Parametric Investigation of Interfacial Heat Transfer and Behavior of the Melt Puddle in Planar Flow Casting Process by Numerical Simulation

摘要

The interfacial heat transfer between a rotating roller surface and a melt puddle, and the thermal and fluid-dynamical behaviors of the melt puddle play an important role in the formation of the amorphous alloy ribbon in the Planar Flow Casting (PFC) process. Several parametric studies, including the melt and the roller thermal conductivities, melt inflow temperature, rotating roller speed and melt ejection velocity have been performed to investigate their effect on interfacial heat transfer and on the behavior of the melt puddle by the solution of a conjugated fluid-solid (melt/roller) mathematical model. With the given process parameters, the theoretical interfacial heat transfer and interfacial temperature, puddle shape, velocity and temperature distribution in the melt puddle, temperature profile of the roller and thermal penetration depth underneath the puddle, and the growth and cooling characteristics of solid/liquid interface are presented and discussed. It is found that the upstream and downstream menisci are sensitive to the variations of these parameters. The casting conditions affect the profile of theoretical interfacial heat transfer coefficient and roller surface temperature. However, the flow patterns in the puddle hardly change except the size of two recircu-lation zones with stagnate flow. As a result of lower roller speed and larger melt ejection velocity, the thermal penetration depth in the roller and the thickness of the ribbon increase, and the solidification rate reduces during the later period of solidification process. The decrease of roller thermal conductivity will lead to a high roller surface temperature and a low thermal penetration depth. The melt with high thermal conductivity has a quicker growth of the solid/liquid interface. The solidification rates of the solid/liquid interface seem to also be slow near the final solidification stage with the decrease of roller thermal conductivity, and with the increase of melt inflow temperature and melt ejection velocity.