Laser processing method and laser processing device

Abstract

To provide a laser processing method and a laser processing device which can suppress variations in a compressive residual stress applied to an object along an object area on a surface of the object.SOLUTION: A laser processing method is a method for irradiating an object area 11 on a surface of an object with a laser beam, and thereby applying a compressive residual stress to the object along the object area 11. The laser processing method includes: a first step of enlarging an area 12 irradiated with the laser beam toward a first side in the object area 11; and a second step of enlarging the area 12 irradiated with the laser beam toward a second side different from the first side in the object area 11.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a laser processing method and a laser processing apparatus. [Background technology]

[0002] A laser processing method is described in which a material layer is irradiated with laser light to impart compressive residual stress to an object. In the laser processing method described in Patent Document 1, an absorbing material layer is formed to have a predetermined thickness in order to impart uniform compressive residual stress to the object. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 8-112681 Summary of the Invention [Problem to be solved by the invention]

[0004] However, simply forming an absorbing material layer to have a predetermined thickness, as in the laser processing method described in Patent Document 1, makes it difficult to impart uniform compressive residual stress to the object along the target area on the surface of the object.

[0005] An object of the present invention is to provide a laser processing method and laser processing apparatus that can suppress variation in compressive residual stress imparted to an object along a target area on the surface of the object. [Means for solving the problem]

[0006] The laser processing method of the present invention is a laser processing method that imparts compressive residual stress to an object along a target area on a surface of the object by irradiating the target area with laser light, and includes a first step of expanding an area irradiated with the laser light in the target area toward a first side, and a second step of expanding the area irradiated with the laser light in the target area toward a second side different from the first side.

[0007] In this laser processing method, the irradiated area of ​​the laser light is expanded toward the first side in the first step, and the irradiated area of ​​the laser light is expanded toward the second side different from the first side in the second step. As a result, the compressive residual stress imparted to the object by the first step decreases toward the first side, and the compressive residual stress imparted to the object by the second step decreases toward the second side different from the first side. Therefore, the variation in the compressive residual stress imparted to the object by the first step and the second step is suppressed compared to the case where, for example, the irradiated area of ​​the laser light is expanded toward the first side in the first step, and the irradiated area of ​​the laser light is expanded toward the first side in the second step. Therefore, according to this laser processing method, it is possible to suppress the variation in the compressive residual stress imparted to the object along the target area on the surface of the object.

[0008] In the laser processing method of the present invention, the first side and the second side may be sides facing each other in the first direction, which makes it possible to more reliably suppress variation in the compressive residual stress imparted to the object by the first step and the second step.

[0009] In the laser processing method of the present invention, in the first step, a first process of moving the irradiation spot of the laser light along each of a plurality of lines extending in a second direction perpendicular to the first direction and aligned in the first direction may be performed sequentially from the second side to the first side, thereby widening the irradiated area of ​​the laser light toward the first side, and in the second step, a second process of moving the irradiation spot of the laser light along each of a plurality of lines extending in the second direction and aligned in the first direction may be performed sequentially from the first side to the second side, thereby widening the irradiated area of ​​the laser light toward the second side. This makes it possible to reliably and easily widen the irradiated area of ​​the laser light toward the first side in the first step, and to reliably and easily widen the irradiated area of ​​the laser light toward the second side different from the first side in the second step.

[0010] In the laser processing method of the present invention, in the first step, as a first process, a process of moving the irradiation spot of the laser light from one side to the other side in the second direction and a process of moving the irradiation spot of the laser light from the other side to one side in the second direction may be alternately performed, and in the second step, as a second process, a process of moving the irradiation spot of the laser light from one side to the other side in the second direction and a process of moving the irradiation spot of the laser light from the other side to one side in the second direction may be alternately performed. Thereby, in the first step, the irradiated area of ​​the laser light can be efficiently expanded toward the first side, and in the second step, the irradiated area of ​​the laser light can be efficiently expanded toward the second side different from the first side.

[0011] The laser processing method of the present invention further includes a third step of expanding the area irradiated with the laser light in the target area toward a third side, and a fourth step of expanding the area irradiated with the laser light in the target area toward a fourth side different from the third side, and the third side and the fourth side may be sides facing each other in a second direction perpendicular to the first direction. This makes it possible to more reliably suppress the variation in compressive residual stress imparted to the target object along the target area on the surface of the target object.

[0012] In the laser processing method of the present invention, in the third step, a third process of moving the irradiation spot of the laser light along each of a plurality of lines extending in the first direction and aligned in the second direction may be performed sequentially from the fourth side to the third side, thereby widening the area irradiated with the laser light toward the third side, and in the fourth step, a fourth process of moving the irradiation spot of the laser light along each of a plurality of lines extending in the first direction and aligned in the second direction may be performed sequentially from the third side to the fourth side, thereby widening the area irradiated with the laser light toward the fourth side. This makes it possible to reliably and easily widen the area irradiated with the laser light toward the third side in the third step, and to reliably and easily widen the area irradiated with the laser light toward the fourth side different from the third side in the fourth step.

[0013] In the laser processing method of the present invention, in the third step, as a third process, a process of moving the irradiation spot of the laser light from one side to the other side in the first direction and a process of moving the irradiation spot of the laser light from the other side to one side in the first direction may be alternately performed, and in the fourth step, as a fourth process, a process of moving the irradiation spot of the laser light from one side to the other side in the first direction and a process of moving the irradiation spot of the laser light from the other side to one side in the first direction may be alternately performed. Thereby, in the third step, the irradiated area of ​​the laser light can be efficiently expanded toward the third side, and in the fourth step, the irradiated area of ​​the laser light can be efficiently expanded toward a fourth side different from the third side.

