Process modeling gas atomization of close-coupled ring-hole nozzle for 316L stainless steel powder production*

Abstract

The paper aims at modeling and simulating the atomization process of the close-coupled ring-hole nozzle in vacuum induction gas atomization (VIGA) for metallic powder production. First of all, the primary atomization of the ring-hole nozzle is simulated by the volume of fluid (VOF) coupled large eddy simulation (LES) model. To simulate the secondary atomization process, we use the method of selecting the droplet sub-model and the VOF model. The results show that the ring-hole nozzle forms a gas recirculation zone at the bottom of the delivery tube, which is the main reason for the formation of an annular liquid film during the primary atomization. In addition, the primary atomization process of the ring-hole nozzle consists of three stages: the formation of the serrated liquid film tip, the appearance and shedding of the ligaments, and the fragmentation of ligaments. At the same time, the primary atomization mainly forms spherical droplets and long droplets, but only the long droplets can be reserved and proceed to the secondary atomization. Moreover, increasing the number of ring holes from 18 to 30, the mass median diameter (MMD, d 50) of the primary atomized droplets decreases first and then increases, which is mainly due to the change of the thickness of the melt film. Moreover, the secondary atomization of the ring-hole nozzles is mainly in bag breakup mode and multimode breakup model, and bag breakup will result in the formation of hollow powder, which can be avoided by increasing the gas velocity.

Numerical analysis of droplet breakup, cooling, and solidification during gas atomisation

“…Three primary breakup modes under different melt mass flow rates, i.e. the melt sheet mode, the hollow annular mode and the fountain mode, were summarised [14,15]. For the secondary breakup, several numerical simulations [16][17][18][19] were performed using discrete particle model (DPM) multiphase method to observe the droplet breakup behaviour and their spatial distribution in the gas flow field.…”