References of "Tchuindjang, Jérôme Tchoufack"
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See detailRapport Final, PROJET RECYLCLAD RW 11-1-7335 : Fabrication de Cylindres Bimétalliques par Rechargement Laser (Laser Cladding) d’Aciers à Outils optimisés sur Axes Réutilisables
Lecomte-Beckers, Jacqueline ULg; Tchuindjang, Jérôme Tchoufack ULg; Dedry, Olivier ULg et al

Report (2013)

Le présent rapport contient les résultats principaux des analyses réalisées au sein du laboratoire MMS (Métallurgie et Science des Matériaux) de l’Université de Liège, durant les deux premières années de ... [more ▼]

Le présent rapport contient les résultats principaux des analyses réalisées au sein du laboratoire MMS (Métallurgie et Science des Matériaux) de l’Université de Liège, durant les deux premières années de la recherche, à savoir la période allant du 01/12/2011 au 30/11/2013. Le service MMS est à la fois partenaire et coordinateur du projet RECYLCLAD. [less ▲]

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See detailStudy of phase transformations within bimetallic rolling mills
Neira Torres, Ingrid ULg; Lecomte-Beckers, Jacqueline ULg; Tchuindjang, Jérôme Tchoufack ULg et al

Scientific conference (2013, September 10)

With the aim of simulating the cooling behavior after a re-austenitizing stage of bimetallic rolling mills, both materials corresponding to spheroidal graphite iron (core material) and high chrome steel ... [more ▼]

With the aim of simulating the cooling behavior after a re-austenitizing stage of bimetallic rolling mills, both materials corresponding to spheroidal graphite iron (core material) and high chrome steel (shell material) must be characterized through thermo physical and mechanical tests as well as microscopic observations. Dilatometer tests were carried out for both materials in order to determinate thermo physical properties such as thermal expansion coefficient and density. Compression tests were also performed in order to estimate the effect of mechanical stress on martensite phase transformation, especially the nature and the type of martensite and start of transformation temperature. However there are some parameters that are still unknown and that are highly difficult to determinate. Inverse simulations are performed through Lagamine code with the aim of finding an estimated value for these parameters or improved parameters, more accurate than the ones already estimated. [less ▲]

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See detailPrediction of residual stresses by FE simulations on bimetallic work rolls during cooling
Neira Torres, Ingrid ULg; Gilles, Gaëtan ULg; Tchuindjang, Jérôme Tchoufack ULg et al

in Computer Methods in Materials Science (2013), 13(1), 84-91

Bimetallic rolls used in the roughing stands of the Hot Strip Mill require mixed properties as a high wear resistance for the shell material and an enhanced toughness for the core material. The bimetallic ... [more ▼]

Bimetallic rolls used in the roughing stands of the Hot Strip Mill require mixed properties as a high wear resistance for the shell material and an enhanced toughness for the core material. The bimetallic roll studied in this paper is obtained from a vertical spin casting process followed by cooling and subsequent heat treatments. Failure of the compound roll sometimes occurs during the cooling stage of the casting route or later during the thermal treatments. It requires to deeply investigate the thermo mechanical metallurgical interactions generated during cooling and heat treatment in order to find the origin of cracks. For this purpose, a thermo metallurgic mechanical finite element model is used. However these numerical simulations require a high amount of mechanical, thermal and metallurgical parameters. In order to determinate these parameters, a study of available data for estimation of mechanical parameters was performed. Thermo physical parameters were obtained by DTA and DSC methods. Metallurgical characterization by inverse numerical method based on available CCT diagrams was performed to determine the TTT diagrams. First cooling numerical simulations are presented, allowing a rough estimate of residual stresses values and the identification of key parameters for predicting accurate residual stresses by sensitivity analysis. [less ▲]

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See detailProcessing of Ti alloys by additive manufacturing: a comparison of the microstructures obtained by laser cladding, selective laser melting and electron beam melting
Reginster, Sylvie ULg; Mertens, Anne ULg; Paydas, Hakan ULg et al

in Materials Science Forum (2013), 765

Additive manufacturing processes such as laser cladding (LC) or selective laser melting (SLM) appear very promising in view of an economic near-net-shape production – and also, in the case of LC, the ... [more ▼]