[0014] The laser processing apparatus of the present invention is a laser processing apparatus that imparts compressive residual stress to an object along a target area by irradiating the target area on the surface of the object with laser light, and is equipped with a support section that supports the object, an irradiation section that irradiates the target area with laser light, and a control section that controls the operation of at least one of the support section and the irradiation section, wherein the control section controls the operation of at least one of the support section and the irradiation section so that the area irradiated with the laser light in the target area spreads toward a first side, and controls the operation of at least one of the support section and the irradiation section so that the area irradiated with the laser light in the target area spreads toward a second side different from the first side.

[0015] According to this laser processing apparatus, similarly to the above-described laser processing method, it is possible to suppress variation in the compressive residual stress imparted to the object along the target area on the surface of the object. Effect of the Invention

[0016] According to the present invention, it is possible to provide a laser processing method and a laser processing apparatus that can suppress variation in compressive residual stress imparted to an object along a target area on the surface of the object. [Brief description of the drawings]

[0017] [Figure 1] 1 is a configuration diagram of a laser processing apparatus according to an embodiment; [Diagram 2] 1 is a plan view of an object for explaining a laser processing method according to an embodiment; [Diagram 3] FIG. 2 is a plan view of an object for explaining the laser processing method according to one embodiment. [Figure 4] 1 is a plan view of an object for illustrating the laser processing methods of Comparative Example 1 and Comparative Example 2. FIG. [Diagram 5] FIG. 13 is a plan view of an object for illustrating the laser processing methods of Comparative Examples 3 and 4. [Figure 6] 1 is an image showing a two-dimensional distribution of compressive residual stress imparted by the laser processing methods of Comparative Example 1 and Comparative Example 2. [Figure 7] 13 is an image showing a two-dimensional distribution of compressive residual stress imparted by the laser processing methods of Comparative Example 3 and Comparative Example 4. [Figure 8] 11 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. [Figure 9] 11 is an image showing a two-dimensional distribution of compressive residual stress imparted by the laser processing method of Example 2. [Figure 10] 1 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 11] 1 is a table showing values ​​of compressive residual stress imparted by the laser processing methods of Comparative Example 5, Example 1, and Example 2. [Figure 12] FIG. 11 is a plan view of an object for illustrating the laser processing method of Modification 1. [Figure 13] FIG. 11 is a plan view of an object for illustrating a laser processing method according to a second modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals, and duplicated explanations will be omitted. [Laser processing equipment]

[0019] As shown in Fig. 1, 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 an apparatus that applies a compressive residual stress to the object 10 along the target area 11 by irradiating the target area 11 on the surface 10a of the object 10 with laser light L. In other words, the laser processing apparatus 1 is an apparatus that performs laser peening on the target area 11 on the surface 10a of the object 10. In the following description, the three mutually orthogonal directions are referred to as the X direction, the Y direction, and the Z direction, respectively. In this embodiment, the Z direction is the first horizontal direction, the X direction is the second horizontal direction perpendicular to the first horizontal direction, and the Y direction is the vertical direction.

[0020] The support unit 2 supports the object 10 so that the surface 10a of the object 10 is perpendicular to the Z direction. The support unit 2 includes, for example, a clamp that holds the object 10, a robot arm, etc. The object 10 is, for example, a plate-shaped member made of a metal material such as copper, aluminum, iron, titanium, etc. When performing laser peening, a protective layer P is formed on the target area 11, and a confinement layer C is formed on the surface of the protective layer P. The protective layer P is a layer that absorbs heat generated by irradiation with the laser light L to protect the target area 11 from the heat. The protective layer P is, for example, a metal or resin layer. The confinement layer C is a layer that confines the plasma generated by irradiation with the laser light L to give the impact of the plasma to the object 10. The confinement layer C is, for example, water supplied to cover the protective layer P.

[0021] The irradiation unit 3 irradiates a target area 11 on the surface 10a of the target object 10 supported by the support unit 2 with laser light L. The irradiation unit 3 two-dimensionally moves an irradiation spot S of the laser light L relative to the target area 11. The irradiation spot S of the laser light L is an irradiation region of the laser light L in the target area 11. In this embodiment, a condensed spot CS of the laser light L is positioned on the target area 11. That is, in this embodiment, the condensed spot CS of the laser light L becomes the irradiation spot S of the laser light L.

[0022] The irradiation unit 3 has a light source 31, an optical axis adjustment unit 32, an optical axis adjustment lens 33, an X-axis movable mirror 34, a Y-axis movable mirror 35, and an objective lens 36. The light source 31 emits a laser light L. The light source 31 is, for example, a semiconductor laser that emits the laser light L by a pulse oscillation method. The optical axis adjustment unit 32 supports the optical axis adjustment lens 33. The optical axis adjustment unit 32 moves the condensed spot CS along the Z direction by moving the optical axis adjustment lens 33 along the Z direction. The X-axis movable mirror 34 moves the condensed spot CS along the X direction by adjusting the inclination of the mirror surface that reflects the laser light L. The Y-axis movable mirror 35 moves the condensed spot CS along the Y direction by adjusting the inclination of the mirror surface that reflects the laser light L. Each of the X-axis movable mirror 34 and the Y-axis movable mirror 35 is, for example, a galvanometer mirror. The objective lens 36 optically corrects the position of the focused spot CS of the laser light L so that the focused spot CS is located on a plane perpendicular to the Z direction. The objective lens 36 is, for example, an f·θ lens.

