Die-strip interactions in horizontal continuous casting of coinage bronze

A novel form of segregation may occur in the continuous casting of copper-zinc alloys. Experience with coinage bronze has shown that alloy and impurity elements accumulate on the surfaces of the graphite mould. If these are subsequently taken back on to the surface of the solidifying metal, a problem of severe localized contamination occurs. Lead may segregate in this way, but this can be eliminated by controlling the purity of the charge. Zinc contamination is greatly influenced by trace quantities of sulphur. The addition of a sulphide-forming element to the melt helps to overcome this problem.