Numerical Simulations and Experimental Study of Liquid Metal Flow Around Sand Core

[+] Author and Article Information
Sayavur I. Bakhtiyarov

 New Mexico Institute of Mining and Technology, Mechanical Engineering Department, 122 Weir Hall, 801 Leroy Place, Socorro, NM 87801-4796

J. Fluids Eng 128(3), 541-547 (Oct 25, 2005) (7 pages) doi:10.1115/1.2175160 History: Received February 11, 2005; Revised October 25, 2005

This paper presents the results of experimental and numerical studies of the hot distortion phenomenon in the phenolic urethane cold box systems used in metal casting. Dual Pushrod Dilatometry has been used to measure a thermal expansion/contraction of phenolic urethane cold box sand core specimens at temperatures ranging from 20°C to 600°C. High temperature tensile tests showed that the tensile strength of the phenolic urethane cold box sand cores is significantly affected by the bench life, temperature and binders level. High temperature hot distortion furnace tests on cylindrical cores showed that some coatings increase the temperature limit when distortion starts, but application of coating cannot prevent distortion. The hot distortion test during metal casting showed that regardless of the application of coating, the type of coating, and anti-veining additives, all cores with density greater than the density of the molten metal (magnesium alloy) were significantly distorted. Numerical simulations of the liquid metal flow around the cylindrical sand core and analysis of dynamic forces acting on the core during the fill process showed that a buoyancy force is the major contributor to the hot distortion. It is concluded that the one of the solutions in preventing the hot distortion of sand cores is optimizing their weight, which will balance the buoyancy force and will bring the resultant force to the minimum. The hot distortion test castings using optimized sand cores with density almost equal to the density of the molten magnesium proved our predictions, and hot distortion has been prevented.

Copyright © 2006 by American Society of Mechanical Engineers
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Figure 1

Variation of thermal expansion/contraction of sand core specimens with temperature

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Figure 2

CFD model of molten metal flow past a semicircle cylinder

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Figure 3

Mold filling patterns simulated by FLOW-3D software

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Figure 4

Variation of the resultant force exerted on the core with liquid metal head

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Figure 5

Sand core specimens in the mold for hot distortion tests

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Figure 6

Magnesium hot distortion test casting

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Figure 7

Hot distortion test casting with zircon sand cores

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Figure 8

Hot distortion test casting with silica+1%SIO sand cores

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Figure 9

Hot distortion test casting with silica sand cores

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Figure 10

Effect of core gases on force balance

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Figure 11

Hot distortion test casting with silica sand cores in aluminum (above) and magnesium (below) castings



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