Modeling of the formation of microporosity in alloys.

摘要

A complete mathematical model, consisting of a continuum model and a gas evolution model, was established for the prediction of shrinkage- and gas-caused porosity in castings. The model allows simultaneous calculation of transient temperature, velocity, pressure, and porosity distributions in a solidifying casting. Fluid flow caused by both natural convection and solidification contraction, as well as change of global domain due to shrinkage, were considered. A parametric study was performed to investigate the effects of various solidification variables in the formation of microporosity, including the use of chilling, initial gas content, characteristics of heat transfer between the casting and the mold, casting size, and riser height. It was found that a low initial gas content in the molten metal and casting conditions that facilitate solidification-rate decrease the formation of microporosity. The calculated porosity distribution in 1% Cr-steel alloys compares favorably with published experimental data.