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GILSONITE IN FOUNDRY
Gilsonite is combined with coal and other ingredients as an additive in foundry sands to insure the quality of the molded part. The lower gas evolution should reduce ventilation load on the pouring floor. The physical property relationships developed in new sand mixes were confirmed by sand using Gilsonite as an additive. Casting finish of a Gilsonite mix has been equal to sea coal.
Gilsonite is also used as a carbonated additive in casting sands that creates smoother plates on gray iron castings. In a lower temperature than coal, it makes the material volatile so that it improves the process of separating the metal from the mold. Moreover, the surface of the mold is smoother and cleaner. Gilsonite can be used as an additive to or a replacement to sea coal or other common carbonated additives in foundry. One of the great advantages of using Gilsonite on sand mold is increasing the hot resistance, increasing the pure (dry) resistance, decreasing the penetration and increasing the hardness of the mold. Physical Sand properties with Gilsonite resin are equal or superior to sea coal at significantly lower additive levels. Gilsonite improves sand density, water requirements and strength (green, dry, baked, and hot). Gas evolution curves show that Gilsonite volatilizes more rapidly than sea coal. Gilsonite has the same total volatiles as sea coal at one-third the additive level.
During pouring, the gases given off from the carbonaceous additives form a gaseous film which prevents the molten metal from making direct contact with the clay-coated sand grains, reducing sand-metal contact and consequently burn-on. When heated, the carbonaceous materials provide volatile, hydrocarbon gases which then pyrolyse to deposit a lustrous carbon graphitic layer in the metal-mold interface region. This deposition acts as a physical barrier to iron silicate formation as well as not being readily wetted by molten iron. The combination effect is to inhibit burn-on and penetration.
Reduce imperfections due to the rapid reactions
Improve sand peel from casting at shakeout
Produce smoother, cleaner casting surface
Minimize imperfections, casting losses, scrap
Three times as much gas generated as sea coal for better mold release
High lustrous carbon for better finish
Reductive atmosphere for less reaction between mold & casting
for fewer imperfections
Gilsonite can be used as an additive for Foundry or Casting sands. It significantly increases the resistance and hardness of the mold and improves the quality of the surface.