| 摘要 |
PURPOSE:To form a plating layer having high quality with decreased use of an atmosphere gas by solidifying and recovering the Zn vapor in the atmosphere gas to be supplied into the down chute and reusing the solidified Zn in the stage of supplying the steel strip after a heat treatment by the down chute to a hot dip Zn-Al alloy coating liquid cell and plating the steel strip. CONSTITUTION:The steel strip 6 from a heat treatment furnace 3 is passed through the down chute 4 and a snout 9 then through a molten Zn-Al alloy for plating and is pulled upward. The costly reducing atmosphere gas (H2+N2) is supplied into the down cute 4 to prevent the oxidation of the steel strip 6. The Zn in the molten Zn-Al alloy evaporates and flows together with the atmosphere gas into the heat treatment furnace 3 where zinc white powder solidifies on the surface of the steel strip. An atmosphere sealing device 13 is provided above the down chute 4 in order to prevent such solidification and at the same the Zn vapor-contg. gas is passed through a metal solidifying chamber 16 by which the gas is cooled and the Zn vapor contained therein is solidified and separated. The clean atmosphere gas is heated in a heater 18 and is circulated to the down chute 4 or the heat treatment furnace 3 for reuse.
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