Removal of Iron from a Secondary Al-Si Die-Casting Alloy by Metal Melt Filtration in a Laboratory Filtration Apparatus

The influence of chemical composition and cooling rate is investigated on a secondary die-casting alloy with the aim of reduction of iron using metal melt filtration in a specially developed laboratory filtration apparatus. Based on the defined thermal conditions of the device, differential scanning calorimetry (DSC) cooling curves are determined to obtain formation temperatures of the primary iron-containing intermetallic phases (also called sludge phases) for an EN AC-AlSi9Cu3(Fe) alloy with different contents of Fe, Mn, and Cr. The DSC samples are then analyzed metallographically, and the results are compared with CalPhaD calculations. After that, the temperature of the sludge formation is adjusted using furnace-operating curves to confirm the presence of the intermetallic phases by sedimentation and filtration trials. The Fe content is reduced by about 50%, as shown by chemical analysis based on remelted materials in optical emission spectroscopy. The elements Mn and Cr decrease by approximate to 66% and 86% after filtration at 620 degrees C, respectively.