| 摘要 |
PURPOSE:To produce the title steel sheet having excellent seam weldability and corrosion resistance to painting at a low cost by successively applying chromium plating, tin plating, heating, cooling, and electrolytic chromating to the surface of a cold-rolled steel sheet under specified conditions. CONSTITUTION:A chromium plating layer of 30-300mg/m<2>, expressed in terms of metallic chromium, per one face is formed on the surface of a cold-rolled steel sheet. Cathodic electrolysis is applied in an acidic soln. at <=about 1pH contg. one or both of H2SO4 and HCl or not applied to form a tin plating layer of 100-600mg/m<2> per one face on the chromium plating layer. The steel sheet is heated at a temp. higher than the m.p. of the tin plating layer (about 240-290 deg.C) to melt the tin plating layer, and then the sheet is heated and cooled so that quenching and solidification are completed in at least one second. Furthermore, an electrolytically chromated layer of 3-30mg/m<2>, expressed in terms of metallic chromium, per one face is formed.
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