Comportement mécanique d'un acier C-Mn lors du laminage intercritique

Abstract : In order to predict the mechanical behaviour of steel during intercritical rolling, we need to know the mechanical behaviour of both phases in the intercritical conditions (i.e. ferrite and austenite), to have an accurate description of the phase transformation, and to use a homogenisation model. A finite element homogenisation method has been developed, using Voronoï cells to describe a two-phase metal, and a procedure has been developed in order to fit an existing mesh on the Voronoï polyhedrons. The numerical, mechanical and statistical conditions needed to get reliable results have been determined. By comparing these results with semi-analytical models, the self-consistent model using the Suquet extension to non-linear behaviour has been selected. As the maximum strain in a compression test is much smaller than in industrial conditions, we need to determine the most relevant part of the thermomechanical path from the mechanical behaviour point of view. An austenitising treatment at 1200°C leads to a mechanical behaviour with no strain-hardening for ferrite, which is supposed to be the case in the industrial conditions. An austenitising treatment at such temperature is also needed to impede recrystallisation of austenite at the finishing rolling mill (temperature below 900°C), where the intercritical rolling is performed. It is shown that the deformation at the roughing mill has almost no effect on the mechanical behaviour on the finishing rolling mill. The phase transformation kinetics were also studied, highlighting the effect of strain below the no recrystallisation temperature. However, the analysis of tests carried out on a plasto-dilatometer is shown to be very difficult. The modelled mechanical behaviour has been compared with experimental results of compression tests and rolling trials. The correspondence between experimental and model results is satisfactory.
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  • HAL Id : tel-00443808, version 1

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Philippe Thibaux. Comportement mécanique d'un acier C-Mn lors du laminage intercritique. Mécanique [physics.med-ph]. École Nationale Supérieure des Mines de Paris, 2001. Français. ⟨NNT : 2001ENMP1097⟩. ⟨tel-00443808⟩

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