Based on the plant trials and the developed coupled mathematical model of electromagnetism, turbulent fluid flow, heat and solute transport, the effect of F-EMS position on the degree of bloom macrosegregation cast with combination stirring (M+F-EMS) has been evaluated and compared for medium carbon steel, 40Cr, and high carbon steel, GCr15. The optimum F-EMS position is mainly related to the solidification characteristic of the molten steel in the liquid pool that depends on the average natural convection velocity and solidification time during the final solidification stage. For a given steel grade and a given F-EMS position, the trend of centre porosity and shrinkage cavity variations is to first decrease and then increase with increasing casting speed. The optimal solidification ratio at the F-EMS centre is increased as the carbon content increases due to the increasing solidification time, where the optimal solidification ratios for GCr15 and 40Cr are 72 and 68% respectively.