Method for producing galvanized zinc-magnesium galvanized hot-dip coating and flat steel products with such plating

摘要

A process may be utilized to produce a galvannealed Zn—Mg hot dip coating that provides improved corrosion protection on a steel substrate, and to a flat steel product having such characteristics. To this end, a steel substrate may be subjected to hot dip coating in an Fe-saturated melt bath heated to 350-650° C., wherein the melt bath comprises in percent by weight 0.1-0.16% Al, 0.1-0.6% Mg, and also 2% Si, 1% each of Ni or Cu, 0.3% Co, 0.0001% Mn, 0.5% Sr, 0.1% each of Pb, B, Bi or Cd, 0.2% each of REM, Ti or Cr, or 0.5% Sn, with the balance being zinc and unavoidable impurities. Further, a galvannealing treatment may be conducted in which the steel substrate is kept at 450-800° C. for 10-25 seconds to produce a galvannealed Zn—Mg hot dip coating on the steel substrate. The coating may comprise Zn, unavoidable impurities, and in percent by weight 0.10-0.5% Al, 5.0-15.0% Fe, 0.10-0.8% Mg and 2 % Si, 1% each of Ni, Cu, 0.3% Co, 0.0001% Mn, 0.5% Sr, 0.1% each of B, Bi, Cd, Pb, 0.2% each of Cr, Ti, REM, 0.01% Sn.”