Effect of TiO2 on the viscosity and structure of low-fluoride slag used for electroslag remelting of Ti-containing steels

Abstract

The viscosity of CaF2–CaO–Al2O3–MgO–(TiO2) slag was measured using a rotating crucible viscometer. Raman spectroscopy analysis was performed to correlate the viscosity to slag structure. The viscosity of the slag was found to decrease with increasing TiO2 content in the slag from 0 to 9.73wt%. The activation energy decreased from 95.16 kJ/mol to 79.40 kJ/mol with increasing TiO2 content in the slag. The introduction of TiO2 into the slag played a destructive role in Al–O–Al structural units and Q4 units by forming simpler structural units of Q2 and Ti2O6 4− chain. The amount of Al–O–Al significantly decreased with increasing TiO2 content. The relative fraction of Q4 units in the [AlO4]5−-tetrahedral units shows a decreasing trend, whereas the relative fraction of Q2 units and Ti2O6 4− chain increases with increasing TiO2 content accordingly. Consequently, the polymerization degree of the slag decreases with increasing TiO2 content. The variation in slag structure is consistent with the change in measured viscosity.