REMELTING OF SCRAP CONTAINING TUNGSTEN AND NICKEL IN THE ELECTRIC-ARC FURNACE

Remelting of the metallic scrap containing tungsten and nickel and thermodynamic properties of slag containing tungsten oxide are discussed. Tungsten and nickel in the metallic scrap have to be separated before the scrap may be used for melting of some steels (for example, high speed steel). To separate tungsten and nickel, such scrap (waste drills) was remelted in the 25 t electric arc furnace under oxidizing conditions. Tungsten was oxidised and transferred to the slag phase, while nickel remained in the metal. Further, the slag containing tungsten oxide was used in the melting of high speed steel. Metal containing nickel was utilized in the constructional steel production. Technology of the scrap remelting was developed on the basis of thermodynamic analysis of slag containing tungsten oxide and tungsten slag-metal partition. It was found that the coefficient of tungsten distribution between iron and basic CaO-SiO2-Fe(t)O-WO3 slag increases with increasing slag basicity. In the industrial oxidising heats a slag of high basicity was used, it secured 94% tungsten extraction from scrap to the slag.