Effet des procédés de mise en forme et des traitements thermiques associés sur les propriétés d'emploi et la géométrie des pièces métalliques pour l'industrie – THERMIDE

The manufacturing of metal parts through metallurgical processes generally includes, on the one hand, shaping operations (forging, rolling, drawing, spinning…), and on the other hand, thermal treatments (normalizing, austenitizing, quenching and tempering) that could be associated or not with deformation operations. There are different problems arising directly from these manufacturing processes: • uncontrolled strains with bad consequences on the geometry. Industrialists often increase the margins to overcome the problem. • Specific structures: grain size that is not adapted to some implementation or utilization characteristics, such as weldability, machinability, controllability and mechanical characteristics. This leads to the increase of the costs and of the manufacturing time due to the yield (metal scrap consumption), the finishing operations, the reprocessing and even the discard. Being able to control the appearance of strains and the grain size thus represents a highly important issue for the industrialists. The industrial objectives of the present project, presented within the «Pôle Nucléaire Bourgogne» (Burgundy's nuclear power cluster), are to reduce the costs and manufacturing time of the nuclear components, thanks to a better control of strains, grain size and structure. In order to reach those industrial objectives, the proposed action involves both industrialists and researchers in the development of physical models of strain and microstructure evolution (including recovery and recrystallization process) during the shaping operation and the thermal treatments. Faced with the complexity of a complete simulation of such techniques, a particular attention will be paid to the modelling of dynamic recrystallization process, the formulation of which stays completely open of date. To be validate and exploitable, these models will require: - experimental investigations considering in-situ conditions, - compatiblility with the finite element calculations of the shaping and thermal treatments, currently used by the industrialists to model the thermo-mechanical evolutions of the metal parts. The various applications will concern the materials used in the manufacturing of nuclear components (different grades of steels) as well as a model material (tantalum). People will be able to use that methodology later for other materials in other industrial fields, taking into consideration an efficient characterization of the material