Initial Flow Analysis in Crucible-Nozzle During Planar Flow Melt Spinning Process

Abstract

Planar flow melt spinning is a one-step casting process to produce amorphous ribbons. The process involves ejection of molten metal from the crucible through a slit nozzle on to a rotating cooling wheel by gas pressure. Initial non-uniform flow through the nozzle blocks the flow passage, leading to casting failure. Fully developed flow is required to obtain a uniform flow rate at the exit of the nozzle slit. This requires the accurate design of the lower portion of the crucible-nozzle. Manufacturing of the crucible with various designs and experimentation with the modified nozzle consumes time and cost. Hence a numerical model is developed to investigate the flow patterns in the crucible-nozzle for few designs. The volume of fluid technique with fluid-structure interaction has been employed along with conservation equations and temperature dependent viscosity equation. Molten metal flow in a straight or curved nozzle wall with straight slit edge, straight nozzle wall with chamfered slit edges and with no-slit passage have been simulated and compared. Nozzle with straight wall and no slit passage shows better flow patterns and fully developed flow is attained within 4 milliseconds. Temperature is more uniform in the flow passage and melt pressure is higher than the atmospheric pressure, recommends the nozzle with no slit passage. The model can be used for any material-nozzle design combinations employed in the planar flow melt spinning process to predict the flow through the slit passage. The model can also be used for 278simulation of flow in an extruder die in polymer processing to study the effect of sudden contraction of the reservoir with a large diameter to exit passage of smaller diameter like tube or orifice.