| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for manufacturing a high strength cold rolled steel sheet synthetically satisfying the characteristics required for an automobile steel sheet such as required strength, deep drawability and corrosion resistance. SOLUTION: Steel having a composition which consists of, by weight, <=0.01% C, <=0.5% Si, 0.1-1.5% Mn, 0.005-0.015% S, 0.01-0.10% Al, <=0.006% N, 0.030-0.006% P, 0.1-0.5% Cu, 0.02-0.15% of effective Ti [where (effective Ti)=(total Ti%)-(48/12)C%-(48/32)S%$-(48/14)N% is satisfied], 0.1-0.5% Ni and the balance Fe with inevitable impurities and in which P, Cu and effective Ti satisfy the relation of inequality Cu%/64+(P%/31)×[3×10<3>×(effective Ti%)/48]>=0.01%, is used. After the steel is heated to >=1125 deg.C, it is hot-rolled, coiled at 550 to 750 deg.C, pickled, cold-rolled at a >=60% rolling rate and successively subjected to recrystallization-annealing at 750 to 950 deg.C.
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