PRODUCTION OF SN MULTILAYER-COATED STEEL SHEET HAVING EXCELLENT CORROSION RESISTANCE, WELDABILITY, AND COATING PERFORMANCE

摘要

PURPOSE:To improve the corrosion resistance, electric weldability, and coating performance of a steel sheet by laminating an Ni planted layer, an Ni-Fe plated layer, and an Sn plated layer on the surface of the steel sheet, heating and melting the layers, and then forming a chromate coated film. CONSTITUTION:The lowermost Ni plated layer in 3-150mg/m2 deposition amt. per one face is provided on the surface of a steel sheet. the Ni-Fe alloy plated layer contg. =30% Ni is then laminated in 50-500mg/m2 deposition amt., and further the Sn plated layer is laminated in 300-2,000mg/m2. The material is subsequently heated and melted at 235-280 deg.C, and a dense alloy layer having excellent corrosion resistance is formed by the brief alloying reaction between the substrate coated layer and the Sn layer. A chromate coated film layer is formed on the laminated plated layer in 5-50mg/m2 deposition amt., expressed in temrs of metallic Cr. An Sn multilayer coated steel sheet having excellent weldability, coating property, and corrosion resistance after coating can be obtained by this method.