a plate-shaped component made of a metal material such as copper, aluminum, iron, or titanium. During laser shot peening, a protective layer P is formed on the object area 11. A sealing layer C is formed on the surface of the protective layer P. The protective layer P is a layer that absorbs heat to protect the object area 11 from heat generated by laser L irradiation. The protective layer P may be, for example, a metal or resin layer. The sealing layer C is a layer that encloses the plasma generated by laser L irradiation when it impacts the object 10. The sealing layer C may be, for example, water supplied in a manner that covers the protective layer P.

[0039] The irradiation unit 3 irradiates a laser L onto an object region 11 on the surface 10a of an object 10 supported by the support unit 2. The irradiation unit 3 moves the irradiation spot S of the laser L two-dimensionally relative to the object region 11. The irradiation spot S of the laser L is the irradiation area of ​​the laser L in the object region 11. In this embodiment, the focusing spot CS of the laser L is located on the object region 11. That is, in this embodiment, the focusing spot CS of the laser L becomes the irradiation spot S of the laser L.

[0040] The illumination unit 3 includes a light source 31, an optical axis adjustment unit 32, an optical axis adjustment lens 33, an X-axis movable reflector 34, a Y-axis movable reflector 35, and an objective lens 36. The light source 31 emits a laser beam L. The light source 31 is, for example, a semiconductor laser that emits the laser beam L via pulse oscillation. The optical axis adjustment unit 32 supports the optical axis adjustment lens 33. The optical axis adjustment unit 32 moves the focusing spot CS along the Z-direction by moving the optical axis adjustment lens 33 along the Z-direction. The X-axis movable reflector 34 moves the focusing spot CS along the X-direction by adjusting the tilt of the reflector surface of the laser beam L. The Y-axis movable reflector 35 moves the focusing spot CS along the Y-direction by adjusting the tilt of the reflector surface of the laser beam L. The X-axis movable reflector 34 and the Y-axis movable reflector 35 are, for example, current reflectors. The objective lens 36 optically corrects the position of the focusing spot CS of the laser beam L so that the focusing spot CS is located on a plane perpendicular to the Z-direction. Objective lens 36 is, for example, an f-θ lens.

[0041] The control unit 4 controls the operation of the irradiation unit 3, causing the irradiation spot S to move along a predetermined trajectory on the target area 11. The control unit 4 includes, for example, a processing unit 41, a storage unit 42, and an input receiving unit 43. The processing unit 41 is configured as a computer device including a processor, memory, storage, and communication devices. In the processing unit 41, the processor executes software (programs) read from the memory, controls the reading and writing of data from the memory and the storage, and controls communication with the communication devices. The storage unit 42 is a hard disk or the like, storing various types of data. The input receiving unit 43 is an interface unit that receives various types of data input from the operator. In this embodiment, the input receiving unit 43 is configured as a GUI (Graphical User Interface).

[0042] [Laser processing methods]

[0043] The laser processing method implemented in the laser processing apparatus 1 described above will be explained. This laser processing method involves irradiating a laser L into a target region 11 on the surface 10a of an object 10, thereby imparting compressive residual stress to the object 10 along the target region 11. In other words, this laser processing method involves performing laser shot peening on the target region 11 on the surface 10a of the object 10. In this embodiment, the irradiation unit 3 is controlled by the control unit 4 to perform the first, second, third, and fourth steps described below. Furthermore, as an example, in the first, second, third, and fourth steps, the output of the laser L, the area of ​​the irradiation spot S, and the shape are constant.

[0044] First, the object 10 is prepared. In this embodiment, in the laser processing apparatus 1, the object 10 is supported by the support 2, and the object area 11, the irradiation conditions of the laser L, etc., are set by the control unit 4. In this embodiment, as... Figure 2 As shown in (a), one side in the X direction (first direction) is designated as the first side, and the other side in the X direction is designated as the second side. That is, the first side and the second side are opposite to each other in the X direction. Furthermore, one side in the Y direction (the second direction perpendicular to the first direction) is designated as the third side, and the other side in the Y direction is designated as the fourth side. That is, the third side and the fourth side are opposite to each other in the Y direction. As an example, the object region 11 is a rectangular region having two opposite sides in the X direction and two opposite sides in the Y direction.

[0045] Next, in the target region 11, the irradiated area 12 of the laser L is extended toward the first side (first step), expanding the irradiated area 12 to the entire target region 11. Specifically, in the target region 11, the irradiated area 12 is extended toward the first side by sequentially performing a first process from the second side to the first side, in which the irradiated spot S is moved along multiple lines L1 that extend in the Y direction and are equally spaced in the X direction. In this embodiment, as the first process, the process of moving the irradiated spot S from the third side to the fourth side (from one side in the second direction to the other side) and the process of moving the irradiated spot S from the fourth side to the third side (from the other side in the second direction to one side) are performed alternately. In addition, the interval between adjacent lines L1 is about 1 / 2 of the width of the irradiated spot S in the X direction.

