| 摘要 |
PROBLEM TO BE SOLVED: To provide a cold rolled steel sheet excellent in resistance to secondary working brittleness and deep drawability by specifying the components of steel, the crystalline grain size after annealing, and the ratio of the crystalline grain size after annealing to the crystalline grain size of hot rolled plate, respectively. SOLUTION: This cold rolled steel sheet has a composition consisting of, by weight, 0.0005-0.006% C, 0.02-0.50% Mn, <=0.01% P, <=0.01% S, <=0.005% N, 0.01-0.1% Ti, and the balance Fe with inevitable impurities and satisfying Ti>(48/12)×C+(48/14)×N+(48/32)×S. Further, the crystalline grain size (DA) after annealing is regulated to <=40μm, and also the ratio G (G=DA/DH) of the crystalline grain size (DA) after annealing to the crystalline grain size (GH) of hot rolled plate is regulated to 1.3-3.0. This cold rolled steel sheet has excellent resistance to secondary working brittlement and deep drawability even after subjected to plating treatment and application of organic coating.
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