| 摘要 |
In order to perform friction stir welding with excellent economy and high weld strength and reliability, a rotating tool (3) has a tool body (3a) having a shoulder face (3b) formed in the distal end portion thereof and a pin-shaped projection (3d) formed so as to protrude from the shoulder face (3b), and a backing tool (4) has a tool body (4a) having a pressure maintaining face (4b) formed in the distal end portion thereof and a cavity (4d) for receiving a distal end part of the projection (3d). The rotating tool (3) and the backing tool (4) are arranged opposite each other on the front side and back side of a weld zone (J) of a metal plate. The rotating tool (3) is moved toward the backing tool (4) while the backing tool (4) is held and the rotating tool is rotated, the distal end of the projection (3d) of the rotating tool is inserted into the cavity (4d) of the backing tool so that the weld zone is interposed, and the shoulder face (3b) of the rotating tool is pressed against the front side of the weld zone. In this state, the rotating tool (3) and the backing tool (4) are moved along the weld zone, and the entire area of the weld zone in the plate thickness direction is friction-stirred by the rotating tool (3).
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