5th International Conference on Advances in Solidification Processes (ICASP-5) 5th International Symposium on Cutting Edge of Computer Simulation of Solidification, Casting and Refining (CSSCR-5)

The existence of oxide inclusions (e.g. Al2O3) in the steel melt is unavoidable. Most of these nonmetallic inclusions come from the steel-making process. During solidification, some of these inclusions remain in the melt and interact with melt flow and the growing crystals. The movement of solid oxide inclusions in steel melt is directly numerically simulated through coupling the solid particle moving dynamics with the Navier-Stokes equations, which are solved using a vector-valued method based on the adaptive finite element method in three dimensions. Prior to this simulation, the settling of a single spherical Nylon solid particle in water is firstly calculated and then benchmarked by the experimental measurements, which shows a very good agreement of the terminal velocity between simulations and experiments. Then settling of many particles is performed to verify the treatments of collision between particles and collision between a particle and walls. With these benchmarks and numerical tests, the liquid-particle interaction dynamics are incorporated into the phase-field model for the alloy dendritic crystal growth. The natural convection due to the solutal buoyancy is also taken into account. Two-dimensional numerical simulations of flotation of many light oxide inclusions in the interdendritic region during solidification are performed. Simulations show that when considering the inclusion flotation, the interdendritic melt convection becomes orders of magnitude stronger than that only considers the solutal buoyancy. The inclusion flotation during directional solidification not only changes the flow strength but also alters the selection process of primary dendrites. In the multiple equiaxed solidification, the large-size inclusions lead to the flow of inclusion and melt, and thereby generating a flow passage between dendritic crystals. Most of the particles flow to the top along this passage when the dendritic branches are not well developed. While the dendritic arms become sufficiently large, more and more inclusions are blocked by the dendrites near this passage.