Distribution Behavior of Titanium Between Ferrosilicon Melt and CaO-SiO2-Al2O3 Slag: Thermochemical and Structural Assessments

Abstract

The titanium distribution ratio (LTi) between ferrosilicon (FeSi) melt and the CaO-SiO2-Al2O3 slag was measured at 1773 K (1500 °C). FeSi-slag equilibration was carried out using various slag compositions. The LTi was presented against the Vee ratio (pct CaO/pct SiO2 = C/S) between 0.3 and 1.2, and Al2O3 content from 5 to 20 mass pct. The LTi exhibited minima at about C/S=0.7(±0.1) at a fixed Al2O3 content. In a C/S < 0.7 regime, i.e., relatively acidic melts, Ti4+ ions were considered as network forming [TiO4]-tetrahedron unit in the aluminosilicate framework. However, in a C/S > 0.7 regime, i.e., relatively basic melts, Ti4+ ions were considered to form the [TiO5]-pyramid structure unit compensated by Ca2+. When adding Al2O3 into the basic melts over 10 mass pct, [AlO4]-tetrahedrons take Ca2+ ions for charge compensation, resulting in a decrease of stability of [TiO5] unit because of Ca2+ depletion. At a greater than 10 mass pct Al2O3 content in the basic melts, Ti4+ replaced Al3+ to form the [TiO4]-tetrahedron unit, decreasing the activity coefficient of TiO2 in the slag. © The Minerals, Metals & Materials Society and ASM International 2024.