Manganese and silicon distribution between slag and metal in silicomanganese production

Abstract

Laboratory measurements have been carried out to investigate the equilibrium distribution of manganese and silicon between slag and metal in silicomanganese production. Graphite crucibles have been used to study equilibrium between Mn-Si-Csat alloys and MnO-SiO2-CaO-Al2O3-MgO slags in CO gas at 1 600 °C, 1 650 °C and 1 700 °C. The equilibrium content of Si in the metal is mainly controlled by the temperature, the silica content of the slag and the mass ratio R = (CaO+MgO)/Al2O3. The silicon content increases with the temperature and the silica content, and decreases with increasing R-ratio. The silicon content remains approximately the same when some MgO replaces CaO in the slag. The equilibrium content of MnO in silicomanganese slags is primarily controlled by the temperature and the silica content of the slag. Addition of Al2O3 to acid slags will result in somewhat lower MnO contents, and addition to more basic slags has the opposite effect. The equilibrium content of MnO in the slag is slightly increased when some CaO is replaced by MgO.