Therinodynamics of TiO(x) in Blast Furnace-Type Slags

Equilibrium studies between CaO-SiO(2)-10 pct MgO-Al(2)O(3)-TiO(1.5)-TiO(2) slags, carbon-saturated iron, and a carbon monoxide atmosphere were performed at 1773 K to determine the activities of TiO(1.5) and TiO(2) in the slag. These thermodynamic parameters are required to predict the formation of titanium carbonitride in the blast furnace. In order to calculate the activity of titanium oxide, the activity coefficient of titanium in carbon-saturated iron-carbon-titanium alloys was determined by measuring the solubility of titanium in carbon-saturated iron in equilibrium with titanium carbide. The solubility and the activity coefficient of titanium obtained were 1.3 pet and 0.023 relative to 1 wt pet titanium in liquid iron or 0.0013 relative to pure solid titanium at 1773 K, respectively. Over the concentration range studied, the effect of the TiO(x) content on its activity coefficient is small. In the slag system studied containing 35 to 50 pet CaO, 25 to 45 pet SiO(2), 7 to 22 pet Al(2)O(3) and 10 pet MgO, the activity coefficients of TiO(1.5) and TiO(2) relative to pure solid standard states range from 2.3 to 8.8 and from O.I to 0.3, respectively. Using thermodynamic data obtained, the prediction of the formation of titanium carbonitride was made. Assuming hypothetical TiO(2) i.e., total titanium in the slag expressed as TiO:,, and using the values of the activity coefficients of TiO(1.5), and TiO(2) determined, the equilibrium distribution of titanium between blast furnace-type slags and carbonsaturated iron was computed. The value of [pet Ti]/(pct TiO(2)) ranges from 0.1 to 0.2.