Influence of Filter Structure and Casting System on Filtration Efficiency in Aluminum Mold Casting

Abstract

AbstractCeramic foam filtershavebeen usedin aluminum foundries since 1974 to increase the purity of the melt. In practice, the implementation of the foam ceramic filter in the casting system is in most cases a question of space on the pattern plate. It does not follow any defined rules but is at best guided by design recommendations from the filter manufacturers. To increase the filtration efficiency, the filter position in the casting system is examined. For this, 20 and 30 ppi filters were scanned with computer tomography (CT). The data from the CT were then loaded into the simulation program Flow 3D. With this program, four different filter positions as well as the influence of the filter length and roughness of the filter surface are investigated concerning their filtration effectiveness. The simulation results are subsequently evaluated with casting trials. For this, four different molds for four different filter positions were created. The same alloy (AlSi7) was used for the trials as for the simulation. To study the behavior of particles during the filtration process, impurities were added to the melt using 3 wt.% Al2O3 - Metal Matrix Composite. After the samples were casted, the filters are cut out and the Al2O3 particles in the filter are counted for each filter position. The comparability of the casting trials and the results of the simulation have been examined.