Friction stir welding method

Abstract

To provide a friction stir welding method which can suppress crack in an interface direction.SOLUTION: A friction stir welding method is given in which while pushing a probe P against one of overlapped members to be joined, the probe P is rotated and moved to weld the members. The probe P is moved so that a joint line 30 is bent by 90 degrees toward a welded engagement region at a welding terminal end part 30B.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a friction stir welding method. [Background technology]

[0002] Patent Document 1 discloses a joining method in which a rotating stirring shaft is inserted into overlapping joining parts to perform friction stir welding. In the joining method described in Patent Document 1, the strength of the joining end is improved by moving the tool in an arc at the end of the joining line. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-152759 Summary of the Invention [Problem to be solved by the invention]

[0004] The friction stir welding described in Patent Document 1 can easily join dissimilar materials without distortion. However, there is room for improvement in terms of suppressing cracks in the interface direction.

[0005] An object of the present invention is to provide a friction stir welding method that can suppress cracks in the interface direction. [Means for solving the problem]

[0006] The friction stir welding method according to claim 1 is a friction stir welding method in which a probe is pressed against one of the overlapping joining parts and moved while rotating the probe, and the probe is moved so that the joining line bends by 90 degrees or more toward the already joined joining area at the joining end portion.

[0007] In the friction stir welding method according to claim 1, the overlapping joining parts are joined by pressing a probe against one of the overlapping joining parts and moving the probe while rotating the probe. This allows dissimilar materials to be joined without distortion and with little energy.

[0008] In addition, the probe is moved so that the joining line bends by 90 degrees or more toward the already joined joint area at the joining end. This causes the joining end to be sandwiched between the joining areas on both sides, suppressing cracks in the direction of the interface.

[0009] A friction stir welding method according to a second aspect of the present invention is the method of the first aspect, wherein the welding line is bent at the welding terminal end portion toward the welding start portion.

[0010] In the friction stir welding method according to claim 2, by bending the welding line toward the welding start portion, no extra welding is required when drawing the welding line in a circle, for example.

[0011] A third aspect of the friction stir welding method is the same as the first aspect, wherein the probe is moved so that the welding line is circular.

[0012] In the friction stir welding method according to claim 3, by moving the probe so that the welding line is circular, circular welding members can be efficiently welded.

[0013] A fourth aspect of the friction stir welding method is the same as the third aspect, wherein the probe is moved in the welding terminal end portion toward the inside of the circle toward the welding starting end portion.

[0014] In the friction stir welding method according to claim 4, by moving the probe toward the inside of the circle, the weld end portion can be protected from external forces more effectively than when the probe is moved toward the outside of the circle.

[0015] A friction stir welding method according to claim 5 is based on claim 1, wherein the joining members include a bottom plate that holds a vehicle battery, and a bracket that is disposed on an upper surface of the bottom plate and to which the vehicle battery is fastened.

[0016] In the friction stir welding method according to claim 5, strength can be ensured even for a bracket that supports a heavy object such as a vehicle battery. [Effects of the Invention]

[0017] As described above, according to the friction stir welding method of the present invention, it is possible to suppress cracks in the interface direction. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 2 is a perspective view showing a bottom plate and a bracket joined by a friction stir welding method according to an embodiment. [Figure 2] FIG. 2 is an enlarged plan view showing a main part of the bracket in the embodiment. [Figure 3] FIG. 2 is a schematic plan view showing the start and end portions of a joining line. [Figure 4] FIG. 4 is a cross-sectional view taken along line 4-4 in FIG. 2. [Figure 5] 5 is a cross-sectional view corresponding to FIG. 4, showing a state joined by a friction stir welding method according to a comparative example. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0019] A friction stir welding method according to an embodiment will be described with reference to the drawings.

[0020] 1 is a perspective view showing a bracket 12 and a bottom plate 14 joined by a friction stir welding method according to an embodiment. Note that the arrows FR, UP, and LH in the figure respectively indicate the forward, upward, and leftward directions of a vehicle on which the bottom plate 14 is mounted. In the following description, unless otherwise specified, the terms "front-rear," "up-down," and "left-right" refer to front-rear in the front-rear direction of the vehicle, up-down in the up-down direction of the vehicle, and left-right in the left-right direction (width direction) of the vehicle, respectively.

[0021] As shown in FIG. 1, the bottom plate 14 to which the friction stir welding method of this embodiment is applied is a plate-shaped member for holding a vehicle battery 16, and is formed in a substantially flat plate shape from a metal such as iron or an aluminum alloy.

