Method and apparatus for producing zinc-aluminum alloy-coated steel sheet with superior workability and corrosion resistance

Abstract

Disclosed is a method for producing a zinc-aluminum-based alloy-coated steel sheet with superior workability and corrosion resistance by coating a base zinc-aluminum-based alloy-coated steel sheet in a coating bath comprising 35 to 55% by weight of zinc, 0.5 to 3% by weight of silicon, 0.005 to 1.0% by weight of chromium, 0.01 to 3.0% by weight of magnesium, 0.001 to 0.1% by weight of titanium, and the balance of aluminum and inevitable impurities.

What is claimed is: 
     
         1 . A device for forming a nitrogen cloud in a circumference of a coated steel sheet ascending from a coating bath, the device being disposed between the coating bath surface to produce a zinc-aluminum-based alloy-coated steel sheet and an air knife, the device comprising:
 lower nitrogen supply bars spaced from the surface of the coating bath by a predetermined distance, the lower nitrogen supply bars discharging nitrogen gas in a direction of the surface of the coating bath along the circumference of the coated steel sheet;   a side cover extending upward at an angle from a side of the lower nitrogen supply bars in a direction of the coated steel sheet; and   upper nitrogen supply bars formed on the upper surface of the side cover and discharging the nitrogen gas downward.