Numerical simulation of flow and temperature evolution during the initial phase of steady-state solidification

Abstract

Steady-state solidification processes have been used widely in the materials industry for the production of single crystals and metal ingots or near-net-shape products. In these processes, the formation of some macro defects such as thermal cracking, hot tearing, surface cracking, etc., has been found to initiate during the starting phase of the operation and has been affected by the fluid flow, heat transfer and solidification that are dynamically evolving during that period of time. In this paper, a numerical study of these developing fluid flow and thermal phenomena during the initial phase of steady-state solidification processes is presented. The deforming finite-element method, coupled with a mixed Eulerian-Lagrangian formulation, is used to represent the growth of metal being solidified and the accompanying dynamic fluid flow and thermal behavior. Two sets of results obtained using the algorithm are presented. The first one is concerned with the evolution of temperature and solidification phenomena during a round ingot casting process, as it evolves from the beginning of casting operation to a steady state, whilst the second one describes the fluid flow field and its effect on the temperature distribution in a metal spreading caster during the initial stage. These results show that the time-varying, complex fluid flow and thermal phenomena during continuous-casting processes can be very well represented by the computational algorithm. It is found that, for the round ingot casting, the temperature field changes drastically at the initial stage but evolves slowly afterwards. For the spreading casting process, however, the fluid flow and the thermal field are strongly coupled, and ignoring the fluid flow effect may result in substantial error in numerical predictions.