Laser-welded joints and laser welding methods

Abstract

To provide a laser welding joint and a laser welding method preventing the recess of a terminal area of a welding bead.SOLUTION: A laser welding joint S1 includes a first bead 10 formed along a first path R1, and a second bead 20 formed along a second path R2. The second bead 20 is formed so that a side part portion 20S of the second bead 20 is overlapped with a terminal end area 10A of the first bead 10. A start point of the second path R2 is a position different from a terminal point of the first path R1.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a laser welded joint and a laser welding method. [Background Art]

[0002] Patent Document 1 discloses a laser welding method in which, in order to reduce depressions in the end region of a weld bead, the scanning direction is reversed at the end of forward laser scanning over a predetermined section, and reverse laser scanning is performed while shifting such that the forward laser scanning and a part of the weld bead partially overlap each other. [Prior Art Literature] [Patent Literature]

[0003] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2012-135794 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] In the above method, as a result of turning back at the end of the forward laser scanning, the irradiation time at the end tends to be long. Therefore, heat input at the end increases, the base material melts excessively, and as a result, there is a risk that depressions may occur in the weld bead.

[0005] The present invention has been made in consideration of the above facts, and an object of the present invention is to provide a laser welded joint and a laser welding method capable of preventing depressions in the end region of a weld bead. [Means for Solving the Problem]

[0006] The laser welded joint according to the first aspect includes: a first bead formed along a first path; and a second bead formed along a second path, wherein the second bead is formed such that a side portion or a start end portion of the second bead overlaps an end region of the first bead, and a start point of the second path is located at a position different from an end point of the first path.

[0007] In this embodiment, the laser-welded joint includes a first bead formed along a first path and a second bead formed along a second path. Here, the second bead is formed such that its side portion or starting end overlaps with the terminal region of the first bead. Since molten metal irradiated by laser irradiation has the property of flowing in the opposite and perpendicular directions to the scanning direction, forming the second bead in this way allows the depression formed in the terminal region of the first bead to be filled with the molten metal flowing in the process of forming the second bead (second irradiation process). Furthermore, the starting point of the second path is at a different location from the ending point of the first path. In other words, laser irradiation is temporarily stopped at the ending point of the first path and then restarted from a different location (the starting point of the second path), which suppresses excessive heat input due to the return of the laser beam and thus prevents the formation of depressions.

[0008] In the second embodiment of the laser-welded joint, the second bead extends in a direction substantially perpendicular to the end region of the first bead, and the starting end of the second bead overlaps with the end region of the first bead.

[0009] In this embodiment, the second bead extends in a direction substantially perpendicular to the end region of the first bead, and the starting end of the second bead overlaps with the end region of the first bead. Since the direction in which the molten metal flows is mainly opposite to the scanning direction, this embodiment allows for effective filling of holes. In this context, "approximately vertical" refers to an angle within the range of 90 degrees ± 10 degrees.

[0010] In the third embodiment of the laser-welded joint, the second bead extends in a direction substantially parallel to the end region of the first bead, and the lateral portion of the second bead overlaps with the end region of the first bead.

[0011] In this embodiment, the second bead extends in a direction substantially parallel to the end region of the first bead, and the lateral portion of the second bead overlaps with the end region of the first bead. Since the molten metal also flows in a direction perpendicular to the scanning direction, this method can also be used to fill holes. In this context, "approximately parallel" refers to a range of 0 degrees ± 10 degrees.

[0012] In the fourth embodiment of the laser-welded joint, in the third embodiment, the scanning direction of the second path is toward the endpoint of the first path.

[0013] In this embodiment, the scanning direction of the second path is toward the endpoint of the first path. Therefore, compared to the embodiment where the scanning direction of the second path is toward the starting point of the first path, the heat input state in the overlapping portion of the first and second paths can be made equivalent, and thus the weld cross-section of the overlapping portion can be controlled to be the same.

