Effect of Electromagnetic Stirring on Solidification Structure and Central Porosity of Large‐Sized Round Bloom in Continuous Casting

The effect of strand (S‐) and final (F‐) electromagnetic stirring (EMS) on solidification structure characteristic of a φ690 mm continuously cast round bloom has been investigated industrially and theoretically. The newly designed S1‐EMS equipped just below the foot zone takes great effect on both equiaxed ratio and distribution alignment, as well as central porosity. Larger current S1‐EMS leads to higher equiaxed ratio, more symmetrical equiaxed zone, and smaller diameter of central porosity, and the effect is much more obvious than conventional S2‐EMS and F‐EMS. It is also noticed that there should be a saturation effect of S1‐EMS on the promotion of equiaxed dendrite nucleation. The S2‐EMS is beneficial for the expanding of equiaxed zone and improving of central porosity. When S1‐EMS is weak, strong S2‐EMS results in more asymmetrical equiaxed zone. However, when S‐EMS is strong, strong S2‐EMS results in more symmetrical distribution of equiaxed zone. The F‐EMS takes a little impact on the expanding of equiaxed zone in the large‐sized round bloom, and almost no effect on the alignment. The central porosity, however, is improved by F‐EMS with the help of decrease in temperature gradient and compensation of solidification contraction.