PURPOSE: To maintain the section shape at the time of secondary forming such as bending and to improve the impact energy absorption performance at the time of collision when an extrude-forming piece made of aluminum alloy used as an automobile member is extruded.
CONSTITUTION: By controlling the temperature of a part of a molding die 21 of an extrusion machine 20 by the heating action of a heating member 28 and the cooling action of a cooling member 29, at the time of extrusion of aluminum alloy, a low strength part 22a where a crystalline structure is coarsened and which is small in tensile strength, low in the yield point and large in elongation and a high strength part 22b where a crystalline structure is fined and which is large in tensile strength, high in the yield point and small in elongation are formed on the extrude-forming piece 22. By executing secondary forming such as bending on the low strength part 22a, the section shape of the extrude- forming piece 22 can be maintained. Further, at the time of collision, the low strength part 22a is crushed easily and the absorption performance of impact energy becomes high.
NAKAGAWA NARIYUKI
MAKUCHI YUTAKA
