Carbon‐Bonded Alumina Spaghetti Filters by Alginate‐Based Robo Gel Casting

Abstract

Metal melt filtration has become very popular over the past decades as it provides the possibility of removing nonmetallic inclusions from metal melts and reduces the amount of flow turbulence during mold filling. However, especially, the filtration of steel melts is associated with particularly harsh conditions which might require special filter solutions regarding increased strength and specified flow path. Herein, a novel approach for the manufacturing of cellular ceramic materials is investigated. Thereby, a slurry containing alginate is pumped into an aqueous solution containing Ca 2+ or Ba 2+ ions. The natural capability of the alginate for gelation leads to the in situ stiffening of the slurry in contact with the cross‐linking solution. Periodic strut patterns can be realized by moving the nozzle with the aid of a computer‐assisted robotic system. The influence of sodium alginate and solid content on the slurry rheology and the process parameters is analyzed based on a fixed carbon‐bonded alumina composition. Furthermore, alternative combinations of alginate types and alkaline earth sources are tested on their suitability for gel casting and their influence on the residual carbon content after pyrolysis. A suitable filter is successfully applied in steel melt immersion tests.