[0023] The control unit 4 controls the operation of the irradiation unit 3 so that the irradiation spot S moves on the target area 11 along a predetermined trajectory. The control unit 4 has, 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, a memory, a storage, a communication device, and the like. In the processing unit 41, the processor executes software (programs) loaded into the memory, etc., and controls reading and writing of data in the memory and storage, as well as communication by the communication device. The storage unit 42 is a hard disk, etc., and stores various data. The input receiving unit 43 is an interface unit that receives input of various data from an operator. In this embodiment, the input receiving unit 43 constitutes a GUI (Graphical User Interface). [Laser processing method]

[0024] A laser processing method performed in the above-mentioned laser processing apparatus 1 will be described. The laser processing method is a method of applying compressive residual stress to the object 10 along the target area 11 by irradiating the target area 11 on the surface 10a of the object 10 with laser light L. In other words, the laser processing method is a method of performing laser peening on the target area 11 on the surface 10a of the object 10. In this embodiment, the control unit 4 controls the irradiation unit 3 to perform the first step, second step, third step, and fourth step described below. Note that, as an example, the output of the laser light L and the area and shape of the irradiation spot S are constant in the first step, second step, third step, and fourth step.

[0025] First, the target object 10 is prepared. In this embodiment, in the laser processing apparatus 1, the target object 10 is supported by the support unit 2, and the target area 11, the irradiation conditions of the laser light L, and the like are set by the control unit 4. In this embodiment, as shown in FIG. 2(a), one side in the X direction (first direction) is the first side, and the other side in the X direction is the second side. That is, the first side and the second side are sides opposite each other in the X direction. Also, one side in the Y direction (second direction perpendicular to the first direction) is the third side, and the other side in the Y direction is the fourth side. That is, the third side and the fourth side are sides opposite each other in the Y direction. As an example, the target area 11 is a rectangular area having two sides opposite each other in the X direction and two sides opposite each other in the Y direction.

[0026] Next, the irradiated area 12 of the laser light L in the target area 11 is expanded toward the first side (first step), and the irradiated area 12 is expanded to the entire target area 11. Specifically, in the target area 11, a first process of moving the irradiation spot S along each of a plurality of lines L1 extending in the Y direction and arranged at equal intervals in the X direction is sequentially performed from the second side to the first side, thereby expanding the irradiated area 12 toward the first side. In this embodiment, as the first process, a process of moving the irradiation spot S from the third side to the fourth side (from one side to the other side in the second direction) and a process of moving the irradiation spot S from the fourth side to the third side (from the other side to one side in the second direction) are alternately performed. Note that the interval between adjacent lines L1 is about 1 / 2 the width of the irradiation spot S in the X direction.

[0027] 2(b), the irradiated area 12 of the laser light L in the target area 11 is expanded toward the second side (second step), and the irradiated area 12 is expanded to the entire target area 11 (i.e., the irradiated area 12 is expanded again to the entire target area 11 so as to overlap the irradiated area 12 expanded to the entire target area 11 in the first step). Specifically, the irradiated area 12 is expanded toward the second side by sequentially performing a second process in the target area 11 from the first side to the second side, in which the irradiated spot S is moved along each of a plurality of lines L2 extending in the Y direction and arranged at equal intervals in the X direction. In this embodiment, as the second process, a process of moving the irradiated spot S from the third side to the fourth side and a process of moving the irradiated spot S from the fourth side to the third side are alternately performed. Note that the interval between adjacent lines L2 is about 1 / 2 the width of the irradiated spot S in the X direction. In this embodiment, each line L2 coincides with each line L1.

[0028] 3(a), the irradiated area 12 of the laser light L in the target area 11 is expanded toward the third side (third step), and the irradiated area 12 is expanded to the entire target area 11 (i.e., the irradiated area 12 is expanded again to the entire target area 11 so as to overlap the irradiated area 12 expanded to the entire target area 11 in each of the first and second steps). Specifically, the irradiated area 12 is expanded toward the third side by sequentially performing a third process in which the irradiation spot S is moved along each of a plurality of lines L3 extending in the X direction and arranged at equal intervals in the Y direction in the target area 11 from the fourth side to the third side. In this embodiment, as the third process, a process of moving the irradiation spot S from the second side to the first side (from one side to the other side in the first direction) and a process of moving the irradiation spot S from the first side to the second side (from the other side to one side in the first direction) are alternately performed. The interval between adjacent lines L3 is about half the width of the irradiation spot S in the Y direction.

[0029] 3(b), the irradiated area 12 of the laser light L in the target area 11 is expanded toward the fourth side (fourth step), and the irradiated area 12 is expanded to the entire target area 11 (i.e., the irradiated area 12 is expanded again to the entire target area 11 so as to overlap the irradiated area 12 expanded to the entire target area 11 in each of the first step, the second step, and the third step). Specifically, in the target area 11, a fourth process is performed in which the irradiation spot S is moved along each of a plurality of lines L4 extending in the X direction and arranged at equal intervals in the Y direction, from the third side to the fourth side, thereby expanding the irradiated area 12 toward the fourth side. In this embodiment, as the fourth process, a process of moving the irradiation spot S from the second side to the first side and a process of moving the irradiation spot S from the first side to the second side are alternately performed. Note that the interval between adjacent lines L4 is about 1 / 2 the width of the irradiation spot S in the Y direction. In this embodiment, each line L4 coincides with each line L3.

[0030] As described above, by carrying out the first step, the second step, the third step, and the fourth step, compressive residual stress is imparted to the object 10 along the target area 11. In other words, the above-mentioned laser processing method is a method for manufacturing an object to which compressive residual stress is imparted along the target area 11. Note that, in the above-mentioned laser processing method, it is sufficient that the irradiation of the laser light L is carried out so that "at least a part of the irradiated area 12 expanded in the first step", "at least a part of the irradiated area 12 expanded in the second step", "at least a part of the irradiated area 12 expanded in the third step", and "at least a part of the irradiated area 12 expanded in the fourth step" overlap each other in the target area 11. In other words, in the above-mentioned laser processing method, the area to which the laser light L is irradiated so that "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 with each other is the target area 11. [Action and Effects]