[0046] Next, as Figure 2 As shown in (b), in the target region 11, the irradiated area 12 of the laser L is extended toward the second side (second step), expanding the irradiated area 12 to the entire target region 11 (i.e., expanding the irradiated area 12 to the entire target region 11 again in a manner overlapping with the irradiated area 12 expanded to the entire target region 11 in the first step). Specifically, in the target region 11, the irradiated area 12 is extended toward the second side by sequentially performing a second process from the first side to the second side, moving the irradiated spot S along multiple lines L2 that extend in the Y direction and are equally spaced in the X direction. In this embodiment, as the second process, the process of moving the irradiated spot S from the third side to the fourth side and the process of moving the irradiated spot S from the fourth side to the third side are alternately performed. In addition, the interval between adjacent lines L2 is about 1 / 2 of the width of the irradiated spot S in the X direction. In this embodiment, each line L2 is consistent with each line L1.

[0047] Next, as Figure 3As shown in (a), in the target region 11, the irradiated area 12 of the laser L is extended toward the third side (third step), and the irradiated area 12 is extended to the entire target region 11 (that is, the irradiated area 12 is extended to the entire target region 11 again in a manner that overlaps with the irradiated area 12 that was extended to the entire target region 11 in the first step and the second step, respectively). Specifically, in the target region 11, the irradiated area 12 is extended toward the third side by performing a third process, which moves the irradiated spot S along multiple lines L3 that extend in the X direction and are equally spaced in the Y direction, sequentially from the fourth side to the third side. In this embodiment, as the third process, the process of moving the irradiated spot S from the second side to the first side (from one side in the first direction to the other side) and the process of moving the irradiated spot S from the first side to the second side (from the other side in the first direction to one side) are performed alternately. In addition, the interval between adjacent lines L3 is about 1 / 2 of the width of the irradiated spot S in the Y direction.

[0048] Next, as Figure 3 As shown in (b), in the target region 11, the irradiated area 12 of the laser L is extended toward the fourth side (fourth step), expanding the irradiated area 12 to the entire target region 11 (i.e., expanding the irradiated area 12 to the entire target region 11 again in a manner overlapping with the irradiated areas 12 that were expanded to the entire target region 11 in the first, second, and third steps, respectively). Specifically, in the target region 11, the irradiated area 12 is extended toward the fourth side by sequentially performing a fourth process from the third side to the fourth side, in which the irradiated spot S is moved along multiple lines L4 that extend in the X direction and are equally spaced in the Y direction. In this embodiment, as the fourth process, the process of moving the irradiated spot S from the second side to the first side and the process of moving the irradiated spot S from the first side to the second side are performed alternately. In addition, the interval between adjacent lines L4 is about 1 / 2 of the width of the irradiated spot S in the Y direction. In this embodiment, each line L4 is consistent with each line L3.

[0049] As described above, compressive residual stress is applied to the object 10 along the object region 11 by performing the first, second, third, and fourth steps. That is, the above-described laser processing method is a method for manufacturing an object to which compressive residual stress is applied along the object region 11. Furthermore, in the above-described laser processing method, irradiation with laser L is sufficient as long as "at least a portion of the irradiated area 12 expanded in the first step," "at least a portion of the irradiated area 12 expanded in the second step," "at least a portion of the irradiated area 12 expanded in the third step," and "at least a portion of the irradiated area 12 expanded in the fourth step" overlap in the object region 11. In other words, in the above-described laser processing method, the area irradiated with laser L in an overlapping manner of "at least a portion of the irradiated area 12 expanded in the first step," "at least a portion of the irradiated area 12 expanded in the second step," "at least a portion of the irradiated area 12 expanded in the third step," and "at least a portion of the irradiated area 12 expanded in the fourth step" is the object region 11.

[0050] [Functions and Effects]

[0051] In the above-described laser processing method, in the first step, the irradiated area 12 of the laser L is extended toward a first side, and in the second step, the irradiated area 12 of the laser L is extended toward a second side. As a result, the compressive residual stress imposed on the object 10 in the first step decreases toward the first side, and the compressive residual stress imposed on the object 10 in the second step decreases toward the second side. Furthermore, in the third step, the irradiated area 12 of the laser L is extended toward a third side, and in the fourth step, the irradiated area 12 of the laser L is extended toward a fourth side. As a result, the compressive residual stress imposed on the object 10 in the third step decreases toward the third side, and the compressive residual stress imposed on the object 10 in the fourth step decreases toward the fourth side. Therefore, for example, compared to the case where the irradiated area 12 of the laser L is extended toward the first side in the first, second, third, and fourth steps respectively, the non-uniformity of the compressive residual stress imposed on the object 10 is suppressed. Therefore, according to the laser processing method described above, it is possible to suppress the uneven compressive residual stress imparted to the object 10 by the object region 11 along the surface 10a of the object 10.

[0052] In the laser processing method described above, the first and second sides are opposite to each other in the X direction, and the third and fourth sides are opposite to each other in the Y direction. This allows for more reliable suppression of uneven compressive residual stress imparted to the object 10.

