To provide a method for manufacturing a strength member for an automobile, having high bending reaction force at the initial stage of collision and having a cross section shape enabling the reduction of its manufacturing cost and weight.
The method is for manufacturing a square steel tube having a square cross section, wherein a square steel tube having a tensile strength of ≥690 MPa and a square cross section is manufactured by cold-drawing a round steel tube. In the method, a round steel tube having a tensile strength of ≥590 MPa is used, and the outer peripheral length reduction Or is 10-40%, as shown in the formula (1) as follows: 10≤Or=[(L0-L)/L0]×100≤40 (wherein, L0 is the outer peripheral length (mm) of the round steel tube before cold drawing; and L is the outer peripheral length (mm) of the square steel tube after cold drawing).
TERADA YOSHIO
KOYUMIBA MOTOFUMI
NIIYAMA FUMIHIKO
SAWADA SHINYA
Hisataka Tanaka
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