Patent attributes
A friction stir welding tool 1 includes a rotor 2 to be attached to a rotation-drive section and a probe 3 concentrically provided on a distal end surface of the rotor 2. A provisional joining projection 4 is concentrically provided on a distal end surface of the probe 3. A relation 0.3 D≦d≦0.8 D is satisfied, where D represents a diameter (mm) of the distal end surface of the probe 3, and d represents a diameter (mm) of the contour of a transverse cross section of the provisional joining projection 4. The provisional joining projection 4 has a length of 0.3 to 2 mm. This friction stir welding tool can improve the work efficiency of friction stir welding and can carry out friction stir welding which is excellent in welding quality after main friction stir welding.
