Zinc vapour

is an accompanying phenomenon of melting which is unavoidable when melting plate materials containing zinc. The zinc vapour emitted from the melt must be extracted and filtered out by suitable extraction devices. The negative effects on the durability of acidic crucibles can be reduced to a reasonable level by suitable measures. Using the following procedure, the working life of a crucible should not be significantly lower than when working with zinc-free plate: The sintering charge and the complete 2nd and 3rd charges are melted with zinc-free scrap. From the 4th charge, scrap contaminated with zinc can be used. After interruptions in operations, the 1st charge is again melted with zinc-free scrap.