| 摘要 |
PURPOSE:To obtain an Al hot dipped steel sheet having improved heat resistance and high-temp. strength by annealing continuously the Ti-contg. steel sheet in a reducing atmosphere and conducting the steel sheet to an Al plating bath through a snout in an inert gaseous atmosphere in which the contents of hydrogen and oxygen are controlled. CONSTITUTION:A continuous annealing furnace 1 is constituted of an oxygen free furnace A, a reducing furnace B and a cooling furnace C. The Ti-contg. steel strip 3 is annealed or normalized in the atmosphere of a reducing gas in the furnace A and the furnace B. The strip is then passed through the snout 4 after cooling and through the Al hot dipping bath 6, by which the strip is subjected to Al plating. The inert gas controlled to <=1,000ppm hydrogen concn. and <=10ppm oxygen concn. is introduced through a pipe 7 onto the bath 6 of the snout 4 to cover the space above the bath 6. Since the strip 3 passes through the snout 4 maintained in the inert gaseous atmosphere, the formation of scum is obviated and the wettability is improved. The Al hot dipped steel sheet having a uniform thickness and good appearance is thus obtd.
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