| 摘要 |
PURPOSE:To improve the corrosion resistance of a cold rolled steel sheet after painting and the suitability to phosphating by forming thickened layers contg. prescribed percentages of C, P, Ti and Cr on the surfaces of a cold rolled steel sheet to a prescribed thickness. CONSTITUTION:Thickened layers contg., by weight, 0.5-3.5% C, 0.5-4% P, 0.05-3% Ti and 0.3-2% Cr and/or 0.1-4% Cu are formed on the surfaces of a cold rolled steel sheet as an inner layer to 5-300Angstrom thickness per one side to obtain the titled cold rolled steel sheet. The cold rolled steel sheet as the inner layer contains 0.01-0.15% C, <=0.3% Si, 0.05-0.45% Mn, <=0.03% P, 0.025% S, 0.01-0.1% sol.Al and one or more among 0.03-0.1% P, 0.03-0.2% Ti, <=1% Cr and <=0.3% Cu.
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