Numerical Simulation of White Spot Formation in Vacuum Arc Remelting

Coupling fluid flow, heat transfer, solidification, and particle dissolution behavior, the white spot formation in the vacuum arc remelting process is simulated. The effect of particle initial diameter, dropping position, and dropping height on the remelting behavior is investigated. The results show that the particle from the electrode drops through the arc zone with gravity force and the diameter is reduced in the high-temperature zone. As the diameter is lower than 5 mm, the particle completely dissolves and the white spot formation can be eliminated. The particle dissolution is less affected by the liquid pool depth, but it is mainly affected by the high-temperature zone distribution, which is closely related to the electric arc generation. Because of the limited high-temperature zone near the ingot side surface, the particle from the ingot crown is more difficult to remelt, compared with that from the electrode. Moreover, it is found that the dropping height obviously affects the particle remelting behavior. As the dropping height decreases from 25 to 0, the particle critical diameter that can fully dissolve increases from 4.2 to 6.6 mm.