Claudia Voigt

Effect of the Filter Surface Chemistry on the Filtration of Aluminum

The influence of the filter surface chemistry of alumina skeletons on the filtration effect was tested with five different oxide coating materials (Al2O3, spinel, mullite, TiO2, and SiO2). All prepared filters were casted successfully under industrial conditions. The casted aluminum samples showed no contamination caused by the filters. The evaluation of the casted filters by means of SEM and EDX showed that the amount of inclusions in the area of the run in is larger than in the middle and the run out of the filter. The most non-metallic inclusions were found in the casted filters Al2O3+Al2O3 and Al2O3+spinel. The wetting experiments yielded for all tested materials a non-wetting behavior whereby Al2O3 and spinel showed higher wetting angle than mullite, TiO2, and SiO2.

Assessment of Active Filters for High Quality Aluminium Cast Products

The quality requirements of aluminium products are constantly increasing. It is critical that ingots and billets have the least amount of inclusions in the as-cast product. Filtration is therefore applied to all critical products, ceramic foam filtration (CFF) being the most frequently used technique. In an attempt to increase inclusion capture by CFF the influence of the filter surface chemistry on the filtration efficiency of aluminium alloys has been evaluated. Lab scale filters have been produced with coatings of different chemical composition. The filters have been characterized prior to usage and lab scale casts have been made on a pilot unit in conjunction with two LiMCA for inclusion removal efficiency determination. The paper will present the results from the characterization done and the observations will be discussed.