Dendritic model for macrosegregation prediction of large scale castings

• A dendritic model was used to predict macrosegregation of an industrial ingot.
• Secondary dendrite arm spacing (SDAS) plays an important role on final characteristic of segregation.
• The quasi A-segregation is mainly caused by the instability of interdendritc flow.
• Ingot size effect plays more important role than thermal conduction in the formation of the negative segregation zone under hot top.

A dendritic model with the consideration of heat transfer conservations, solute transfer conservations, melt convection, grain nucleation and growth, and the sedimentation of crystal was introduced to predict the macrosegregation of large scale casting. The model was validated by a Pb-5 wt.% Sn classic benchmark experiment and then used to predict the macrosegregation of a 3.3-ton industrial Fe-4.5 wt.% C ingot. Secondary dendrite arm spacing (SDAS) was considered in present model and SDAS was found plays an important role on liquid flow and affects final characteristic of segregation. The quasi A-segregation caused by the instability of interdendritic flow was presented in this study. A negative segregation zone under hot top was presented and the ingot size effect plays more important role than cooling conduction on the formation.