| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an Si-containing cold-rolled steel sheet excellent in chemical conversion processability and corrosion resistance after coating, an advantageous method for manufacturing the same, and an automobile member using the Si-containing cold-rolled steel sheet. <P>SOLUTION: The method for manufacturing the Si-containing cold-rolled steel sheet comprises: pickling a cold-rolled, continuously annealed steel sheet, preferably using a pickling solution wherein nitric acid concentration is over 100 g/L and 200 g/L or less and a ratio R of hydrochloric acid concentration to nitric acid concentration is 0.01 to 0.25 (HCl/HNO<SB POS="POST">3</SB>), thereby removing an Si-containing oxide layer formed on a surface layer of the steel sheet and reducing a surface coverage ratio of iron oxides formed on the surface layer of the steel sheet to ≤85%, wherein the steel sheet comprises 0.5-3.0 mass% Si and preferably further comprises 0.01-0.30 mass% C, 1.0-7.5 mass% Mn, ≤0.05 mass% P, ≤0.01 mass% S and ≤0.06 mass% Al; and carrying out an electrolysis treatment in an Ni-containing aqueous solution, thereby depositing Ni at a range of 1-100 mg/m<SP POS="POST">2</SP>on the surface of the steel sheet. <P>COPYRIGHT: (C)2013,JPO&INPIT |
