SFB 920: Multifunctional Filters for Metal Melt Filtration - a Contribution to Zero Defect Materials

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There exists an increasing pressure on the metal making and metal using industry to remove solid and liquid inclusions such as deoxidation products, sulfides, nitrides carbides etc. and thereby improve metal cleanliness. It is well known that size, type and distribution of non-metallic inclusions in metal exert considerable effects on the mechanical properties of the cast products. The vision of this collaborative research centre is to create a new generation of metal qualities via melt filtration with superior mechanical properties for use in light weight structures and high demand construction materials. The aim of the collaborative research centre is an enormous reduction of non metallic inclusions in the metal matrix by the use of intelligent filter materials as well as filter systems with a functionalized filter surface. Especially in the third period a new generation of combined refining filter systems will be the focus. The metal melt comes first in contact with a reactive filter which generates gas bubbles in the melt as well as activates gas bubbles on the surface of the inclusions. As a result a kind of flotation of the inclusions towards the slag on the surface of the melt takes place. Further the high reactivity as well as the gas bubbles contribute to the agglomeration of the fine inclusions to big clusters which flow due to buoyancy forces to the surface of the melt or are filtrated on the surface of active filters, which do not form gas bubbles but provide on their functionalized surfaces the same chemistry as the inclusions for a sufficient adhesion and as a result for a sufficient filtration of the inclusions. With this approach a purification higher than 95 % can be achieved. The modelling is focusing mainly on the several contributions of the gas bubbles and on the in situ formed reactive layers on the surface of the reactive filters as well as they generate codes with respect to the thermomechanical and functional properties of the filters for a 3D-printing of filter structures which are then end shaped with the aid of a robot-assisted flame spraying technique. The flow dynamic conditions in the filter during casting are of great importance for the proper design of the filter macrostructure. A material as well as a flow computer aided micro- and macrostructure filter design based on investigated filtration mechanisms will lead to high purification efficiencies with superior properties – strength, fracture toughness, fatigue- of the cast steel, iron, aluminum and magnesium components. In addition other applications such as the electronic industry via filtration of copper or the thin aluminum foil production will profit from the scientific results. The target for a higher material efficiency and reduction of energy and CO2-emissions is coming closer in the near future.