[0053] In the above-described laser processing method, in the first step, a first process is performed sequentially from the second side to the first side, moving the irradiation spot S of the laser L along multiple lines L1 extending in the Y direction and arranged in the X direction, thereby expanding the irradiated area 12 of the laser L toward the first side. Thus, in the first step, the irradiated area 12 of the laser L can be reliably and easily expanded toward the first side. In the above-described laser processing method, in the second step, a second process is performed sequentially from the first side to the second side, moving the irradiation spot S of the laser L along multiple lines L2 extending in the Y direction and arranged in the X direction, thereby expanding the irradiated area 12 of the laser L toward the second side. Thus, in the second step, the irradiated area 12 of the laser L can be reliably and easily expanded toward a second side different from the first side.

[0054] In the above-described laser processing method, in the first step, as a first process, the process of moving the irradiation spot S of the laser L from one side to the other in the Y direction and the process of moving the irradiation spot S of the laser L from the other side to one side in the Y direction are alternately performed. Therefore, in the first step, the irradiated area 12 of the laser L can be efficiently extended toward the first side. In the above-described laser processing method, in the second step, as a second process, the process of moving the irradiation spot S of the laser L from one side to the other in the Y direction and the process of moving the irradiation spot S of the laser L from the other side to one side in the Y direction are alternately performed. Therefore, in the second step, the irradiated area 12 of the laser L can be efficiently extended toward a second side different from the first side.

[0055] In the above-described laser processing method, in the third step, a third process is performed sequentially from the fourth side to the third side, in which the irradiation spot S of the laser L is moved along multiple lines L3 extending in the X direction and arranged in the Y direction, thereby expanding the irradiated area 12 of the laser L toward the third side. Thus, in the third step, the irradiated area 12 of the laser L can be reliably and easily expanded toward the third side. In the above-described laser processing method, in the fourth step, a fourth process is performed sequentially from the third side to the fourth side, in which the irradiation spot S of the laser L is moved along multiple lines L4 extending in the X direction and arranged in the Y direction, thereby expanding the irradiated area 12 of the laser L toward the fourth side. Thus, in the fourth step, the irradiated area 12 of the laser L can be reliably and easily expanded toward a fourth side different from the third side.

[0056] In the above-described laser processing method, in the third step, as a third process, the process of moving the irradiation spot S of the laser L from one side to the other in the X direction and the process of moving the irradiation spot S of the laser L from the other side to one side in the X direction are alternately performed. Therefore, in the third step, the irradiated area 12 of the laser L can be efficiently extended toward the third side. In the above-described laser processing method, in the fourth step, as a fourth process, the process of moving the irradiation spot S of the laser L from one side to the other in the X direction and the process of moving the irradiation spot S of the laser L from the other side to one side in the X direction are alternately performed. Therefore, in the fourth step, the irradiated area 12 of the laser L can be efficiently extended toward a fourth side different from the third side.

[0057] According to the laser processing apparatus 1 described above, similarly to the laser processing method described above, it is possible to suppress the uneven compressive residual stress imparted to the object 10 by the object region 11 along the surface 10a of the object 10.

[0058] [Comparative Examples and Implementation Examples]

[0059] First, the laser processing methods of Comparative Examples 1, 2, 3, and 4 will be described. The laser irradiation conditions in the laser processing methods of Comparative Examples 1, 2, 3, and 4 are as follows.

[0060] Laser irradiation conditions

[0061] Wavelength: 1053nm

[0062] Pulse energy: 300mJ

[0063] Pulse width: 10ns (rectangular)

[0064] Focusing size: approximately 0.8 × 0.8 mm

[0065] Intensity: 4.7 GW / cm 2

[0066] Repetition frequency: 2Hz

[0067] Conditions of the object

[0068] Material: Aluminum alloy (A2024)

[0069] Shape: 49×49mm

[0070] Thickness: 3mm

[0071] Object area: 2×10mm

[0072] Protective layer: Resin tape (thickness: less than 100μm)

[0073] Enclosed layer: water flow

[0074] In the laser processing method of Comparative Example 1, such as Figure 4 As shown in (a), in the target area, a process is performed sequentially from one side to the other in the X direction, moving the laser irradiation spot along six lines (dashed lines) extending in the Y direction and arranged in the X direction, thus expanding the laser-irradiated area from one side to the other in the X direction (laser irradiation step). In the laser processing method of Comparative Example 1, four laser irradiation steps were performed. Figure 4 In (a), the number assigned to each line indicates the order in which the laser beam moves along the line, and the arrow assigned to each row indicates the direction in which the laser beam moves along the line.

[0075] In the laser processing method of Comparative Example 2, such as Figure 4 As shown in (b), in the target area, a process was performed in which the laser irradiation spot was moved along six lines (dashed lines) extending in the Y direction and arranged in the X direction, respectively. That is, the process was performed in the order of the first line starting from one side in the X direction, the sixth line starting from that side, the second line starting from that side, the fifth line starting from that side, the third line starting from that side, and the fourth line starting from that side. In the laser processing method of Comparative Example 2, this process was performed four times. Figure 4 In (b), the numbering of each line indicates the order in which the laser beam moves along the line, and the arrows in each row indicate the direction in which the laser beam moves along the line.

