Carbon-Bonded Filter Materials and Filter Structures with Active and Reactive Functional Pores for Steel Melt Filtration

Abstract

AbstractThere 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. In terms of this contribution a new generation of metal qualities via melt filtration with superior mechanical properties for use in light weight structures and high demand construction materials are explored. The main target 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 a new generation of combined refining filter systems will be illustrated. 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. Another topic is dealing with carbon-bonded filter materials based on environmentally friendly binder system based on lactose and tannin. Furthermore, functional calcium aluminate coatings in combination with carbon are studied with regard to their impact on the active/reactive filtration and flotation in steel melts, respectively. Another major focus is the investigation of water-soluble filter skeleton-templates, which are produced by 3D-hybrid-printing techniques and coated by flame spraying technology. Subsequently, the filter skeleton-templates are removed in water, avoiding sharp-edged cavities inside the filter.