ZINC-MAGNESIUM ALLOY PLATED STEEL SHEET EXCELLENT IN CORROSION RESISTANCE IN EDGE FACE AND ITS PRODUCTION

摘要

PROBLEM TO BE SOLVED: To produce a Zn-Mg alloy plated steel sheet showing excellent corrosion resistance even in cut edge faces. ;SOLUTION: This steel sheet is the one in which a Zn-Mg alloy layer (primary layer) having ≤0.5wt.% Mg concn., a Zn-Mg alloy layer (secondary layer) having 2 to 6wt.% Mg concn., a Zn-Mg alloy layer (third layer) having 7 to 20%wt.% Mg concn., a Zn-Mg alloy layer (fourth layer) having 2 to 6wt.% Mg concn. and a Zn-Mg alloy layer (fifth layer) having ≤0.5wt.% Mg concn. are successively laminated, and the third layer has a mixed structure in which Zn₂Mg and Mg enter into solid solutions. The secondary layer and fourth layer are ones formed according to necessary and are formed by Zn phases in which Zn₁₁Mg₂ phases and Mg enter into solid solutions. On the boundary with the base steel, a Zn-Fe alloy layer or a Zn-Fe-Mg alloy layer having ≤0.5μm layer thickness is preferably formed.;COPYRIGHT: (C)1997,JPO