In order to produce cast components, which meet the quality requirements of the automotive and aerospace industries, the control of liquid metal quality prior to the casting process is essential. Rotary degassing is the most commonly used melt treatment method in the foundry industry, which can effectively reduce the inclusion and solute hydrogen content of the metal. This procedure is often combined with fluxing, which allows more efficient inclusion removal during melt processing. In this study, the effects of rotary degassing treatments executed with and without flux addition on the melt cleanliness were compared. The quality of the molten metal was characterized by the microscopic inspection of K-mold specimens, X-ray computed tomography of reduced pressure test samples, and by Density-Index evaluation. The inclusions found on the fracture surfaces of K-mold samples were analyzed with energy-dispersive X-ray spectroscopy. Based on the results, rotary degassing coupled with flux addition can be an effective inclusion and solute hydrogen removal technique that can significantly improve melt quality. On the other hand, rotary degassing executed without flux addition can increase the inclusion content of the melts. This can be attributed to the chemical reaction between the liquid alloy and the N 2 purging gas during the degassing process. It was also found that inclusion content highly influences the tendency to porosity formation.
The presence of inclusions such as oxides, carbides or refractory particles can be harmful to the mechanical and surface characteristics of castings. Inclusion-rich metals result in lower fluidity and feeding capability during casting. Nowadays, solid fluxes are widely used in foundries in order to reduce the inclusion content of aluminium melts. In this study, the effect of four different fluxes on the melt quality was studied. First, the inclusion content of the flux-treated melt, and then the properties of the fluxes (i.e. chemical composition and melting temperature) were examined.
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