[0076] In the laser processing method of Comparative Example 3, such as Figure 5 As shown in (a), in the target area, a process was performed in which the laser irradiation spot was moved along six lines (dashed lines) extending in the Y direction and arranged in the X direction, respectively. That is, the process was performed in the order of the third line from one side in the X direction, the fourth line from that side, the second line from that side, the fifth line from that side, the first line from that side, and the sixth line from that side. In the laser processing method of Comparative Example 3, this process was performed four times. Figure 5 In (a), the number assigned to each line indicates the order in which the laser beam moves along the line, and the arrow assigned to each line indicates the direction in which the laser beam moves along the line.

[0077] In the laser processing method of Comparative Example 4, such as Figure 5As shown in (b), in the target area, a process was performed in which the laser irradiation spot was moved along six lines (dashed lines) extending in the Y direction and arranged in the X direction, respectively. That is, the process was performed in the order of the first line starting from one side in the X direction, the sixth line starting from that side, the third line starting from that side, the fifth line starting from that side, the second line starting from that side, and the fourth line starting from that side. In the laser processing method of Comparative Example 4, this process was performed four times. Figure 5 In (b), the number assigned to each line indicates the order in which the laser beam moves along the line, and the arrow assigned to each line indicates the direction in which the laser beam moves along the line.

[0078] The two-dimensional distribution of compressive residual stress imparted by the laser processing methods of Comparative Examples 1, 2, 3, and 4 was measured using an X-ray residual stress measuring device. The measurement conditions for the two-dimensional distribution of compressive residual stress are as follows.

[0079] Measurement conditions for the two-dimensional distribution of compressive residual stress

[0080] X-ray size: φ0.5mm

[0081] Measurement range: 3×4mm

[0082] Interval: 0.25mm

[0083] Tube ball: Co

[0084] The two-dimensional distribution of compressive residual stress imparted by the laser processing method in Comparative Example 1 is shown below. Figure 6 As shown in (a), the distribution decreases from one side to the other in the X direction. Additionally, in Figure 6 In (a), the compressive residual stress is represented by a negative value (as discussed later). Figure 6 (b) Figure 7 (a) and Figure 7 The same applies to (b).

[0085] The two-dimensional distribution of compressive residual stress imparted by the laser processing method in Comparative Example 2 is shown below. Figure 6 As shown in (b), in one half of the object region along the X direction, the distribution decreases from one side of the X direction toward the other. On the other hand, in the other half of the object region along the X direction, the two-dimensional distribution decreases from the other side of the X direction toward one side.

[0086] The two-dimensional distribution of compressive residual stress imparted by the laser processing method in Comparative Example 3 is shown below. Figure 7As shown in (a), in one half of the object region along the X direction, the distribution decreases from the other side of the X direction toward one side. On the other hand, in the other half of the object region along the X direction, the two-dimensional distribution decreases from one side of the X direction toward the other side.

[0087] By comparing the two-dimensional distribution of compressive residual stress imparted by the laser processing method in Example 4, as shown... Figure 7 As shown in (b), in one half of the object region along the X direction, the distribution decreases from one side of the X direction toward the other. On the other hand, in the other half of the object region along the X direction, the two-dimensional distribution decreases from the other side of the X direction toward one side.

[0088] Based on the above results, it is confirmed that the compressive residual stress imposed on the object decreases on the side of the object region that extends towards the laser-irradiated area. Furthermore, it is confirmed that the distribution of the compressive residual stress imposed on the object is non-uniform even when the laser-irradiated area in the object region randomly expands from a sparse state to a dense state.

[0089] Next, the laser processing methods of Comparative Example 5, Example 1, and Example 2 will be described. The laser irradiation conditions in the laser processing methods of Comparative Example 5, Example 1, and Example 2 are as follows.

[0090] Laser irradiation conditions

[0091] Wavelength: 1064nm

[0092] Pulse energy: 42mJ

[0093] Pulse width: 39.4 ns (Gaussian)

[0094] Focusing size: φ0.19mm

[0095] Intensity: 3.8 GW / cm 2

[0096] Repetition frequency: 300Hz

[0097] Conditions of the object

[0098] Material: Aluminum alloy (A2024)

[0099] Shape: 49×49mm

[0100] Thickness: 3mm

[0101] Object area: 3×3mm

[0102] Protective layer: Aluminum strip (thickness: less than 100μm)

[0103] Enclosed layer: water flow

[0104] In the laser processing method of Comparative Example 5, a step of extending the irradiated area of ​​the laser from one side to the other in the X direction in the target area was performed four times (equivalent to the first step in the laser processing method of the above embodiment).

[0105] In the laser processing method of Embodiment 1, the steps of extending the laser-irradiated area in the target area from one side to the other in the X direction (equivalent to the first step in the laser processing method of the above embodiment) are performed alternately twice each, and the steps of extending the laser-irradiated area in the target area from the other side to one side in the X direction (equivalent to the second step in the laser processing method of the above embodiment) are performed alternately twice each.

