| 摘要 |
<p>A steel sheet comprising C, Si, Mn, P, S, Al, N, Cu, Co, Cr and Nb with the balance being Fe and other inevitable impurities and having excellent corrosion resistance for an automobile muffler, which is inexpensive in the manufacturing cost and exhibits very excellent condensation water corrosion resistance and high strength, and a method for producing the same are provided. A method for producing a cold rolled steel sheet having excellent corrosion resistance comprises the steps of: manufacturing a steel slab comprising, by weight percent, 0.01% or less of C, 0.1 to 0.3% of Si, 0.3 to 0.5% of Mn, 0.015% or less of P, 0.015% or less of S, 0.02 to 0.05% of Al, 0.004% or less of N, 0.2 to 0.6% of Cu, 0.01 to 0.04% of Co, 0.1 to 0.3% of Cr and 0.005 to 0.05% of Nb with the balance being Fe and other inevitable impurities, wherein a T value defined by an expression, T=60-780ÎC(%)-15ÎSi(%)-20ÎMn(%)-12ÎCu(%)-10ÎCo(%)-8ÎCr(%), is 35 or more, and a Nb/C ratio defined by an expression, Nb/C ratio=(Nb(%)/93)/(C(%)/12), is 0.5 to 2.0; reheating the slab, and hot rolling the reheated slab at a rolling temperature of an Ar3 transformation point or more during the final rolling operation to manufacture a hot rolled steel sheet; cold rolling the hot rolled steel sheet at a reduction ratio in thickness of 50 to 90% to manufacture a cold rolled steel sheet; and continuously annealing the cold rolled steel sheet in a temperature range of 500 to 900 deg.C for 10 seconds to 30 minutes.</p> |
