Numerical Study On The Macroscopic Transport Phenomena Of Continuous Casting Process Under Electromagnetic Force

The electromagnetic stirring(EMS)technology is widely used for the continuous casting process.Its metallurgical effect for improving the quality of cast products is mainly obtained through flow pattern control of molten steel in the stirring region.The EMS devices has become a conventional configuration of the continuous casting machine.Since the complexity of transport phenomena in continuous casting process under the electromagnetic force,it is difficult to investigate metallurgical behavior through plant measurements and physical experiments.Thus,the paper performs a series of studies on the transport behavior of continuous casting process by numerical simulation.A new integral numerical model is proposed to calculate the electromagnetic torque based on FEM,which is validated using the measured data by an independently designed electromagnetic torque measurement device.The optimum frequency can be confirmed by calculating the maximum electromagnetic torque of the strand.The thicker the copper mold and the larger the strand section size,the smaller the optimum frequency.However,the law of the optimal frequency changes if the installation position of the stirrer is too much lower than the mold exit,the optimal frequency maybe no longer exists.The mushy zone coefficient strongly affects the prediction of fluid flow and solidification behavior of the continuous casting numerical simulation process.Based on the previous theoretical investigation,the expression of the mushy zone coefficient is proposed.The effect of mushy zone coefficient on the melt flow and solidification phenomena is quantitative analyzed.The value of the mushy zone coefficient ranging from 1×108 to 5×108 is suggested.A coupled magnetohydrodynamics model is developed to describe the fluid flow and solidification in a bloom continuous casting mold with electromagnetic stirring(M-EMS).A swirling flow field along the axial direction of the strand is observed in the mold region with the application of M-EMS.With the increment of current intensity,the impact depth reduces,and the superheat of molten steel can be dissipated remarkably due to the increased tangential velocity.Besides,the turbulence zone lower down as the installation position of the stirrer moving down,and the flow pattern changes accordingly.Based on segmentation calculation method,a 3D numerical model coupling the electromagnetic field,melt flow and solidification in the whole casting domain is established for round billet casting.The swirling flow of melt in the mold region is unsteady state with periodic bias flow for round billet casting with M-EMS.The crater end moves forward by 0.32 m with the application of M-EMS.The swirling flow mainly occurs in the stirrer region with final electromagnetic stirring(F-EMS)due to the flow resistance of the mushy zone.For the round billet casting,the tangential velocity of melt increases and the temperature of the melt in the mushy zone decreases as the current intensity and frequency increasing.The macroscopic segregation phenomenon of bloom continuous casting process is simulated including solute transport.Results show that positive segregation forms at the edge of the initial shell in the mold region.However,the solidified shell becomes negative segregation zone as the solidification proceeding.The maximum segregation degree of the strand is reduced from 1.292 to 1.254 with the application of F-EMS.The location of F-EMS is also an important factor,which affects the metallurgical behavior.A solidification ratio of 0.7 and centre solid fraction of 0.1 is optimal for this study.