| 摘要 |
<p>A cold rolled steel sheet comprising C, Cu, S, Al, N, P, B, Nb and the balance of Fe and other unavoidable impurities, which is capable of enhancing yield strength and lowering in-plane anisotropy by CuS precipitates in bake-hardening type interstitial free steel, and a method for manufacturing the same are provided. A bake-hardening type cold rolled steel sheet with excellent formability comprises, by weight percent, 0.001 to 0.01% of C, 0.01 to 0.2% of Cu, 0.005 to 0.08% of S, 0.1% or less of Al, 0.004% or less of N, 0.2% or less of P, 0.0001 to 0.002% of B and 0.001 to 0.05% of Nb with the balance being Fe and other inevitable impurities, wherein the Cu, S, Nb and C satisfy (Cu/63.5)/(S/32)=1 to 30, and Cs(solute carbon) satisfies 5 to 30, wherein Cs=(C-NbÎ12/93)Î10000, and wherein CuS precipitates have an average size of 0.2 mum or less.</p> |
