Measurements and Model Estimations of Viscosities of the MnO-CaO-SiO₂-MgO-Al₂O₃ Melts

The viscosities of the MnO (0 to 55 mass pct)-CaO-SiO₂-MgO (5 mass pct)-Al₂O₃ (20 mass pct) melts were measured by rotating cylinder method in the temperature range from 1573 K to 1873 K (1300 °C to 1600 °C). The measurements were carried out in the atmosphere of flowing CO/CO₂ gas mixture with a volume ratio of 99/1, and molybdenum crucible and spindle were adopted. The results reveal that MnO is a viscosity reducing component, and the effect of MnO is more notable in the melts with higher ratio of CaO to SiO₂. For example, in the melts with the mass ratio of CaO to SiO₂ equal to 0.6, the addition of 5 mass pct MnO only slightly reduced the viscosities. Comparatively, the addition of 5 mass pct MnO made the viscosities of the melts with the mass ratio of CaO to SiO₂ equal to 1.0 and 1.5 decrease remarkably. Based on the measured data, the viscosities estimation model proposed in our previous study was extended to the system containing MnO, and the model parameters were determined. The model can estimate and predict the viscosities of the aluminosilicate melts containing MnO well, and then some iso-viscosity contours of this system were calculated. From the iso-viscosity contours, it can be seen that MnO is almost equivalent to CaO in reducing the viscosities in the melt with high SiO₂ content, while with the decrease of the SiO₂ content MnO becomes more effective than CaO.