Friction stirring and joining tools

Abstract

To provide a tool for friction stir welding capable of forming a sound welding portion by effectively suppressing the generation of burrs in the welding portion, especially height of the burrs, and reducing a load in a post-process.SOLUTION: A tool for friction stir welding 10 includes a body portion 11, a probe 12, a shoulder portion 23, and a circumferential groove 14 formed around the probe 12. When groove depth of the circumferential groove 14 is d and axial length of the probe 12 is L, d>0.33×L.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a friction stir welding tool for joining workpieces by utilizing frictional heat generated by the rotation of a probe. [Background technology]

[0002] Friction stir welding (FSW) is a method in which a probe attached to the tip of a tool is rotated while the tip of the probe is pressed against the butt joint of the materials to be welded, and the probe is pressed into the materials to be welded and moved along the butt joint, joining the materials through frictional heat and stirring.

[0003] Friction stir welding can produce good welds when highly fluid materials such as aluminum are used as the welded materials, but burrs may form on the butt joint surface depending on the insertion depth of the probe and the dimensional accuracy of the welded materials. In other words, when the probe is pressed against the welded materials while rotating, material that flows out to the outside of the probe becomes a burr. If the burrs generated by friction stir welding are small, they can be removed by brushing, but if they are large, they must be removed by cutting, making burr removal in subsequent processes difficult.

[0004] Regarding such problems, Patent Document 1 discloses a friction stir welding jig that is configured to satisfy the conditions of 0.5R≦r≦0.95R, 0.025R≦W≦0.25R, and 0.01L≦d≦0.33L, where r is the inner diameter of the circumferential groove of the friction stir welding jig, R is the diameter of the jig body, W is the width of the circumferential groove, d is the depth of the circumferential groove, and L is the length of the probe, thereby suppressing the generation of burrs. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 3283439 Summary of the Invention [Problem to be solved by the invention]

[0006] However, welding using the friction stir welding jig described in Patent Document 1 does not necessarily have a sufficient effect of suppressing burrs, and further improvement has been desired.

[0007] The present invention has been made in consideration of the above-mentioned problems, and its object is to provide a friction stir welding tool that can effectively suppress the occurrence of burrs at the joint, particularly the height of the burrs, to form a sound joint and reduce the burden on subsequent processes. [Means for solving the problem]

[0008] The above object of the present invention can be achieved by the following configuration of a friction stir welding tool.

[0009] A friction stir welding tool comprising: a columnar main body; and a probe protruding in an axial direction from a shoulder portion of the main body; and wherein a tip of the probe is pressed against workpieces while being rotated to generate frictional heat, thereby joining the workpieces; the shoulder portion has a circumferential groove on the outer side in the circumferential direction of the probe; A friction stir welding tool, wherein d>0.33×L, where d is the groove depth of the circumferential groove from the surface of the shoulder portion and L is the axial length of the probe. [Effects of the Invention]

[0010] The friction stir welding tool of the present invention can effectively suppress the occurrence of burrs in a welded joint, particularly the height of the burrs, thereby forming a sound welded joint and reducing the burden on subsequent processes. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a side view of a main part of a friction stir welding tool according to one embodiment of the present invention. [Figure 2A]FIG. 2A is a side view of a main part of a conventional friction stir welding tool used in a comparative test. [Figure 2B] FIG. 2B is a side view of a main part of the friction stir welding tool according to this embodiment used in the comparative test. [Figure 3] FIG. 3 is a conceptual diagram showing the test conditions in the comparative test. [Figure 4] FIG. 4 is a graph showing the test results of the comparative test. [Figure 5] FIG. 5 is a graph showing the relationship between the ratio of the groove depth to the probe length (d / L) and the ratio of the groove volume to the probe volume. [Figure 6] FIG. 6 is a graph showing test results of the ratio of the groove depth to the probe length (d / L) and the maximum value of the burr height. DETAILED DESCRIPTION OF THE INVENTION

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a friction stir welding tool according to the present invention will be described in detail below with reference to the drawings. As shown in FIG. 1, the friction stir welding tool 10 has a columnar main body 11 that is rotated by a rotation drive motor (not shown), and a probe 12 that is approximately cylindrical and has a smaller diameter than the main body 11, and is integrally molded coaxially with the tip of the main body 11.

