Editorial

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. Within the Collaborative Research Center 920 “Multi-functional filters for metal melt filtration – a contribution towards zero defect materials” funded by the German Research Foundation (Deutsche Forschungsgemeinschaft, DFG) at the Technische Universität Bergakademie Freiberg focuses on researching a new generation of metal qualities also during recycling 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. The present special issue focuses in a comprehensive way on selected results covering the entire chain of filtration, from the research of the filter materials, the understanding of filtration mechanisms and kinetics, the contribution of the gas phase up to the mechanical properties of the end metallic products in means of ductility, strength and fatigue. A total of 19 scientific projects with more than 30 funded researchers are working together by bridging different disciplines. A very important subject is also the qualification of the research assistants with the aim of getting a doctorate degree completed by different soft skills. On behalf of the whole team, we would like to thank all the journal editors as well as review members and invite you to share with us our results and awake your curiosity getting in touch with our CRC for fruitful discussions in this interdisciplinary scientific field. “Funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – Project-ID 169148856 – SFB 920”