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Some steels are severely affected by hot tear. The industrial stakes in terms of quality and productivity are large. But predicting the associated internal and surface defects remains out of reach, forestalling a rational optimization of the processes, for two essential reasons: (1) In the casting of ingots, the phenomenon occurs during filling, in a stage where no simulation software is capable of providing a correct stress condition. (2) The phenomenon is still poorly understood and the various criteria proposed hitherto are inadequate. In consequence, four major objectives are defined to make possible the complete and predictive simulation of these processes: (3) Advance our knowledge of the various physical phenomena involved, relying on numerical simulation on small scales (solidification microstructure) so as to specify the nature of the macroscopic fracture criteria. (4) Set in place a methodology of identification of the rheological parameters of selected steels, along with parameters of fracture criteria, using an extensive array of instrumented tests. (5) Extend the capabilities of numerical simulation by modelling the fluidstructure coupling in the solidification condition, to predict a pertinent thermomechanical state during filling. (6) Develop a process improvement methodology using this enriched numerical simulation. CTIF is contributing to the following work: (1) Development of a hot tearing specimen and instrumented melts; (2) Simulations of the melts - Modelling; (3) Validation of the hot tearing criteria in Thercast. This study is part of the Agence Nationale de la Recherche-funded CRACRACKS project (Concerted Research for Analysis of CRACK phenomena during Solidification of steels, Projet ANR-07-MAPR-0008).