High-strength cold-rolled steel having a tensile strength of 1500 MPa or more and excellent moldability and a manufacturing method thereof

摘要

The present invention has a tensile strength of 1500 MPa or more and is excellent in moldability and contains 0.25 to 0.40% of C, 1.50 to 2.50% of Si, 2.0 to 3.0% of Mn, 0.03 to 0.06% Al, 0.02% or less of P, 0.01% or less of S, 0.01% or less of N, 0.1 to 1.0% of Cr and 0.1 to 0.5% of Mo, the balance being Fe and other inevitable impurities To a high strength cold rolled steel. Wherein the microstructure of the high strength cold rolled steel comprises 5% -20% retained austenite and 70% -90% martensite, wherein the ratio of the carbon concentration of the retained austenite to the carbon concentration of the martensite is greater than 3.5 And less than 15. The high-strength cold-rolled steel has high strength and excellent moldability through rational material design and micro-structure control.