Calcium aluminate system is widely used in several ceramic and metallurgical materials and processes such as tundish and mold slags for continuous casting process. In the case of mold powders, they play significant role during the steel solidification process and knowing its physicochemical properties is crucial in the study of slag behavior. In this context, the crystallization tendency of the mold powders plays a significant role in essential properties such as viscosity-which is fundamental to the efficiency of the casting process. In the present study, the effect of a water vapor atmosphere on the crystallization behavior of the CaO-Al 2 O 3 join is investigated using the single hot thermocouple technique. Distinct crystallization behaviors in presence of water vapor atmosphere are observed, according to the temperature range. Hindering of crystallization onset occurs at a temperature range above 1150 °C. For the temperature range below 1150 °C, crystallization improvement can be observed. The resulting time-transformation-temperature diagrams show the influence of temperature on the effect of water vapor upon crystallization, denoting the amphoteric nature of water.
The effect of MgO and low TiO 2 content on the solidification of CaO-SiO 2 -Al 2 O 3 based mold fluxes is investigated. The crystallization and viscosity behaviors are analyzed using single hot thermocouple technique (SHTT) and rotating viscometer, respectively. Continuous-cooling-transformation (CCT) results point to an increase of critical cooling rate (CCR) with increasing MgO content. Conversely, the presence of TiO 2 seems to mitigate the effect of MgO on the crystallization due to the strong glass former characteristic of titanium dioxide. Viscosity measurements show an increase with increasing MgO content in slags containing TiO 2 . Break temperatures (T br ) are compared to the onset crystallization temperatures from CCT experiments. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis results indicate the presence of melilite (Al 2 Ca 2 Mg 0.5 O 7 Si 1.5 ) for all samples of mold flux containing both MgO and TiO 2 .
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