Welding method and welding device

Abstract

Provided is a welding method and welding device that can suppress the generation of pores due to the inclusion of gas inside a casting when the casting is laser-welded. The welding method according to the present invention is a welding method for laser-welding a casting. In this welding method, after a first laser irradiation of the casting, a second laser irradiation of the casting is performed in the same path as the first laser irradiation.

Description

Technical Field

[0001] This invention relates to a welding method and a welding apparatus. Background Technology

[0002] Patent document 1 describes a technique for laser welding of castings.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2020-006376 Summary of the Invention

[0004] However, in the technology described in Patent Document 1, pores may be generated due to the presence of gas inside the metal.

[0005] Therefore, it is desirable to develop a technology that can suppress porosity caused by the presence of gas inside the casting during laser welding.

[0006] The welding method involved in this invention uses laser welding of castings. After the casting is irradiated with a first laser, it is irradiated with a second laser along the same path as the first laser irradiation.

[0007] The welding apparatus of the present invention is used for laser welding of castings. The welding apparatus includes a laser irradiator that, after irradiating the castings with a first laser, irradiates the castings with a second laser along the same path as the first laser irradiation.

[0008] Invention Effects

[0009] According to the present invention, a welding method and welding apparatus are provided that can suppress porosity caused by the presence of gas inside the casting during laser welding. Attached Figure Description

[0010] Figure 1 This is a schematic diagram showing the welding state of the welding method according to an embodiment of the present invention.

[0011] Figure 2 Through Figure 1 The experimental results of welding castings using the welding method are plotted as porosity relative to the amount of gas after the first laser welding and the second laser welding.

[0012] Figure 3 Through Figure 1 The experimental results of the first laser welding of the casting using the welding method are shown in the diagram schematically representing the welded cross-section.

[0013] Figure 4 Through Figure 1 The experimental results of the second laser welding of the casting using the welding method are shown in the diagram schematically representing the welded cross-section.

[0014] Figure 5 This is a schematic diagram showing the state of welding based on the welding method involved in the comparative example. Detailed Implementation

[0015] The present invention will now be described through embodiments thereof, but the invention as defined in the claims is not limited to these embodiments. Furthermore, not all configurations described in the embodiments are necessarily necessary to solve the problem.

[0016] (Implementation Method)

[0017] The following uses Figure 1 The welding method and welding apparatus involved in this embodiment will be described. Figure 1 This is a schematic diagram showing the welding state based on the welding method involved in this embodiment.

[0018] The welding method involved in this embodiment (hereinafter referred to as "this method") is, for example, laser welding. Figure 1 The method of casting a part like the casting 20 shown. Hereinafter, casting 20 will be referred to as casting material 20.

[0019] In this method, a welding apparatus for laser welding castings is used in laser welding. As an example of this welding apparatus, one can give the following... Figure 1 The welding apparatus 10 is illustrated in the figure. The welding apparatus 10 includes: a head 11; and two welding torches 12 and 13, which are arranged in the head 11 at intervals from each other. Furthermore, although not shown, the welding apparatus 10 includes: a mechanism for moving the head 11 relative to the casting material 20; and a control unit for controlling the movement and laser irradiation.

[0020] The casting material 20 that becomes the object of laser welding can be a casting material 20 in which multiple castings are arranged side by side along its surface 21, or a casting material 20 in which multiple castings are stacked along its cross-section 22. Here, surface 21 refers to the side on which laser welding will be performed. Alternatively, the casting material 20 that becomes the object of laser welding can be, for example, a casting that is to be repaired, such as one with cracks. Regardless of the shape or material of the casting material 20, it is acceptable as long as laser welding can be performed.

[0021] In this method, after the casting material 20 is subjected to a first laser irradiation, the casting material 20 is subjected to a second laser irradiation along the same path as the first laser irradiation. Therefore, the welding apparatus 10 includes a laser irradiator that irradiates the casting material 20 with a first laser and then irradiates it with a second laser along the same path as the first laser irradiation.

[0022] The laser irradiator may, for example, include: a first laser irradiation section for performing first laser irradiation; and a second laser irradiation section for performing second laser irradiation. That is, the welding apparatus 10 may include such a first laser irradiation section and a second laser irradiation section. Figure 1 In the example, the first laser irradiation unit is exemplified by a welding torch 12 that irradiates the surface 21 of the casting material 20 with a laser beam 12A. Furthermore, in Figure 1 In the example, the second laser irradiation unit is a welding torch 13 that irradiates the surface 21 of the casting material 20 with a laser beam 13A.

