Process to increase yield of fines in gas atomized metal powder using melt overpressure

摘要

A method for increasing the yield of fine and ultrafine powder from a metal or metal alloy, including such high surface tension metals and alloys as copper, Fe-based alloys, Cu-Al-Fe alloys and Ni-Cr-Fe-B-Si alloys. A pressurized stream of molten metal is atomized by a cone of impinging gas streams, the apex of the gas cone being less than 50 mm from the melt outlet and 11-24 mm from the gas orifices. The gas velocity is greater than 100 m/sec, and the mass flow ratio of melt to gas is less than 0.10. The melt stream is pressurized by introducing pressurizing gas to an overpressure zone above the melt, e.g. in a sealed crucible.