Electromagnetic particle separation in the cold crucible melting with novel type bottom pouring nozzle

Abstract

The cold crucible melting technique is proven to be most effective to obtain reactive metal castings and produce high quality metal powders for aerospace, automotive and medical applications. A weak point of this technology is the graphite/ceramic nozzle used to pour the molten alloy through the bottom opening, which has very limited life time (several minutes) and adds contamination to the high quality final material. The paper uses the mathematical modelling technique, previously validated on multiple similar cases, to investigate a new type of non-consumable nozzle made of copper segments. During the dynamic melting the nozzle entrance is protected by a thin solidifying layer of the same alloy as the main melt. The AC electromagnetic (EM) field effects are investigated for the possibility to extract particles (impurities, precipitates, oxides, bubbles, etc.) from the melt. The dynamics of particles are affected by the hydrodynamic drag, buoyancy, turbulent fluctuations and the EM force via the local pressure distribution. The EM force leads to high mixing rates, transitional flow structures and turbulence of the melt, contributing to the particle dispersion, transport and separation to a desired location. The paper demonstrates effects of flow on the time dependent particle 'swarm' transport and separation to the side solidified 'skull'.