Thermodynamic model of metallothermic smelting of ferromolybdenum

Ferromolybdenum, used in alloy steel production, is made by the batch reduction of molybdenum oxide by silicon and aluminium at high temperatures. In this work, the technology of the process has been reviewed and representative charge mixes compared. A computational thermodynamics model was developed and used to investigate the relationships between charge composition and ferroalloy grade and quality, indicated by its silicon content. The model predicted satisfactorily the composition of the ferromolybdenum and waste slag from a typical charge mixture. The silicon content depended on the ratio of silicon to molybdenum oxide in the charge and was not sensitive to the assumed smelting temperature or activity coefficient of silicon in the alloy. Losses of molybdenum to slag as dissolved oxide were predicted to be much lower than published industrial data, suggesting that losses in practice are mostly due to the inclusion of unsettled ferromolybdenum droplets.