Improvement of carbon segregation in billet by final-EMS, based on segmented continuous casting model

Abstract

Based on magnetohydrodynamics and solidification theory, a three-dimensional segmented continuous casting model, coupling electromagnetic phenomena, fluid flow, heat transfer and solidification, and solute distribution, was established using COMSOL. Simulation results revealed a positive segregation, with a degree of approximately 1.05, was observed beneath the meniscus, and as the position moved downward, a mild negative segregation, with a degree of approximately 0.97, emerged at a distance of about 10 mm from the wall due to the washing effect on the solidification front. Within the natural convection zone, an asymmetric distribution of carbon segregation between the loose and fixed sides was evident, influenced by the thermal solutal buoyancy. With an increase in the electrical current applied for the final electromagnetic stirring (F-EMS), the Lorentz forces responsible for agitating the molten steel became more pronounced, resulting in a more uniform distribution of carbon. This indicated that the introduction of F-EMS accelerated convection between the molten steel and the mushy zone, facilitating the redistribution of solutes. At an F-EMS current of 250 A–8 Hz, the carbon distribution exhibited the highest uniformity, reducing the degree of segregation at the billet centre from 1.30 to 1.22, a decrease of 0.08. The incorporation of F-EMS effectively addressed centreline segregation issues, and the calculated carbon concentration distribution under both F-EMS and non-F-EMS conditions closely matched experimental measurements.