Effect of SiO2 and TiO2 on the Crystal Morphology of CaF2Al2O3CaO‐Based Electroslag Remelting Slag

Abstract

The effect of SiO2 and TiO2 on the crystal morphology of 60%CaF220%Al2O320%CaO‐type electroslag remelting (ESR) slags are investigated by thermodynamic simulations, differential scanning calorimetry, X‐ray diffraction, scanning electron microscope, and energy dispersive X‐ray spectroscopy. The results suggest that the addition of TiO2 and SiO2 changes the type, amount, and sequence of crystal precipitation. CaF2 is confirmed to be the main crystalline phase in the slag, the morphology of which depends on the slag composition and cooling rate: As SiO2 content increases, the crystal morphology of CaF2 in the slag changes from dendrites with smooth surface and relatively large secondary dendrite arm spacing to dendrites with sharp tips and relatively small secondary and tertiary dendritic arm spacings. A classical crystallographic model, Jackson α factor, is proved to correctly predict the crystal morphology as observed in the experiments. It is inferred that the addition of 5 wt% TiO2 and 4 wt% SiO2 and a proper cooling rate are favorable to improve the lubrication property of 60%CaF220%Al2O320%CaO‐type ESR slags.