High-strength cold-rolled steel sheet and high-strength hot-dip galvanized steel sheet excellent in ductility and bendability, and methods for producing them

摘要

Provided is a high strength cold rolled steel sheet having a tensile strength of 980 MPa or higher and excellent ductility and bendability. The high strength cold rolled steel sheet has a specified component composition. The structures at a position of ¼ sheet thickness in the steel sheet has certain area ratio of ferrite relative to the entire structure, certain area ratio of a mixed structure of fresh martensite and retained austenite relative to the entire structure, certain region in which the concentration of Mn is enriched, certain standard deviation of the fraction of a region in which the concentration of Mn is enriched, and certain concentration of Mn in a ferrite phase.