FeCr<SUB>2</SUB>O<SUB>4</SUB>およびMgCr<SUB>2</SUB>O<SUB>4</SUB>の炭素還元におよぼす酸化物と還元生成物層の性状の影響

Abstract

The reduction rates of powdered FeCr2O4 and MgCr2O4 in a graphite crucible as reductant have been measured by means of thermo-balance under an argon atmosphere at temperatures from 1773 to 2073 K. Depending on particle size of oxide and temperature, there is the transition from one reaction mechanism to another as the reduction progresses.The rates of reduction increase with increasing particle size, particularly in the early stage of reduction. The overall rate of reduction is controlled by gas dfffusion through the interparticle pores within the powder.At lower temperatures, the reduction of fine particles is drastically retarded by the formation of densely sintered layers of oxide and the reduction product.At higher temperatures, the reduction of FeCr2O4 is markedly accelerated as a consequence of the direct reduction by carbon dissolved in molten Fe-Cr-C alloy. The reduction of MgCr2O4 is sluggish at the later stage because of slower diffusion in the sintered layers of Cr-C alloy and MgO with high melting points.