[0031] In the above laser processing method, the irradiated area 12 of the laser light L is expanded toward the first side in the first step, and the irradiated area 12 of the laser light L is expanded toward the second side in the second step. As a result, the compressive residual stress imparted to the object 10 by the first step decreases toward the first side, and the compressive residual stress imparted to the object 10 by the second step decreases toward the second side. Furthermore, the irradiated area 12 of the laser light L is expanded toward the third side in the third step, and the irradiated area 12 of the laser light L is expanded toward the fourth side in the fourth step. As a result, the compressive residual stress imparted to the object 10 by the third step decreases toward the third side, and the compressive residual stress imparted to the object 10 by the fourth step decreases toward the fourth side. Therefore, for example, the variation in the compressive residual stress imparted to the object 10 is suppressed compared to a case in which the irradiated area 12 of the laser light L is expanded toward the first side in each of the first step, the second step, the third step, and the fourth step. Therefore, according to the above-described laser processing method, the variation in the compressive residual stress imparted to the object 10 along the target area 11 on the surface 10a of the object 10 can be suppressed.

[0032] In the above laser processing method, the first side and the second side are opposite to each other in the X direction, and the third side and the fourth side are opposite to each other in the Y direction. This makes it possible to more reliably suppress the variation in the compressive residual stress imparted to the object 10.

[0033] In the above laser processing method, in the first step, a first process of moving the irradiation spot S of the laser light L along each of a plurality of lines L1 extending in the Y direction and aligned in the X direction is sequentially performed from the second side to the first side, thereby expanding the irradiated area 12 of the laser light L toward the first side. This allows the irradiated area 12 of the laser light L to be reliably and easily expanded toward the first side in the first step. In the above laser processing method, in the second step, a second process of moving the irradiation spot S of the laser light L along each of a plurality of lines L2 extending in the Y direction and aligned in the X direction is sequentially performed from the first side to the second side, thereby expanding the irradiated area 12 of the laser light L toward the second side. This allows the irradiated area 12 of the laser light L to be reliably and easily expanded toward the second side different from the first side in the second step.

[0034] In the above laser processing method, in the first step, as a first process, a process of moving the irradiation spot S of the laser light L from one side to the other side in the Y direction and a process of moving the irradiation spot S of the laser light L from the other side to one side in the Y direction are alternately performed. Thereby, in the first step, the irradiated area 12 of the laser light L can be efficiently expanded toward the first side. In the above laser processing method, in the second step, as a second process, a process of moving the irradiation spot S of the laser light L from one side to the other side in the Y direction and a process of moving the irradiation spot S of the laser light L from the other side to one side in the Y direction are alternately performed. Thereby, in the second step, the irradiated area 12 of the laser light L can be efficiently expanded toward the second side different from the first side.

[0035] In the above laser processing method, in the third step, the third process of moving the irradiation spot S of the laser light L along each of the multiple lines L3 extending in the X direction and aligned in the Y direction is performed sequentially from the fourth side to the third side, thereby expanding the irradiated area 12 of the laser light L toward the third side. This makes it possible to reliably and easily expand the irradiated area 12 of the laser light L toward the third side in the third step. In the above laser processing method, in the fourth step, the fourth process of moving the irradiation spot S of the laser light L along each of the multiple lines L4 extending in the X direction and aligned in the Y direction is performed sequentially from the third side to the fourth side, thereby expanding the irradiated area 12 of the laser light L toward the fourth side. This makes it possible to reliably and easily expand the irradiated area 12 of the laser light L toward the fourth side, which is different from the third side, in the fourth step.

[0036] In the above laser processing method, in the third step, as the third process, a process of moving the irradiation spot S of the laser light L from one side to the other side in the X direction and a process of moving the irradiation spot S of the laser light L from the other side to one side in the X direction are alternately performed. Thereby, in the third step, the irradiated area 12 of the laser light L can be efficiently expanded toward the third side. In the above laser processing method, in the fourth step, as the fourth process, a process of moving the irradiation spot S of the laser light L from one side to the other side in the X direction and a process of moving the irradiation spot S of the laser light L from the other side to one side in the X direction are alternately performed. Thereby, in the fourth step, the irradiated area 12 of the laser light L can be efficiently expanded toward the fourth side different from the third side.

[0037] According to the laser processing apparatus 1, similarly to the above-mentioned laser processing method, it is possible to suppress variation in the compressive residual stress imparted to the object 10 along the target area 11 on the surface 10a of the object 10. [Comparative Examples and Examples]

[0038] First, there will be described the laser processing methods of Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4. The laser light irradiation conditions in the laser processing methods of Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4 are as follows. Laser light irradiation conditions Wavelength: 1053nm Pulse energy: 300mJ Pulse width: 10ns (rectangular) Focus size: approx. 0.8 x 0.8 mm Strength: 4.7GW / cm 2 Repetition frequency: 2Hz Conditions of the object Material: Aluminum alloy (A2024) Shape: 49×49mm Thickness: 3mm Target area: 2 x 10 mm Protective layer: Resin tape (thickness: 100 μm or less) Confinement layer: running water

[0039] In the laser processing method of Comparative Example 1, as shown in (a) of Fig. 4, in the target area, a process of moving the irradiation spot of the laser light along each of six lines (lines shown by dashed lines) extending in the Y direction and aligned in the X direction was performed sequentially from one side to the other in the X direction, thereby expanding the irradiated area of ​​the laser light toward the other side in the X direction (laser light irradiation step). In the laser processing method of Comparative Example 1, the laser light irradiation step was performed four times. In (a) of Fig. 4, the number attached to each line indicates the order in which the irradiation spot of the laser light was moved along the line, and the arrow attached to each line indicates the direction in which the irradiation spot of the laser light was moved along the line.

