Traditional methods for the production of transition metals from their ores
usually include the electric arc smelting of the ore or concentrate to
produce a ferroalloy. This is subsequently refined to produce either a
ferroalloy or to produce the metal or metallic carbide. Recent trends in the treatment of iron ores have seen the development of
many processes for solid state carbothermic reduction followed by
melting of the prereduced iron to produce steel and similar types of
processes are under consideration for the production of ferroalloys. There
are clear potential savings in energy and control of emissions from such
processes. This paper discusses some research which is currently
underway at La Trobe University into the solid state carbothermic
reduction of chromium and tungsten ores to produce the metallic
ferroalloy or the carbide for subsequent further processing. The kinetics
of the carbothermic reduction of both chromite and scheelite were found
to be dominated by gaseous CO rather than by direct carbon reduction.
However the diffusion of carbon into the ore is certainly an important
feature of the process. The production of tungsten carbide from the metal
is the slow step in tungsten reduction. The development of phases during reduction were studied using a
scanning electron microscope and an electron probe and knowledge of the
phases produced allows analysis of the reduction process.