Press-forming method of tubular part having cross section of irregular shape, and tubular part having cross section of irregular shape formed by the press-forming method

摘要

A method of press-forming a tubular part having a cross section of an irregular shape crushes a steel tube between an upper die and a lower die in order to form a V-shaped cross section. When the curvature radius of a tip of the upper die is defined as R₁, the curvature radius of a bottom portion of the lower die corresponding to the tip of the upper die is defined as R₂, and the wall thickness of the steel tube is defined as t; R₁, R₂, and t satisfy R₁+2t=R₂ and 1.5t≦R₁≦3t.