Joining method, joining system

Abstract

To provide a joining method and so on that can reduce a hardness of a weld zone.SOLUTION: A joining method has: a welding process in which a first work-piece W1 and a second work-piece W2 are welded by irradiating a surface of a butt part in the state that the ends of the first work-piece W1 and the second work-piece W2 in a center line direction are butted with laser beam L; a re-irradiation process in which a weld zone We, which has been generated in the welding process, is irradiated again with laser beam L with second output smaller than first output that is an output in the welding process.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a bonding method and a bonding system. [Background technology]

[0002] For example, Patent Document 1 describes a laser welding method for welding multiple overlapping steel plates by laser screw welding, which is characterized by carrying out a welding process for welding the multiple steel plates by laser screw welding, and a re-heat input process for re-inputting heat to the outermost peripheral portion of the weld nugget of the weld portion created in the welding process. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-153851 A Summary of the Invention [Problem to be solved by the invention]

[0004] If the hardness of the welded joint between two components joined by laser welding is high, the fatigue strength is low. An object of the present invention is to provide a joining method and the like that can reduce the hardness of a welded portion. [Means for solving the problem]

[0005] The present invention, which was completed with respect to this object, is a joining method comprising: a welding step of welding two rod-shaped members by butting their ends in the center line direction together and irradiating a laser beam onto a surface of the butted portion; and a re-irradiation step of irradiating the laser beam again to the weld created in the welding step with a second output that is smaller than the first output that is the output in the welding step. Effect of the Invention

[0006] According to the present invention, it is possible to provide a joining method and the like that can reduce the hardness of a welded portion. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram illustrating an example of a schematic configuration of a bonding system according to an embodiment. [Diagram 2] 6A to 6C are diagrams illustrating an example of a process for joining a first workpiece and a second workpiece. [Diagram 3] 6A to 6C are diagrams illustrating an example of a process for joining a first workpiece and a second workpiece. [Figure 4] 6 is a diagram showing an example of the relationship between the number of times a first workpiece and a second workpiece are rotated and the output of a laser beam. FIG. [Diagram 5] 11 is a diagram showing an example of the hardness of the workpieces after the first workpiece and the second workpiece are joined in a step of joining the first workpiece and the second workpiece; FIG. [Figure 6] FIG. 11 is a diagram showing an example of hardness of a workpiece according to a comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a diagram showing an example of a schematic configuration of a bonding system 1 according to an embodiment. The joining system 1 includes a laser irradiation device 10, a rotation device 20 that rotates a workpiece W to be welded, and a control device 50 that controls the operation of the laser irradiation device 10 and the rotation device 20.

[0009] The laser irradiation device 10 includes an oscillator 11 that oscillates laser light L (see FIG. 2), a laser head 12 that irradiates the laser light L, and a manipulator 13 that holds the laser head 12 and moves it. There is no particular limitation on the laser source of the laser irradiation device 10. Examples of the laser source include a YAG laser, a CO2 laser, a fiber laser, a disk laser, and a semiconductor laser. The means for holding and moving the laser head 12 is not limited to the manipulator 13. Any mechanism may be used as long as it is capable of moving the laser head 12 in a direction intersecting the center line direction (e.g., in the vertical direction) described later.

[0010] The rotation device 20 includes a support unit 30 that supports the workpiece W, and a drive unit 40 that rotates the support unit 30. Here, the workpiece W is two rod-shaped members, and the rod-shaped members can be, for example, a cylindrical shaft or a tube. Hereinafter, one of the two rod-shaped members may be referred to as the "first workpiece W1" and the other rod-shaped member may be referred to as the "second workpiece W2". In addition, the center line direction of the cylindrical or cylindrical workpiece W may be simply referred to as the "center line direction". The first workpiece W1 and the second workpiece W2 are not limited to those whose size (in other words, length) in the center line direction is larger than their outer diameter, and may be those whose outer diameter is larger than their size in the center line direction. In addition, the first workpiece W1 and the second workpiece W2 are not limited to those whose shape is cylindrical or cylindrical, and may be elliptical cylindrical or elliptical cylindrical, or may be rectangular prism or rectangular cylindrical.

