Copper smelting slag usually contains 1–6 wt% copper, which can be recovered by pyrometallurgical and flotation processes. However, the tailing slags still consist of 0.3–0.7 wt% Cu and 35–45 wt% Fe equivalents to those in the copper and iron ores, respectively. Most of the research was focused on the recovery of iron from the tailing slags. Copper can increase the mechanical strength, corrosion resistance and antibacterial property of some steels. A new process to recover copper and iron directly and fully from hot copper smelting slag is proposed to produce Cu-Fe alloy for steel production. Effects of flux, temperature, reaction time, reductant type and addition on the recovery of copper and iron were investigated by high-temperature experiments and thermodynamic calculations. It was found that, with 5% CaO and 13–16% carbon additions, most of the copper and iron can be recovered from copper smelting slag at 1350–1400 °C. The copper and iron contents of the reduced slag are lower than 0.1% and 0.5%, respectively, at optimum condition. The new process has the advantages of low energy consumption, low flux addition and high recovery of copper and iron.

Cu and Cr are the essential alloying elements for low-Ni stainless steels. An effective and economical method has been developed for the direct production of Cu-Cr-Fe master alloys through the synergistic reduction of chromite and copper smelting slag. The smelting conditions for synergy reduction were systematically investigated by combining thermodynamic calculations and high-temperature experiments. The results indicate that synergistic reduction drives the reactions of Cr₂O₃, FeO, and Cu₂O with carbon in a positive direction, which can increase their recovery and decrease the flux and fuel costs. The optimum slag composition was identified to control the (CaO + MgO)/(SiO₂ + Al₂O₃) ratio between 0.62 and 0.72, where the slag is fully liquid, resulting in an efficient separation of the alloy from the slag. At 1550 °C, with 50 wt% chromite and 50 wt% copper smelting slag as raw materials, a Cu-Cr-Fe alloy containing 5.2 wt% Cu, 28.6 wt% Cr and 57.9 wt% Fe was produced, while the contents of FeO, Cu₂O, and Cr₂O₃ in the final slag were 0.057 wt%, 0.059 wt%, and 0.23 wt%, respectively.