Strength members for automobile bodies, front side members, and side structures of automobile bodies

摘要

Provided is a strength member for an automobile body such as a side member or a pillar, which has a bending portion bent in two dimensions or three dimensions and has an ultrahigh strength with a tensile strength exceeding 1100 MPa. It is constituted by a cylindrical body having a closed section that has a bending section bent in two dimensions or three dimensions, a cutting or drilling scheduled section, and a planned welding section, and does not have a flange facing outward. The tube is heat treated so that the tensile strength is 600MPa or more and 1100MPa or less in the remaining part excluding this ultra high strength heat treated part that has been heat treated so that the tensile strength exceeds 1100MPa. Strength member for automobile body comprising the above-described high-strength heat-treated portion and / or low-strength heat-treated portion which is the above-described cutting or drilling scheduled portion and welding scheduled portion and has been heat-treated so that the tensile strength is less than 600 MPa It is.