EXPERIMENTAL STUDIES ON AL2O3 INCLUSION REMOVAL FROM STEEL MELTS USING CERAMIC FILTERS

Filtration tests were made on Al-deoxidized iron melts in a 50 kg vacu um induction melting and casting unit using commercial foam, multi-hol e and loop filters. Samples from the solidified metal were prepared fo r chemical analysis and quantitative metallography. Al2O3 inclusions w ere produced by the addition of pure Al to the oxidized metal. Filtrat ion efficiencies based on the content of chemically analysed total oxy gen or oxide particle size distribution were evaluated. Filtration of pure iron melts using ceramic foam filters reaches efficiencies up to 90%. A minimum of total oxygen content around 20 to 30 ppm is attained independent from the initial oxygen content of the melt. The lowest l evels are achieved when 25 ppi foam filters are applied. Filtration te sts using 100 cpsi multi-hole filters for pure iron reveal filtration efficiencies of 80% and total removal of inclusions larger than 20 mu m in diameter. Filtration efficiencies of 72 to 84% for pure iron were obtained using ceramic loop filters of different string diameters. Fr om the evaluation of volume flow capacities and filter resistances it was evident that casting time is prolonged up to the threefold as comp ared to casting tests without integrated filters. Filtration of steel melts using ceramic foam, multi-hole or loop filters is an effective t ool. High separation efficiencies are achieved, but filtration capacit ies of the porous filter media are limited in view of large steel volu mes.