[0014] In the fifth embodiment of the laser-welded joint, in any of the first to fourth embodiments, the second bead is formed under conditions where only the upper plate melts and the lower plate does not.

[0015] In this embodiment, the second bead is formed under conditions where only the upper plate melts and the lower plate does not. Therefore, melting and other issues caused by laser irradiation during the formation of the second bead can be prevented.

[0016] A laser welding method according to a sixth embodiment includes: a first irradiation step of irradiating a laser along a first path to form a first bead; a moving step of moving the sight from the end point of the first path to the start point of a second path without irradiating a laser; and a second irradiation step of irradiating a laser along the second path to form a second bead, wherein the second irradiation step is performed such that the flow of molten metal due to the second irradiation step is toward the terminal region of the first bead.

[0017] According to this embodiment of the laser welding method, the laser-welded joint of the first embodiment can be manufactured. [Effects of the Invention]

[0018] As described above, in the laser welded joint and the laser welding method according to the present invention, depression in the end region of a weld bead is prevented. [BRIEF DESCRIPTION OF THE DRAWINGS]

[0019] [Figure 1] FIG. 1 is a plan view showing the laser welded joint of a first embodiment. [Figure 2] FIG. 2 is a plan view showing the laser welded joint of a second embodiment. [Figure 3] FIG. 3 is a diagram for explaining the start end, end end and side portions of a second bead. [MODE FOR CARRYING OUT THE INVENTION]

[0020] [First Embodiment] Hereinafter, a laser welding method and a laser welded joint S1 according to the first embodiment of the present invention will be described with reference to FIG. 1.

[0021] FIG. 1 is a schematic plan view (a view seen from a direction perpendicular to an upper plate) showing the laser welded joint S1 manufactured by the laser welding method of the first embodiment.

[0022] The laser welded joint S1 includes a first bead 10 and a second bead 20. The laser welded joint S1 is, for example, a lap joint, but may be a T-shaped through joint or other types of joints.

[0023] The laser welding method includes a first irradiation step, a moving step, and a second irradiation step.

[0024] (First Irradiation Step) The first irradiation step is a step of irradiating laser along a first path R1 to form the first bead 10. As illustrated, the first path R1 is, for example, a linear path, but is not limited thereto and may be a curved path. Laser irradiation in the first irradiation step is performed under a condition that penetrates at least the upper plate, and joins the upper plate and a lower plate together.

[0025] (Moving Step) The movement process involves moving the target from the endpoint of the first path R1 to the starting point of the second path R2 without irradiating with a laser. In each diagram, the black circles represent the starting points of the arrows indicating the first path R1 and the second path R2, and the arrowheads represent the endpoints.

[0026] The movement process in this embodiment consists of a movement process in the width direction and a movement process in the reverse direction. The width direction movement process is the process of moving the target in the width direction. Here, the width direction refers to the bead width direction in the end region 10A of the first bead 10. The reverse movement process is the process of moving the target in the reverse direction. Here, "reverse direction" means the direction along the terminal region 10A of the first bead 10, which is the opposite direction to the scanning direction in the first irradiation process. In this embodiment, the widthwise movement step is followed by the reverse movement step. However, the widthwise movement step may be performed after the reverse movement step.

[0027] (Second irradiation process) The second irradiation step involves irradiating the material with a laser along the second path R2 to form the second bead 20. In this embodiment, the second path R2 is a path parallel to the vicinity of the endpoint of the first path R1, and is positioned at a widthwise offset relative to the vicinity of the endpoint of the first path R1. The molten metal irradiated by the laser flows in the opposite and perpendicular directions to the scanning direction. Therefore, the molten metal flowing perpendicular to the scanning direction from the second irradiation process can fill the depression in the terminal region 10A of the first bead 10. As a result of this second irradiation process, as shown in Figure 1, the lateral portion 20S of the second bead 20 (see Figure 3) overlaps with the terminal region 10A of the first bead 10.

