To suitably spot weld a superposed part of a center part of a workpiece when manufacturing a closed cross section metal member having two closed cross section parts extending in parallel with a recess groove interposed from a rectangular flat plate-like workpiece.
Opposite edge parts S0, S0 of the rectangular flat plate-like workpiece W0 are notched to form an intermediate member W1 where a notched part m of one edge part and a non-notched part n of the other edge part are arranged to face with each other. The non-notched part n of the member W1 is folded back and the workpiece forms an intermediate member W2 where two-layer laminated parts A and single layer parts B are alternately arranged side by side at both edge parts S1, S2. The member W2 is folded to one surface side to gather both the edge parts S1, S2 of the member W2 to the center part of the member W2 and both the edge parts S1, S2 are folded to the other surface side. The center part of the member W2, the end part of the laminated part A of one edge part, and the end part of the single layer part B of the other edge part are superposed to form an intermediate member W3 so that the superposed part L of the member W3 is joined to form a final member.
KAMIOKA TOSHITSUGU
YAMAMOTO KENICHI
MURASE KENJI
SAITO NAOKO
Mitsuo Tanaka
Fukuoka Masaaki
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