AUTOMOBILE MEMBER AND ITS PRODUCTION METHOD

摘要

PROBLEM TO BE SOLVED: To provide an automobile member in which tensile strength after quenching and tempering or after hot forming-tempering is≥980 MPa, the balance between strength and ductility is excellent, and also, the softening of the weld heat-affected zone is reduced. SOLUTION: The automobile member has a composition comprising, by mass, 0.10 to 0.25% C,≤1.5% Si, 1.0 to 3.0% Mn,≤0.10% P,≤0.005% S, 0.01 to 0.5% Al,≤0.010% N and 0.10 to 1.0% V, also satisfying (10Mn+V)/C≥50, and the balance Fe with inevitable impurities. Further, the volume ratio of a tempered martensitic phase is controlled to≥80%, the precipitation number of carbides comprising V with the particle diameters of≤20 nm is controlled to≥1,000 pieces per unit volume ofμm3, and also, the average particle diameter of the carbides comprising V with the particle diameters of≤20 nm is controlled to≤10 nm. COPYRIGHT: (C)2006,JPO&NCIPI