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

Abstract

The effect of SiO 2 and TiO 2 on the crystal morphology of 60%CaF 2 ─20% Al 2 O 3 ─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 TiO 2 and SiO 2 changes the type, amount, and sequence of crystal precipitation. CaF 2 is confirmed to be the main crystalline phase in the slag, the morphology of which depends on the slag composition and cooling rate: As SiO 2 content increases, the crystal morphology of CaF 2 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% TiO 2 and 4 wt% SiO 2 and a proper cooling rate are favorable to improve the lubrication property of 60% CaF 2 ─20%Al 2 O 3 ─20%CaO-type ESR slags.