TY - JOUR
T1 - Simulation of fluid and inclusions dynamics during filtration operations of ductile iron melts using foam filters
AU - Dávila-Maldonado, O.
AU - Adams, A.
AU - Oliveira, L.
AU - Alquist, B.
AU - Morales, R. D.
N1 - Funding Information:
One of the authors (ODM) expresses his gratitude to Concejo Nacional de Ciencia y Tecnologia (CoNa-CyT) for the scholarship provided to carry out his doctoral studies at the Instituto Politecnico Nacional, Mexico City. Another author (RDM) expresses his gratitude to the institutions Sistema Nacional de Investigadores (SNI) and Comision de Fomento de Actividades Academicas (COFAA). The authors are most grateful to Foseco, Inc. (Grant No. SWIFT-1) for its support of this research and for allowing the publication of the results.
PY - 2008/12
Y1 - 2008/12
N2 - The use of ceramic foam filters in ductile iron foundries to reduce the number of inclusions that reach the casting has been widely accepted. However, the exact mechanisms contributing to foam filter effectiveness are not yet known; this limits the ability to maximize filter performance and inclusion reduction. The objective of this work is to qualify and quantify the effects of the foam filter structure on inclusion retention. This has been accomplished through the development of a three-dimensional (3-D) mathematical model, based on physical water modeling and mathematical simulations. It was found that the casting rate and inclusion density play minor roles in the capture ratio, while inclusion size is the most influent variable. One mechanism for capturing inclusions involves the direct impact of an inclusion on the web wall and its adhesion after crossing over the liquid film. Two additional mechanisms involve the entrainment of inclusions by buoyancy-lift forces into low-velocity fields and the ulterior adhesion through buoyancy effects. The second mechanism is the entrainment of inclusions into microrecirculating flows; the inclusions remain in these flows for times that exceed the mold filling time. The latter mechanism has limited intensity for inclusions approximately 30 to 100 μm in size. In order to enhance the effects of this mechanism in this range of sizes, the vorticity magnitude in the microfree shear flows in the filter's pores must be increased, through changes in the structure geometry of this device.
AB - The use of ceramic foam filters in ductile iron foundries to reduce the number of inclusions that reach the casting has been widely accepted. However, the exact mechanisms contributing to foam filter effectiveness are not yet known; this limits the ability to maximize filter performance and inclusion reduction. The objective of this work is to qualify and quantify the effects of the foam filter structure on inclusion retention. This has been accomplished through the development of a three-dimensional (3-D) mathematical model, based on physical water modeling and mathematical simulations. It was found that the casting rate and inclusion density play minor roles in the capture ratio, while inclusion size is the most influent variable. One mechanism for capturing inclusions involves the direct impact of an inclusion on the web wall and its adhesion after crossing over the liquid film. Two additional mechanisms involve the entrainment of inclusions by buoyancy-lift forces into low-velocity fields and the ulterior adhesion through buoyancy effects. The second mechanism is the entrainment of inclusions into microrecirculating flows; the inclusions remain in these flows for times that exceed the mold filling time. The latter mechanism has limited intensity for inclusions approximately 30 to 100 μm in size. In order to enhance the effects of this mechanism in this range of sizes, the vorticity magnitude in the microfree shear flows in the filter's pores must be increased, through changes in the structure geometry of this device.
UR - http://www.scopus.com/inward/record.url?scp=57349189396&partnerID=8YFLogxK
U2 - 10.1007/s11663-008-9190-2
DO - 10.1007/s11663-008-9190-2
M3 - Artículo
SN - 1073-5615
VL - 39
SP - 818
EP - 839
JO - Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science
JF - Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science
IS - 6
ER -