Convective Heat Transfer During Electron Beam Evaporation of Liquid Metals

摘要

Electron beam evaporation of liquid metals is aninnovative technology increasingly used in industry to producevery thin coatings of high purity. In this process the surface of ametal ingot, placed in a water-cooled copper crucible, is heatedby bombarding it with a high-energy electron beam gun. Thematerial melts, forming a free surface and eventually starting toevaporate. The rising vapor cloud condensates as a thin film ona moving substrate. The strong energy input at the free surfacegives rise to vigorous thermocapillary and buoyancy-drivenconvective motion within the melt, leading to unwelcome heatlosses. This paper aims to show how these losses can be reducedby optimizing the geometry of the crucible and by using externalmagnetic fields. We present both experimental and numerical results.