[0106] In the laser processing method of Embodiment 2, these steps are performed once each in the following order: the step of extending the laser-irradiated area in the target area from one side to the other in the X direction (equivalent to the first step in the laser processing method of the above embodiment); the step of extending the laser-irradiated area in the target area from the other side to one side in the X direction (equivalent to the second step in the laser processing method of the above embodiment); the step of extending the laser-irradiated area in the target area from one side to the other in the Y direction (equivalent to the third step in the laser processing method of the above embodiment); and the step of extending the laser-irradiated area in the target area from the other side to one side in the Y direction (equivalent to the fourth step in the laser processing method of the above embodiment).

[0107] The two-dimensional distribution of compressive residual stress imparted by the laser processing methods of Comparative Example 5, Example 1, and Example 2 was measured using an X-ray residual stress measuring device. The measurement conditions for the two-dimensional distribution of compressive residual stress are as follows.

[0108] Measurement conditions for the two-dimensional distribution of compressive residual stress

[0109] X-ray size: φ0.5mm

[0110] Measurement range: 5.0 × 2.5 mm

[0111] Interval: 0.25mm

[0112] Tube ball: Co

[0113] By comparing the laser processing method in Example 5, the two-dimensional distribution of the compressive residual stress imparted to the object region is as follows: Figure 8As shown in (a), the distribution decreases from one side to the other in the X direction. The two-dimensional distribution of the compressive residual stress imparted to the object region by the laser processing method of Example 1 is as follows: Figure 8 As shown in (b), the two-dimensional distribution of compressive residual stress obtained by the laser processing method of Comparative Example 5 is characterized by suppressed non-uniform distribution. The two-dimensional distribution of compressive residual stress imparted along the object region by the laser processing method of Example 2 is shown below. Figure 9 As shown, compared to the two-dimensional distribution of compressive residual stress obtained by the laser processing method in Example 1, the non-uniform distribution is suppressed. Furthermore, in Figure 8 of (a), Figure 8 (b) and Figure 9 In this context, compressive residual stress is represented by a negative value.

[0114] Figure 10 This is a graph showing the distribution of compressive residual stress imparted by the laser processing methods of Comparative Example 5, Example 1, and Example 2. Figure 10 In this context, "X-direction position" refers to the position along the X-direction, and "average residual stress in the Y-direction" refers to the average compressive residual stress imparted to the portion along the Y-direction at each X-direction position. For example... Figure 10 As shown, regarding the average residual stress in the Y direction of the object region, when considering the difference between the maximum and minimum values, the value obtained by the laser processing method of Example 1 is smaller than the value obtained by the laser processing method of Comparative Example 5, and the value obtained by the laser processing method of Example 2 is smaller than the value obtained by the laser processing method of Example 1. Furthermore, in Figure 10 In this context, compressive residual stress is represented by a negative value (as discussed later). Figure 11 The same applies to China.

[0115] Figure 11 This table represents the numerical values ​​of compressive residual stress imparted by the laser processing methods of Comparative Example 5, Example 1, and Example 2. Figure 11 In this context, "maximum value" refers to the value along... Figure 8 of (a), Figure 8 (b) and Figure 9 The minimum compressive residual stress is assigned to the object region (within the 3×3mm dashed box). "Minimum" refers to the maximum compressive residual stress assigned along this object region, and "Average" refers to the average compressive residual stress assigned along this object region. "Deviance" refers to the magnitude of the deviation of the compressive residual stress value assigned along this object region from the average value, and "Deviance / |Average|" refers to the proportion by which the compressive residual stress value assigned along this object region deviates from the average value. For example... Figure 11As shown, regarding "deviation" and "deviation / |average value|", the value obtained by the laser processing method of Example 1 is smaller than that obtained by the laser processing method of Comparative Example 5, and the value obtained by the laser processing method of Example 2 is smaller than that obtained by the laser processing method of Example 1. That is, the compressive residual stress imparted along the object region in Example 1 is more uniform than that imparted along the object region in Comparative Example 5. Furthermore, the compressive residual stress imparted along the object region in Example 2 is more uniform than that imparted along the object region in Example 1.

[0116] [Variation Example]

[0117] This disclosure is not limited to the above-described embodiments and examples. A laser processing method of Modified Example 1 will be described. In the laser processing method of Modified Example 1, as... Figure 12 As shown in (a), the irradiated area 12 of the laser L is extended outward (first side) within the target area 11 (first step), as... Figure 12 As shown in (b), the irradiated area 12 of the laser L is extended inward (second side) within the target area 11 (second step). Specifically, in the first step, as... Figure 12 As shown in (a), the irradiation spot S of the laser L is moved along a vortex-shaped line from the center of the object region 11 to the outer edge of the object region 11. In the second step, as... Figure 12 As shown in (b), the irradiation spot S of the laser L is moved from the outer edge of the target region 11 along a vortex-shaped line to the center of the target region 11. Alternatively, the irradiation spot S of the laser L can be moved along nested annular lines arranged in the target region 11. As an example, by sequentially moving the irradiation spot S along multiple annular lines from the inner annular lines to the outer annular lines, the irradiated area 12 of the laser L is expanded outward in the target region 11 (first step). Next, by sequentially moving the irradiation spot S along multiple annular lines from the outer annular lines to the inner annular lines, the irradiated area 12 of the laser L is expanded inward in the target region 11 (second step). In this modified laser processing method, each step is performed in the order of first step and second step, but each step can also be performed in the order of second step and first step.

