| 摘要 |
PROBLEM TO BE SOLVED: To produce a precipitation type and fine-grain type thin steel sheet which has a low yield ratio, and has excellent workability and weldability. SOLUTION: The low yield ratio high strength cold rolled steel sheet has a substantially ferritic metallic structure essentially consisting of ferrite having the average grain size of <=5μm, and has a yield ratio of <=70%. The steel sheet contains, as chemical components, by mass, 0.016 to 0.2% C, <=2.0% Si, <=2.5% Mn, <=0.1% P, <=0.01% S, <=0.1% sol. Al, <=0.01% N and one or more kinds selected from 0.025 to 1% Ti, 0.01 to 1.5% Nb and 0.01 to 1% V, and the balance substantially iron. As chemical components, one or more kinds selected from <=1% Cu, <=1% Ni, <=1% Cr, <=1% Mo and <=0.01% B can further be incorporated therein.
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