Effect of Swirling Flow Submerged Entry Nozzle on Solidification and Macrosegregation Behavior of a Round Bloom with Mold and Final Electromagnetic Stirring

Macrosegregation defect is one of the main concerns during continuous casting which strongly deteriorates the steel quality. In this study, a mathematical model was established to investigate the effect of a novel swirling flow submerged entry nozzle (SEN) on solidification and macrosegregation behavior of a curved round bloom with the diameter of 178 mm. The results show that the impinging flow phenomenon observed in a conventional single-port SEN casting was effectively eliminated by adopting the new method. Under the effect of the rotational stirring coming out from the swirling flow SEN, the dissipation rate of molten steel super-heat was improved. Specifically, compared to when conventional SEN combined with mold and final electromagnetic stirring (M-EMS and F-EMS) was used, the steel super-heat in mold center was reduced by about 8 K. Moreover, the thickness of solidified shell was increased by 1 mm. By applying the swirling flow SEN, carbon solute was found to be evenly distributed on the cross-section of the round bloom. The negative and positive segregation zone was reduced by 48.3 and 73.1 pct, respectively, compared to when a conventional SEN with M-EMS and F-EMS was adopted. The segregation degree at bloom center was reduced from 1.32 to 1.16. Furthermore, when the swirling flow SEN with M-EMS and F-EMS stirring was used, the central segregation degree was found to be increased from 1.16 to 1.37 compared to only swirling flow SEN used. This is due to a strong stirring at the solidification front, which increased the transfer of solute to the bloom center.