[0023] The welding device 10 positions the head 11 relative to the casting material 20 towards... Figure 1 The hollow arrow indicates the direction of travel. The first molten pool 23 is formed by a laser beam 12A from the welding torch 12. The first molten pool 23 is formed to include first pinholes 24, providing penetration channels for the molten metal to penetrate deep into the metal. First pores 25 are also formed in the first molten pool 23.

[0024] exist Figure 1 In the diagram, regions A1 to A4, indicating the corresponding states, are depicted on the underside of the casting material 20. The laser beam 13A directs the casting material 20 towards... Figure 1 The hollow arrow moves in the direction of the movement, so region A1 represents the first melting state, and region A2 represents the first solidification state after the melting state.

[0025] Furthermore, the path of the laser beam 13A based on the welding torch 13 is set to be the same as the path of the laser beam 12A. The welding apparatus 10 adjusts the position of the head 11 relative to the casting material 20 towards... Figure 1 Moving in the direction indicated by the hollow arrow, it can sequentially perform the first laser irradiation and the second laser irradiation. In this way, the laser irradiator is configured to perform two laser scans on the same line.

[0026] The second molten pool 26 is formed by a laser beam 13A irradiated from the welding torch 13 onto the surface 21, which forms a molten pool and solidifies as shown in the first molten pool 23. The second molten pool 26 is formed including second pinholes 27, providing penetration channels for the molten metal to penetrate deep into the surface. Secondary pores 28 are also formed in the second molten pool 26. Figure 1 In the diagram, region A3 represents the region in the second melting state, and region A4 represents the solidified state after the melting state.

[0027] The second laser irradiation is performed, for example, along the same straight line as the first laser irradiation, or along the same path. Therefore, the number of pores 28 in the second irradiation is reduced compared to the number of pores 25 exemplified in the first irradiation. Thus, in this embodiment, pores are removed by irradiating the same path after the first laser irradiation.

[0028] Thus, in this method, after laser irradiation, the laser is irradiated along the same path with a time difference, causing the state of the molten pool to shift from the molten state shown in region A1 to the solidified state shown in region A2, the molten state shown in region A3, and the solidified state shown in region A4. In this method, by subjecting the welded part to state changes such as being melted by laser and then solidified by air cooling, remelted, and solidified, porosity can be reduced.

[0029] Furthermore, the time interval between the first laser irradiation and the second laser irradiation can be adjusted, for example, by the movement speed of the head 11. This time interval can be changed according to the material of the casting material 20 to be laser welded.

[0030] Furthermore, the aforementioned laser irradiator may include a mechanism for adjusting the interval between the first laser irradiation section exemplified by welding torch 12 and the second laser irradiation section exemplified by welding torch 13 in order to adjust the aforementioned time interval. In any case, the adjustment of the aforementioned time interval can be performed by changing the distance interval of this mechanism and changing the moving speed of the head 11.

[0031] As described above, in this method, the area to which the first laser welding was performed is irradiated again with laser light. The output of this second laser irradiation can be the same as or less than the output of the first laser irradiation. Even if the output of the second laser irradiation is set to be less than the output of the first laser irradiation, a second molten pool can be formed as long as the aforementioned time interval is set to an appropriate short value. Furthermore, by setting the output of the second laser irradiation to be less than the output of the first laser irradiation, not only can the generation of porosity caused by the second laser irradiation be reduced, but energy savings can also be achieved.

[0032] Next, use Figures 2-4 , for through Figure 1 The results of the test on welding casting material 20 using the welding method are explained. Figure 2 It is a graph showing the relationship between gas quantity and porosity after the first and second laser welding. Figure 3 Through Figure 1 The experimental results of the first laser welding of the casting material 20 using the welding method are shown in a diagram schematically representing the welded cross-section. Figure 4 Through Figure 1 The experimental results of the second laser welding of the casting material 20 using the welding method are shown in a diagram schematically illustrating the welded cross-section. Figures 2-4 In this study, as an example of casting material 20, the internal condition of the welded part was observed using cast aluminum.

[0033] exist Figure 2In the diagram, the horizontal axis represents the amount of gas contained in the casting material 20, and the vertical axis represents the porosity after welding. Here, porosity refers to the amount of porosity divided by the volume of the welded part. Figure 2 As shown, regardless of the amount of gas contained, the porosity after a second weld is reduced compared to after a single weld.

