20th International Forgemasters Meeting - IFM 2017

During the solidification of large ingots, fluid flow and the sedimentation of solid grains can lead to the development of inhomogeneities in chemistry over length scales of a metre or more. This chemical segregation, referred to as macrosegregation, must be understood by manufacturers if they are to produce components that are as homogeneous as possible. This paper explores our current understanding of how macrosegregation arises in large castings, and the methods by which we can predict and track segregation. Discussions make use of the measurements made on an experimental 12-tonne steel ingot, as well as observations of small-scale experiments using the transparent NH4Cl-H2O system. Simple models, such as those utilising Rayleigh numbers, are highlighted, as well more complex simulation procedures that couple together equations for a number of different phenomena. The final section of the paper describes a state-of-the art multi-phase model and its predictions.