[0011] The support unit 30 has a first support member 31 that grips one end of the first workpiece W1 in the center line direction, and a second support member 32 that grips one end of the second workpiece W2 in the center line direction. The first support member 31 and the second support member 32 can be exemplified as a well-known spindle chuck. That is, the first support member 31 and the second support member 32 have a function of gripping one end of the first workpiece W1 and the second workpiece W2, respectively, and a function of rotating the first workpiece W1 and the second workpiece W2. In addition, the first support member 31 and the second support member 32 support the first workpiece W1 and the second workpiece W2 so that they are horizontal (in other words, so that the center line direction is horizontal).

[0012] The driving unit 40 may be, for example, a motor that rotates. The driving unit 40 has a rotation shaft connected to the first support member 31.

[0013] In the rotating device 20, the first support member 31 and the second support member 32 are arranged so as to be symmetrical with respect to a plane perpendicular to the center line direction. The second support member 32 moves in the center line direction relative to the first support member 31, and it is possible to bring the other end of the first workpiece W1 that is not gripped by the first support member 31 and the other end of the second workpiece W2 that is not gripped by the second support member 32 into abutment with each other.

[0014] In the rotation device 20, the support portion 30 rotates in a state in which the ends of the first workpiece W1 and the second workpiece W2 are butted against each other, and the drive portion 40 rotates to rotate the support portion 30 and thereby rotate the workpiece W.

[0015] The control device 50 is composed of a CPU (Central Processing Unit) (not shown), a ROM (Read Only Memory) (not shown), a RAM (Random Access Memory) (not shown), etc. The ROM stores basic programs executed by the CPU, application programs, various settings, etc. The CPU uses the RAM as a working area and executes application programs read from the ROM or a storage unit to control the operation of the laser irradiation device 10 and the operation of the drive unit 40. For example, the control device 50 can separately and independently control the rotation of the workpiece W, the position of the laser head 12 relative to the workpiece W, and the output of the laser light L irradiated from the laser head 12.

[0016] The joining system 1 configured as above can weld the first workpiece W1 and the second workpiece W2 by rotating them around a center line while butting their ends together and irradiating the surface Wo of the butted portion with laser light L. Furthermore, the joining system 1 can reduce the hardness within a predetermined range from the surface Wo of the welded portion We (see FIG. 3) between the first workpiece W1 and the second workpiece W2 after welding. This will be described in detail below.

[0017] 2 and 3 are diagrams showing an example of a process for joining a first workpiece W1 and a second workpiece W2. FIG. 4 is a diagram showing an example of the relationship between the number of times the first workpiece W1 and the second workpiece W2 are rotated (hereinafter, may be referred to as the "number of revolutions") and the output of the laser light L. In FIG.

[0018] (Welding process) As shown in Fig. 2, the control device 50 rotates the first workpiece W1 and the second workpiece W2 around the center line with their ends butted together. Then, the first workpiece W1 and the second workpiece W2 are welded together by irradiating the butted portion of the first workpiece W1 and the second workpiece W2 with laser light L. Hereinafter, this process is referred to as the welding process.

[0019] In the welding process, the output of the laser light L is set to a predetermined first output. The position of the laser head 12 is determined so that the focal point of the laser light L is on the surfaces Wo of the first workpiece W1 and the second workpiece W2. Then, while being irradiated with the laser light L of the first output, the first workpiece W1 and the second workpiece W2 are rotated a predetermined first number of revolutions.

[0020] The first output is an output sufficient to weld the first workpiece W1 and the second workpiece W2 together, and depends on the material and size of the first workpiece W1 and the second workpiece W2. For example, when the first workpiece W1 and the second workpiece W2 are carbon steel for machine construction (e.g., S45C tempered material) with a diameter of 38 (mm), the first output can be 3000 (W) or more, for example, 3500 (W). The first number of revolutions can be 2 revolutions. The speed at which the first workpiece W1 and the second workpiece W2 are rotated is constant, and the moving speed of the surface Wo of the first workpiece W1 and the second workpiece W2 can be 2 (m / min), for example. The first number of revolutions for irradiating the first output laser light L may be at least one revolution. For example, the first output laser light L may be irradiated for about one revolution (e.g., 365 degrees), and then the output of the laser light L may be gradually reduced during the second revolution.

