5th International Conference on Advances in Solidification Processes (ICASP-5) 5th International Symposium on Cutting Edge of Computer Simulation of Solidification, Casting and Refining (CSSCR-5)

The industrial sectors of energy and transport require the development of equipment with high levels of safety and performance. These requests compel steelmakers to develop cast products with a high microstructural, chemical and mechanical homogeneity. As part of the SOFT-DEFIS project, collaboration between academic and industrials partners has been developed to optimize steel ingots quality in response to these expectations. The numerical modeling activity presented here is part of this project and aims at predicting the formation of solidification grain structures - columnar or equiaxed - and associated segregations. In addition, comparisons between simulation results and experimental analyzes of industrial ingots are planned as validation step. A finite element approach is proposed for the modeling of grain structures development [1]. A level set method is applied in order to track the columnar front interface and a dendritic growth kinetics model is used to estimate its velocity. Equiaxed grains then develop in the undercooled liquid domain. A solid, an intra-granular liquid and an extra-granular liquid phases are associated to each columnar or equiaxed microstructure with specific chemical compositions. This original approach make possible to model the evolution of solidification progress at the level of elementary volumes and the exchanges between the two types of grain structure. The conservation equations are solved using a splitting method [2]. Thus, their complexity is reduced by a sequential and time-decoupled resolution of the macroscopic transport and microscopic growth stages. Finally, at the scale of the ingot, the macrosegregation process is simulated considering the convective transport induced by buoyancy forces and the transport of equiaxed grains [3]. 1D and 2D simulation cases demonstrate the interest and efficiency of this approach. In addition, the importance to distinguish columnar and equiaxed grain structures is shown, in particular to predict the segregation processes and to improve the resolution steps. The model is applied, finally, to the scale of industrial foundry parts to predict the evolution of the developed structures and segregated zones, in comparison with the experimental analyzes of the project partners. [1] N. Leriche, Doctorat de l’Université de Lorraine, 2015 [2] M. Založnik, H. Combeau, An operator splitting scheme for coupling macroscopic transport and grain growth in a two-phase multiscale solidification model: Part I–Model and solution scheme, Comp. Mater. Sci. 48 (2010) 1-10 [3] T.T.M. Nguyen, Doctorat ParisTech, 2015