Gas shield for atomization with reduced heat flux

Abstract

Apparatus for close coupled atomization of melts of metals having high melting points with low superheats is taught. The atomization apparatus includes means for supplying melt to be atomized at the relatively low superheat, melt guide means for guiding the melt as a stream to an atomization zone and a gas supply and means for delivering the gas as a stream to the atomization zone where both the melt supply and gas supply to the atomization zone are in very close proximity. The melt supply has an inwardly tapered lower end disposed immediately above the atomization zone. The gas supply surrounds the melt guide tube and the gas is delivered as a jet against the melt emerging from the melt guide tube. The temperature of the gas impacting the end of the melt guide tube is very low because of the gas expansion. The tendency for this gas to withdraw heat from the melt guide tube and cause a freeze-up is reduced by providing a shield for guiding the gas from the gas supply to the orifice where most of the gas expansion and cooling takes place. The gas shield contacts the melt supply tube at its lower end and conducts heat from the melt supply tube toward its upper end. The gas shield is kept very thin, and at least one groove is formed laterally in the gas shield to inhibit and reduce the flow of heat from the lower portion to the upper portion of the gas shield.