[0040] In the laser processing method of Comparative Example 2, as shown in (b) of FIG. 4, in a half area on one side in the X direction of the target area, a process of moving the irradiation spot of the laser light along each of three lines (lines shown by dashed lines) extending in the Y direction and aligned in the X direction was performed in the following order. That is, the process was performed in the order of the first line from one side in the X direction, the sixth line from the one side, the second line from the one side, the fifth line from the one side, the third line from the one side, and the fourth line from the one side. In the laser processing method of Comparative Example 2, the process was performed four times. In (b) of FIG. 4, the number attached to each line indicates the order in which the irradiation spot of the laser light was moved along the line, and the arrow attached to each line indicates the direction in which the irradiation spot of the laser light was moved along the line.

[0041] In the laser processing method of Comparative Example 3, as shown in (a) of FIG. 5, in a half area on one side in the X direction of the target area, a process of moving the irradiation spot of the laser light along each of three lines (lines shown by dashed lines) extending in the Y direction and aligned in the X direction was performed in the following order. That is, the process was performed in the order of the third line from one side in the X direction, the fourth line from the one side, the second line from the one side, the fifth line from the one side, the first line from the one side, and the sixth line from the one side. In the laser processing method of Comparative Example 3, the process was performed four times. In (a) of FIG. 5, the number attached to each line indicates the order in which the irradiation spot of the laser light was moved along the line, and the arrow attached to each line indicates the direction in which the irradiation spot of the laser light was moved along the line.

[0042] In the laser processing method of Comparative Example 4, as shown in (b) of FIG. 5, in the target area, the process of moving the irradiation spot of the laser light along each of six lines (lines shown by dashed lines) extending in the Y direction and aligned in the X direction was performed in the following order. That is, the process was performed in the order of the first line from one side in the X direction, the sixth line from the one side, the third line from the one side, the fifth line from the one side, the second line from the one side, and the fourth line from the one side. In the laser processing method of Comparative Example 4, the process was performed four times. In (b) of FIG. 5, the number attached to each line indicates the order in which the irradiation spot of the laser light was moved along the line, and the arrow attached to each line indicates the direction in which the irradiation spot of the laser light was moved along the line.

[0043] The two-dimensional distribution of compressive residual stress imparted by the laser processing methods of Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4 was measured by an X-ray residual stress measurement device. The measurement conditions for the two-dimensional distribution of compressive residual stress were as follows. Measurement conditions for two-dimensional distribution of compressive residual stress X-ray size: φ0.5mm Measurement range: 3 x 4 mm Spacing: 0.25mm Tube:Co

[0044] The two-dimensional distribution of the compressive residual stress imparted by the laser processing method of Comparative Example 1 was a distribution that decreased from one side to the other side in the X direction, as shown in Fig. 6(a). Note that in Fig. 6(a), the compressive residual stress is shown as a negative value (the same applies to Fig. 6(b), Fig. 7(a) and Fig. 7(b) described later).

[0045] As shown in FIG. 6(b), the two-dimensional distribution of the compressive residual stress imparted by the laser processing method of Comparative Example 2 was such that in a half area on one side in the X direction of the target area, the stress decreased from one side in the X direction to the other side, while in a half area on the other side in the X direction of the target area, the stress decreased from the other side in the X direction to one side.

[0046] As shown in FIG. 7(a), the two-dimensional distribution of the compressive residual stress imparted by the laser processing method of Comparative Example 3 was such that in a half area on one side in the X direction of the target area, the stress decreased from one side in the X direction to one side, while in a half area on the other side in the X direction of the target area, the stress decreased from one side in the X direction to the other side.

[0047] As shown in FIG. 7(b), the two-dimensional distribution of the compressive residual stress imparted by the laser processing method of Comparative Example 4 was such that in a half area on one side in the X direction of the target area, the stress decreased from one side in the X direction to the other side, while in a half area on the other side in the X direction of the target area, the stress decreased from the other side in the X direction to one side.

[0048] From the above results, it was demonstrated that the compressive residual stress imparted to the target object decreases toward the side where the area irradiated with the laser beam expands in the target area. It was also demonstrated that the distribution of the compressive residual stress imparted to the target object varies even if the area irradiated with the laser beam expands randomly from a sparse state to a dense state in the target area.

[0049] Next, there will be described the laser processing methods of Comparative Example 5, Examples 1 and 2. The laser light irradiation conditions in the laser processing methods of Comparative Example 5, Examples 1 and 2 are as follows. Laser light irradiation conditions Wavelength: 1064nm Pulse energy: 42mJ Pulse width: 39.4ns (Gaussian) Focus size: φ0.19mm Strength: 3.8GW / cm 2 Repetition frequency: 300Hz Conditions of the object Material: Aluminum alloy (A2024) Shape: 49×49mm Thickness: 3mm Target area: 3×3mm Protective layer: Aluminum tape (thickness: 100 μm or less) Confinement layer: running water

[0050] In the laser processing method of Comparative Example 5, the step of expanding the area irradiated with laser light in the target area from one side to the other side in the X direction (a step corresponding to the first step in the laser processing method of the above embodiment) was performed four times.

[0051] In the laser processing method of Example 1, a step of expanding an area irradiated with laser light in a target area from one side to the other side in the X direction (a step corresponding to the first step in the laser processing method of the above embodiment) and a step of expanding an area irradiated with laser light in a target area from the other side to one side in the X direction (a step corresponding to the second step in the laser processing method of the above embodiment) were alternately performed twice each.

[0052] In the laser processing method of Example 2, a step of expanding the area irradiated with laser light in the target area from one side to the other side in the X direction (a step corresponding to the first step in the laser processing method of the above embodiment), a step of expanding the area irradiated with laser light in the target area from the other side to one side in the X direction (a step corresponding to the second step in the laser processing method of the above embodiment), a step of expanding the area irradiated with laser light in the target area from one side to the other side in the Y direction (a step corresponding to the third step in the laser processing method of the above embodiment), and a step of expanding the area irradiated with laser light in the target area from the other side to one side in the Y direction (a step corresponding to the fourth step in the laser processing method of the above embodiment) were performed once each in the above order.

