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Molding methods silver anniversary.

This year, the honor of presenting the Molding Methods and Materials Div Silver Anniversary paper was given to Richard Green, AIMCOR.

In 1964, Green had presented a classic discussion with T. Barlow, both then with International Minerals and Chemical Corp, on achieving optimum densities in high strength, high clay, green sands.

Green noted that when the first draft of the abstract was published high strength, high density sands constituted anything over 80 mold hardness, and any sand in excess of 16 psi green strength was considered unique. There were no methylene blue or compactibility tests to quantify the sand coating or density.

But these advances notwithstanding, the chemistry and physical aspects of coating sand grains and methods for achieving the optimum means of physically linking sand-grain-to-sand-grain remain relatively unchanged. Sufficient time and mechanical agitation still play an important role, but moisture/clay content does not guarantee proper bonding.

The 1964 paper reported that the addition of 1 % cereal reduced both mold hardness and density if the sand was jolted or rammed. Also, density and mold hardness increased if the cereal sands were subjected to high pressure squeeze. Therefore, cereal increased squeezeability, but reduced ramability.

New research has found that the use of a high pressure additive can increase density with less squeeze pressure. This increase in density, at the same squeeze pressure, is accomplished by increasing the lubricity of the sand and improving squeezeability. Density and permeability are interrelated. Permeability is a direct function of density because density is a direct measure of the voids between the sand grains.

Current research has confirmed, a direct relationship between permeability and density, directly relating green sand compression to clay levels as squeeze pressure increases.
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Publication:Modern Casting
Date:Jun 1, 1990
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