SI-CONTAINING HIGH STRENGTH COLD ROLLED STEEL SHEET, PRODUCTION METHOD THEREFOR, AND VEHICLE MEMBER

摘要

A Si-containing high-strength cold rolled steel sheet has a chemical composition comprising C: 0.02ˆ¼0.3 mass%, Si: 0.8ˆ¼2.0 mass%, Mn: 1.0ˆ¼5.0 mass% and the remainder being Fe and inevitable impurities with a ratio of Si content to Mn content (Si/Mn) exceeding 0.4, and has a tensile strength TS of not less than 780 MPa, wherein a metallic structure of the steel sheet surface contains polygonal ferrite and/or bainitic ferrite having a Si concentration of not more than 3.0 mass% and a grain size of not more than 10 µm and does not have a Si-containing oxide layer on the steel sheet surface.