20th International Forgemasters Meeting - IFM 2017

A non-neglecting percentage of the final quality of forged pieces is originally depending on the ingot parts from which they are made. It is well known that the ingot defects like hot tears or cracks are rooted at the first beginning of the solid shell birth. Damages result from the competition between hydrostatic pressure within the turbulent flow of the liquid zone and the solidifying skin under tensile stresses and strains state. In addition, the thermal energy extracted from the cast product by the mold has huge impact of the thickness of the shell. Among other parameters, it depends on the air gap growth issued from the shrinkage of the solidifying metal together with the deformation of the mold components. Numerically speaking, the method able at taking all that complex and coupled phenomena into account through an accurate way is a fluid/structure model. Indeed, a standard CFD method does not represent the solid behavior, so that the stresses, strains, air gap evolution due to the shrinkage of the shell are not reachable. In that paper, a new 3D fluid/structure model involving the turbulent fluid flow and the solid constitutive equation is described. The management of the dedicated “liquid time step” allowing high velocity motion into the liquid phase of the alloy coupled with the “solid time step” dealing with the solid phase and the corresponding slow motion, is described. An application on an ingot casting process considering the coupling with the deformation of the mold is presented. Moreover, based on that model, the segregation within the ingot is tracked. Grain structure resulting from a CAFE method coupled with the cooling of the ingot is also performed and shown. In addition, the top powder is accounted as deformable body following the shrinkage of the top surface of the ingot. The exothermic reaction is considered as well in order to estimate its impact on the cooling time and the final quality of the cast product. This one can be therefore transferred to a forging code for a complete simulation of the fabrication of the forged piece.