REDUCTION OF CENTER POROSITY OF ROUND BILLET BY ELECTROMAGNETIC STIRRING IN HORIZONTAL CONTINUOUS-CASTING

In order to reduce center porosity of round billet in horizontal conti nuous casting, experiments of electromagnetic stirring (EMS) were carr ied out for two kinds of stainless steel containing Nb and Ti, which h ad a tendency to enhance center porosity. Combined electromagenetic st irrings in mold (M-EMS), in strand (S-EMS) and in final solidification region (F-EMS) were applied to continuous casting of 263 mm phi round billet. It has been found that the combined stirrings of M-EMS, S-EMS and F-EMS are most effective to reduce center porosity of the billet. A lack of the stirrings decreases the effect an the reduction of cent er porosity. S-EMS was proved to have the effect to disperse equiaxed crystals in the molten steel, which were formed in the mold by M-EMS a nd consequently, enable uniform packing of the equiaxed crystals in th e center of billet. F-EMS was proved to be most effective, when it was applied for the liquid core diameter of 40 mm to 80 mm. F-EMS is thou ght to have the effect to secure the fluidity of mushy zone in the cen ter of billet by the stirring of 15 Hz, but has no influence on solidi fication structure.