To improve the accuracy of formation of a closed cross-sectional member in a method of manufacturing the closed cross-sectional member made of metal, in which the closed cross-sectional member is manufactured by press-forming the projecting part of a planar workpiece.
The method of manufacturing the closed cross-sectional member which is formed from the planar workpiece W1 made of metal, includes: a first press-forming step where the planar workpiece is press-formed into a projective shape and also a projecting part W2a projecting in the opposite direction to the projective top surface part is formed; a second press-forming step where a closed cross section is made by displacing projective side face parts on both sides to inward side respectively by press-forming the projecting part in the direction opposite to the projecting direction; and a tab part forming step where tab parts W2f are formed integrally in the end parts in the longitudinal direction of the planar workpiece in the projecting part of the planar workpiece. The second press-forming step is performed by positioning the tab parts which are formed in the tab forming stage to a press-forming die 60 for press-forming the projecting part in the direction opposite to its projecting direction.
MIZOGAMI TATSUSHI
MURASE KENJI
ISHIDA YASUAKI
Mitsuo Tanaka
Fukuoka Masaaki