EIGA-type electrode melting for highest-purity cast parts

S. Spitans - H. Franz - B. Sehring - S. Bogner

ALD Vacuum Technologies GmbH, Otto-von-Guericke-Platz 1, 63457 Hanau, Germany

Abstract
Electrode Induction Melting Inert Gas Atomization (EIGA) is the state-of-the-art pro- cess for high-quality spherical powder production. In the EIGA process the lower end of the vertically hanged pre-alloyed electrode is continuously fed into the region of ∼ 102 kHz electromagnetic (EM) field created by a conical coaxial induction coil located below. Induction melting takes place and a flow in a thin layer is formed at the conical tip of the electrode resulting in a metal down-stream on the axis. The application of electrode induction melting for investment casting could be exceptionally beneficial for achieving the highest cleanliness of the cast parts. However, the electrode induction melting for metallic powder production is currently a well-established technique only for relatively small melt rates (such as <2 kg/min). On top of that, the melt cannot be significantly superheated due to the small thickness of the liquid layer at the conical electrode tip and the fact that material instantly leaks out of the zone of EM heating as it turns liquid due to the gravity and pinching Lorentz forces. In the present work, we are using numerical modelling and experimental validation to demonstrate how the high-melt-rate and high-superheat electrode induction melting can be designed for investment casting applications. Figs 11, Refs 9.