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La solidification est une étape clé pour la fabrication de la plupart des produits métalliques. Pendant la couléeou la fabrication additive, la microstructure de base pour toutes les étapes de traitement suivantes et pour lespropriétés finales du produit est formée. Les défauts et la hétérogénéité de la structure et de la compositionchimique peuvent être introduits à différentes échelles, de l'échelle des interfaces entre phases jusqu’à l'échelledu produit. La description de la genèse des microstructures, macrostructures et des défauts de solidification estrendue difficile par à la large gamme d'échelles (du micron au mètre) et par les nombreux aspects de la physiquequ’impliquent les phénomènes élémentaires. Des modèles multi-échelles sont développés pour couplerles échelles. Ce mémoire présente d’abord les travaux de recherche sur la solidification dans des procédés industrielsde coulée, en se focalisant sur les couplages entre le transport à l'échelle du procédé et la germinationet la croissance des microstructures. À travers les résultats, les limitations des modèles macroscopiques multiéchellesdans la description des phénomènes à petite échelle sont également présentées. La modélisation mésoscopiqueest développée ensuite avec l’objectif principal de l'utiliser dans une approche de changementd’échelle (upscaling) vers des modèles macroscopiques afin d'améliorer la description de la cinétique de croissancedes microstructures à l'échelle du procédé. Les premières résultats de changement d’échelle sont présentés.Finalement les projets de recherche qui se développeront dans les années à venir sont exposés.

The control of the carbon macrosegregation level in steel ingots is important for the structural integrity of the final component. Previous studies using the SOLID® multiscale modelling software have shown that in order to obtain predictive results for the macrosegregation and the grain structure (CET, grain morphology) in steel ingots, a model needs to account for fragmentation of columnar dendrites as a source of equiaxed grains. The goal of this study is to show that a numerical model that takes into account fragmentation can describe the formation of the structures and the macrosegregation during solidification of a large steel ingot. The present article describes how fragmentation is taken into account in the multiphase numerical model used in the simulations. The simulation results are compared to experimental data from a 9.8 tonne ingot cast in A5/6 steel by ArcelorMittal Industeel. The model correctly reproduces the major features of the experimentally observed structure and macrosegregation. We show that the structures are formed very early on during solidification, whereas macrosegregation develops much more gradually. Our results also underline the importance of liquid flow and grain movement in order to correctly predict the final structure and macrosegregation.

International audience

International audience

V diplomski nalogi opisujemo nadzorno enoto, ki bo vinarjem prihranila čas pri pretakanju mošta ali vina. Nadzorna enota je na eni strani sestavljena iz elektro omarice in dveh stikal –pretočnega stikala za merjejnje količine tekočine in nivojskega stikala za nadziranje vklopa in izklopa črpalke. Oboje komunicira preko kabla s platformo Arduino. Na drugi strani preko bluetooth HC-06 modula pošiljamo odčitane podatke s senzorjev na aplikacijo na telefonu, kjer lahko spremljamo količino tekočine v cisternah. Nadzorna enota je splošen model in ne velja samo za črpalko, ki smo jo uporabili pri projektu. Važno je le, da je črpalka enofazna. The graduation thesis describes a control unit that will save time for wine producers when pumping must (a wine making term which means unfermented grapes, in nonprofessional’s terms), or wine. On the one hand, the control unit is composed of an electrical box and two switches. First, a liquid flow switch for measuring the liquid level and the second, a level switch for controlling the turning on and off of the pump. Both switches communicate via cable with the Arduino platform. On the other hand, bluetooth HC-06 module sends data readings from switches into the app on the phone, where the amount of liquid in the tank is monitored. The control unit is a generic model and does not apply only to the pump, which was used in the project. It is also, of utmost importance that the pump is single-phased.

International audience

International audience; Prediction of solidification structures and defects such as grain microstructures, macrosegregations and microporosities is a key issue for industry. Models that predict these structures at the process scale need to account for couplings between various physical phenomena across several imbricated length scales. The goal of this presentation is to provide an overview of existing multiscale models and their principles, as well as of the specific algorithms needed to solve the large number of strongly coupled partial differential equations. Recent applications of these models to industrial solidification processes (casting of steel ingots, DC casting of aluminum alloys) are presented. Their ability to help in the understanding of complex phenomena, such as the competition between nucleation and growth of grains in the presence of convection of the liquid and of grain motion, is demonstrated and their predictive capabilities are discussed. Finally, the key remaining questions for future research are addressed.

International audience