A method of production of high strength thin-gauge steel sheet excellent in elongation and hole expandability

摘要

The present invention provides high strength thin-gauge steel sheet with excellent elongation and hole expandability having a tensile strength of 500 MPa or more and a method of production of high strength thin-gauge steel sheet with excellent elongation and hole expandability enabling production of this on an industrial scale, that is, high strength thin-gauge steel sheet comprising, by mass%, t: 0.03 to 0.25%, Si: 0.4 to 2.0%, Mn: 0.8 to 3.1%, P0.02%, S0.02%, Al‰ 2.0%, N_0.01%, and a balance of Fe and unavoidable impurities and having a microstructure comprising ferrite with an area fraction of 10 to 85% and residual austenite with a volume fraction of 1 to 10%, an area fraction of 10% to 60% of tempered martensite, and a balance of bainite.