Influencing the Hydrogen Porosity in Aluminum Casting by (Re)active Filter Materials

Nonmetallic inclusions and pores are the most common sources of aluminum casting defects. For this reason, great importance is attached to cleaning the aluminum melts, especially in secondary metallurgy. Herein, the results of several experiments in which innovative filter materials are tested with regard to their influence on hydrogen porosity in castings made of an AlCu4Ti alloy are presented. Reactive filter materials based on spodumene (LiAl(Si₂O₆)) are applied and compared with conventional ceramic foam filters made of alumina and new active carbon‐bonded alumina filters. It is found that spodumene has two different functions. On the one hand, the use of a spodumene‐containing filter material promotes the formation of gaseous hydrogen and, on the other hand, it can be assumed that some of the hydrogen is bound within the filter. Above phenomena are dependent on the reactivity of the filter coating. Therefore, spodumene in appropriate amounts can contribute to a reduction of porosity in the casting.