[0118] The laser processing method of Modified Example 2 will be described. In the laser processing method of Modified Example 2, the object region 11 is divided into multiple regions, and the laser processing method of the above embodiment is performed in each of the multiple regions. For example, as Figure 13As shown, the object region 11 is divided into four regions arranged in two rows and two columns along the X and Y directions. By performing the laser processing method of the above embodiment in parallel in these four regions, even when the object region 11 is wide, the time required to apply compressive residual stress to the object 10 along the object region 11 can be shortened.

[0119] In the laser processing apparatus 1 of the above embodiment, the control unit 4 controls the operation of the irradiation unit 3, causing the irradiation spot S to move along a predetermined trajectory on the target area 11. However, the control unit 4 only needs to control the operation of at least one of the support unit 2 and the irradiation unit 3. For example, the control unit 4 can control the operation of the support unit 2, causing the irradiation spot S to move along a predetermined trajectory on the target area 11. Alternatively, the control unit 4 can control the operation of both the support unit 2 and the irradiation unit 3, causing the irradiation spot S to move along a predetermined trajectory on the target area 11.

[0120] In the laser processing method of the above embodiments, in the first step and the second step, the process of moving the irradiation spot S from the third side to the fourth side or the process of moving the irradiation spot S from the fourth side to the third side are alternately performed. However, in the first step and the second step, the process of moving the irradiation spot S from the third side to the fourth side or the process of moving the irradiation spot S from the fourth side to the third side can be performed continuously.

[0121] In the laser processing method of the above embodiments, in the third and fourth steps, the process of moving the irradiation spot S from the first side to the second side or the process of moving the irradiation spot S from the second side to the first side are alternately performed. However, in the third and fourth steps, the process of moving the irradiation spot S from the second side to the first side or the process of moving the irradiation spot S from the first side to the second side can be performed continuously.

[0122] In the laser processing method of the above embodiment, each line L2 is consistent with each line L1, but as long as multiple lines L2 extend in the Y direction and are arranged in the X direction, each line L2 may not be consistent with each line L1. Similarly, in the laser processing method of the above embodiment, each line L4 is consistent with each line L3, but as long as multiple lines L4 extend in the X direction and are arranged in the Y direction, each line L4 may not be consistent with each line L3.

[0123] In the laser processing method of the above embodiments, multiple lines L1 are arranged at equal intervals, but the multiple lines L1 can also be arranged at unequal intervals. Similarly, in the laser processing method of the above embodiments, multiple lines L2 are arranged at equal intervals, but the multiple lines L2 can also be arranged at unequal intervals. Similarly, in the laser processing method of the above embodiments, multiple lines L3 are arranged at equal intervals, but the multiple lines L3 can also be arranged at unequal intervals. Similarly, in the laser processing method of the above embodiments, multiple lines L4 are arranged at equal intervals, but the multiple lines L4 can also be arranged at unequal intervals.

[0124] In the laser processing method of the above embodiment, the interval between adjacent lines L1 is approximately half the width of the irradiation spot S in the X direction, but it can also be greater than half the width of the irradiation spot S in the X direction. That is, there can be regions between adjacent lines L1 where the laser L is not irradiated twice. Furthermore, the interval between adjacent lines L1 is preferably less than half the width of the irradiation spot S in the X direction. That is, it is preferable to irradiate adjacent lines L1 with laser L more than twice. Further, the interval between adjacent lines L1 is preferably half the width of the irradiation spot S in the X direction. That is, it is preferable to irradiate adjacent lines L1 without repeating the laser L twice. In this case, the irradiated area 12, which is uniformly irradiated with laser L, can be extended towards the first side.

[0125] Similarly, in the laser processing method of the above embodiment, the interval between adjacent lines L2 is approximately half the width of the irradiation spot S in the X direction, but it can also be greater than half the width of the irradiation spot S in the X direction. That is, there can be regions between adjacent lines L2 where the laser L is not irradiated twice. Furthermore, the interval between adjacent lines L2 is preferably less than half the width of the irradiation spot S in the X direction. That is, it is preferable to irradiate with the laser L more than twice between adjacent lines L2. Further, the interval between adjacent lines L2 is preferably half the width of the irradiation spot S in the X direction. That is, it is preferable to irradiate with the laser L twice without repetition between adjacent lines L2. In this case, the irradiated area 12, which is uniformly irradiated with the laser L, can be extended towards the second side.

[0126] Similarly, in the laser processing method of the above embodiment, the interval between adjacent lines L3 is approximately half the width of the irradiation spot S in the Y direction, but it can also be greater than half the width of the irradiation spot S in the Y direction. That is, there can be regions between adjacent lines L3 where the laser L is not irradiated twice. Furthermore, the interval between adjacent lines L3 is preferably less than half the width of the irradiation spot S in the Y direction. That is, it is preferable to irradiate with laser L more than twice between adjacent lines L3. Further, the interval between adjacent lines L3 is preferably half the width of the irradiation spot S in the Y direction. That is, it is preferable to irradiate with laser L twice without repetition between adjacent lines L3. In this case, the irradiated area 12, which is uniformly irradiated with laser L, can be extended towards the third side.