[0022] A plurality of brackets 12 are arranged on the upper surface of the bottom plate 14. In this embodiment, as an example, two brackets 12 are arranged spaced apart in the vehicle width direction, but this is not limited thereto, and three or more brackets may be arranged. Furthermore, the positions of the brackets 12 are not particularly limited.

[0023] The two brackets 12 are formed in approximately the same cylindrical shape. Specifically, the brackets 12 include a substantially cylindrical bracket main body 12A and a flange portion 12B provided at the lower end of the bracket main body 12A and overlapped with the bottom plate 14. A bolt hole 12C through which a bolt can be inserted is formed in the upper surface of the bracket main body 12A.

[0024] The vehicle battery 16 is configured to be able to store power to be supplied to a motor for driving the vehicle, and includes an outer shell, a battery case 16A. The battery case 16A houses multiple battery packs (not shown), each of which stores electricity.

[0025] The battery case 16A is provided with fastening pieces 18 at positions corresponding to the brackets 12. For example, the fastening pieces 18 are formed integrally with the battery case 16A and protrude outward from the outer surface of the battery case 16A.

[0026] An insertion hole 18A is formed in the fastening piece 18. The insertion hole 18A of the battery case 16A and the bolt hole 12C of the bracket 12 are formed to communicate with each other when the vehicle battery 16 is placed in a predetermined position. Therefore, after the vehicle battery 16 is placed and positioned on the bottom plate 14, a fastener such as a bolt (not shown) can be inserted from above the insertion hole 18A and screwed into the bolt hole 12C, thereby fastening the vehicle battery 16 to the bottom plate 14. Note that a weld nut may be welded to the inside of the bracket 12 in advance, and the bolt may be screwed into the weld nut.

[0027] FIG. 2 is an enlarged plan view of a main portion of the bracket 12 according to the embodiment. As shown in FIG. 2, the flange portion 12B of the bracket 12 is joined to the bottom plate 14 by friction stir welding (FSW), and a weld line 30 is substantially circular. The weld line 30 is a linear portion formed by a path traced when a probe, which is a tool, is moved while being pressed against the bracket 12. The bracket 12 and the bottom plate 14 are joined in the area surrounding the weld line 30. That is, in the present embodiment, the probe is moved so that the weld line 30 becomes circular. Thus, in the present embodiment, the joining is performed by rotating and moving the probe while pressing it against one of the brackets 12 of the overlapping joined members.

[0028] FIG. 3 is a schematic plan view showing the start and end portions of the weld line 30. As shown in FIG. 3, the weld start portion 30A and the weld end portion 30B of the weld line 30 are offset in the radial direction, and the weld end portion 30B is located radially outward of the weld start portion 30A. For example, the probe P may be moved from the weld start portion 30A to gradually increase the radius of the arc while welding, so that the weld end portion 30B is located radially outward of the weld start portion 30A. For ease of explanation, the trajectory of the probe P is depicted by a two-dot chain line in FIG. 3; however, in reality, the welded weld area is agitated, making the trajectory of the probe P invisible.

[0029] Here, the probe P is moved so that the joining line 30 is bent by 90 degrees or more toward the joined region at the joining end portion 30B of the joining line 30. In this embodiment, as an example, the moving direction of the probe P in the portion immediately before the bending is approximately perpendicular to the moving direction of the probe P in the portion immediately after the bending.

[0030] In this embodiment, the probe P is moved at the joint termination portion 30B so that the joint line 30 bends toward the joint starting portion 30A. That is, at the joint termination portion 30B, the probe P is moved toward the inside of the circle toward the joint starting portion 30A of the joint line 30. In this embodiment, the end of the joint line 30 slightly overlaps the joint region at the starting end, but this is not limited thereto, and there may be a gap between the starting end and the end.

[0031] Fig. 4 is a cross-sectional view taken along line 4-4 in Fig. 2. As shown in Fig. 4, the cross section of the joint end portion 30B has a long radially extending joint area because the joint line 30 is moved toward the joint start portion 30A.

[0032] After the probe P is moved to the joint terminal end portion 30B, the probe P is pulled upward to form the probe hole 32. In this embodiment, the probe P is moved so that the joint line 30 is bent at the joint terminal end portion 30B toward the joint starting end portion 30A, and therefore the probe hole 32 is located more inward than the radial center portion of the joint area.

[0033] (action) Next, the operation of the friction stir welding method according to this embodiment will be described.

[0034] In this embodiment, the overlapping joining members are joined by rotating and moving the probe P while pressing it against one of the overlapping bracket 12 and bottom plate 14. This allows different materials to be joined without distortion using little energy.

