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

摘要

Disclosed is 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 5 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. With the device, it is possible to produce a zinc-aluminum-based alloy-coated steel sheet which exhibits superior workability through control of an intermetallic compound layer (Zn-Al-Si-Cr) and formation of AlCr 2 due to Cr component present in 5 the coating layer, reduces detachment of the coating layer and cracks of coating occurring during molding, exhibits superior corrosion resistance even after processing and has considerably superior corrosion resistance due to Mg2 Si alloy phase and inhibition of oxide film formation.