| 主权项 |
1. A rotary tool for friction stir spot-welding, which is used to perform a friction stir spot-welding operation on a stack of two aluminum members, the rotary tool having a cylindrical tool body rotatable about its axis, and a probe which is provided in a central part of a distal end portion of the tool body so as to extend coaxially with the tool body, and which is inserted into the stack of the two aluminum members, the rotary tool being characterized in that:
the probe has a stepped structure consisting of: a cylindrical intermediate probe having an outside diameter smaller than that of the tool body and projecting from the distal end portion of the tool body so as to extend coaxially with the tool body; and a cylindrical central probe having an outside diameter smaller than that of the intermediate probe and projecting from the intermediate probe so as to extend coaxially with the intermediate probe; and a distal end face of the tool body gives a first shoulder surface which is gradually recessed in a radially inward direction and which is connected to a proximal portion of the intermediate probe at a position radially inwardly spaced apart from an outer periphery of the distal end face of the tool body, while a distal end face of the intermediate probe gives a second shoulder surface which is gradually recessed in a radially inward direction and which is connected to a proximal portion of the central probe at a position radially inwardly spaced apart from an outer periphery of the distal end face of the intermediate probe. |
