Modeling of solidification of molten metal droplet during atomization

Abstract

A mathematical model to describe the solidification behavior of an atomized droplet during flight, in terms of nucleation temperature, recalescence temperature, nucleation position, solid fraction at nucleation temperature, and droplet temperature and velocity, is formulated. The concept of transient nucleation is applied to model the short nucleation event. A maximum droplet velocity exists, beyond which the droplet velocity shows an inflection phenomenon during the flight. The velocity of smaller droplets is higher at a shorter flight distance and lower at a longer flight distance. Variations of the gas flow patterns have more effects on smaller droplets, and the effects are more significant at a longer flight distance. A minimum surface heat-transfer coefficient exists as the droplet flies. Prior to nucleation or recalescence, smaller droplets have lower temperature at a given flight distance. Smaller droplets have lower nucleation temperature. Medium-size (around 80-µm) droplets fly over the shortest flight distance before the nucleation starts. Smaller droplets have a larger solid fraction at the end of recalescence. Atomization gas has more effects on the droplet momentum than on the heat content of the droplet.