Melt Cleanliness Comparison of Chlorine Fluxing and Ar Degassing of Secondary Al-4Cu
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id metal cleanliness is one of the most important factors that influence cast part’s quality. High-quality cast parts require the melt to be subjected to several treatments prior to casting. These are mainly based on degassing and fluxing operations. Degassing is typically carried out by purging either nitrogen or argon gas through the melt in order to reduce the hydrogen content. Fluxing is the process of adding chemicals either to avoid oxide formation on the surface or to reduce inclusions in the melt. Zhou[1] used the thermodynamic and kinetic approaches to investigate the removal of inclusions from aluminum melt. Gaustad[2] has reviewed many of these in his work. Badowski[3] used LIMCA to analyze the effect of chlorine on the dross formation by comparing impeller and lance. It was concluded that dross formation increased with disturbance to the surface during degassing. Kendrick[4] used rotary degasser and MURAT C¸OLAK, Assistant Professor, is with the Engineering Faculty, Materials Science and Nanotechnology, Bayburt University, 69000 Bayburt, Turkey. Contact e-mail: [email protected] RAMAZAN KAYIKCI, Associate Professor, is with the Faculty of Technology, Metallurgical and Materials Engineering, Sakarya University, 54187, Sakarya, Turkey. DERYA DISPINAR, Associate Professor, is with the Faculty of Engineering, Metallurgical and Materials Engineering, Istanbul University, 34320, Istanbul, Turkey. Manuscript submitted July 15, 2015. Article published online July 12, 2016. METALLURGICAL AND MATERIALS TRANSACTIONS B
suggested that dross formation was lowered using vortex generation by manual addition of flux during operation (instead of injection through the lance). Liping[5] used C2Cl6 refining during rotary degassing and carried out mechanical tests and concluded that there was no significant difference between the tensile properties when C2Cl6 was used. Tenorio[6] suggested that molten flux could wrap the oxides and sediment to the bottom of the crucible. Utigard[7,8] suggested that the selection of flux needs to be made based on the purpose such as Na or Mg. Dispinar[9] has evaluated painted, anodized, and untreated aluminum foils’ recycling efficiency and found that as long as the surface oxide was not introduced into the melt (whether painted or anodized), the remaining melt always exhibits the same melt quality and mechanical properties. It was also reported by Dispinar[9] that 97 pct yield could be achieved without the need to use any chemicals. Majidi[10] looked into the temperature required for the fluxes to be efficient and found that 1013 K (740 °C) was the optimum temperature for removing oxides. Damoah[11] used Al2O3 filters and reacted them with HF gas to produce AlF3 to remove impurities. There are various tablets commercially available on the market. Among these, chlorine-based tablets used in degassing processes are known to have harmful effects on the environment and human health; thus, their use is decreasing every day. In addition, many European countries have banned the use of such chemicals. Although L
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