Patent ID: 9212411
Filing Date: 2015-12-15
Classification: C21D,C22C,Y10T

Abstract:
1. A high-strength steel sheet comprising a composition containing, in mass percent, 0.08% to 0.20% of carbon, 0.2% to 1.0% of silicon, 0.5% to 2.5% of manganese, 0.04% or less of phosphorus, 0.005% or less of sulfur, 0.05% or less of aluminum, 0.07% to 0.20% of titanium, and 0.30% to 0.80% of vanadium, the balance being iron and incidental impurities, and having a metallographic structure comprising 80% to 98% by volume of a ferrite phase and a second phase, wherein a sum of amounts of titanium and vanadium contained in precipitates having a size of less than 20 nm is 0.150% by mass or more, and a difference (HV α −HV S ) between hardness (HV α ) of the ferrite phase and hardness (HV S ) of the second phase is −300 to 300.