Physical Modeling of Fluid Flow in Ladles of Aluminum Equipped with Impeller and Gas Purging For Degassing
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for automotive applications are commonly produced by foundry processes. The quality of the final casting depends (among other factors) on the refining stage where impurities and dissolved gases are removed from the melt. Hydrogen is without any doubt the only and the most detrimental dissolved gas affecting the physical and mechanical properties of the aluminum castings due to the porosity created in them by this gas. However, other gases such as oxygen and chlorine form compounds with aluminum such as Al2O3, other oxides, and chlorides with other alloying elements. Oxygen must be prevented to reach the liquid aluminum, and then a layer of salt fluxing is added at the top surface during degassing to prevent oxidation and formation of nonmetallic incluEUDOXIO RAMOS GO´MEZ, formerly Graduate Student in Materials Science and Engineering Department, Facultad de Quı´ mica, UNAM, Edificio ‘‘D’’, Circuito de los Institutos s/n, Cd. Universitaria, C.P. 04510, Mexico, DF, Mexico, is now Numerical Simulation Consultant with the Cavendish Mexico, DF, Mexico. ROBERTO ZENIT, Researcher, is with the Materials Research Institute UNAM, Cd. Universitaria, CARLOS GONZA´LEZ RIVERA and MARCO A. RAMI´REZ-ARGA´EZ, Professors, are with the Materials Science and Engineering at the Metallurgical Engineering Department, Facultad de Quı´ mica, UNAM, Edificio ‘‘D’’, Circuito de los Institutos s/n, Cd. Universitaria. Contact e-mail: [email protected] GERARDO TRA´PAGA, Professor, is with the Centro de Investigacio´n y de Estudios Avanzados del IPN, Unidad Quere´taro, Libramiento Norponiente 2000, Fracc. Real de Juriquilla, C.P. 76230, Quere´taro, Mexico. Manuscript submitted June 4, 2012. Article published online April 11, 2013. 974—VOLUME 44B, AUGUST 2013
sions.[1] Chlorine is no longer used in degassing the aluminum and so, inert gases such as Ar and N2 are now the preferred purging gases.[2] It is important to remove hydrogen and nonmetallic inclusions from the liquid aluminum when the casting to be produced requires the highest quality standards as in the case of automobile, aeronautic, or aerospace parts. Some of the relevant nonmetallic inclusions to be removed are Al2O3 from oxidation, Al4C3 (aluminum carbides form primary aluminum production), inclusions coming from the refractory-lining materials (C, SiO2, or CaO), or if the alloy contains Mg, magnesium oxides, or spinels (MgO, MgAl2O4). Also chlorides (MgCl2, NaCl, CaCl2, etc.), borides and fluxing salt are part of these nonmetallic inclusions to be removed from aluminum alloy baths.[3] Inert gas injection in an aluminum ladle through an impeller–injector is the most efficient technology employed in industry with the aim of refining aluminum by eliminating nonmetallic inclusions and by removing dissolved gases which are detrimental for the physical and mechanical properties of the final product. Although earlier studies by Sieverts,[4] Ransley and Neufeld[5] and Opie and Grand[6] incorporated the fundamentals to understand the degassing process of aluminum, the first mechanical device to dega
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