Évolution de la modélisation du procédé VAR : contribution à la description de la dispersion inclusionnaire dans le puits liquide et à la prévention de défauts de solidification

Abstract : This thesis deals with the modelling of Vacuum Arc Remelting process (VAR) using the numerical software SOLAR. The first aim of the study is a better description of several physical phenomena which occur during melting, in order to extend the application of the software to simulate the remelting of steel. The evolution in the modelling of transport phenomena in the secondary ingot is based on three major improvements: - lateral thermal transfer modelling, in order to take into account the formation of a gap between the ingot and the mould walls, a possible injection of a neutral gas, and the heating of water in the coolant circuit, according to its flow, - a better turbulence model, since the k-E model implemented previously in the numerical code was not accurate enough to correctly descri~ the flow of the liquid metal in the pool, - a new method to simulate the ingot growth, based on a cyclic operation of splitting and growth/migration of control volumes, which reproduces the continuous growth of the secondary ingot and allows for the refinement of the mesh close to the free surface. Finally, the improved model has been validated by comparison with experimental results provided from four remeltings carried out on full-scale furnaces. The second objective is the characterization of the quality of the manufactured products in terms of inclusion cleanliness and risk of freckles segregated channel generation. ln order to describe the behaviour of inclusions in the liquid pool, a trajectory model, adapted to account for turbulent flows, was validated and then implemented in the code. Various particle behaviours were distinguished. A study on the risk of freckles generation led to the establishment of a criterion particularly weIl adapted to the process. A generalization of this criterion, suggested in this work, would allow the prediction of the probable orientation of such segregated channels.
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Theses
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http://docnum.univ-lorraine.fr/prive/INPL_T_2004_QUATRAVAUX_T.pdf
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Submitted on : Thursday, March 29, 2018 - 12:36:50 PM
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Thibault Quatravaux. Évolution de la modélisation du procédé VAR : contribution à la description de la dispersion inclusionnaire dans le puits liquide et à la prévention de défauts de solidification. Autre [cond-mat.other]. Institut National Polytechnique de Lorraine, 2004. Français. ⟨NNT : 2004INPL037N⟩. ⟨tel-01750058⟩

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