Journal: Transactions of the American Foundrymen's Society V 67 P 553-576, 1959 (24 p)
Author: Cowles, R J
The difficulty of poor collapsibility, predominate
as a limitation in the sodium silicate-C02 method of
sand bonding, is obviated by establishing simple laboratory test methods to determine an optimum quantity
of sodium silicate binder. This is designated as the
minimum critical percentage for each sand considered.
Additives such as sugar, coarse grain silica flour and
iron oxide, properly used, contribute to the flowability,
ramming qualities and green strength and enhance collapsibility as well as provide hot strength and cushion
ing during thermal changes.
The binder requirements should be developed on the
hypothesis of adhesive bonding rather than on the
basis of a mortar composition, which fills voids between
the grains. Adhesive binders are most effective in thin
films and with the greatest number of sand grain to
grain adhesive contacts uniformly distributed in the
sand structure. The viscosity and penetrating qualities
of the binder composition determine the degree of correlation that binder requirements have to B.E.T.
specific area measurements.
The B.E.T. data can be used to designate those sands
which will need more or less binder than their AFS
fineness number indicates. A straight line correlation
between minimum critical percentage and a dimension
al parameter calculated from AFS fineness data, shape
factors, ratio multipliers and specific volume ratios
raised to the fourth power is given.
The limitations due to high relative humidity and the
use of clay additives are discussed. Experimental data,
as well as numerous references, are used to support
$15.00 for members
$10.00 for corporate members
$30.00 for nonmembers
1695 North Penny Lane
Schaumburg, IL 60173
Tel: 800.537.4237, 847.824.0181