STEEL SHEET COATED WITH ZINC-ALUMINUM ALLOY BY HOT DIPPING AND HAVING SUPERIOR RESISTANCE TO STRIPPING OF ALLOY LAYER WITH LAPSE OF TIME AND ITS MANUFACTURE

摘要

PURPOSE:To prevent the stripping of an alloy layer formed on a steel sheet by hot dipping due to deterioration with the lapse of time by hot dipping the steel sheet with a hot dipping bath contg. prescribed percentages of Al, Sb and Zn and a restricted amount of impurities such as Pb and Sn and by rapidly cooling the hot dipped steel sheet under prescribed conditions. CONSTITUTION:A hot dipping bath consisting of 0.3-10wt% Al, 0.2-1wt% Sb, 0.02wt% in total of impurities such as Pb and Sb and the balance Zn is prepd. A steel sheet is hot dipped with the hot dipping bath and air-cooled. The hot dipped steel sheet may rapidly be cooled at 50-300 deg.C/sec cooling rate immediately before the resulting alloy layer is solidified. Thus, the spangles of the alloy layer is made fine.