Numerical investigation on effect of electromagnetic stirring on macrosegregation in continuously cast round bloom via three-phase solidification model

Abstract

Based on our previously proposed three-phase solidification model, a comprehensive analysis on the impact of the only electromagnetic stirring (EMS) and combined EMS on the microscopic structure evolution and solute segregation behavior in a 500 mm diameter 42CrMo steel of continuously cast round bloom. The results indicate that M-EMS has a notable impact on expediting the dissipation of superheat, enhancing the initiation of grain formation, and enlarging the equiaxed region. The percentage of equiaxed grains increased from 59.26 to 63.37% with the increment in current intensities of M-EMS from 250 to 350 A. However, higher M-EMS current intensities were found to enhance local positive segregation in the transition zone between columnar and equiaxed grains. The impact of M-EMS on improving center positive segregation was minimal, as the ratio of center positive segregation remained consistently around 1.17. Furthermore, the implementation of F-EMS demonstrated its effectiveness in reducing center positive segregation. The ratio of center positive segregation decreased from 1.14 to 1.10, when the current intensity increases from 150 to 250 A. However, it should be noted that F-EMS alone did not contribute to the expansion of the equiaxed zone. On the other hand, when M-EMS was combined with F-EMS (referred to as combined EMS), it showed potential in mitigating center segregation during continuous casting round blooms. The benefits observed with M-EMS in terms of promoting grain nucleation and expanding the equiaxed grain zone were also evident in this combined EMS process. Furthermore, a notable enhancement in the equiaxed grain ratio up to 60.13% was observed combined EMS models were simultaneously employed during continuous casting of round blooms. And, there was a reduction in center segregation ratio for round blooms to as low as 1.09.