Arc distribution as a key driver of inclusion redistribution in Vacuum Arc Remelting (VAR)

A transient numerical model is developed to investigate inclusion transport and entrapment during full ingot growth in the Vacuum Arc Remelting (VAR) of the nickel-based superalloy GH4720Li. The model resolves the coupled electromagnetic field, melt-pool flow, solidification, and Lagrangian inclusion motion, enabling a quantitative assessment of arc behavior and inclusion entry conditions. Parametric studies show that increasing side arcing, whereby a portion of the electric current passes through the crown and along the lateral wall of the electrode toward the mold, produces a shallower melt-pool profile, weakens outward inclusion transport, and shifts inclusion entrapment away from the ingot sidewall toward the ingot interior. A constricted arc distribution, which produces a deeper and narrower melt pool, modifies the flow structure and enhances inward-directed transport, thereby reducing peripheral accumulation and promoting a more radially distributed inclusion pattern. Drip-short events, defined as the formation of molten metal bridges between the electrode and the ingot, introduce inclusions at greater depths, leading to a more distributed entrapment pattern throughout the melt pool. Model predictions are validated against experimental observations, providing quantitative guidance for improving ingot cleanliness.