Crystallization Behavior of Rutile in the Synthesized Ti-bearing Blast Furnace Slag Using Single Hot Thermocouple Technique

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The present paper constructed the time-temperature-transformation (TTT) diagram of the synthesized titanium-bearing blast furnace (Ti-BF) slag using single hot thermocouple technique (SHTT) in order to study the crystallization behavior of rutile. A combination of X-ray Diffraction (XRD), Electron Probe Micro Analysis (EPMA) and Scanning Electron Microscope (SEM) equipped with Energy-dispersive X-ray spectroscopy (EDX) were applied to determine the structure and the composition of the crystals in the synthesized Ti-BF slag. It was found that rutile with rod shape was formed in the wide range of isothermal temperatures from 1160°C to 1320°C, and CaMgSi2O6, CaAl2Si2O8 as well as CaTiSiO5 were precipitated with further decreasing isothermal temperature. At a fixed isothermal temperature, the diameter of rutile increased slightly, whereas the length of rutile increased linearly with holding time. When increasing the isothermal temperature, the diameter of rutile increased linearly, while the growth rate of the length of rutile initially increased and followed by a decrease with further increasing isothermal temperature. The growth rate of the length of rutile had a maximum value (7.74 μm/s) at 1260°C. The mechanism of crystal growth was also discussed, and the results indicated that rutile with one-dimensional growth was observed in the slag melt.