Friction stir welding joint and friction stir joint using this joint

摘要

PROBLEM TO BE SOLVED: To provide a friction stir welding coupling capable of reliably preventing the occurrence of an unwelded part which may be a cause of root cracking of a joint member without eliminating an excess thickness part, and to provide a friction stir welding method using the friction stir welding coupling.SOLUTION: Butted surfaces P of an edge part of one side member 10 provided with a first upper surface protrusion part 11 and a first lower surface protrusion part 12, and an edge part of the other side member 20 provided with a second upper surface protrusion part 21 and a second lower surface protrusion part 22 are welded by friction stir welding by the use of a rotation tool 30, the edge part of the other side member 20 is provided with an extension part 23 extending along a lower surface of the first lower surface protrusion part 12 of the one side member from a lower edge of the butted surface P and, within a range (H2) of the thickness of the extension part 23, friction stir welding of the butted surface P is performed.