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Gilsonite has been extensively researched for years and many technical articles have been written about carbonaceous additives used in foundry sand
Much of this research and publication focuses on the effect of various carbonaceous materials on casting quality, gas development rate, gloss carbon, soil activity and volatile composition
The objective of this research was to compare the effect of different commonly used carbonaceous materials on the properties of foundry sand
These data were compared with available information on system sand performance with respect to properties and casting finish
Laboratory tests have been conducted to determine the effects of five commonly used carbonaceous additives in new sand mixtures
The additives evaluated were sea coal, pitch, petroleum asphalt, “coarse” gilsonite and “fine” ground and blown asphalt
The tests include evaluation of the physical properties of the new sand mix with about 1% volatile at 900°F (482
2°C) and 40% compatibility
Physical sand properties developed with non-marine carbonaceous materials were similar to or better than marine coal at significantly lower additives
Gilsonite and asphalt mixtures have been found to improve physical properties of density, water requirement and green, dry, fire and hot strength
Further improvement in sand-green, baked, and hot foundry strength has been obtained by increasing the grind fineness of gilsonite and is believed to result in better sanding with a finer material
Higher strength can cause improved sand wetting by thermoplastic asphalt materials
The gas evolution curve indicated that gilsonite and asphalt react faster than marine coal, but the total gas volume was much lower
Gilsonite in the one-third layer of sea coal and one-third of the asphalt sea coal additives had the same total volatiles A foundry study showed that gilsonite casting finishes are equivalent to sea coal and better than most other alternatives
Another study with System Sand confirmed the laboratory results of this research on new sand mixtures on sand properties and casting finish Five foundry grade carbonaceous sand additives were evaluated
They were:
a) Marine coal (ground, dust-free, bituminous coal)
b) Pitch (coal tar pitch)
c) petroleum asphalt (weathering residue from petroleum cracking towers)
D) Gilsonite (natural American asphalt)
E) Blow asphalt (air purified asphalt)
– Effect of gilsonite All mixtures containing additives required a higher water content to achieve the same compaction capacity
This would be expected as there is more surface area for coating
The moisture content of a marine coal mix will be higher than that of gilsonite or asphalt in sand because there is less ash and residue in the asphalt material – Properties of green sand The density and sample weight of the pitch and asphalt mixtures were higher than that of the marine coal mixture
This strongly indicates sand fluidity due to excellent surface lubrication
The increase in weight in the sample confirms the work of AFS Committee 80-A
These research results have been verified in foundry applications with the distinct advantage of tight casting dimensional tolerances and consistent casting loads
Brittleness is an indicator of the edge holding capacity of compacted sand
Lower values indicate greater wear resistance
Pitch and finely ground gilsonite mixtures were the lowest in brittleness, indicating improved sand adhesion due to these additives
Higher AFS fineness gilsonite provides better sand adhesion, possibly due to better binder distribution in the mixture
All other blends have lower but comparable brittleness values
– Dry properties This indicates that asphalt and gilsonite have higher thermal strength than marine coal or pitch
Finely powdered gilsonite provides the highest thermal strength of all mixtures
The high dry and baked hot energies achieved by gilsonite have been field confirmed by production of die casting molds and heavy machine tooling
It is interesting to note that, despite the low density of carbon, the thermal strength of microgilsonite is higher than that of other additives perhaps this effect is due to better wetting of silica particles by gilsonite
– Thermal power Volatile matter and loss on ignition are shown in Table VI
The 900°F (482
2°C) volatiles were comparable for all additives
Losses from combustion or combustion showed similarly comparable magnitudes for the three asphalt materials
The greatest loss occurred when sea coal and pitch mixture were ignited
This was expected since these two mixtures contain the most carbonaceous material
It is interesting to note that Mixture 1, which contains only bentonite, still had more than 0
5% loss during annealing
This verifies the presence of water crystallization in the bentonite
– Volatile, loss on ignition and gasification rate of the test mixtures Wind evolution was determined by instruments developed by H
W
Dietert Company and so designed that all interior surfaces are maintained above 110°C (230°F) so that the liberated gas volume includes water vapor
It shows that marine coal blends initially more slow gas evolution, but produce much higher gas volumes than mixtures 3, 4, 5, 6 and 7
Marine coal probably evolves gas at slightly higher temperatures than asphalt materials Pitch mix gas initially evolved slightly faster than marine coal, but the total was less than sea-coal and more than three asphalts
In mixtures 4, 5, and 7, the gas evolved slightly faster than the sea coal and pitch, but the total gas was lower
In laboratory tests, gilsonite emitted minimal fumes
Gilsonite and marine coal were compared as additives to the system sand
Unpublished data concerning recycling sand prepared with both additives over a period of 20 cycles
The composition of the sand systems used in the tests
– Composition of sand mixture Using marine coal required more tempered water to achieve compaction capacity comparable to recycling sand
This result confirms observations regarding moisture content in mixtures prepared in the laboratory
Higher marine coal levels resulted in lower permeability with similar compactness
The casting finish was evaluated in recycling sand additive tests
Gilsonite and marine coal were judged to be equal in resistance to surface faults
The penetration and sand adhesion was slightly better with the sea cabbage mixes