[0021] (Reirradiation process) After the welding process, the control device 50 again irradiates the laser light L at the second output, which is smaller than the first output, to the welded portion We generated at the butted portion of the first workpiece W1 and the second workpiece W2 welded in the welding process. In addition, when irradiating again, as shown in FIG. 3, the position of the laser head 12 is determined so that the focal point of the laser light L is shifted from the surface Wo of the first workpiece W1 and the second workpiece W2. For example, after the welding process, the laser head 12 is moved in a direction perpendicular to the center line direction (in other words, in the vertical direction). Since the focal point of the laser light L is shifted from the surface Wo of the first workpiece W1 and the second workpiece W2, the laser light L is irradiated to a range including the welded portion We generated in the welding process. This process is called a re-irradiation process.

[0022] The second output is an output necessary to reduce the hardness within a predetermined range (for example, 2 (mm)) from the surface Wo of the welded portion We between the first workpiece W1 and the second workpiece W2, and depends on the material and size of the first workpiece W1 and the second workpiece W2. For example, when the first workpiece W1 and the second workpiece W2 are carbon steel material for machine construction (for example, S45C tempered material) with a diameter of 38 (mm), the second output can be exemplified as 1000 (W) or more and 1500 (W) or less (in other words, for example, 28% or more and 43% or less of the first output). More specifically, the second output can be exemplified as 1200 (W) (in other words, 34% of the first output). In addition, the amount of deviation of the focus of the laser light L can be exemplified as, for example, 0.5 to 1.5 times the diameter of the first workpiece W1 and the second workpiece W2.

[0023] Then, in a state where the defocused laser light L of the second output is irradiated, the first workpiece W1 and the second workpiece W2 are rotated a predetermined second number of revolutions. The second number of revolutions can be, for example, three revolutions, which is more than the first number of revolutions. Alternatively, the second number of revolutions may be four to six revolutions. The speed at which the first workpiece W1 and the second workpiece W2 are rotated in the re-irradiation step is constant, and can be, for example, the same as the speed in the welding step.

[0024] In the re-irradiation step, after rotating the laser beam L for the second number of revolutions while irradiating the laser beam L with the defocused second output, the position of the laser head 12 and the rotation speed of the first workpiece W1 and the second workpiece W2 are kept unchanged, and the output of the laser beam L is gradually reduced from the second output to the third output. The third output can be exemplified as 10% to 30% of the second output. More specifically, the third output can be exemplified as 15% of the second output (for example, 180 (W) when the second output is 1200 (W)). Then, the output of the laser beam L is gradually reduced from the second output to the third output while rotating the first workpiece W1 and the second workpiece W2 for a predetermined third number of revolutions. The third number of revolutions can be exemplified as 5 revolutions.

[0025] After the re-irradiation step is completed, the control device 50 stops the rotation of the first workpiece W1 and the second workpiece W2, and sets the output of the laser light L to zero.

[0026] FIG. 5 is a diagram showing an example of the hardness of the workpiece W after the first workpiece W1 and the second workpiece W2 are joined together in the above-mentioned step of joining the workpiece W1 and the second workpiece W2. FIG. 6 is a diagram showing an example of the hardness of the workpiece Wc according to the comparative example.

[0027] The horizontal axis in Figures 5 and 6 indicates the distance in the center line direction, with the boundary between the first workpiece W1 and the second workpiece W2 being 0 (mm), the first workpiece W1 side being a positive (+) distance, and the second workpiece W2 side being a negative (-) distance.

