| 摘要 |
PROBLEM TO BE SOLVED: To provide a hot rolled steel sheet having high strength, moreover good in stretch flanging properties in particular, excellent in workability and also having excellent characteristics even in fatigue characteristics. SOLUTION: This steel sheet is composed of steel satisfying, by mass, 0.03 to 0.10% C, <=2% Si, 0.5 to 2% Mn, <=0.08% P, <=0.01% S, <=0.01% N and 0.01 to 0.1% Al and moreover contg. >0.26 to 0.50% Ti and/or 0.15 to 0.8% Nb, and the balance Fe with inevitable impurities, and in the cross-sectional metallic structure, a granular bainitic-ferritic structure occupies >=80 area%.
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