Modeling of Hot Tearing and Other Defects in Casting Processes

AS COMPUTATIONAL MODELS MATURE, their practical benefit to improving casting processes is growing. Accurate calculation of fluid velocities, temperature, microstructure, and stress evolution is just the first step. Achieving tangible improvements to casting processes requires the accurate prediction of actual casting defects and product properties. Defects that form during solidification are important not only to the casting engineer but also to engineers involved in subsequent manufacturing processes and evaluation. Solidification defects are responsible for many of the defects in final manufactured products and failures in service. They originate from inclusion entrapment, segregation, shrinkage cavities, porosity, mold-wall interactions, cracks, and many other sources that are processspecific. Casting defects can be modeled by extending the results of casting simulations through postprocessing and/or by solving further coupled equations that govern these phenomena. The prediction of defect formation is made difficult by the staggering complexity of the phenomena that arise during commercial casting processes. This article introduces some of the concepts involved in modeling some of these solidification defects and focuses in more detail on hot tearing.