[0035] 3, the probe P is moved so that the joint line 30 is bent by 90 degrees or more toward the already joined joint area at the joint termination portion 30B of the joint line 30. As a result, as shown in FIG. 4, the joint termination portion 30B is sandwiched between the joint areas on both sides, and the bracket 12 and the bottom plate 14 are sufficiently joined on both sides of the probe hole 32, thereby suppressing cracks in the interface direction.

[0036] The above effects will be explained in comparison with a comparative example.

[0037] Fig. 5 is a cross-sectional view corresponding to Fig. 4, showing a state joined by a friction stir welding method according to a comparative example. As shown in Fig. 5, in the friction stir welding method according to the comparative example, the weld start end and the weld end portion of the weld line 100 are in the same position. Therefore, at the weld end portion 100A, the weld width between the bracket 12 and the bottom plate 14 is shortened by the amount corresponding to the formation of the probe hole 102. As a result, there is a possibility that cracks will occur in the direction of the interface between the bracket 12 and the bottom plate 14.

[0038] In contrast, in the friction stir welding method according to this embodiment, as shown in FIG. 4, the width of the joining area on both sides of the probe hole 32 at the joining termination portion 30B is sufficiently secured, so that cracks in the interface direction can be effectively suppressed.

[0039] In addition, in this embodiment, by bending the joining line 30 toward the joining start end portion 30A, there is no need for additional joining of the joining line 30. In particular, by moving the probe P so that the joining line 30 becomes circular as in this embodiment, circular joining members can be joined efficiently.

[0040] Furthermore, in this embodiment, by moving the probe P toward the inside of the circle, the joint terminal portion 30B can be protected from external forces more effectively than when the probe P is moved toward the outside of the circle. In this way, the strength of the bracket 12 can be ensured even when the bracket 12 supports a heavy object such as a vehicle battery 16.

[0041] The friction stir welding method according to the present invention has been described above, but it goes without saying that it can be embodied in various forms without departing from the spirit and scope of the present invention. For example, in the above embodiment, as shown in Fig. 3, the weld line 30 is bent at a substantially right angle at the weld termination portion 30B, but this is not limited to this, and the weld line 30 may be bent at an angle greater than 90 degrees. In this case, the probe P is moved toward the weld region at an acute angle, and as in this embodiment, both sides of the weld termination portion 30B are sandwiched between the weld regions.

[0042] In the above embodiment, the probe P is moved so that the joining line 30 is substantially circular, but this is not limiting. For example, the probe P may be moved in a substantially rectangular shape or a substantially polygonal shape.

[0043] Furthermore, in the above embodiment, as shown in Fig. 1, a method for joining the bottom plate 14 that holds the vehicle battery 16 and the bracket 12 that is disposed on the top surface of the bottom plate 14 and to which the vehicle battery 16 is fastened has been described, but the present invention is not limited to this. It can be widely applied to methods for joining other members by overlapping them together.

[0044] The following additional notes are provided regarding the above-described embodiments.

[0045] (Appendix 1) A friction stir welding method in which a probe is pressed against one of overlapping joining members and the probe is moved while rotating, A friction stir welding method in which the probe is moved so that the welding line bends by 90 degrees or more toward the already welded welding region at the welding end portion. (Appendix 2) 2. The friction stir welding method according to claim 1, wherein the welding line is bent at the welding end portion toward the welding start portion. (Appendix 3) 3. The friction stir welding method according to claim 1, wherein the probe is moved so that the welding line becomes circular. (Appendix 4) 4. The friction stir welding method according to claim 3, wherein at the welding end portion, the probe is moved toward the inside of the circle toward the welding start portion. (Appendix 5) The friction stir welding method according to any one of appendix 1 to appendix 4, wherein the joining member includes a bottom plate that holds a vehicle battery and a bracket that is arranged on an upper surface of the bottom plate and to which the vehicle battery is fastened. [Explanation of symbols]

[0046] 12 Bracket (jointing member) 14 Bottom plate (joint member) 16 Vehicle battery 30 Joining line 30A joint start end 30B Joint end part P probe

Claims

1. A friction stir welding method in which a probe is pressed against one of overlapping joining members and the probe is moved while rotating, The friction stir welding method includes moving the probe so that the welding line bends by 90 degrees or more toward the already welded welding region at the welding end portion.

2. The friction stir welding method according to claim 1 , wherein the welding line is bent at the welding end portion toward the welding start portion.

3. The friction stir welding method according to claim 2 , wherein the probe is moved so that the welding line is circular.

4. The friction stir welding method according to claim 3 , wherein the probe is moved inward of the circle at the welding end portion toward the welding start portion.

5. 2. The friction stir welding method according to claim 1, wherein the joining members include a bottom plate that holds a vehicle battery, and a bracket that is disposed on an upper surface of the bottom plate and to which the vehicle battery is fastened.

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