[0013] The tip surface 13 of the main body 11 (excluding the probe 12) is flat, and a shoulder portion 23, which is an annular flat surface, is formed on the outer periphery of the probe 12. A circumferential groove 14 having a substantially V-shaped cross section is provided on the shoulder portion 23 on the outer periphery of the probe 12. In other words, the area between the probe 12 and the circumferential groove 14 and on the outer periphery of the circumferential groove 14 is the shoulder portion 23, which is flat.

[0014] Here, if the height of the shoulder portion 23 on the outer periphery side of the circumferential groove 14 is higher than the height of the shoulder portion 23 on the inner periphery side of the circumferential groove 14, the plastically flowed workpieces will be more likely to flow out, as will be described later, so it is desirable that these be the same height. Note that the circumferential groove 14 is not limited to having a V-shaped cross section, and may have a U-shaped cross section, for example.

[0015] The circumferential groove 14 holds the workpieces that have become plastically fluid due to frictional heat with the rotating probe 12 within the circumferential groove 14, thereby preventing them from being expelled as burrs to the outside of the shoulder portion 23. The flat shoulder portion 23 also acts to hold the plastically fluidized workpieces within the weld region.

[0016] Next, the friction stir welding tool 10 of this embodiment satisfies the following formula (1), where the axial length of the probe 12 from the shoulder portion 23 is L and the groove depth of the circumferential groove 14 from the surface of the shoulder portion 23 is d.

[0017] d>0.33×L (1)

[0018] As will be shown in the test results described later, by satisfying d>0.33×L, good welding results can be obtained with less burrs generated after welding due to the effects of the circumferential groove 14 and shoulder portion 23. The reason for this is presumably that a balance is achieved between the effect of the workpieces that have been plastically fluidized by frictional heat with the probe 12 being stored in the circumferential groove 14 and the effect of the shoulder portion 23 pressing the plastically fluidized workpieces against the welding region, thereby suppressing the generation of burrs.

[0019] The friction stir welding tool 10 of this embodiment satisfies d>0.33×L, but in order to more effectively exert the above-mentioned effects, it is preferable that d>0.50×L be satisfied.

[0020] Next, the results of a preliminary test conducted to compare the size of burrs formed when aluminum plates, which are the workpieces, are joined using a friction stir welding tool 10A of a conventional shape shown in FIG. 2A and the friction stir welding tool 10 of this embodiment having a circumferential groove 14 shown in FIG. 2B, will be described. (Preliminary Examination)

[0021] The shape and dimensions of a conventional friction stir welding tool 10A are shown in Fig. 2A, and the shape and dimensions of the friction stir welding tool 10 of this embodiment, which is provided with a circumferential groove 14, are shown in Fig. 2B. Using both welding tools 10A and 10, aluminum plates, which were the workpieces, were joined under the test conditions shown in Fig. 3, and the sizes of the burrs were compared.

[0022] Specifically, aluminum plates with thicknesses of 2.0 mm and 1.4 mm were placed butt-together, and the friction stir welding tools 10A, 10 were tilted 2.45° toward the thinner plate relative to the joining line (i.e., at an inclination angle of 2.45°).The friction stir welding tools 10A, 10 were rotated at a rotational speed of 2000 rpm, and the plates were joined at a welding speed of 2.0 m / min, and the heights of the burrs produced after joining were compared.

[0023] The test results are shown in Figure 4.

[0024] 4, the burr height generated on the 1.4 mm thick aluminum plate side was about 0.2 mm for both tools, with no significant difference observed, but the maximum burr height generated on the 2.0 mm thick aluminum plate side was 0.8 mm for the conventional friction stir welding tool 10A, whereas it was significantly reduced to 0.5 mm for the friction stir welding tool 10 of this embodiment equipped with the circumferential groove 14. Therefore, the burr suppression effect of the circumferential groove 14 was confirmed.

[0025] (d / L confirmation test) Next, aluminum plates were joined using four friction stir welding tools 10, No. 1 to No. 4, which had different ratios (d / L) of the groove depth d of the circumferential groove to the axial length L of the probe, and the maximum burr heights for each were compared.