[0053] 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 by an X-ray residual stress measurement device. The measurement conditions for the two-dimensional distribution of compressive residual stress were as follows. Measurement conditions for two-dimensional distribution of compressive residual stress X-ray size: φ0.5mm Measurement range: 5.0 x 2.5 mm Spacing: 0.25mm Tube:Co

[0054] The two-dimensional distribution of the compressive residual stress imparted along the target area by the laser processing method of Comparative Example 5 was a distribution that decreased from one side to the other side in the X direction, as shown in (a) of FIG. 8. The two-dimensional distribution of the compressive residual stress imparted along the target area by the laser processing method of Example 1 was a distribution with suppressed variation, as shown in (b) of FIG. 8, compared to the two-dimensional distribution of the compressive residual stress by the laser processing method of Comparative Example 5. The two-dimensional distribution of the compressive residual stress imparted along the target area by the laser processing method of Example 2 was a distribution with suppressed variation, as shown in FIG. 9, compared to the two-dimensional distribution of the compressive residual stress by the laser processing method of Example 1. In addition, in (a) of FIG. 8, (b) of FIG. 8, and FIG. 9, the compressive residual stress is shown as a negative value.

[0055] 10 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. In FIG. 10, "X-direction position" means a position in the X direction, and "Y-direction average residual stress" means "the average value of compressive residual stress imparted to a portion along the Y direction" at each X-direction position. As shown in FIG. 10, when focusing on the difference between the maximum and minimum values ​​of the Y-direction average residual stress in the target area, the value of the difference 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.

[0056] FIG. 11 is a table showing the values ​​of the compressive residual stress imparted by the laser processing methods of Comparative Example 5, Example 1, and Example 2. In FIG. 11, "maximum value" means the minimum value of the compressive residual stress imparted along the target area (within the dotted frame of 3×3 mm) shown in FIG. 8(a), FIG. 8(b), and FIG. 9, respectively, "minimum value" means the maximum value of the compressive residual stress imparted along the target area, and "average value" means the average value of the compressive residual stress imparted along the target area. "Deviation" means the magnitude of the variation of the value of the compressive residual stress imparted along the target area from the average value, and "deviation / |average value|" means the rate of variation of the value of the compressive residual stress imparted along the target area from the average value. As shown in FIG. 11, for "deviation" and "deviation / |average value|", the value by the laser processing method of Example 1 was smaller than the value by the laser processing method of Comparative Example 5, and the value by the laser processing method of Example 2 was smaller than the value by the laser processing method of Example 1. That is, the compressive residual stress imparted along the target area in Example 1 is more uniform than the compressive residual stress imparted along the target area in Comparative Example 5. Also, the compressive residual stress imparted along the target area in Example 2 is more uniform than the compressive residual stress imparted along the target area in Example 1. [Variations]

[0057] The present invention is not limited to the above-mentioned embodiment and example. A laser processing method of Modification 1 will be described. In the laser processing method of Modification 1, as shown in (a) of FIG. 12, the irradiated area 12 of the laser light L in the target area 11 is expanded toward the outside (first side) (first step), and as shown in (b) of FIG. 12, the irradiated area 12 of the laser light L in the target area 11 is expanded toward the inside (second side) (second step). Specifically, in the first step, as shown in (a) of FIG. 12, the irradiation spot S of the laser light L is moved along a spiral line from the center of the target area 11 to the outer edge of the target area 11. In the second step, as shown in (b) of FIG. 12, the irradiation spot S of the laser light L is moved along a spiral line from the outer edge of the target area 11 to the center of the target area 11. Note that the irradiation spot S of the laser light L may be moved along each of the annular lines arranged in a nested manner in the target area 11. As an example, a process of moving the irradiation spot S along each of a plurality of annular lines is performed sequentially from the inner annular line to the outer annular line, thereby expanding the irradiated area 12 of the laser light L outward in the target area 11 (first step). Next, a process of moving the irradiation spot S along each of a plurality of annular lines is performed sequentially from the outer annular line to the inner annular line, thereby expanding the irradiated area 12 of the laser light L inward in the target area 11 (second step). In the laser processing method of the first modification example, the steps are performed in the order of the first step and the second step, but the steps may be performed in the order of the second step and the first step.

[0058] A laser processing method of Modification 2 will be described. In the laser processing method of Modification 2, the target area 11 is divided into a plurality of areas, and the laser processing method of the above embodiment is performed in each of the plurality of areas. For example, as shown in FIG. 13, the target area 11 is divided into four areas arranged in two rows and two columns along the X direction and the Y direction. By performing the laser processing method of the above embodiment in parallel in each of the four areas, it is possible to shorten the time required to impart compressive residual stress to the target object 10 along the target area 11, even if the target area 11 is large.

[0059] In the laser processing apparatus 1 of the above embodiment, the control unit 4 controls the operation of the irradiation unit 3 so that the irradiation spot S moves on the target area 11 along a predetermined trajectory, but 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 may control the operation of the support unit 2 so that the irradiation spot S moves on the target area 11 along a predetermined trajectory. Alternatively, the control unit 4 may control the operation of the support unit 2 and the operation of the irradiation unit 3 so that the irradiation spot S moves on the target area 11 along a predetermined trajectory.

[0060] In the laser processing method of the above embodiment, 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 was alternately performed, but 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 may be performed continuously.

[0061] In the laser processing method of the above embodiment, in the third step and the fourth step, 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, was alternately performed, but in the third step and the fourth step, 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 may be performed continuously.

