Investigation of Effects of SiO₂ Content and Cooling Rate on Crystallization in Fe₂O₃-CaO-SiO₂ System Using In Situ Confocal Laser Scanning Microscopy

The crystallization behaviors of the Fe₂O₃-CaO-SiO₂ system in a non-equilibrium state with various chemical compositions and cooling rates were investigated by confocal laser scanning. Equilibrium samples were prepared in melt states and cooled at a rate of 1 K/min to produce samples in quasi-equilibrium states. The effect of SiO₂ on the phase constitution was investigated using Image Analyzer, and the changes of the phase ratios were analyzed using activity values of Fe₂O₃ calculated using FactSage 7.1. The Continuous cooling transformation diagram of the Fe₂O₃-CaO-SiO₂ system was obtained for various cooling rates. The temperatures at which the primary phase formed for various SiO₂ contents and cooling rates differed from the equilibrium temperatures, and the phase-formation temperature ranges varied with the cooling rate. In addition, the reduction degree of each sample was measured to determine the effect of SiO₂ content and cooling rate on the Fe₂O₃-CaO-SiO₂ system. The reduction degree in the FeO₃-CaO-SiO₂ system is dominantly influenced by the SiO₂ bond-phase morphology (CF, C₂S, C₃S, or glass) rather than the cooling rate.