DISSOLUTION RATE OF ALUMINA INTO MOLTEN CAO-SIO2-AL2O3-MGO SLAGS

Dissolution rates of sintered alumina into molten CaO-SiO2-9mass%Al2O3-10mass%MgO slags were measured by rotating specimen method. Experiments were conducted at various revolution speeds, temperatures, and CaO/SiO2 ratioes, and the microstructures of specimens after experiments were examined by EPMA. Based on these results, the dissolution mechanism was discussed. The dissolution rate of alumina increased with increasing revolution speed and rising temperature. These results suggested that the dissolution rate was controlled by mass transport in the boundary layer of molten slags. The dissolution rate of alumina decreased rapidly as increasing CaO/SiO2 from 0.64 to 0.80 and then increased rapidly as increasing CaO/SiO2 from 0.80 to 1.00. According to the EPMA analysis, a compact deposition of MgO . Al2O3 spinel particles in slag and a formation of CaO . 6Al(2)O(3) compounds in alumina were confirmed in the specimen immersed into the slag of CaO/SiO2=0.80. It was estimated that these reaction proudcts suppressed the flow oi slag components to decrease the dissolution rate. However. MgO . Al2O3 spinel particles observed in the specimen immersed into other slags were scattered, and might not disturb the flow of slag component, so that the dissolution rate was not retarded.