Patent ID: 7686896
Filing Date: 2010-03-30
Classification: C21D,C22C

Abstract:
1. A high-strength steel sheet having excellent deep drawability, an average r value of 1.2 or more, and a composition, which is free of V, comprising by % by mass: C: about 0.010 to about 0.050%; Si: about 1.0% or less; Mn: about 1.0 to about 3.0%; P: about 0.005 to about 0.1%; S: about 0.01% or less; Al: about 0.005 to about 0.5%; N: about 0.01% or less; Nb: about 0.01 to about 0.3%; and the balance substantially including Fe and inevitable impurities, the Nb and C contents in steel satisfying the relation, (Nb/93)/(C/12)=0.2 to less than 0.5 (wherein Nb and C represent the contents (% by mass) of the respective elements) and C in solution is, 47 to 83% of total C content and the steel microstructure containing a ferrite phase and a martensite phase at area ratios of about 50% or more and about 1% or more, respectively, and having a grain size of 8 μm or less.