Combined steel melt filtration through reactive and active filters

A combined filtration system was investigated for the first time in the present work. A reactive filter was immersed in a steel melt containing artificially generated endogenous inclusions. After extracting the filter, the melt was poured through a second filter and into a crucible where it cooled down. The second filter had a pure aluminum oxide flame-sprayed coating, in order to prevent reactions and only remove pre-existing inclusions. It was observed that the immersion of a reactive, coated filter generally resulted in larger inclusions. When no casting was performed, or when the second filter was omitted, smaller remaining inclusions were found. Calcium aluminate based coatings resulted in the creation of new multiphase inclusions (and less alumina). Although these results cannot be directly compared with state-of-the-art industrial filtration procedures, active filtration seems so far the most promising approach to produce steel of improved quality. In addition, filters with a calcium aluminate-based coating might be interesting in the production of steel with tailored inclusions for special applications