Influence of Applied Magnetic Field on the Cleanliness of Electroslag Ingots

Applying an external magnetic field during electroslag remelting effectively regulates ingot cleanliness. However, existing studies have mainly focused on the combination of 50 Hz AC and a transverse magnetic field, while the influence of magnetic fields on inclusion behavior under DC power remains unclear. In this study, 304 L stainless steel was used to compare the effects of transverse and axial magnetic fields on the distribution of nonmetallic inclusions under AC and DC power. The results show that the external magnetic field does not change the inclusion types or the overall size distribution dominated by fine inclusions. Under AC, a 4.5 mT transverse magnetic field eliminates coarse inclusions larger than 20 μm, while an 8.8 mT axial magnetic field provides the best comprehensive suppression. Under DC, a 0.15 mT transverse magnetic field is sufficient to remove inclusions larger than 20 μm, while a 17.6 mT axial magnetic field gives the best suppression. DC’s unidirectional constant electromagnetic force has strong refinement and dispersion effects, but when too strong it can tear the slag–metal interface and introduce coarse inclusions. AC’s alternating electromagnetic force has lower fragmentation efficiency, but may resonate at specific frequencies, causing an abnormal increase in coarse inclusions.