Modeling the Effect of Combined Electromagnetic Stirring Modes on Macrosegregation in Continuous Casting Blooms

Macrosegregation is one of the most frequently observed defects in continuous casting blooms, which causes nonconformity in ultrasonic flaw detection of rolled products. To investigate the influence of combined EMS modes (M-EMS + F-EMS) on macrosegregation, a 3D multiphase solidification model based on the volume-averaged Eulerian approach was established to simulate the electromagnetic field, fluid flow, microstructural evolution, and solute transport of heavy-rail steel blooms subjected to different EMS processes. In this model, a hybrid model of the mushy zone and a back-diffusion model were introduced into the momentum and solute conservation equations to realize the calculation of microstructural evolution and solute transport with electromagnetic stirring. The predicted magnetic induction intensity, macrostructure, and macrosegregation were verified with Tesla meter measurements, etched macrostructure analysis, and infrared carbon-sulfur analysis. The calculation results showed that M-EMS had little effect on the improvement of the positive centerline segregation, whereas F-EMS effectively reduced the positive centerline segregation. Moreover, a combination of these EMS modes could further reduce the positive centerline segregation in continuous casting blooms. The change in solute concentration caused by M-EMS could be inherited by the position of F-EMS, which could enhance the metallurgical effects of F-EMS. These results were also verified through an industrial application.