New perspective on the interface reaction and morphology evolution in the reduction of manganese silicate for silicomanganese alloy production

Abstract

SiMn alloy is the largest consumption product in the Mn series alloys. Manganese silicates generated during the pre-treatment procedures of manganese ores are the main ingredient for SiMn alloy production. However, conventional cognition is that manganese and silicon in the silicates are respectively reduced to Mn7C3 and SiC by carbon, and then the carbides interact to form alloy. In current study, pure MnSiO3 was synthesized firstly and then a new perspective on the interface reaction and morphology evolution for the reduction of pure MnSiO3 were investigated via XRD, SEM, XPS and thermodynamics analyses. Interface reaction showed that the MnSiO3 was firstly reduced to manganese carbides and SiO2, and then the SiO2 was further reduced by the carbides to generate SiMn alloy. The intermediate product Mn7C3 played a crucial role since the reduction of SiO2 by newly born Mn7C3 preferentially conducted than the carbon reductant. Morphology evolution of the interface between C and MnSiO3 as well as thermodynamic calculations of Mn-Si-O and Mn-Si-C-O systems were minutely clarified in this work to clarify the reduction mechanism. In addition, decomposition of SiMn alloy to SiC ceramic at 1700 °C was an important inducement to illustrate the frangibility of industrial SiMn alloy product.