A MODIFIED FREE-SURFACE TREATMENT FOR THE MODELING OF PUDDLE FORMATION IN PLANAR FLOW CASTING PROCESS

The planar flow casting (PFC) process for rapid solidification of metallic materials has been in commercial use to produce thin strips of glassy or microcrystalline mateirals. The conditions of melt puddle between nozzle and rotating wheel affect significantly the quality and dimensional uniformity of the downstream ribbon. A previous study had developed a mathematical model to analyze the shape of the puddle and the momentum transfer phenomena during the formation of puddle. The model was based on a computational fluid dynamics technique, called the SOLA-VOF scheme, which possesses the capability of treating transient fluid flow problems with evolution of free boundaries. The balance between the inertia effect and the surface tension effect has to be reached for the formation of a steady puddle. The previous model, however, had employed a rather simplified treatment for the free surface boundary conditions. In this study a more accurate treatment of the free surface boundary conditions is proposed. The results show that the modified treatment results in a wider puddle and a longer time is required for the steady puddle to be formed. With the model, we also evaluate the effects of different process variables on the puddle and compare the difference of the simplified treatments with the modified treatments for the free surface boundary conditions. The results reveal that the modified treatments of the free surface boundary conditions results in a more wider melt puddle near the substrate than the puddle near the nozzle. This is more consistent to the experimental observation.