[0028] The starting point of the second path R2 is located upstream from the position corresponding to the recess 15 formed in the terminal region 10A of the first bead 10. This allows the recess 15 to be properly filled by the molten metal flowing perpendicular to the scanning direction. The position of the recess 15 may be the position where the recess 15 is expected to occur, or it may be the position where the recess 15 is detected by a sensor or the like.

[0029] The second irradiation step is preferably performed under conditions where only the upper plate melts and the lower plate does not. This is because the main purpose of the second irradiation step is to fill the depression 15 formed in the terminal region 10A of the first bead 10 with the flow of molten metal produced by the second irradiation step.

[0030] Since the second bead 20 is formed to process the terminal region 10A of the first bead 10, the length of the second path R2 is shorter than that of the first path R1. The length of the second path R2 is not particularly limited, but is, for example, 2 to 3 mm.

[0031] <Effects and Effects> Next, the effects and advantages of this embodiment will be described.

[0032] In this embodiment, the laser-welded joint S1 includes a first bead 10 formed along a first path R1 and a second bead 20 formed along a second path R2. Here, the second bead 20 is formed such that its lateral portion 20S overlaps with the terminal region 10A of the first bead 10. Since molten metal irradiated by a laser has the property of flowing in a direction perpendicular to or opposite to the scanning direction, forming the second bead in this way allows the depression 15 formed in the terminal region 10A of the first bead 10 to be filled by the second irradiation process. Furthermore, the starting point of the second path R2 is different from the ending point of the first path R1. In other words, laser irradiation is temporarily stopped at the ending point of the first path R1, and then restarted from a different position (the starting point of the second path R2), which suppresses excessive heat input due to reversal and thus prevents the occurrence of depressions.

[0033] Furthermore, in this embodiment, the second bead 20 extends in a direction parallel to the end region 10A of the first bead 10. The lateral portion 20S of the second bead 20 overlaps with the end region 10A of the first bead 10. Since the molten metal flows not only in the opposite direction to the scanning direction but also perpendicular to it, the hole can be filled by forming the second bead 20 in this way.

[0034] Furthermore, in this embodiment, the scanning direction of the second path R2 is toward the endpoint of the first path R1. Therefore, compared to an embodiment where the scanning direction of the second path R2 is toward the starting point of the first path, the heat input state in the overlapping portion of the first path R1 and the second path R2 can be made equivalent, and thus the weld cross-section of the overlapping portion can be controlled to be the same.

[0035] Furthermore, in this embodiment, the second bead 20 is formed under conditions where only the upper plate melts and the lower plate does not. Therefore, it is possible to prevent melting and other issues caused by laser irradiation (laser irradiation in the second irradiation process) when forming the second bead 20.

[0036] [Second Embodiment] Next, with reference to Figure 2, a laser welding method and a laser-welded joint S2 according to a second embodiment of the present invention will be described.

[0037] Figure 2 is a schematic plan view (viewed from a direction perpendicular to the top plate) of a laser-welded joint S2 manufactured by the laser welding method of the second embodiment.

[0038] The laser-welded joint S2 of the second embodiment includes a first bead 10 and a second bead 20, similar to the first embodiment, but the configuration of the second bead 20 differs mainly from that of the first embodiment. The laser welding method of the second embodiment, like the first embodiment, comprises a first irradiation step, a moving step, and a second irradiation step, but differs mainly in the second irradiation step from the first embodiment.

[0039] In the second embodiment, the second path R2 in the second irradiation step is a path that starts at a position shifted in the width direction from the vicinity of the endpoint of the first path R1, and is a path perpendicular to the vicinity of the endpoint of the first path R1. The molten metal irradiated by the laser flows in the opposite direction and perpendicular to the direction of laser propagation. Therefore, the molten metal flowing in the opposite direction to the scanning direction from the molten metal irradiated by the second irradiation step can fill the depression in the terminal region 10A of the first bead 10. As a result of this second irradiation step, as shown in Figure 1, the starting end 20A of the second bead 20 (see Figure 3) overlaps with the terminal region 10A of the first bead 10.

