HIGH-STRENGTH STEEL SHEET AND METHOD FOR PRODUCING SAME

摘要

Through the disclosed method, it is possible to obtain a highly ductile and high tensile strength high-strength steel sheet having a tensile strength of at least 1470 MPa and a tensile strength × total elongation of at least 29000 MPa · % by means of: a steel composition containing at least 0.30% and no more than 0.73% C, no more than 3.0% Si, no more than 3.0% Al, at least 0.7% Si+Al, at least 0.2% and no more than 8.0% Cr, no more than 10.0% Mn, at least 1.0% Cr+Mn, no more than 0.1% P, no more than 0.07% S, and no more than 0.010% N, the remainder being Fe and unavoidable impurities; and a steel structure of which the area ratio of martensite to the total steel sheet structure is 15-90% inclusive, the amount of residual austenite is 10-50% inclusive, at least 50% of said martensite is tempered martensite, the area ratio of said tempered martensite to the total steel sheet structure is at least 10%, and the area ratio of polygonal ferrite to the total steel sheet structure is 10% or less (including 0%).