Removal of Inclusions from Aluminum Through Filtration

Abstract

Filtration experiments were carried out using both an AlF 3 slurry-coated and an uncoated Al 2 O 3 ceramic foam filter to study the removal of nonmetallic inclusions and impurity elements. The results showed that the 30-ppi ceramic foam filter removed up to 85 pct inclusions from aluminum. Several pictures of two-and three-dimensional morphologies of both nonmetallic and intermetallics inclusions also have been presented. The following contributing mechanisms for the removal of nonmetallic inclusions in the deep-bed filtration mode are proposed:(1) collision with walls and interception effect and (2) the formation of both intermetallic and nonmetallic inclusion bridges during filtration. Fluid dynamics modeling of inclusion attachment to the filter walls showed that most inclusions, especially those with larger sizes, are entrapped at the upper part of the filter, whereas smaller inclusions are dispersed well throughout the filter. The calculated inclusions removal fractions for the 30-ppi filter showed that almost all inclusions>125 lm are removed, and inclusions~5 lm in size are removed up to 85 pct. The interfacial energy between two collided same-size inclusions was calculated, indicating that a strong clustering of inclusions may result within the filter window. Magnesium impurities were removed up to 86 pct by the AlF 3 slurry-coated filter. The filter acted in active filtration mode in addition to the contribution of the air oxidation of dissolved [Mg], which was calculated to be 13 pct. The total mass transfer coefficient of dissolved [Mg] to the reaction interface was calculated to be 1.15 9 10 À6 m/s.

Numerical Modeling of Flow Conditions during Steel Filtration Experiments

“…[19][20][21][22][23] Acosta et al [19,20] determined the filtration efficiency for the flow of molten aluminum through CCF for the cases of short-and long-term filtration modes by perfoming numerical simulation. In order to simulate the melt flow inside the filter, they approximated the filter structure as an idealised unit cell.…”

Interaction of AlSi7Mg with Oxide Ceramics

“…[1][2][3][4][5][6][7][8] During the last years, new filtering techniques and new active filter materials have been developed to expand the range of application and to improve filter efficiency. [9][10][11][12][13][14][15] Hereby, several authors supposed an influence of the wetting behavior on the filtration efficiency. [15][16][17][18] But there are fundamental differences in determining the wettability of aluminum and its alloys by the classic sessile drop technique comparing to the wettability during real filtration terms.…”

Non‐Isothermal Simulations of Aluminum Depth Filtration

“…Davila-Maldonado et al [12] modeled the ductile iron filtration, employing a commercial FVM code, comprising a turbulence model for solving the 3D fluid flow. A similar approach was also used by Damoah and Zhang [13] in order to study the melt flow during aluminum filtration. Furthermore, Werzner et al [14,15] predicted the flow of molten metal inside an idealized filter structure employing an MRT-LBM model.…”

“…[10,11,14,15] The trajectories of inclusions are most often determined by numerically solving the equation of motion for the particles. [3,4,[8][9][10][11][12][13][14][15] In the present work, both fluid flow and heat transfer during the aluminum depth filtration are considered. In particular, the influence of local temperature variation on the fluid flow and the particle deposition due to temperature-dependent density and viscosity of the melt is investigated.…”