HIGH-STRENGTH COLD-ROLLED STEEL SHEET HAVING EXCELLENT FORMABILITY AND COLLISION CHARACTERISTICS AND HAVING TENSILE STRENGTH OF 980 MPa OR MORE, AND METHOD FOR PRODUCING SAME

摘要

Disclosed herein is a high-strength cold-rolled steel sheet, in which the metal structure at a position of ¼ of the sheet thickness satisfies (1) to (4): (1) an area ratio of ferrite is more than 10% to 65% or less, with a balance being a hard phase including quenched martensite and retained austenite and including at least one selected from the group consisting of bainitic ferrite, bainite, and tempered martensite; (2) a volume ratio V_γ of retained austenite is 5% to 30%; (3) an area ratio V_MA of an MA structure in which quenched martensite and retained austenite are combined is 3% to 25%, and an average circle-equivalent diameter of the MA structure is 2.0 μm or less; and (4) a ratio V_MA/V_γ of the area ratio V_MA of the MA structure to the volume ratio V_γ of the retained austenite is 0.50 to 1.50.