Effect of Mold Electromagnetic Stirring and Final Electromagnetic Stirring on the Solidification Structure and Macrosegregation in Bloom Continuous Casting

The solidification structure and macrosegregation are investigated in different current intensities of mold electromagnetic stirring (M-EMS) and final electromagnetic stirring (F-EMS) by a series of industrial trials during the 20CrMnTi bloom continuous casting (CC) process. With the current intensity of M-EMS increasing from 100 to 390 A, the deflection angle of columnar dendrites increases from 25.0 to 32.49 deg. With the current intensity of M-EMS increasing from 0 to 390 A, the equiaxed crystal ratio increases from 20.4% to 25.7% and center porosity varies little. With the increasing current intensity of M-EMS, the negative segregation in the subsurface and positive segregation in the columnar-to-equiaxed transition (CET) zone deteriorate gradually. The M-EMS has little effect on the center-positive segregation, and the center-positive segregation is maintained at 1.37-1.40. With the current intensity of F-EMS increasing from 0 to 500 A, the equiaxed crystal ratio is within 25.3-25.8%, and the large center porosities disappear instead of numerous fine spots in the equiaxed zone. The degree of center-positive segregation decreases from 1.48 to 1.30. For the CC process, to obtain a better internal quality of 20CrMnTi bloom, the optimal current intensities of M-EMS and F-EMS are 0 and 500 A, respectively.