Patent ID: 6524726
Filing Date: 2003-02-25
Classification: C21D,C22C,C23C,Y10T

Abstract:
A cold-rolled steel sheet excellent in formability, panel shapeability and dent-resistance, consisting essentially of 0.005 to 0.015% by weight of C, 0.01 to 0.2% by weight of Si, 0.2 to 1.5% by weight of Mn, 0.01 to 0.07% by weight of P, 0.006 to 0.015% by weight of S, 0.01 to 0.08% by weight of sol. Al, not higher than 0.004% by weight of N, not higher than 0.003% by weight of O, 0.04 to 0.23% by weight of Nb, the amounts of Nb and C meeting the relationship given in formula (1), and a balance of Fe and unavoidable impurities, said cold-rolled steel sheet meeting the relationship given in formula (2):1.0exp(&egr;)Ã—(5.29Ã—exp(&egr;)âˆ’4.19)&lE;&sgr;/&sgr;0.2&lE;exp(&egr;)Ã—(5.64Ã—exp(&egr;)âˆ’4.49)â€ƒâ€ƒ(2) where 0.0020.2 represents a 0.2% proof stress, and &sgr; represents a true stress relative to &egr;.