[0034] use Figure 3 and Figure 4 The actual cross-sections inside the welded section are compared. Specifically, the pores 35 present in the first cross-section 30, which is the welded section after the first weld, are compared with the pores 48 present in the second cross-section 40, which is the welded section after the second weld. From this comparison, it can be seen that... Figure 3 and Figure 4 In the image, the number of pores, represented by black particles, decreased after the second welding compared to the first welding.

[0035] This reduction in porosity is due to the following reasons. First, due to the entrapment of air or vaporized release agent during molding, high-pressure gases are contained within the casting material. Thus, compared to conventional stretching materials, the casting material contains gases within the metal. Furthermore, in the casting material, the compressed gas that melts and is contained within the metal during the initial melting process is released under pressure, causing it to expand and solidify within the molten pool, thereby forming pores. The expanded gas that cannot escape to the outside before the molten pool solidifies remains as pores in the weld area.

[0036] However, upon remelting, only the pressure-released pores remain in the weld, with almost no new pores forming due to expansion. Therefore, in this method, the time for the molten portion to be discharged can be determined, resulting in a reduction of porosity in the weld.

[0037] use Figure 5 The comparative examples provide supplementary explanations of the effectiveness of this method. Figure 5 This is a schematic diagram showing the state of welding based on the welding method involved in the comparative example.

[0038] In the welding method described in the comparative example, laser beam 52A scans the surface 61 of the casting material 60 only once in the direction of the hollow arrow, thereby performing laser welding. Therefore, as shown in the cross-section 62 of the casting material 60, a large number of pores 65 are generated in other areas of the pinhole 64. This state is, for example, as shown in... Figure 3 The state illustrated in the first section 30.

[0039] In contrast, in this embodiment, as described above, when laser welding the casting, two laser welding operations are performed along the same path, therefore, for example... Figure 4As illustrated in the second section 40, it is possible to suppress the formation of porosity due to the presence of gas inside. Moreover, in this embodiment, a casting material that suppresses the formation of porosity can be provided, thus reducing the possibility of poor quality from the viewpoints of strength and sealing.

[0040] Furthermore, the present invention is not limited to the above-described embodiments, and appropriate modifications can be made without departing from the spirit of the invention.

[0041] For example, the configuration of the welding apparatus 10 according to the above embodiments is not limited to the structure shown in the figure; any structure capable of performing both the first laser welding and the second laser welding is acceptable. A more specific example will be given. Figure 1 The example given is that the welding apparatus 10 has two laser irradiation units, exemplified by welding torches 12 and 13, arranged separately from each other. However, the welding apparatus 10 may also have only one laser irradiation unit. In this case, it is sufficient to control the laser irradiation unit to perform the first laser irradiation and the second laser irradiation with a time difference. The time interval between the first laser irradiation and the second laser irradiation may vary depending on the material of the casting, etc.

[0042] Furthermore, in the above embodiment, an example of two-stage laser welding based on the first and second laser irradiations was described, but it is also possible to construct a configuration of three or more-stage laser welding based on three or more laser irradiations.

[0043] Symbol Explanation

[0044] 10-Welding device, 11-Head, 12-Welding torch, 12A-Laser beam, 13-Welding torch, 13A-Laser beam, 20-Casting (casting material), 21-Surface, 22-Section, 23-First molten pool, 24-First pinhole, 25-First porosity, 26-Second molten pool, 27-Second pinhole, 28-Second porosity, 30-First section, 35-First porosity, 40-Second section, 48-Second porosity.

Claims

1. A welding method for laser welding castings, characterized in that, After the casting is irradiated with a first laser, the casting is irradiated with a second laser along the same path as the first laser irradiation.

2. The welding method according to claim 1, characterized in that, The output of the second laser irradiation is less than the output of the first laser irradiation.

3. A welding apparatus for laser welding castings, characterized in that, have: A laser irradiator that, after irradiating the casting with a first laser, irradiates the casting with a second laser along the same path as the first laser irradiation.

4. The welding apparatus according to claim 3, characterized in that, The output of the second laser irradiation is less than the output of the first laser irradiation.

5. The welding apparatus according to claim 3 or 4, characterized in that, The laser irradiator includes: A first laser irradiation unit, which performs the first laser irradiation; and The second laser irradiation unit performs the second laser irradiation.

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