The Role of Mold Electromagnetic Stirring in the Dissipation of Superheat during the Continuous Casting of Billets

Abstract

Mold electromagnetic stirring (M-EMS), as an additional engineering measure, has been widely used to optimize fluid flow and heat transfer, and hence to control ascast structures and macrosegregation. [5][6][7][8][9][10][11] The swirling flow generated by M-EMS can effectively speed up the superheat dissipation in the mold region, and as a consequence, the equiaxed nuclei originating from crystal fragmentation or heterogeneous nucleation can survive the superheat and form the central equiaxed zone. [12,13] Due to the harsh environment and high cost of field experiments, numerical modeling has become an effective tool for investigating transport behavior with M-EMS. Yu et al. [14] developed a mathematical model to investigate the effect of M-EMS on the flow field, temperature profile, and inclusion trajectories in round billet continuous casting. They found that the core temperature was dramatically reduced with M-EMS. An et al. [15] proposed a 3D mathematical model to study the effect of current intensity and frequency on fluid flow, and the simulation results also indicated that M-EMS tends to accelerate superheat dissipation. However, solidification was ignored in the above studies.Ren et al. [16] developed a mathematical model to investigate the influence of M-EMS on fluid flow, heat transfer, and solidification in round bloom continuous casting. They found that M-EMS prevents the superheated jet from moving downward and thus accelerates superheat dissipation in the mold region. Li et al. [17] proposed a coupled magnetohydrodynamics (MHD) model to study the electromagnetic field, fluid flow, and solidification with M-EMS in bloom continuous casting. The maximum melt swirling flow velocity was found to be remarkably decreased when considering solidification. Meanwhile, the M-EMS-induced swirling flow was beneficial for preventing the superheated melt from moving down into the liquid core below. Trindade et al. [18] used a coupled numerical model to study the fluid flow, temperature distribution, and solidification of round billet continuous casting under M-EMS. They found that M-EMS tends to decrease the temperature in the strand center and locally reduce the shell thickness due to the increase in the tangential velocity close to the wall. However, common drawbacks of the previous models are as follows: 1) they used a relatively rough mixture-based model to study the solidification characteristics. The solid shell is simply calculated based on the lever rule, which omits some important

Study on Stirring Effect of Spiral Magnetic Field in Continuous Casting of Round Blooms

“…As can be seen from the figure, with the RMF, the velocity of the molten steel greater than 0.02 m s À1 is mainly concentrated in the center of the stirrer, with the axial width accounts for 13.7% of the whole stirring area. Moreover, it can be seen that the molten steel has an obvious phenomenon of upward reflux at the center of the stirrer, resulting in a large decrease in the velocity of molten steel, which is caused by the secondary flow [35,36] caused by the EMS. While the SMF has an intense swirling effect in the whole region affected by the secondary flow, forcing the disordered molten steel to flow spirally in the casting direction, and the axial width of the molten steel with velocity greater than 0.02 m s À1 can be 49.1%.…”