| 摘要 |
PROBLEM TO BE SOLVED: To provide a high strength cold rolled steel sheet excellent in yield strength and formability, and to provide a method of manufacturing the same.SOLUTION: A cold rolled steel sheet has a component composition that includes, by mass, 0.10-0.25% of C; 0.50-2.40% of Si; 1.00-3.00% of Mn; 0.001-0.10% of Al; 0.05-0.30% of Ti; at most 0.100% of P (including 0%); at most 0.010% of S (including 0%); at most 0.006% of N (including 0%); and a remainder including iron and inevitable impurities, and includes 40-70% of ferrite (α) by an area rate, wherein the remainder is a structure comprising tempered martensite having 330-450 Hv of hardness, the α has a structure that includes by an area rate: 20-60% of non-recrystallized ferrite having 5 μm of an average crystal grain size; 10-20% of cooled α having at most 3 μm of a crystal grain size; and at most 5% (including 0%) of recrystallization α, wherein an average connection rate of αs is at most 0.25. |
