| 摘要 |
PROBLEM TO BE SOLVED: To provide a welded joint structure and a hollow material made of metal, by which defective welding such as thermal strain, a crack, a shift, etc., has been avoided, that is, which have satisfactory welding states and high joint strength. SOLUTION: A hollow material P1 has been assembled and manufacture from four tabular split pieces 10, 20, 30 and 40 having wide widths. In the adjacent part of adjacent split bodies, the inside surface of the side edge part of the split piece 10 on the one side and the end face of the side edge part of the split piece 20 on another side, are butted. Further, the side face of a projecting part 13 provided on the inside surface of the intermediate part of the split piece 10 on the one side and the inside surface of the side edge part of the split piece 20 on another side, and abutted. In this state, the side face of the projecting part 13 and the abutted part of the inside surface of the side edge part of the split piece on another side, have been welded (weld zones W1) by friction-stir welding performed by inserting the working head of a welding tool into this abutted part from the outside surface of the split piece 10 on the one side.
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