[0062] In the laser processing method of the above embodiment, each line L2 coincides with each line L1, but as long as the multiple lines L2 extend in the Y direction and are lined up in the X direction, each line L2 does not have to coincide with each line L1. Similarly, in the laser processing method of the above embodiment, each line L4 coincides with each line L3, but as long as the multiple lines L4 extend in the X direction and are lined up in the Y direction, each line L4 does not have to coincide with each line L3.

[0063] In the laser processing method of the above embodiment, the multiple lines L1 are arranged at equal intervals, but the multiple lines L1 do not have to be arranged at equal intervals. Similarly, in the laser processing method of the above embodiment, the multiple lines L2 are arranged at equal intervals, but the multiple lines L2 do not have to be arranged at equal intervals. Similarly, in the laser processing method of the above embodiment, the multiple lines L3 are arranged at equal intervals, but the multiple lines L3 do not have to be arranged at equal intervals. Similarly, in the laser processing method of the above embodiment, the multiple lines L4 are arranged at equal intervals, but the multiple lines L4 do not have to be arranged at equal intervals.

[0064] In the laser processing method of the above embodiment, the interval between adjacent lines L1 is about 1 / 2 the width of the irradiation spot S in the X direction, but it may be larger than 1 / 2 the width of the irradiation spot S in the X direction. That is, there may be an area between adjacent lines L1 where the laser light L is not irradiated twice. Note that the interval between adjacent lines L1 is preferably smaller than 1 / 2 the width of the irradiation spot S in the X direction. That is, it is preferable to irradiate the laser light L twice or more between adjacent lines L1. Furthermore, it is preferable that the interval between adjacent lines L1 is 1 / 2 the width of the irradiation spot S in the X direction. That is, it is preferable to irradiate the laser light L twice between adjacent lines L1 without overlapping. In this case, the irradiated area 12 irradiated uniformly with the laser light L can be expanded toward the first side.

[0065] Similarly, in the laser processing method of the above embodiment, the interval between adjacent lines L2 is about 1 / 2 the width of the irradiation spot S in the X direction, but may be larger than 1 / 2 the width of the irradiation spot S in the X direction. That is, there may be an area between adjacent lines L2 where the laser light L is not irradiated twice. Note that the interval between adjacent lines L2 is preferably smaller than 1 / 2 the width of the irradiation spot S in the X direction. That is, it is preferable to irradiate the laser light L twice or more between adjacent lines L2. Furthermore, it is preferable that the interval between adjacent lines L2 is 1 / 2 the width of the irradiation spot S in the X direction. That is, it is preferable to irradiate the laser light L twice between adjacent lines L2 without overlapping. In this case, the irradiated area 12 irradiated uniformly with the laser light L can be expanded toward the second side.

[0066] Similarly, in the laser processing method of the above embodiment, the interval between adjacent lines L3 is about 1 / 2 the width of the irradiation spot S in the Y direction, but may be larger than 1 / 2 the width of the irradiation spot S in the Y direction. That is, there may be an area between adjacent lines L3 where the laser light L is not irradiated twice. Note that the interval between adjacent lines L3 is preferably smaller than 1 / 2 the width of the irradiation spot S in the Y direction. That is, it is preferable to irradiate the laser light L twice or more between adjacent lines L3. Furthermore, it is preferable that the interval between adjacent lines L3 is 1 / 2 the width of the irradiation spot S in the Y direction. That is, it is preferable to irradiate the laser light L twice between adjacent lines L3 without overlapping. In this case, the irradiated area 12 irradiated uniformly with the laser light L can be expanded toward the third side.

[0067] Similarly, in the laser processing method of the above embodiment, the interval between adjacent lines L4 is about 1 / 2 the width of the irradiation spot S in the Y direction, but may be larger than 1 / 2 the width of the irradiation spot S in the Y direction. That is, there may be an area between adjacent lines L4 where the laser light L is not irradiated twice. Note that the interval between adjacent lines L4 is preferably smaller than 1 / 2 the width of the irradiation spot S in the Y direction. That is, it is preferable to irradiate the laser light L twice or more between adjacent lines L4. Furthermore, it is preferable that the interval between adjacent lines L4 is 1 / 2 the width of the irradiation spot S in the Y direction. That is, it is preferable to irradiate the laser light L twice between adjacent lines L4 without overlapping. In this case, the irradiated area 12 irradiated with the laser light L uniformly can be expanded toward the fourth side.

[0068] In the laser processing method of the above embodiment, the first process of moving the irradiation spot S of the laser light L along each of the multiple lines L1 is performed sequentially from the second side to the first side, but it does not have to be performed sequentially. For example, the first process may be performed from the second side to the first side by skipping some of the multiple lines L1, and the process of moving the irradiation spot S of the laser light L along the skipped part of the lines may be performed after the first process. Similarly, in the laser processing method of the above embodiment, the second process of moving the irradiation spot S of the laser light L along each of the multiple lines L2 is performed sequentially from the first side to the second side, but it does not have to be performed sequentially. For example, the second process may be performed from the first side to the second side by skipping some of the multiple lines L2, and the process of moving the irradiation spot S of the laser light L along the skipped part of the lines may be performed after the second process.

[0069] In the laser processing method of the above embodiment, the third process of moving the irradiation spot S of the laser light L along each of the multiple lines L3 is performed sequentially from the fourth side to the third side, but it does not have to be performed sequentially. For example, the third process may be performed from the fourth side to the third side by skipping some of the multiple lines L3, and the process of moving the irradiation spot S of the laser light L along the skipped part of the lines may be performed after the third process. Similarly, in the laser processing method of the above embodiment, the fourth process of moving the irradiation spot S of the laser light L along each of the multiple lines L4 is performed sequentially from the third side to the fourth side, but it does not have to be performed sequentially. For example, the fourth process may be performed from the third side to the fourth side by skipping some of the multiple lines L4, and the process of moving the irradiation spot S of the laser light L along the skipped part of the lines may be performed after the fourth process.

