Abstract
If high-performance aluminium castings are to be produced, the melt quality needs to be properly assured. Multiple tests for melt quality assessment exist and have previously been analysed. In most studies, the techniques were used separately. In this work, reduced pressure, fluidity, Prefil and tensile tests were evaluated. A commercial EN 46000 alloy was used as the base material with additions of 25 and 50 wt% machining chips to degrade the melt quality. In reduced pressure and fluidity tests, oxides floated to the top of samples, decreasing the reliability. Bifilm index increased with addition level, but not correspondingly. Density index, Prefil and fluidity tests did not present significant variations, and tensile properties only deteriorated with the 50 wt% addition level. The investigated techniques provided information, but measuring the melt quality reliably remains a challenge.
Highlights
One of the challenges that the aluminium casting industry faces today is related to the reduction in the variation in mechanical properties and to ensuring the quality of castings
From the reduced pressure test (RPT), it was observed that the density index (DI) did not change significantly, and the scatter only increased for the L25 condition
According to the melt cleanliness (MC) number ranges given by the Pressure filtration (Prefil) service provider,[13] all three melts would be considered ‘‘clean’’ in an industrial environment
Summary
One of the challenges that the aluminium casting industry faces today is related to the reduction in the variation in mechanical properties and to ensuring the quality of castings. The presence of inclusions such as oxides (i.e. bifilms, spinel), carbides or refractory particles can be harmful to mechanical, physical and surface characteristics.[1] Over the past years, multiple tools have been proposed for assessing the melt quality. Some of these tools include reduced pressure test (RPT), fluidity tests, Porous Disc Filtration Apparatus (PoDFA)/Pressure filtration (Prefil).[2]. The bifilm index (BI) introduced by Dispinar and Campbell[3] is the sum of the maximum length of the pores in a cross section of a sample solidified under reduced pressure.
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