Cold-rolled high-strength steel having a tensile strength of 1500 MPa or more and excellent formability, and a method for producing the same

摘要

Cold-rolled high-strength steel having a tensile strength of 1500 MPa or more and excellent formability, and the chemical element composition is mass%, C: 0.25 to 0.40%, Si: 1.50 to 2 .50%, Mn: 2.0-3.0%, Al: 0.03-0.06%, P ≦ 0.02%, S ≦ 0.01%, N ≦ 0.01%, and 0. It is at least one of 1 to 1.0% Cr and 0.1 to 0.5% Mo, the balance being Fe and other inevitable impurities, and the microstructure of the cold-rolled high-strength steel Is a cold-rolled high-strength steel having 5-20% retained austenite and 70-90% martensite, and the ratio of carbon concentration of retained austenite to martensite is more than 3.5 and less than 15 . The cold-rolled high-strength steel sheet has high strength and excellent formability by rational component design and fine structure control. [Selection figure] None