Dissolution of alumina particles in CaO-Al2O3-SiO2-MgO slags

The dissolution behaviour of alumina particles in CaO-Al2O3-SiO2-MgO slags was studied by confocal scanning laser microscopy. Three different slag systems were investigated to evaluate the effect of changing the MgO content in a high silica tundish slag, and the effect of decreasing the silica content when dissolving the particles in a ladle slag. A particle of 80 mum diameter dissolved in 50 s in a simulated ladle slag but needed 100 s to dissolve in a high silica slag at the same temperature. When the silica content was decreased, a decrease in the alumina particle dissolution time was noted. During dissolution of alumina particles in a slag containing MgO, the alumina particle reacts with the slag to form an MgAlO4 layer, No reaction layer was observed during the dissolution of alumina particles in slags that did not contain MgO. This work suggests that the dissolution time of large alumina particles is significant, increasing with particle size and with decreased temperature.