Effect of electromagnetic stirring on macro-segregation in continuous casting blooms of heavy-rail steel U75V

To mitigate macro-segregation and enhance the internal homogeneity of heavy-rail steel bloom, this study investigated the macro-segregation under the combined effect of electromagnetic field on solute transport and solidification structure nucleation by using an Euler-Euler model and a volume-averaging method. The results showed that the forced fluid flow intensifies negative segregation in the stirring and washing zone and promotes solute transport toward the bloom center. Meanwhile, the formation of nucleation and heat transfer was strengthened during the solidification process, which determined the evolution of central segregation. As the mold electromagnetic stirring (M-EMS) current increased from 150 to 350 A, the segregation ratio decreased from 0.96 to 0.93, and the grain density increased from 9.0×10 8 to 1.0×10 9 m -3 . The central carbon segregation of the bloom first decreased and then increased with increasing final electromagnetic stirring (F-EMS) current intensity. As the intensity current reached 450 A, the central segregation increased. This study also found that the tangential flow velocity, which significantly influences stirring effectiveness, is notably affected by the solid fraction ( f s ) in the mushy zone. When the f s reached 0.98, the tangential velocity dropped to 0 m·s -1 . Through numerical simulation, the optimized electromagnetic stirring parameters were obtained as: M-EMS at 250 A and F-EMS at 250∼350 A, which achieved a balanced improvement in bloom cross-section homogeneity and lower central segregation. Comprehensively considering both energy consumption and the uniformity control effect, industrial applications were carried out with M-EMS and F-EMS current intensities of 250 A. The carbon segregation range across the bloom section was optimized from 0.95∼1.03 to 0.98∼1.02. The maximum value of central segregation was reduced from 1.22 to 1.14.