To provide a method of manufacturing a member having a closed cross section made of metal, by which the member having the closed cross section made of metal is manufactured from a planar workpiece made of the metal and which is excellent in weldability in the butt end parts.
When manufacturing the member having a closed cross section from the planar workpiece made of the metal, this method includes: a first press forming stage where the planar workpiece W1 is press-formed into a projected shape and also a projecting part W2a which is projected in the opposite direction is formed in the projecting top surface; a second press forming stage where projecting side face parts W3, W4 are displaced respectively to the inward side by press-forming the projecting part; and a welding stage where the end parts W3e, W4e of the projecting side face parts are welded each other. Furthermore, this method includes an extended part forming stage where an extended part W5 which is lapped in the inside of the end part W3e of the other projecting side face part W3 is formed when the end parts of the projecting side face parts welded mutually in the end part W4e of one projecting side face part W4. The welding stage is performed by supplying a filler metal between the extended part which is formed in the end part of one projecting side face part and the end part of the other projecting side face part.
ISHIDA YASUAKI
SAITO NAOKO
SHINOMORI MASATOSHI
Mitsuo Tanaka
Fukuoka Masaaki
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