METHOD FOR MAKING A GALVANNEALED STEEL SHEET WITH AN EXCELLANT ANTI-POWDERING

摘要

The method increases anti-powdering of hot rolled galvanized steel strips by modifying cooling method and keeping aluminum concentration adequate in a molten zinc bath. The method comprises (A) galvanizing hot rolled steel strip (2) in molten zinc bath (1) containg 0.12 to 0.14 wt.% of aluminum; (B) heat treating of the strips continuously in the heating stages (3) at 500 to 520 C; (C) maintaining at the maintaing stages (4); and (D) fog cooling at the first fog cooling stage (5) and the second cooling stage (6) at the cooling rate of 20 to 40C per second.