[0127] Similarly, in the laser processing method of the above embodiment, the interval between adjacent lines L4 is approximately half the width of the irradiation spot S in the Y direction, but it can also be greater than half the width of the irradiation spot S in the Y direction. That is, there can be regions between adjacent lines L4 where the laser L is not irradiated twice. Furthermore, the interval between adjacent lines L4 is preferably less than half the width of the irradiation spot S in the Y direction. That is, it is preferable to irradiate with laser L more than twice between adjacent lines L4. Further, the interval between adjacent lines L4 is preferably half the width of the irradiation spot S in the Y direction. That is, it is preferable to irradiate with laser L twice without repetition between adjacent lines L4. In this case, the irradiated area 12, which is uniformly irradiated with laser L, can be extended towards the fourth side.

[0128] In the laser processing method of the above embodiment, a first process is performed sequentially from the second side to the first side, causing the irradiation spot S of the laser L to move along multiple lines L1 respectively. However, this process may not be performed sequentially. For example, a portion of the multiple lines L1 may be skipped when performing the first process from the second side to the first side, or the process of moving the irradiation spot S of the laser L along the skipped portion of the lines may be performed after the first process. Similarly, in the laser processing method of the above embodiment, a second process is performed sequentially from the first side to the second side, causing the irradiation spot S of the laser L to move along multiple lines L2 respectively. However, this process may not be performed sequentially. For example, a portion of the multiple lines L2 may be skipped when performing the second process from the first side to the second side, or the process of moving the irradiation spot S of the laser L along the skipped portion of the lines may be performed after the second process.

[0129] In the laser processing method of the above embodiment, a third process is performed sequentially from the fourth side to the third side, in which the irradiation spot S of the laser L moves along multiple lines L3 respectively. However, this process may not be performed sequentially. For example, a portion of the multiple lines L3 may be skipped when performing the third process from the fourth side to the third side, or the process of moving the irradiation spot S of the laser L along the skipped portion of the lines may be performed after the third process. Similarly, in the laser processing method of the above embodiment, a fourth process is performed sequentially from the third side to the fourth side, in which the irradiation spot S of the laser L moves along multiple lines L4 respectively. However, this process may not be performed sequentially. For example, a portion of the multiple lines L4 may be skipped when performing the fourth process from the third side to the fourth side, or the process of moving the irradiation spot S of the laser L along the skipped portion of the lines may be performed after the fourth process.

[0130] In the laser processing method described above, each step is performed in the order of first step, second step, third step, and fourth step, but the order of the steps can be adjusted. Specifically, the steps can be performed in the order of first step, third step, second step, and fourth step. Alternatively, the steps can be performed in the order of first step, third step, fourth step, and second step.

[0131] In the laser processing method of the above embodiment, the third and fourth steps are performed, but only the first and second steps need to be performed. Since the irradiated area 12 of the laser L can be extended towards two different sides in this case, the unevenness of the compressive residual stress imparted to the object 10 along the object region 11 can be suppressed. Furthermore, when only the first and second steps are performed, the irradiation by the laser L is sufficient as long as at least a portion of the irradiated area 12 extended in the first step and at least a portion of the irradiated area 12 extended in the second step overlap in the object region 11. In other words, when only the first and second steps are performed, the area irradiated by the laser L in which at least a portion of the irradiated area 12 extended in the first step and at least a portion of the irradiated area 12 extended in the second step overlap is the object region 11.

[0132] In the laser processing method of the above embodiment, the first side and the second side are sides that are opposite to each other in the X direction, but the first side and the second side only need to be sides that are opposite to each other in a predetermined direction. Furthermore, the first side and the second side only need to be sides that are different from each other. If the first side and the second side are sides that are different from each other, then compared to the case where the irradiated area 12 of the laser L is extended toward the first side in the second step, the non-uniformity of the compressive residual stress imparted to the object 10 by the first step and the second step can be suppressed. In addition, when the first side and the second side are represented by vectors of the same magnitude, the angle between the vector representing the first side (i.e., the vector toward the first side) and the vector representing the second side (i.e., the vector toward the second side) is preferably greater than 90 degrees and less than 180 degrees. That is, the vector representing the first side and the vector representing the second side preferably have vector components that are opposite to each other in a predetermined direction. In this case, in this predetermined direction, the non-uniformity of the compressive residual stress imparted to the object 10 along the object area 11 can be suppressed. For reference, the case where the angle between the vector representing the first side and the vector representing the second side is 180 degrees is the case where the first side and the second side are opposite to each other.