[0028] The vertical axis in Figure 5 is the depth (distance toward the center line) from the surface Wo of the first workpiece W1 and the second workpiece W2, and shows the hardness (HV) at depths of 0.2 (mm), 1 (mm), and 2 (mm). The vertical axis in FIG. 6 indicates the hardness (HV) at a depth of 1 (mm) of the workpiece Wc according to the comparative example.

[0029] The hardness shown in FIG. 5 is the hardness when the process of joining the first workpiece W1 and the second workpiece W2 was performed under the following conditions. The first workpiece W1 and the second workpiece W2 were made of S45C tempered material with a diameter of 3.8 (mm). The first output was 3500 (W), the second output was 1200 (W), the third output was 180 (W), the first number of revolutions was 2, the second number of revolutions was 3, and the third number of revolutions was 5. In the re-irradiation process, the focus was shifted by 30 (mm).

[0030] The hardness shown in Fig. 6 is the hardness when the welding process is performed on the first workpiece W1 and the second workpiece W2 under the same conditions as above. In other words, the workpiece Wc according to the comparative example is a workpiece in which the first workpiece W1 and the second workpiece W2 are welded in the above-mentioned welding process and the re-irradiation process is not performed. As shown in Fig. 6, the workpiece Wc according to the comparative example in which the re-irradiation process is not performed exceeds 600 (HV) within a range of ±1.2 (mm) from the boundary between the first workpiece W1 and the second workpiece W2. In contrast, as shown in Figure 5, when the above-mentioned joining process was performed, the hardness was lower than 500 (HV) at depths of 0.2 (mm), 1 (mm), and 2 (mm), even within a range of ±1.2 (mm) from the boundary between the first workpiece W1 and the second workpiece W2.

[0031] As described above, the joining method for joining the first workpiece W1 and the second workpiece W2 includes a welding step of butting ends of the first workpiece W1 and the second workpiece W2, which are two rod-shaped members, in the center line direction and irradiating the butted portion with a laser beam L to weld the first workpiece W1 and the second workpiece W2. The joining method also includes a re-irradiation step of irradiating the welded portion We created in the welding step with the laser beam L again at a second output that is smaller than the first output that is the output in the welding step.

[0032] The workpieces W joined by the above-mentioned joining method have a lower hardness of the welded portion We generated in the welding process, compared to, for example, the workpieces Wc according to the comparative example in which the re-irradiation process is not performed. As a result, the workpieces W joined by the above-mentioned joining method have a higher fatigue strength than, for example, the workpieces Wc according to the comparative example in which the re-irradiation process is not performed. Therefore, even if a torsional fatigue test cannot be passed by the workpieces Wc according to the comparative example, the workpieces W joined by the above-mentioned joining method can pass it.

[0033] As described above, the second output is set to reduce the hardness of the welded portion We. In the re-irradiation step, the focus of the laser light L is shifted from the surface Wo, and the laser light L is irradiated to a range including the welded portion We. Therefore, in the re-irradiation step, the hardness of the welded portion We can be reduced with high reliability.

[0034] In addition, the welding process and the re-irradiation process are performed successively while the first workpiece W1 and the second workpiece W2 are butted against each other and rotated. This allows the workpieces to be joined more quickly than, for example, when the welding process and the re-irradiation process are not performed successively.

[0035] In addition, the welding process involves irradiating a first number of revolutions at a first output, and the re-irradiation process involves irradiating a second number of revolutions at a second output, and then irradiating a third number of revolutions at an output smaller than the second output. This allows for joining with high accuracy and high fatigue strength.

[0036] In addition, the output is gradually reduced from the second output while the first workpiece W1 and the second workpiece W2 are rotated in a butted relationship. This allows the re-irradiation process to be completed more quickly than when the rotation is stopped once after the irradiation for the second number of revolutions is completed. The manner in which the output is gradually reduced from the second output is not limited. For example, the output may be reduced continuously from the second output to the third output, or may be reduced in stages.

