Patent ID: 6280538
Filing Date: 2001-08-28
Classification: C21D,C22C,Y02P

Abstract:
A hot rolled high strength steel sheet comprising a steel comprising:C :0.05 .about. 0.15% Si :0.5 .about. 2.0% Mn :0.5 .about. 2.0% P :0.05% or less S :0.010% or less Al :0.005 .about. less than 0.10%,and the balance of Fe and inevitable impurities, whereinthe structure of said steel mainly comprises a ferrite phase, a retained austenite phase and a bainite phase, and the amount of said ferrite phase, V(F), is 60.about.95 area %, the amount of the retained austenite phase, V(.gamma.), is 3.about.15 vol %, the amount of the bainite phase, V(B), in the area ratio is 1.5 times or more of the amount of the retained austenite phase, the average hardness of the bainite phase is 240-400 Hv, and the average grain size of the ferrite phase is 5.0 .mu.m or more.