Shape Factor Effect on Inclusion Sedimentation in Aluminum Melts

Abstract

The quality requirements of aluminum products are steadily increasing, and the presence of non-metallic inclusions have a large impact on the quality of aluminum products. Sedimentation is a widely applied technique to remove inclusions and the settling characteristic of particles is one of the most important parameters determining the removal efficiency. The settling characteristics can be modeled analytically through different approaches. A comparison of settling according to the Stokes and Schiller and Naumann drag force formulations was investigated and showed that Stokes drag is relevant for inclusions in aluminum melts. The settling of particles is analytically and experimentally investigated in this study by using a shape factor “K” based on Stokes law and online particle tracking by LiMCA (Liquid Metal Cleanliness Analyzer), respectively. The effect of the shape factor on settling velocities was observed clearly and the measured data show considerably slower settling than traditional models, indicating the effect of melt flow due to thermal convection.