Simulation of Fluid and Inclusions Dynamics during Filtration Operations of Ductile Iron Melts Using Foam Filters
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tration is a common practice throughout the world in the daily casting operations of ductile iron and other metals. It is recognized as a highly efficient method for delivering clean metals into the casting cavity. Filtration is the simplest and least costly way to capture inclusions before they reach the casting. Ceramic foam filters are widely used for this purpose, because of their demonstrated ability to reduce casting inclusions. Components made from cleaner castings have longer fatigue life and greater strength. To attain the maximum clean iron benefits of filtration, a better understanding of how inclusions are trapped or captured by a filter is necessary. If the mechanisms of filtration are more clearly understood, our ability to develop more efficient filters will be considerably enhanced. While many investigations have been conducted, most conclusions were drawn by O. DA´VILA-MALDONADO, Graduate Student, is with the Department of Metallurgy and Materials Engineering, Instituto Politecnico Nacional-ESIQIE, Mexico City, Mexico D.F., CP. 07338. A. ADAMS, Senior Engineer, is with Foseco Metallurgical, Inc., Cleveland, OH 44142. L. OLIVEIRA, Simulation Engineer, is with Foseco Industrial e Comercial Ltda., Sa˜o Paulo 05575000, Brazil. B. ALQUIST, CEO, is with Foseco Morval, Inc., Guelph, ON N1H 1C7, Canada. R.D. MORALES, Professor, is with the Department of Metallurgy and Materials Engineering, Instituto Politecnico NacionalESIQIE, Mexico City, and is President, K & E Technologies, Fdo. Amilpa And. 8 No. 7, Col. El Risco CTM, Mexico D.F., CP. 07090. Contact e-mail: [email protected] Manuscript submitted January 21, 2008. Article published online October 24, 2008. 818—VOLUME 39B, DECEMBER 2008
inference from the physical observations of the pressure drop and velocity and the application of permeability coefficients. The objective of the research presented here is to develop a three-dimensional (3-D) mathematical model based on physical modeling and mathematical simulations that will enable us to understand all of the forces, melt-flow patterns, and melt-inclusion interactions that affect the path of an inclusion as molten metal flows through a ceramic foam filter.
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LITERATURE REVIEW
During the 1980s, considerable interest in moltenmetal-filtration technologies arose. Early studies involved the use of alumina and silica-alumina systems as filter materials.[1,2] The physicochemical aspects of filtration, including the surface tension properties of the phases involved and the filter structure, were addressed by various researchers.[3–5] The application of ceramic filters to the continuous casting of steel was also proposed,[6,7] but the length of the casting cycles rendered filters useless, either because of clogging or excessive wear or both. More recently, the effects of the filter structure on priming and on the efficiency of filtration have been investigated.[8–10] These studies examined the effects of the most important forces acting on inclusions, such as buoyancy and drag. A common characteristic of all these studies and of other w
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