Patent ID: 6540846
Filing Date: 2003-04-01
Classification: C21D,C22C

Abstract:
A high-strength hot-rolled steel sheet superior in stretch-flanging properties and fatigue properties, the steel sheet comprising, in mass %,0.03-0.10% C, less than 2% Si, including 0%, 0.5-2% Mn, less than 0.08% P, including 0%, less than 0.01% S, including 0%, less than 0.01% N, including 0%, 0.01-0.1% Al, and at least one of 0.26-0.5% Ti and 0.25-0.8% Nb, wherein a granular bainitic ferrite structure accounts for more than 80% by area in a sectional metallographic structure of the steel sheet.