Rate of reduction of MnO in slag by liquid iron was studied at mainly 1 600°C. Experiments were carried out with liquid iron containing carbon from 0.8% to saturation and CaO-SiO₂-Al₂O₃ slag containing about 5%MnO. Evolution of CO gas was observed with X-ray technique. Reduction of MnO in slag took place by exchange reaction with iron and reaction with carbon in iron.
Reaction rate was interpreted by the rate equation derived from the assumption that the reaction was controlled by transfers of reacting components.
Calculated mass transfer coefficient of MnO in slag was in the same order of the value obtained for the study of rate of transfer of manganese between liquid iron free of carbon and slag. Therefore, it was considered that the stirring of slag phase by CO bubbles was not so intensive.