A study on the Ti Deoxidation equilibrium in liquid iron equilibrated with CaO-Al2O3 ladle slag system

Abstract

Titanium deoxidation experiments were carried out at 1873K using CaO-Al2O3 slags to determine the titanium distribution ratios between slag and Fe and Fe-11Cr melts containing 0.38~1.0 mass% Ti. The result showed that the titanium distribution ratio increases as the slag basicity increases in CaO-Al2O3 type slag. Titanium in slag existed as Ti3+ and Ti4+. TiO2 or Ti4+ was found to be the predominant form in CaO-Al2O3 slag under the present experimental condition. In order to check if the ratio of Ti3+/Ti4+ in slag was dependent on PO2 , a gas/slag equilibrium experiment was carried out at 1873K. As a result, the relation between log Ti3+/Ti4+ and logPO2 shows a linear relationship with a slope of -1/4. Using available thermodynamic data of titanium deoxidation equilibrium in liquid iron, the activity coefficient of TiO2, rTiO2 in CaO-Al2O3 slag was determined. The activity coefficient of TiO2 shows nearly a constant value of 0.62 over a wide slag composition range of XCaO/XAl2O3 = 1.2 ~2.4 in CaO-Al2O3 slags at 1873K. In order to control the Ti yield during Ti addition practice, the control of oxygen potential in liquid steel would be most effective. This can be done by the complex deoxidation of Al and Ti in liquid steel and the slag composition control.