Selective Migration of Multi‐Type Inclusions in Rare Earth Steel Through Geometric Matching of Pulsed Electric Current Frequency

Rare earth elements modify inclusions but generate fine particles that cause blockage of continuous casting nozzles. While pulsed electric current drives inclusions migration, the mechanism by which frequency modulates current distribution remains unclear. This study investigated inclusions migration in GCr15 rare earth steel (0–50 000 Hz) via experiments and simulations. Results reveal a non‐linear frequency‐efficiency relationship. An optimal frequency of 5000 Hz achieved a 62.17% removal rate by driving inclusions away from the electrode. Mechanistically, the non‐uniform current field amplifies the current density difference across inclusions by 19.3 times compared to uniform current field. Consequently, there are significant differences in the migration behavior of different types of inclusions, which are positively correlated with differences in inclusion size, electrical conductivity, and projection area perpendicular to the electric current. Specifically, the migration rates show the following order: silicates > rare earth oxides > rare earth oxysulfides > manganese sulfide > simple oxides. Crucially, a geometric matching criterion is proposed: when the width of frequency‐induced current density enrichment zone matches the geometric characteristic dimension of the melt, the purification efficiency reaches its maximum value. These findings offer a theoretical strategy for selecting frequency parameters based on melt geometry for deep purification.