Green sand for aluminum typically uses olivine sand (a mixture of the minerals forsterite and fayalite, which is made by crushing dunite rock). Green sand casting for non-ferrous metals typically does not use coal additives (as found in an iron foundry), since the CO created does not prevent oxidation. There are many Green Sand recipes that vary the proportion of clay, water and sand grains, but they all try to produce a sand mixture that is compactable, yields a good surface finish, and provide the ability of the hot molten metal to degas. Bentonite clay (primary binder): 7 to 13%.Sand Mixture: silica sand (SiO2), chromite sand (FeCr2O4), or zircon sand (ZrSiO4), 75 to 85%, sometimes with a proportion of olivine, staurolite, or graphite.The molding sand used in this process relies on a well proven binder system hat includes water, clay and some organic compounds. The description of “Green Sand” has no bearing on the color of the sand, the name comes from the fact that the sand mold is not “set”, it is still in the “green” or uncured state even when the metal is poured in the assembled mold. Pattern precision and alignment between cope and drag.The process has 4 primary factors considered important:
Therefore, with aluminum green sand is generally used to form simple shapes and parts that aren’t susceptible to leakage. When used to form parts out of aluminum alloys, the sand mixture does have an impact on the final quality due to the potential for hydrogen gas pick up in the metal from the moisture in the sand.
The major benefit of this process is that the sand is easily recycled with low smell and a low ecological impact. However it is also used for some high volume projects also. Green sand casting is generally considered the easiest casting system because it is possible to use an existing part as a pattern for a 1-off project.
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