Minerals & Metallurgical Processing, cilt.24, ss.115-120, 2007 (SCI Expanded İndekslerine Giren Dergi)
Ferrochromium produced by smelting chromite ores is an important alloying component in the steel industry. Ore, coke and fluxes are mixed and reacted in an arc jilrnace for a smelting process offerrochromi1ll11. In addition to this process, pre-reduction of chromite are with carbon is an important industrial process. In all these processes, the mechanism and kinetics of reduction of chromite with carbon play an important role. In this study, the reduction of Turkish chromite are with carbon was investigated. Chromite and carbon were ground to three different particle size groups. Chromite was mixed with carbon in stoichiometric and excess ratios. The samples were reduced under argon atmosphere at temperatures between 1,200° and 1,350°C. The formed phases and alloy compositions of reduced chromite samples were analyzed by optical microscopy, scanning electron microscope (SEM) with EDAX and X-ray diffraction analysis (XRD). Experimental results showed that the degree of reduction and the reduction rate increased with increasing temperature and decreasing partie/e size. The highest degree of reduction, 61.4%, was obtained at 1,350°C. The reduction took place in three stages: Stage I: transformation of Fe3+ to Fe2+ and formation of metallic nuclei, Stage 2: formation of metallic crust around the particles and Stage 3: growth of the metallic crllSt and coalescence of the metallic phase.
Key words: Chromium ore, Coke, Carbothermic reduction, Ferrochromium, Reduction mechanism.