REACTION EQUILIBRIA IN THE PRODUCTION OF MANGANESE FERROALLOYS

A laboratory investigation has been carried out to determine slag/meta l and slag/metal/gas equilibria relevant to production of manganese fe rroalloys. The metal phase was normally composed of Mn-Si-C-sat alloys , but in some experiments, the alloys contained up to 15 wt pet Fe. Di fferent slag systems were used: MnO-SiO2, MnO-SiO2-CaO, MnO-SiO2-Al2O3 , and quaternary MnO-SiO2-CaO-Al2O3 with fixed CaO/Al2O3 weight ratios of 1.5 and 3. The experiments were normally made in CO gas atmosphere at temperatures ranging from 1450 degrees C to 1600 degrees C. The re sults give comprehensive information about equilibrium relations. Part ial and complete equilibria are illustrated in equilibrium diagrams. P artial equilibrium is a situation in which equilibrium is established with respect to certain variables but not to others, in this case, bet ween slag and metal but not with the gas phase. The effect of temperat ure was found to be of minor importance for the partial slag/metal equ ilibrium, whereas the complete slag/metal/gas equilibrium is considera bly influenced by both temperature and CO pressure. As expected, incre asing temperature and decreasing CO pressure will reduce the equilibri um MnO content of slags. The influence of alumina addition to the slag phase and of iron to the metal phase is also discussed.