PROCESS FOR PREPARING SURFACE-TREATED STEEL STRIPS ADAPTED FOR ELECTRIC RESISTANCE WELDING

摘要

PURPOSE:To manufacture the titled steel sheet having superior weldability and superior durability after coating by successively forming a specified Fe-Ni layer, a specified amount of a tin layer by tinning and a layer consisting of metallic Cr and Cr oxide hydrate on a steel sheet and by specifying the amount of the metallic Cr and the amount of Cr in the Cr oxide hydrate. CONSTITUTION:The 1st layer of an Fe-Ni alloy having a composition satisfying 0.02-0.50wt. ratio of Ni/(Fe+Ni) is formed on a steel sheet. The thickness of the 1st layer is 10-5,000Angstrom . The 1st layer is tinned by 0.1-1g/m<2>, and the resulting tin layer is optionally melted to form the 2nd layer. The 2nd layer is electrolytically chromated to form the 3rd layer consisting of metallic Cr and Cr oxide hydrate. Thus, the titled steel sheet is manufactured. In the 3rd layer, the amount (x) (mg/m<2>) of the metallic Cr and the amount (y) (mg/m<2>) of the Cr oxide hydrate (expressed in terms of Cr) are regulated to x>=2 and 5<=x+y<=20.