Modelling of alloy mixing into steel

Gas stirring of steel in the ladle is widely used in metallurgical industries to homogenise chemical composition and temperature, enhance reaction rates, etc. This study focused on the homogenisation, i.e., the mixing of alloy additions and steel during gas stirring. More specifically, the influence of porous plug location on alloy mixing into steel was studied theoretically. Flow fields were calculated and presented for simultaneous stirring with 2 porous plugs in 4 different arrangements. The alloy mixing into steel in the ladle with these different arrangements was studied with 2 different alloy addition methods. In the 1st method, the alloy was added in a batch at the beginning of the stirring. In the 2nd method, the alloy was added continuously throughout the stirring. When comparing the calculated results for the 4 different pairs of porous plug placements, it was found that centric stirring and centric addition rendered the best average mixing and also the least likelihood for “dead rooms” to develop. However, the combination of centric stirring and addition was found to be extremely sensitive to small variations in alloying position. It was therefore concluded that for steelmaking, the best of the studied alternatives is using 2 porous plugs placed such that their respective radii form an angle of 60°. Verification of calculated steel velocities was done with experimental data taken from a previous publication.