The invention relates to a method of stripping metal sheets coated with molten material and in particular to stripping sheet or sheet material coated in a galvanising or vitreous-coating installation directly after the coated sheet has left a bath of molten coating material, both sides of the strip-like or web-like sheet being blasted with a thin curtain of gas. In addition the invention relates to apparatus for carrying out this method with two opposed gas nozzles which are arranged near and above the bath from which the sheet is drawn, and which form a thin curtain of gas for blasting both sides of the strip-shaped sheet or sheet-like material passing between them.
It is known, in the case of sheet and in particular strip-shaped sheet material which has been coated with molten coating material in a galvanising or vitreous-coating installation, to blast the surfaces of the sheet with a thin curtain of gas in order to strip off surplus coating material and prevent lumps or ribs of the coating material forming on the surfaces and thereby not only giving rise to unattractive surfaces, but also making the coating unnecessarily thick at different regions, representing an unnecessarily high consumption of coating material.
It is known to blast the surfaces of the coated sheet with air. However this leads to oxidation or other actions on the coating material, which again can result in flaws in the coated surfaces. Accordingly there has been a move towards using an inert gas such as nitrogen for blasting the surfaces of the coated sheet. It is true that this does satisfactorily eliminate the oxidation problem, but the gas consumption is relatively high, leading to undesirable increaases in cost.