Additive manufacturing processes such as laser cladding (LC) or selective laser melting (SLM) appear very promising in view of an economic near-net-shape production – and also, in the case of LC, the restoration - of complex and (almost) fully dense parts from Ti alloys. Both techniques involve the melting of a metallic powder with a laser. In the SLM process, the metallic powder is deposited layer by layer in a powder bed and then molten locally according to the desired shape, whereas in LC, the metallic powder is directly projected onto a substrate through a nozzle coaxial with the laser beam. The present research aims at comparing Ti-6Al-4V samples processed by these two techniques with reference samples produced by electron beam melting (EBM), another well established additive manufacturing process (patented by Arcam AB Company) in which a powder bed is molten locally by means of an electron beam. In all three processes, the melt pool undergoes an ultrafast cooling and solidifies very rapidly once the beam has left the area, thus giving rise to strongly out-of-equilibrium microstructures. Yet, each one of these processes also has its own specificities e.g. in terms of scanning strategy and of working atmosphere (low vacuum vs. protective Ar flow). In the present work, the microstructures obtained by these three processes have been compared in details, with a particular attention for characteristics such as porosity, grain size, and the various phases present. Since epitaxial growth of the newly deposited layer on the material previously solidified has been shown [1, 2] to exert a strong influence on the microstructure and on the resulting mechanical properties, great care has been taken to study the microstructural anisotropy associated with each one of the three processes. [less ▲]

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See detailCurrent Developments of Alloyed Steels for Hot Strip Roughing Mills : Characterization of High-Chromium Steel and Semi-High Speed Steel
Lecomte-Beckers, Jacqueline ULg; Sinnaeve, Mario; Tchuindjang, Jérôme Tchoufack ULg

in Iron and Steel Technology (2012)

Two alloys grades for work rolls used in the roughing stand of Hot Strip Mill - high chromium steel (HCS) and semi-high-speed steel (semi-HSS), In this paper, the new semi-high-speed steel grade is studied

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See detailComparison between High Chromium Steel and Semi HSS used in Hot Strip Mill Roughing Stands
Lecomte-Beckers, Jacqueline ULg; Sinnaeve, Mario; Tchuindjang, Jérôme Tchoufack ULg

in Proceedings of the 13th Southern African Roll Users Conference (SARUC 2011) (2011, October)

Two alloys grades for work rolls used in the roughing stand of Hot Strip Mill (HSM) are compared. The first grade known as High Chromium Steel (HCS) is presently the most widely used alloy for such an ... [more ▼]

Two alloys grades for work rolls used in the roughing stand of Hot Strip Mill (HSM) are compared. The first grade known as High Chromium Steel (HCS) is presently the most widely used alloy for such an application, while the second one known as semi-High Speed Steel (semi-HSS) is the new grade developed to improve the overall performance of the work roll in the roughing stands of the HSM. In the present paper, the new semi-HSS grade is studied starting from three chemical compositions closed one to another, the variation in the alloying elements is intended to assess, on one hand the effect of a small increase of the carbon content, and on the other hand the influence of the addition of a strong MC carbide forming element. The comparison of HCS and semi-HSS grades involves many fields. Regarding the metallurgical aspect, such a comparison led to the enhancement of the solidification range, the crystallization behavior and the microstructure in the as-cast condition for both grades. Furthermore, corrosion behavior and performances of the work rolls in service are compared. Various techniques are used in order to characterize both grades, such as Differential Thermal Analysis (to determine phase transformations temperatures, the crystallization behavior and the interval of solidification), hardness measurements, optical microscopy, scanning electron microscopy associated with energy dispersive X ray spectroscopy (to determine the nature and the composition of phases, especially matrix and carbides). Finally micro-macro relations between the nature of the microstructure and the properties of HCS and semi-HSS rolls grades in service conditions could be established. [less ▲]

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