Metal Melt Filtration in a Water-Based Model System Using a Semi-automated Pilot Plant: Experimental Methods, Influencing Factors, Models

Abstract

Even though ceramic foam filters for metal melt filtration have been used in the casting industry for many decades, the filtration mechanisms have not yet been satisfactorily determined. Due to the opaqueness of the melt and the need for high operating temperatures as well as the complexity of the aluminum casting process, filtration experiments are expensive and a detailed insight into the filtration process is hardly achievable. However, the analysis by means of a model system contributes to an essential understanding of the processes taking place. Metal melt systems are characterized by their high surface tension resulting in poor wettability of the solid surfaces in contact with the liquid melt. Therefore, the model system needs to exhibit both similar flow characteristics and wetting properties as the melt system to obtain reliable results. In this study, water was used as the model liquid and the wetting properties of the solid surfaces have been modified to mimic the characteristic wetting behavior of the melt-filter interface. The influence of filter and particle properties as well as process parameters on the filtration efficiency of ceramic foam filters have been investigated. In order to minimize possible overlapping effects in the determination of individual parameters influencing the separation efficiency, care was taken to vary only one parameter, so that the filtration is only dependent on one variable. Besides water-based filtration experiments, it is also possible to have a closer look on interaction forces between inclusion particles and the filter wall and how a higher filtration efficiency can be achieved. Here, too, a water-based model system is beneficial due to the same issues of available devices and costs.