Study On The Equilibrium Of Nb Between The Slag And The Carbon Saturated Iron

The thermodynamic equilibrium of Niobium between iron and slag was studied by simulating reduction atmosphere in blast furnace. The carbon saturated iron of different levels of niobium was as the raw materials. According to the metallurgical slag phase diagram, CaO-MgO-SiO₂ slag system containing Al₂O₃ was for the slag phases. The oxides and compounds were used to synthesiz the slag in the melilite composition. The multiple orthogonal methods was used to optimize the slag composition to be in equilibrium between carbon saturated irons with slag at 1 400℃-1 500℃. Niobium was reduced by carbon in iron and CO + Ar was accessed to protect the reaction system and maintain CO partial pressure in the system through equilibrium experimental system. The change of the distribution ratio of Nb between iron and slag with temperature was studied in the different slag components. The effect of temperature, alkalinity of slag and niobium content in iron on Nb distribution rate between iron and slag was discussed. Niobium activity in liquid iron at equilibrium condition was calculated.The experimental results show that the experimental temperature has a certain influence on the reduction of niobium, and the distribution ratio of Nb between iron and slag is increase with temperature increasing. In strong reducing atmosphere and the presence of excess carbon, a part of Nb is formed into NbC during the reduction reaction. The activity of niobium in iron is 0.5 to 0.8 at the temperatures of 1 400℃ 1 500℃and alkalinity in a range of 0.8 and 1.4. In the experimental condition, the relation of the equilibrium constant K for the reduction reaction of Nb₂O₅ and C in liquid iron with temperature is: lg K = 1686 T+ 1.8.