[0070] In the laser processing method of the above embodiment, the steps are performed in the order of the first step, the second step, the third step, and the fourth step, but the order in which the steps are performed may be changed. Specifically, the steps may be performed in the order of the first step, the third step, the second step, and the fourth step. Alternatively, the steps may be performed in the order of the first step, the third step, the fourth step, and the second step.

[0071] In the laser processing method of the above embodiment, the third step and the fourth step are performed, but at least the first step and the second step may be performed. In this case, the irradiated area 12 of the laser light L can be expanded toward two different sides, so that the compressive residual stress imparted to the target object 10 along the target area 11 can be suppressed from varying. When only the first step and the second step are performed, the irradiation of the laser light L may be performed so that "at least a part of the irradiated area 12 expanded in the first step" and "at least a part of the irradiated area 12 expanded in the second step" overlap each other in the target area 11. In other words, when only the first step and the second step are performed, the area irradiated with the laser light L so that "at least a part of the irradiated area 12 expanded in the first step" and "at least a part of the irradiated area 12 expanded in the second step" overlap each other is the target area 11.

[0072] In the laser processing method of the above embodiment, the first side and the second side are opposite to each other in the X direction, but the first side and the second side may be opposite to each other in a predetermined direction. Furthermore, the first side and the second side may be different from each other. If the first side and the second side are different from each other, the variation in the compressive residual stress imparted to the object 10 by the first step and the second step can be suppressed compared to the case where the irradiated area 12 of the laser light L is expanded toward the first side in the second step. In addition, when the first side and the second side are each represented by a vector having the same magnitude, it is preferable that the angle formed by the vector indicating the first side (i.e., the vector facing the first side) and the vector indicating the second side (i.e., the vector facing the second side) is greater than 90 degrees and is equal to or smaller than 180 degrees. In other words, it is preferable that the vector indicating the first side and the vector indicating the second side have vector components opposite to each other in a predetermined direction. In this case, it is possible to suppress the variation in the compressive residual stress imparted to the object 10 along the target area 11 in the predetermined direction. For reference, when the angle between the vector indicating the first side and the vector indicating the second side is 180 degrees, the first side and the second side are opposite to each other.

[0073] 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 may be opposite to each other in a predetermined direction. Furthermore, the third side and the fourth side may be different from each other. If the third side and the fourth side are different from each other, the variation in the compressive residual stress imparted to the object 10 by the third step and the fourth step can be suppressed compared to the case where the irradiated area 12 of the laser light L is expanded toward the third side in the fourth step. In addition, when the third side and the fourth side are each represented by a vector having the same magnitude, it is preferable that the angle formed by the vector indicating the third side (i.e., the vector facing the third side) and the vector indicating the fourth side (i.e., the vector facing the fourth side) is greater than 90 degrees and is equal to or smaller than 180 degrees. In other words, it is preferable that the vector indicating the third side and the vector indicating the fourth side have vector components opposite to each other in a predetermined direction. In this case, it is possible to suppress the variation in the compressive residual stress imparted to the object 10 along the target area 11 in the predetermined direction. For reference, when the angle formed by the vector indicating the third side and the vector indicating the fourth side is 180 degrees, the third side and the fourth side are opposite to each other.

[0074] The target area 11 is not limited to a flat surface and may be a curved surface. The target area 11 is not limited to a rectangular shape and may be a circular shape or other shape. The lines L1, L2, L3, and L4 are not limited to straight lines and may be curved lines. [Explanation of symbols]

[0075] 1...laser processing device, 2...support part, 3...irradiation part, 4...control part, 10...target object, 10a...surface, 11...target area, 12...irradiated area, L...laser light, S...irradiation spot, L1, L2, L3, L4...lines.

Claims

1. A laser processing method for imparting compressive residual stress to an object along a target area on a surface of the object by irradiating the target area with laser light, the method comprising: a first step of expanding an area irradiated with the laser light in the target area toward a first side; and a second step of expanding an area irradiated with the laser light in the target area toward a second side different from the first side, In the first step and the second step, the irradiation spot of the laser light is moved in a direction intersecting a direction in which the irradiated area is expanded. Laser processing method.

2. A laser processing method for imparting compressive residual stress to an object along a target area on a surface of the object by irradiating the target area with laser light, the method comprising: a first step of outwardly expanding an area irradiated with the laser light in the target area; a second step of expanding an area irradiated with the laser light in the target area toward an inner side different from the outer side.

3. A laser processing apparatus that applies a compressive residual stress to an object along a target area on a surface of the object by irradiating the target area with laser light, the laser processing apparatus comprising: A support portion that supports the object; an irradiation unit that irradiates the target area with the laser light; A control unit that controls an operation of at least one of the support unit and the irradiation unit, The control unit is Controlling the operation of at least one of the support unit and the irradiation unit to move an irradiation spot of the laser light in a direction intersecting a direction in which the irradiated area of ​​the laser light is expanded toward a first side in the target area; controlling an operation of at least one of the support unit and the irradiation unit to move an irradiation spot of the laser light in a direction intersecting a direction in which the irradiated area is expanded so that the irradiated area of ​​the laser light in the target area is expanded toward a second side different from the first side; Laser processing equipment.

4. A laser processing apparatus that applies a compressive residual stress to an object along a target area on a surface of the object by irradiating the target area with laser light, the laser processing apparatus comprising: A support portion that supports the object; an irradiation unit that irradiates the target area with the laser light; A control unit that controls an operation of at least one of the support unit and the irradiation unit, The control unit is controlling an operation of at least one of the support unit and the irradiation unit such that an area irradiated with the laser light in the target area spreads outward; A laser processing device that controls the operation of at least one of the support unit and the irradiation unit so that an area irradiated with the laser light in the target area expands toward an inside different from the outside.

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