Evaluation of Dissolution Rate and Behavior of MgO Carriers for Primary and Secondary Metallurgical Slags

MgO is added in steelmaking to saturate slag and reduce the chemical corrosion of metallurgical vessels. For an effective refractory lining protection, refining and process control, flux must be in solution in the slag within the required process time. The dissolution behavior of different MgO carriers was investigated in primary and secondary steel slags in a static experiment. Fine-grained MgO carriers were charged into the pre-melted liquid slag at 1873 K. After a holding time ranging from 10 to 30 minutes, the crucible containing the sample and slag was quenched with liquid nitrogen. Cross-sectional cuts were made in the fused samples in a water-free environment to perform detailed mineralogical investigations. Based on the sample analysis and MgO concentrations derived from SEM/EDX, the dissolution behavior of MgO carriers was examined. Further investigations continued in a larger vessel under industrial conditions, where some selected carriers were added into the slag during tapping. The effects of the slag basicity, the chemical compositions of the slags and the originating material on MgO saturation were analyzed. The experimentally derived values for MgO saturation were compared with the FactSageTM prediction.