[0040] The starting point of the second path R2 is a position that traces back to the location corresponding to the recess 15 formed in the terminal region 10A of the first bead 10. This allows the recess 15 to be properly filled by the molten metal flowing in the opposite direction to the scanning direction.

[0041] <Effects and Effects> In the laser-welded joint S2 of the second embodiment, the second bead 20 extends in a direction perpendicular to the end region 10A of the first bead 10. The starting end 20A of the second bead overlaps with the end region 10A of the first bead. Since the direction in which the molten metal flows is mainly opposite to the scanning direction, hole filling can be performed more effectively compared to the first embodiment.

[0042] (supplementary explanation) Although embodiments of the present invention have been described above, the present invention is not limited to these embodiments. Further details are provided below for clarity.

[0043] In the above embodiment, a method of joining two plates, an upper plate and a lower plate, was described as a laser welding method. However, the laser welding method of this disclosure is not limited to this, and may also be a method of joining three or more plates.

[0044] In the above embodiment, an example was described in which the movement process consists of a movement process in the width direction and a movement process in the reverse direction. However, the movement process of this disclosure is not limited thereto, and may be, for example, a process of moving the aiming point in an oblique direction in both the width direction and the reverse direction.

[0045] In the first embodiment described above, an example was explained in which the scanning direction of the second irradiation step is toward the endpoint of the first path R1. However, the scanning direction of the second irradiation step in this disclosure may be in the opposite direction. In other words, the starting point and the ending point of the second path R2 may be in the opposite relationship.

[0046] The thickness of the plate materials joined by the laser welding method of the present invention is not particularly limited. However, since the reduction in joint strength due to indentation in the terminal region of the weld bead can be suppressed according to the present invention, it can be used for welding thin plates together (for example, plates with a thickness of 2.0 mm or less, and more specifically, plates with a thickness of 1.2 mm or less). [Explanation of Symbols]

[0047] S1, S2 laser welded joints 10 First bead 10A termination area 20 Second bead 20A starting point 20S lateral part R1 First Route R2 Second Route

Claims

1. The first bead formed along the first path, A second bead formed along a second path, wherein the lateral portion or starting end of the second bead overlaps with the ending region of the first bead, and the starting point of the second path is at a different position from the ending point of the first path. A laser-welded joint including, The second bead extends in a direction substantially perpendicular to the end region of the first bead, The starting end of the second bead overlaps with the ending region of the first bead. Laser-welded joints.

2. The first bead formed along the first path, A second bead formed along a second path, wherein the lateral portion or starting end of the second bead overlaps with the ending region of the first bead, and the starting point of the second path is at a different position from the ending point of the first path. A laser-welded joint including, The second bead extends in a direction substantially parallel to the end region of the first bead, The lateral portion of the second bead overlaps with the end region of the first bead. The length of the second path is 2 to 3 mm. The scanning direction of the second path is toward the starting point of the first path. The second bead is formed under conditions where only the upper plate melts and the lower plate does not. Laser-welded joints.

3. The second bead is formed under conditions where only the upper plate melts and the lower plate does not. The laser-welded joint according to claim 1.

4. A first irradiation step involves irradiating a laser along a first path to form a first bead, A movement step of moving the target from the end point of the first path to the starting point of the second path without irradiating with a laser, A second irradiation step in which a laser is irradiated along the second path to form a second bead, wherein the second irradiation step is performed such that the flow of molten metal due to the second irradiation step is directed toward the terminal region of the first bead, A laser welding method including, The second bead extends in a direction substantially parallel to the end region of the first bead, The lateral portion of the second bead overlaps with the end region of the first bead. The scanning direction of the second path is toward the endpoint of the first path. The second bead is formed under conditions where only the upper plate melts and the lower plate does not. Laser welding method.

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