[0037] As described above, the joining system 1 includes a rotation device 20 that rotates the first workpiece W1 and the second workpiece W2 in a state where the ends in the center line direction of the first workpiece W1 and the second workpiece W2, which are two rod-shaped members, are butted against each other. The joining system 1 also includes a laser irradiation device 10 that irradiates the surface Wo of the butted portion between the first workpiece W1 and the second workpiece W2 with a laser beam L while the rotation device 20 rotates the first workpiece W1 and the second workpiece W2, and a control device 50 that controls the operation of the laser irradiation device 10 and the rotation device 20. The control device 50 sets the laser beam L irradiated by the laser irradiation device 10 to a predetermined first output in order to weld the first workpiece W1 and the second workpiece W2 together, and sets the laser beam L to a second output that is smaller than the first output when the laser beam L is irradiated again to the welded portion We after welding. According to the joining system 1 configured in this manner, the first workpiece W1 and the second workpiece W2 can be joined so as to increase the fatigue strength.

[0038] The control device 50 switches the position of the laser head 12 relative to the first workpiece W1 and the second workpiece W2 so that the focal point of the laser light L is on the surfaces of the first workpiece W1 and the second workpiece W2 when the first output is set, and so that the focal point of the laser light L is shifted from the surfaces when the second output is set. This allows the laser light L to be irradiated to a range including the welded portion We when the laser light L is irradiated at the second output. As a result, the hardness of the welded portion We can be reduced.

[0039] After switching so that the focal points of the laser light L are shifted from the surfaces of the first workpiece W1 and the second workpiece W2, the control device 50 rotates the first workpiece W1 and the second workpiece W2 a predetermined number of revolutions (e.g., the second number of revolutions), and then sets the output to a smaller output than the second output. This allows joining to be performed with high accuracy and high fatigue strength. [Explanation of symbols]

[0040] Reference Signs List 1... joining system, 10... laser irradiation device, 20... rotation device, 50... control device, L... laser light, W1... first workpiece, W2... second workpiece, We... welded portion, Wo... surface

Claims

1. a welding step of butting ends of two rod-shaped members in a center line direction against each other and irradiating a laser beam onto a surface of the butted portion to weld the two rod-shaped members; a re-irradiation process of irradiating the welded portion created in the welding process with the laser light again at a second output that is smaller than the first output that is the output in the welding process; The joining method comprising the steps of:

2. The second output is set to reduce the hardness of the weld. The joining method according to claim 1 .

3. In the re-irradiation step, a focus of the laser light is shifted from the surface, and the laser light is irradiated onto an area including the welded portion. The joining method according to claim 1 .

4. The welding step and the re-irradiation step are performed continuously while the two rod-shaped members are butted against each other and rotated. The joining method according to claim 1 .

5. The welding step includes irradiating the laser beam at the first output for a predetermined first number of revolutions, The re-irradiation step includes irradiating the laser beam with the second output for a predetermined second number of revolutions, and then irradiating the laser beam with an output smaller than the second output for a predetermined third number of revolutions. The joining method according to claim 1 .

6. The two rod-shaped members are butted against each other and rotated, and the output is gradually reduced from the second output in this state. The joining method according to claim 5 .

7. a rotation device that rotates the two rod-shaped members while abutting ends of the two rod-shaped members in a center line direction of the two rod-shaped members; a laser irradiation device that irradiates a laser beam onto a surface of the butted portion of the two rod-shaped members while the rotation device is rotating the two rod-shaped members; A control device for controlling the operation of the laser irradiation device and the rotation device; Equipped with the control device sets the laser light irradiated by the laser irradiation device to a predetermined first output in order to weld the two rod-shaped members, and sets the laser light to a second output that is smaller than the first output when irradiating the laser light again to the welded portion after welding. Joining system.

8. the control device switches the position of the laser head relative to the two rod-shaped members so that the focal point of the laser light is on the surface when the first output is set, and so that the focal point of the laser light is shifted from the surface when the second output is set. The joint system of claim 7.

9. the control device rotates the two rod-shaped members a predetermined number of revolutions after switching the focus of the laser light so as to be shifted from the surface, and then sets the output to a value smaller than the second output. The joint system of claim 8.

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