Article ID: ISIJINT-2018-724
Based on the structure of slag, the revised structure based viscosity model was improved for viscosity prediction of the fully liquid slag in the Al2O3–CaO–MgO–SiO2 quaternary system and its subsystems. Experimental procedures and available data in the literature have been critically reviewed. In this modified model, the oxygen ions bonded with non-compensated Al3+ ions were defined as excess bridge oxygens. The concentration of different types of oxygen ions are calculated and used to express the activation energy. The present model is capable of predicting the viscosities in the Al2O3–CaO–MgO–SiO2 quaternary system and its subsystems over the wide composition and temperature ranges above liquidus within experimental uncertainties; the average of relative errors for this model was found to be 17.97%. CaO has a greater ability to decrease the viscosity than that of MgO in the system without Al2O3 because of the weaker bond strength of CaO. A viscosity maximum occurs for MO–Al2O3–SiO2 (M=Ca or Mg) slag with a fixed SiO2 content. The estimated viscosities decrease with the increase of MgO content, decrease with increasing of the Al2O3/SiO2 ratio at 5 mass% of MgO, and keep almost constant or even slightly increase with the increase of the Al2O3/SiO2 ratio at 10 mass% MgO.