METHOD FOR MAKING A HOT-DIPPED ZINC COATING STEEL SHEET WITH AN EXCELLENT WORKABILITY AND PLATING PROPERTIES

摘要

The method comprises; (a) acid cleaning the hot rolled steel sheet; (b) preheating it at 150-200 deg.C in the preheating region of a furnace for heating treatment under the atmosphere including 10-20 H2 gas and the balance N2 gas; (c) heating it at 520-550 deg.C in the heating region of the furnace; cooling it at 440-470 deg.C in cooling region of the furnace; and (f) dipping it in a galvanizing bath composed of 25 % Al and balance Zn with inevitable impurities. The steel sheet is useful for deck plate, guide rail and pipe for building.