Impact of experimental conditions on material response during forming of steel in semi-solid state
Article dans une revue avec comité de lecture
Semi-solid forming is an effective near-net-shape forming process to produce components with complex geometry and in fewer forming steps. It benefits from the complex thixotropic behaviour of semi-solids. However, the consequences of such behaviour on the flow during thixoforming, is still neither completely characterized and nor fully understood, especially for high melting point alloys. The study described in this paper investigates thixoextrusion for C38 low carbon steel material using dies at temperatures much lower than the slug temperature. Four different process parameters were studied: the initial slug temperature, the die temperature, the ram speed and the presence of a ceramic layer at the tool/material interface. The extruded parts were found to have an exact shape and a good surface state only if the temperature was below a certain value. This critical temperature is not an intrinsic material property since its value depends on die temperature and the presence of the Ceraspray©layer. Two kinds of flow were highlighted: a homogeneous flow controlled by the behaviour of the solid skeleton characterized by a positive strain rate sensitivity, and a non homogeneous flow (macro liquid/solid phase separation) dominated by the flow of the free liquid. With decreasing ram speed, heat losses increase so that the overall consistency of the material improves, leading to apparent negative strain rate sensitivity. Finally, some ways to optimise thixoforming are proposed.
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Communication avec acteSince always, Industry minimizes manufacturing process plan and increases mechanical behaviour. In this topic, the thixoforging process offers important perspectives especially steel thixoforging. It is on the way of ...
Article dans une revue avec comité de lectureBECKER, Eric; LANGLOIS, Laurent; FAVIER, VERONIQUE; PIERRET, Jean-Christophe; CEZARD, Pierre (Springer Verlag, 2008)Since always, Industry minimizes manufacturing process plan and increases mechanical behaviour. In this topic, the thixoforging process offers important perspectives especially steel thixoforging. It is on the way of ...
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Communication avec acteBECKER, Eric; CEZARD, Pierre; MATHIEU, Stéphane; LANGLOIS, Laurent (Association Française de Mécanique, 2007)Analyse l’influence de la vitesse du coulisseau et de la température du lopin (fraction liquide) sur le comportement de l’acier à l’état semi-solide en utilisant un nouvel outillage de filage direct monté sur une presse ...
Article dans une revue avec comité de lectureThe present paper focuses the modelling and the simulation of a direct thixoextrusion test achieved on C38 semi-solid steel. To validate the modelling and the simulation, it is important to get various experimental ...