Modelling of Inclusion Effects on Macrosegregation in Solidifying Steel Ingot with a Multi-phase Approach

Abstract

A multi-phase dendritic solidification model coupled with Euler–Lagrange framework has been established to characterize the effect of inclusions on macrosegregation in steel ingots. The present model includes many important solidification phenomena such as columnar growth, nucleation, growth of equiaxed and dendritic structure of equiaxed crystals, crystal sedimentation, and melt thermal-solutal convection. A dense discrete phase is employed to simulate the motion of the inclusions and their interaction with fluid flow. Fractal theory is applied to consider the morphology of the inclusion clusters. Based on this model, the effects of the inclusion size and cluster morphology have been investigated for the solidification of a 55-ton industrial Fe-0.33 wt pct C ingot. The results show that inclusions around 15 to 20 μm enhance the macrosegregation significantly, while neither small (i.e. 5 μm) nor large (i.e. 30 μm) inclusions have any obvious influence on the macrosegregation. It’s shown how the compactness of the inclusion cluster plays a dominant role in macrosegregation. The mechanism of how the inclusions affect macrosegregation is also discussed. This study provides valuable information for the control of casting defects caused by inclusions.