[0026] As shown in Figure 5, in the friction stir welding tool 10, based on the ratio between the volume of the probe 12 and the volume of the circumferential groove 14, in the parts where d / L is small (i.e., 0.60 or less), the groove volume is smaller than the probe volume, and it is expected that the circumferential groove 14 will not be able to receive all of the plastically flowed workpiece material that overflows from the probe 12. Therefore, the d / L values ​​of the four friction stir welding tools 10 were set in the range of 0.167 to 1.111.

[0027] That is, the specifications of the friction stir welding tools 10 No. 1 to No. 4 were, as shown in Table 1 below, that the axial length L of the probe was 1.8 mm, and the groove depth d of the circumferential groove was 0.3 mm, 0.6 mm, 0.9 mm, and 2.0 mm, respectively.

[0028] The test conditions were as follows: aluminum plates of 2.5 mm and 2.0 mm thickness, 50 mm width and 300 mm length were placed butt-together as the materials to be joined, and a length of 250 mm was joined under the conditions shown in Table 2 below, and the burr height in the evaluation range of 50 to 200 mm was used for evaluation.

[0029] [Table 1]

[0030] [Table 2]

[0031] The test results for burr height versus d / L are shown in Figure 6. As can be seen from Figure 6, the burr height changed significantly around d / L = 0.333, and the burr height produced by the No. 1 friction stir welding tool 10 (d / L = 0.167) was significantly greater than the burr height produced by the Nos. 2 to 4 friction stir welding tools 10 (d / L = 0.333 to 1.111). In other words, it was found that burr height can be suppressed by joining the workpieces using a friction stir welding tool 10 with a d / L of more than 0.33.

[0032] This is thought to be because, when d / L is 0.33 or less, the workpieces that have been plastically fluidized by the probe 12 and overflow cannot be received by the circumferential groove 14, and so flow out of the joint and become burrs. On the other hand, when d / L exceeds 0.33, approximately 60% by volume or more of the plastically fluidized workpieces can be held within the circumferential groove 14, and further, the plastically fluidized workpieces that overflow from the circumferential groove 14 are held down within the joint area by the flat shoulder portion 23, which is thought to effectively suppress the burr height.

[0033] The present invention is not limited to the above-described embodiments and test examples, and modifications and improvements are possible as appropriate.

[0034] As described above, the present specification discloses the following:

[0035] [1] A friction stir welding tool comprising a columnar main body and a probe protruding in the axial direction from a shoulder portion of the main body, the tool rotating and pressing the tip of the probe against the workpieces to generate frictional heat, thereby joining the workpieces, the shoulder portion has a circumferential groove on the outer side in the circumferential direction of the probe; A friction stir welding tool, wherein d>0.33×L, where d is the groove depth of the circumferential groove from the surface of the shoulder portion and L is the axial length of the probe.

[0036] This configuration effectively suppresses the occurrence of burrs at the joint, particularly the height of the burrs, to form a sound joint and reduce the burden on subsequent processes.

[0037] [2] The friction stir welding tool according to the above [1], wherein the surface of the shoulder portion is flat.

[0038] According to this configuration, the workpieces that have plastically flowed and overflowed from the circumferential groove are held down in the joining area by the flat shoulder portion, thereby making it possible to suppress the height of burrs. [Explanation of symbols]

[0039] 10. Friction stir welding tools 11 Main body 12 probes 13 Tip surface of main body (surface of shoulder part) 14 Circumferential groove 23 Shoulder section d Depth of circumferential groove from the surface of the shoulder L Axial length of the probe

Claims

1. A friction stir welding tool comprising a columnar main body and a probe protruding in an axial direction from a shoulder portion of the main body, the tool rotating and pressing a tip of the probe against workpieces to generate frictional heat, thereby joining the workpieces, the shoulder portion has a circumferential groove on the outer side in the circumferential direction of the probe; where d is the depth of the circumferential groove from the surface of the shoulder portion and L is the axial length of the probe, and 0.33×L<d≦0.60×L; A friction stir welding tool, wherein when the volume of the circumferential groove is A and the volume of the probe is B, 0.6≦A / B<1.

0.

2. The friction stir welding tool according to claim 1 , wherein the surface of the shoulder portion is flat.

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