Foundries consistently depend on high-quality Georgia-Pacific metal casting plaster for their casting and match plate needs. Produced from some of the world's purest gypsum, our industrial gypsum plaster is manufactured from exceptional raw materials, up to 99%+ pure, in carefully controlled conditions. The result is a metal casting plaster that can be consistently relied on for the highest levels of integrity.An Exemplary Product Sure to Fit Your NeedsTo satisfy a wide range of customer requirements, we offer a variety of superior calcined gypsum formulations. If, however, one of our standard blends does not meet your exact specifications, we will gladly customize a gypsum formulation especially blended to supply the performance characteristics you require.For more information, contact us today at 1-800-695-6367, or find a sales contact in your area.
From auto parts to scores of other products, much of our modern way of life rides on the ability of gypsum to produce a superior medium for casting metal. Components of aluminum, copper and brass prove it. So do products made of aluminum bronze, magnesium bronze, silicone bronze, nickel aluminum bronze and aluminum alloy.
Foundry shops can gain significant benefits from the inherent qualities found in this company's industrial plasters. Ease of handling and excellent uniformity are key attributes. In addition our industrial plasters have reliable retention characteristics that relentlessly preserve fine details in set plasters.
For all of these reasons, Georgia-Pacific metal casting plasters are the first choice in a variety of applications. They are regularly used for model and pattern making. In addition, they are important to the production of match plates, core and drag plates, as well as loose patterns and core boxes. Our plasters ensure the smoothness needed for the static casting of non-ferrous alloys and contribute to favorable results in the pressure casting of aluminum.
The structure design ensures both uniformity and burnout shrinkage in molds and cores. These unique properties are achieved, in part, by a sand additive that promotes rapid chilling of the metal. Use these plasters for nonferrous alloy casting with an exceptionally fine finish (32 to 125 micro inches) and very close tolerance (.0025in./in.).
Our metal casting plasters are frequently used as a mold media for the pressure and static casting of aluminum match plates, as well as products of beryllium, copper, brass and bronze. They are ideally suited for continuous mixing equipment.
Consistency varies depending on metal casting plaster used.
Consistency, expressed in cc of water per 100 grams of plaster, is the amount of water required to produce a smooth pouring slurry meeting pre-determined specifications when tested. Consistency will vary from one metal casting formula to another. It will remain constant within normal limits for any particular formulation.
Weigh 100 grams of the plaster to within 0.1 gram. Use clean mixing vessel and spatula. Measure the required amount of water into the mixing vessel from a burette or graduated cylinder. Slowly add plaster to water and soak for 1 minute; then mix thoroughly for 2 minutes, stirring at a moderate rate. After mixing, immediately pour slurry out on the plate glass from the height of from 1-1/4 inches. The slurry should pour evenly from the mixing vessel without the aid of a spatula to produce a pat within given specification. If proper measurement is not obtained, repeat test using more or less water until actual consistency is determined.
7.5 to 10.5
Hydrogen ion concentration, or pH, is the degree of acidity or alkalinity, using the numerical value of 7.0 as a neutral point. Acidity falls below this value of 7 and alkalinity above, when tested under the following conditions:
Distilled water at room temperature (65° F - 80° F).
pH test can be made on pat used for setting time test providing tests are carried out using distilled water. To measure pH, tear approximately ½ inch of pHydrion paper from the dispenser provided and lay in contact with surface of pat. Allow interval of time for paper strip to complete color change. Approximately 5 minutes should be sufficient. After paper has undergone complete change in color, remove from pat and compare with color chart provided to determine pH. If color compares with minimum or maximum color on chart provided, duplicate test should be made using higher or lower range paper to determine actual pH.
lbs./cu. ft. to lbs./cu. ft.
DETERMINING WET DENSITY:
Wet density, expressed in pounds per cubic foot, is the weight of the water and plaster mixed together to form a smooth slurry when tested in the following manner:
Container - 7 1/2 oz waxed cup
Weigh dry paper cup to nearest 0.1 gram. Determine volume of paper cup in cc. Pour slurry into cup until full and strike off level with spatula. Weigh cup and contents. Subtract tare weight of cup from total weight. Proceed using following formula:
Metal casting plasters can be prepared with a variety of mixer types. Of these (propeller, turbine and disc), propeller mixers work best for metal casting applications. Results can differ depending on a number of variables: the size of the propeller, bucket and mix; mixer speed; the position of a propeller or disc relative to the slurry depth; and power input.
However, it is generally agreed that a continuous plaster-flow mixing machine ensures the best consistency by monitoring and maintaining proper plaster densities.
It is necessary to drive off free moisture and crystalline water in a mold before the metal can be cast; therefore, proper drying is essential. Plaster has the chemical formulation CaSO4:1/2H2O. Plaster contains some crystalline water from the start. When the plaster is added to the water in mixing, water equal to 18% of the weight of the plaster combines with the plaster to form CaSO4:2H2O. This results in the plaster setting.
Most of the mixing water is entrapped in the set plaster as free moisture. The greater the excess of water over a consistency of 18%, the more free water the mold will contain.
When the plaster mold dries, the free moisture is released, leaving voids. As the drying continues, the chemically combined water is driven off. It is necessary to drive off both the free and the chemically combined (crystalline) water before the metal can be cast.
When completely calcined, the plaster becomes CaSO4. Under standard conditions, water will be vaporized at 212°F. As long as water remains in the mold, it is impossible for the mold temperature to rise above 212°F.
Failure to dry molds adequately results in blows in the casting, excessive shrink marks, porous castings and cracked molds. Drying times depend on oven temperature, velocity, humidity of circulating air, and the size, thickness and porosity of the mold. Molds should be dried in flues and separated from the flame and oven.
For important product fire, safety, and use information, go to gp.com/safetyinfo.
MSDS: #42A Gypsum Plasters (85KB/6pgs)
Fiche Signalétique: #42A Plâtres Industriels (66KB/6pgs)
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