Automobile frame member

摘要

An object of the present invention is to provide a lightweight strengthening member for an automobile, excellent in crush resistance in the axial direction and having high flexural strength. Further, another object thereof is to provide a strengthening member which does not generating cracks even when a high-strength steel sheet is used. The present invention provides: a strengthening member 1 for an automobile, being a lengthy strengthening member 1 having concave portions 3 at the four corners of a basic rectangular cross section 2 and forming a cruciform closed section as a whole, characterized in that the wall thickness of the concave portions 3 is 5 to 30% thicker than the wall thickness of the portions excluding the concave portions, namely, the side walls 4 and the top walls 5; further, a strengthening member 1 for an automobile, characterized in that the hardness of the concave portions 3 is 5% or more higher than the hardness of the portions excluding the concave portions, namely, the side walls 4 and the top walls 5; and furthermore, a strengthening member 1 for an automobile formed by drawing or hydroforming.