High strength steel excellent in uniform elongation properties and method of manufacturing the same

摘要

A high strength steel, including about 0.05 to about 0.25% of C, less than about 0.5% of Si, about 0.5 to about 3.0% of Mn, not more than about 0.06% of P, not more than about 0.01% of S, about 0.50 to about 3.0% of Sol. Al, not more than about 0.02% of N, about 0.1 to about 0.8% of Mo, about 0.02 to about 0.40% of Ti, and the balance of iron and unavoidable impurities, wherein the steel has a structure formed of at least three phases including a bainite phase, and a retained austenite phase in addition to a ferrite phase having a composite carbide containing Ti and Mo dispersed and precipitated therein, wherein the total volume of the ferrite phase and the bainite phase is not smaller than 80%, the volume of the bainite phase is about 5% to about 60%, and the volume of the retained austenite phase is about 3 to about 20%.

主权项

1. A high strength steel sheet excellent in balance between strength and uniform elongation, consisting essentially of about 0.05 to about 0.25% of C, less than about 0.5% of Si, about 0.5 to about 3.0% of Mn, not more than about 0.06% of P, not more than about 0.01% of S, about 0.50 to about 3.0% of Sol, Al, not more than about 0.02% of N, about 0.1 to about 0.8% of Mo, about 0.02 to about 0.40 % of Ti by mass percentage, and the balance of Fe and inevitable impurities, the steel sheet has a structure formed of at least three phases including a banite phase, a retained austenite phase, and a ferrite phase having composite carbides containing Ti and Mo finely precipitated therein in a dispersion state, wherein the total volume of the ferrite phase and the bainite phase is not smaller than about 80%, the volume of the bainite phase is about 5% to about 60%, the volume of the retained austenite phase is about 3 to about 20%, and the steel sheet has a tensile strength of not lower than 780 MPa and a drilled hole expanding ratio of 118-166% and a TS x λ of 112,464 or more.