Impact of experimental conditions on material response during forming of steel in semi-solid state

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

Influence de la vitesse de mise en forme et du cycle de chauffe sur le thixoforgeage des aciers

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 hydraulique. Cette nouvelle conception évite la décélération du vérin rapide pendant la mise en forme. Il permet donc des essais à vitesse constante. Ce travail s’intéresse également à l’écoulement de la matière dans le cas du thixoforgeage de l’acier et montre l’importance d’un couplage entre la température initiale et la vitesse de déformation. Les différentes conditions permettant d’avoir un écoulement homogène et continu, avec un effort de mise en forme faible, sont étudiées et présentées.This paper analyses the influence of two parameters (tool axis speed and billet temperature) on semi-solid steel alloy behaviour. A new design of direct filling tool is proposed and adapted on hydraulic press. This concept avoids the speed decrease during forming process. This works shows thermal exchange influence in thixoforging process in function speed raw and initial temperature inside the billet by analysis forming loads and part geometries

Impact of experimental conditions on material response during forming of steel in semi-solid state

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

Influence de la vitesse de mise en forme et du cycle de chauffe sur le thixoforgeage des aciers

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 hydraulique. Cette nouvelle conception évite la décélération du vérin rapide pendant la mise en forme. Il permet donc des essais à vitesse constante. Ce travail s’intéresse également à l’écoulement de la matière dans le cas du thixoforgeage de l’acier et montre l’importance d’un couplage entre la température initiale et la vitesse de déformation. Les différentes conditions permettant d’avoir un écoulement homogène et continu, avec un effort de mise en forme faible, sont étudiées et présentées.This paper analyses the influence of two parameters (tool axis speed and billet temperature) on semi-solid steel alloy behaviour. A new design of direct filling tool is proposed and adapted on hydraulic press. This concept avoids the speed decrease during forming process. This works shows thermal exchange influence in thixoforging process in function speed raw and initial temperature inside the billet by analysis forming loads and part geometries

Journal des Savants, 1957

Cézard Pierre. Journal des Savants, 1957. In: Romania, tome 79 n°316, 1958. pp. 545-546

Le Moyen Age, LX (4e série, t. IX), 1954

Cézard Pierre. Le Moyen Age, LX (4e série, t. IX), 1954. In: Romania, tome 76 n°302, 1955. pp. 275-276

Le Moyen Age, LXVI, 1960 (4e série, t. XV), 1-2

Cézard Pierre. Le Moyen Age, LXVI, 1960 (4e série, t. XV), 1-2. In: Romania, tome 84 n°335, 1963. pp. 418-421

Le Moyen Âge, LXVII, (4e série, t. XVI), 1961, 1-2

Cézard Pierre. Le Moyen Âge, LXVII, (4e série, t. XVI), 1961, 1-2. In: Romania, tome 85 n°337, 1964. pp. 135-137

Annuaire d'Histoire liégeoise (Commission communale de l'histoire de l'ancien pays de Liège), t. IV, i (1948)

Cézard Pierre. Annuaire d'Histoire liégeoise (Commission communale de l'histoire de l'ancien pays de Liège), t. IV, i (1948). In: Romania, tome 74 n°294, 1953. pp. 254-255

Le Moyen Age, LXXV (4e série, t. XXIV), 1969, 1

Cézard Pierre. Le Moyen Age, LXXV (4e série, t. XXIV), 1969, 1. In: Romania, tome 93 n°371, 1972. pp. 419-420