| 摘要 |
PURPOSE: A method for manufacturing cold rolled steel sheets having superior surface quality is provided, in which with the addition of Cr in steel, graphite deposition on the surface of cold rolled steel sheets is inhibited even when conventional phase annealing is employed. CONSTITUTION: The method for manufacturing cold rolled steel sheets having superior surface quality includes the steps of hot rolling a steel slab comprising C 0.010-0.15 wt.%, Si 0.03 wt.% or less, Mn 0.15-0.90 wt.%, S 0.020 wt.% or less, sol. Al 0.020-0.050 wt.%, Cr 0.03-0.10 wt.%, a balance of Fe and other inevitable impurities; coiling the hot rolled steel sheet at low temperatures of less than 600°C; cold rolling at a reduction ratio of 50 to 80%; and phase annealing the cold rolled steel sheet in the temperature range of 630 to 720°C for more than 40 hours.
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