Review: Possibilities of Steel Scrap Decopperization

Abstract

Copper is one of the most common tramp elements in steel scrap. It originates from recycling of copper-alloyed steels, such as weather-resistant construction steel (up to 0.3 mass% Cu) or austenitic stainless steels (up to 3 mass% Cu). In both cases, corrosion resistance is increased. Certainsteels, on the other hand, be alloyed with Cu to influence the Ms point, ductility and/or antiseptic properties. However, copper increases the risk of hot shortness and cold work hardening in low-alloyed steels, which is even more pronounced if Sn is also present in the alloy. Furthermore, Cu is frequentlyintroduced into the scrap melt unintentionally, when steel scrap contains undiscovered parts or components of Cu or its alloys. Because the oxygen affinity of copper is lower than that of iron, selective oxidization of Cu from steel melts is not possible. Therefore, various alternative decopperization methods have been proposed by researchers, starting from the mid-1950s, up to the present. Among those are, apart from scrap pre-treatment, sortation and physical separation, melt dilution, treatment with chemical elements, carrier-metal equilibration, distillation/volatilization, slag treatment, melt filtration and oxide powder blowing. In this paper, various methods for decopperization of steel scrap melts, as reported in available literature, are being reviewed. This is complemented by pretest results from the Institute of Iron and Steel Technology at TU Bergakademie Freiberg (IIST).