ROLES OF Mn CARBIDES IN CARBOTHERMIC PROCESSES FOR Mn ALLOYS

摘要

The reduction of Mn oxides at pre-smelting steps is an integral part of smelting processes for Mn alloys, and an understanding of its reaction mechanism is expected to contribute to the improvement of processing efficiency for Mn alloys smelting. The phase diagram shows that five Mn carbides are operative in the Mn-C system. Although they are expected to participate in the reduction of Mn oxides, no specific information is available yet to clarify their roles in pre-smelting carbothermic reaction of Mn oxides. Experiments with composite pellets prepared with Mn oxides and graphite powders show that Mn_3O_4 is reduced initially to MnO at about 1130°C and, subsequently, to Mn_7C_3 carbide as temperature increases further. At 1331°C, Mn_7C_3 carbide dissociates to Mn alloy and carbon. The degree of reducing reaction increases with increasing carbon balance in composite pellets and increasing temperatures.