Journal: Transactions of the American Foundrymen's Society V 61 P 327-346, 1953 (20 p)
Author: Fischer, R B
The effect of mold materials, binders and coatings on the liberation of gas in S5-5-5-5 bronze when poured into dry sand
mold cavities was investigated. Melting methods, degassifying
and deoxidizing practices were also studied. The observations
were made on a specially designed casting and the results recorded by photograph. More than 250 test castings have been
Spherical type macro-gas porosity has been observed on 85-5-5-5
bronze poured into oil bonded silica sand molds. Gassing is the
result of a metal-mold reaction or direct absorption of gas which
is liberated upon solidification of the metal.
Many commercial sand binders were tested. Ounce metal
poured in pitch-bonded molds showed no spherical type macroporosity.
Cement bonded and natural sand molds produced
castings practically free of the macro-gas porosity. Molds made
with phenolic, urea, wood resins, etc., gassed ounce metal to
various degrees of intensity. Graphite coatings containing pitch
and a special coating containing zircon filler in a resin-volatile
solvent vehicle inhibited or reduced the gas porosity. These
coatings gave poorer casting surfaces.
Lithium was found to be an effective degassifier but was characterized by higher metal shrinkage. Deoxidizers were tested
and their relation to shrinkage is shown on a special test cast
ing. Metal composition also influences macro gas-porosity.
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