CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2019-066160 filed on Mar. 29, 2019, the contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a friction stir welding tool which includes a probe having a front end surface and an outer circumferential surface, and welds a workpiece by rotating the probe about a rotation axis and embedding the probe inside the workpiece during rotation of the probe.

Description of the Related Art

Japanese Laid-Open Patent Publication No. 2008-307606 discloses, in FIG. 9 and paragraph [0007], a friction stir welding tool having outer circumferential recesses extending along a rotation axis of a probe in an outer circumferential surface of the probe. The outer circumferential recesses have a constant width over the entire length of the outer circumferential recesses.

SUMMARY OF THE INVENTION

In the above described friction stir welding tool, material softened by friction heat of the probe is taken into the outer circumferential recesses from a lateral side of the probe for allowing the softened material to flow plastically toward the front end of the probe. However, since the outer circumferential recesses have a constant width over the entire length of the outer circumferential recesses, the volume of material which can be taken into the outer circumferential recesses is relatively small. Therefore, it may not be possible to sufficiently stir the softened material by the probe, and achieve the suitable welding quality.

The present invention has been made taking such a problem into consideration, and an object of the present invention is to provide a friction stir welding tool which makes it possible to achieve the suitable welding quality.

According to an aspect of the present invention, there is provided a friction stir welding tool including a probe having a front end surface and an outer circumferential surface. The outer circumferential surface includes, formed therein, an outer circumferential recess extending to the front end surface along a rotation axis of the probe, and the friction stir welding tool is configured to rotate the probe about the rotation axis and embed the probe inside a workpiece during rotation of the probe to thereby weld the workpiece. The width of the outer circumferential recess is increased toward a front end of the probe.

In the present invention, the width of the outer circumferential recess is increased toward the front end of the probe. Therefore, in comparison with the case where the outer circumferential recess has a constant width, it is possible to increase the quantity (volume) of softened material taken into the outer circumferential recess. Accordingly, since it is possible to increase the efficiency of stirring the softened material, it is possible to achieve the suitable welding quality.

The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which preferred embodiments of the present invention are shown by way of illustrative example.

