Thickness control of molten metal coatings - blowing gas stream onto coating, esp. during hot dip zinc coating of steel strip or wire

摘要

A substrate, e.g. steel strip or wire is fed through a bath of molten metal, e.g. Zn, to obtain a surface coating. The substrate travels out of the bath in counter-current to a gas stream impinging on the coating; and the flow of the gas is adjusted to control the thickness of the coating. The gas is pref. air fed through a nozzle or a slot nozzle with a venturi profile so the outer air is also drawn through the nozzle. Alternatively, the entire gas stream is provided by an inert or protective gas. Used to obtain coatings of uniform thickness, esp. during continuous hot dip galvanising of steel.