ZN-CR-NI-P ALLOY ELECTROPLATED STEEL SHEET EXCELLENT IN CORROSION RESISTANCE, WELDING PROPERTY AND CHEMICAL CONVERTIBILITY AFTER WORKING

摘要

PURPOSE:To obtain excellent corrosion resistance, chemical convertibility and welding property of steel as plated by specifying the amts. of Cr, Ni and P in a Zn-base alloy plating layer. CONSTITUTION:On the surface of a steel sheet, there is formed a Zn-Cr-Ni-P alloy electroplating layer containing 2-8% Cr, 1-12% Ni, =1.0-5.0% P and the balance Zn to about 20g/m2 coating wt. Sine the affinity of P, Cr and Ni elements is considerably strong, these three elements Cr-Ni-P are more firmaly fixed, and the presence of Ni improves ductility, which improves corrosion resistance after working. Since diffusion of Cr and Ni to chipps during welding is suppressed by coupling of three elements Cr-Ni-P, welding property is improved. With presence of P, phosphate crystals can easily be formed, while with presence of Ni, fine crystals are precipitated to give excellent chemical convertibility.