Thermodynamics of titanium and oxygen dissolved in liquid iron equilibrated with titanium oxides

Abstract

The equilibrium relation of Ti and O dissolved in liquid iron saturated with solid titanium oxides was measured in the temperature range of 1 823 to 1 923 K. Pure Ti2O3(s) phase was identified as the equilibrium deoxidation product for iron melts containing 0.25-4.75 mass% Ti. Using Wagner's formalism, the present results were thermodynamically analyzed to determine the equilibrium constant of Ti deoxidation reaction for the formation of pure Ti2O3(s) and the first- and second-order interaction parameters between Ti and O given as follows in the temperature range of 1 823 to 1 923 K. 2Ti+3O=Ti2O3(s) (0.25 <4.75) log KTi2O3 = 44 238/T - 13.0 eOTi = -1 642/T+0.3358, eOTi=-4 915/T+1.005 rOTi = 0.0385, rOTi = -0.355 The equilibrium titanium oxide phase was identified as Ti3O5(s) for iron melts containing 0.0012-0.25 mass% Ti at 1 873 K. The equilibrium constant of Ti deoxidation reaction for the formation of pure Ti3O5(s) were estimated as follows. 3Ti+5O = Ti3O5(s) (0.0012 <0.25) log KTi3O5 = 72 813/T-21.32 The activity coefficient of Ti in liquid iron at infinite dilution, γ Ti(s)o was assessed as 0.011, 0.014 and 0.018 at 1 823 K, 1 873 K and 1 923 K, respectively. © 2007 ISIJ.