Aluminium Filtration by Bonded Particle Filters

Non-metallic inclusions such as oxides, borides and carbides in aluminium melts are a major cause of product failure during both processing and use. To remove these inclusions, molten aluminium is usually filtered through a mechanical filter such as deep bed-filter, ceramic foam filter or Bonded Particle Filter (BPF). In this study three BPF from Pyrotek have been tested at Hydro’s reference centre in Sunndalsora. The filters had different grit sizes; 6, 10, and 14 (equivalent to 30, 50, and 70 ppi). The filters were mounted in the patent pending Drain Free filter box developed by Hycast. LiMCA was used at the up-stream side of the two coarsest filter (Grit 6 and 10) and both up-stream and down-stream for the finest filter (Grit 14). Three samples from each of the filters have been studied in a light microscope, and inclusions have been counted using image analysis. In addition, PoDFA samples from the test with the finest filter were also analysed and discussed.