[0133] In the laser processing method of the above embodiment, the third side and the fourth side are opposite to each other in the Y direction, but the third side and the fourth side only need to be opposite to each other in a predetermined direction. Furthermore, the third side and the fourth side only need to be different from each other. If the third side and the fourth side are different from each other, the non-uniformity of the compressive residual stress imparted to the object 10 by the third and fourth steps can be suppressed compared to the case where the irradiated area 12 of the laser L is extended towards the third side in the fourth step. In addition, when the third side and the fourth side are represented by vectors of the same magnitude, the angle between the vector representing the third side (i.e., the vector towards the third side) and the vector representing the fourth side (i.e., the vector towards the fourth side) is preferably greater than 90 degrees and less than 180 degrees. That is, the vector representing the third side and the vector representing the fourth side preferably have vector components that are opposite to each other in a predetermined direction. In this case, the non-uniformity of the compressive residual stress imparted to the object 10 along the object area 11 can be suppressed in this predetermined direction. For reference, the case where the angle between the vector representing the third side and the vector representing the fourth side is 180 degrees is the case where the third side and the fourth side are opposite to each other.

[0134] Object region 11 is not limited to a plane; it can also be a curved surface. Object region 11 is not limited to a rectangle; it can also be a circle or other shapes. Lines L1, L2, L3, and L4 are not limited to straight lines; they can also be curves.

[0135] Symbol Explanation

[0136] 1…laser processing device, 2…support, 3…irradiation part, 4…control part, 10…object, 10a…surface, 11…object area, 12…irradiated area, L…laser, S…irradiation spot, L1, L2, L3, L4…line.

Claims

1. A laser processing method, wherein, This is a laser processing method that applies compressive residual stress to an object by irradiating a target area on the surface of the object with a laser. have: The first step is to extend the irradiated area of ​​the laser toward the first side in the target area; and The second step is to extend the irradiated area of ​​the laser in the target region toward a second side different from the first side. The first side is one side in the first direction. The second side is the other side in the first direction. In the first step, a process is implemented to move the laser irradiation spot from one side to the other in a second direction perpendicular to the first direction, or to move the laser irradiation spot from the other side to the first side in the second direction. In the second step, a process is performed to move the laser irradiation spot from one side to the other side in the second direction, or to move the laser irradiation spot from the other side to the same side in the second direction.

2. The laser processing method according to claim 1, wherein, The first side and the second side are sides that are opposite to each other in a first direction.

3. The laser processing method according to claim 2, wherein, In the first step, the irradiated area of ​​the laser is expanded toward the first side by sequentially performing a first process from the second side toward the first side. The first process involves moving the laser irradiation spot along each of a plurality of lines extending in a second direction perpendicular to the first direction and arranged in the first direction. In the second step, the irradiated area of ​​the laser is expanded toward the second side by performing a second process sequentially from the first side to the second side. The second process is to move the irradiated spot of the laser along each of a plurality of lines that extend in the second direction and are arranged in the first direction.

4. The laser processing method according to claim 3, wherein, In the first step, as the first process, processes of moving the laser irradiation spot from one side to the other in the second direction and processes of moving the laser irradiation spot from the other side to the first side in the second direction are alternately implemented. In the second step, as the second process, the process of moving the laser irradiation spot from one side to the other side in the second direction and the process of moving the laser irradiation spot from the other side to the same side in the second direction are alternately implemented.

5. The laser processing method according to any one of claims 2 to 4, wherein, It also has: The third step is to extend the irradiated area of ​​the laser toward a third side in the target area; and The fourth step is to extend the irradiated area of ​​the laser in the target region toward a fourth side, different from the third side. The third side and the fourth side are opposite to each other in a second direction perpendicular to the first direction.

6. The laser processing method according to claim 5, wherein, In the third step, the irradiated area of ​​the laser is expanded toward the third side by sequentially performing a third process from the fourth side toward the third side. The third process involves moving the laser irradiation spot along each of a plurality of lines extending in the first direction and arranged in the second direction. In the fourth step, the irradiated area of ​​the laser is expanded toward the fourth side by performing a fourth process sequentially from the third side to the fourth side. The fourth process is to move the irradiated spot of the laser along each of a plurality of lines that extend in the first direction and are arranged in the second direction.

7. The laser processing method according to claim 6, wherein, In the third step, as the third process, the process of moving the laser irradiation spot from one side to the other in the first direction and the process of moving the laser irradiation spot from the other side to the first side in the first direction are alternately implemented. In the fourth step, as the fourth process, the processes of moving the laser irradiation spot from one side to the other side in the first direction and the processes of moving the laser irradiation spot from the other side to the same side in the first direction are alternately implemented.

8. A laser processing apparatus, wherein, It is a laser processing device that applies compressive residual stress to an object by irradiating a laser beam onto a target area on the surface of the object. have: Support portion, which supports the object; An irradiation unit that irradiates the target area with the laser; and The control unit controls the operation of at least one of the support unit and the irradiation unit. The control unit: The movement of at least one of the support and the irradiation part is controlled such that the irradiated area of ​​the laser extends toward the first side in the target area; and The movement of at least one of the support and the irradiation part is controlled such that the irradiated area of ​​the laser in the target region extends toward a second side different from the first side. The first side is one side in the first direction. The second side is the other side in the first direction. The process involves moving the laser beam from one side to the other in a second direction perpendicular to the first direction, or moving the laser beam from the other side to the first side in the second direction. The process of moving the laser irradiation spot from one side to the other side in the second direction, or the process of moving the laser irradiation spot from the other side to the same side in the second direction, is implemented.

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