STRENGTH MEMBER FOR AN AUTOMOBILE BODY, FRONT SIDE MEMBER, AND SIDE STRUCTURE FOR AN AUTOMOBILE BODY

摘要

A strength member for an automobile body such as a side member or a pillar which has a bent portion which is bent two-dimensionally or three- dimensionally and which has an ultrahigh strength with a tensile strength exceeding 1100 MPa is provided. The strength member for an automobile body has a tubular body which has a closed cross section which does not have an outwardly-extending flange and which has a bent portion which is bent two-dimensionally or three- dimensionally, a portion to be cut or punched, and a portion to be welded. The tubular body has an ultrahigh strength heat-treated portion which has been heat treated to have a tensile strength exceeding 1100 MPa, a high strength heat-treated portion which is the remainder other than the ultrahigh strength heat-treated portion and which has been heat treated to have a tensile strength of at least 600 MPa and at most 1100 MPa, and/or a low strength heat-treated portion which is the portion to be cut or punched or the portion to be welded and which has been heat treated to have a tensile strength of less than 600 MPa.