Green Sand: Green sand is also called as foundry sand or molding sand.
This is utilized for sand casting. When this sand is oiled or moistened, it has
a tendency to pack well and retain the shape. Green sand is a mix of pulverized
coal, water, bentonite clay and sand. Out of these four components, the biggest
part is that of the sand.  There are
several proportions of these four components. The different ratios are used to
adjust the surface finish, moldability and capacity of the hot molten metal to
degas. The prime use of this sand is in the metal casting. The coal is usually
called as sea coal in foundries. The amount of sea coal is less than 5 percent.
It undergoes partial combustion when there is molten metal present and this
causes offgassing of organic vapors.

Green sand is stored in flasks (as
the casters call the container). These are boxes that do not have a bottom or
lid. This box is divided into two half parts and these are connected together.
These halves are called as the top or cope and bottom or drag flask.

As per its name, green sand is not
green in color. The word “green? is used as it is used in the wet state.

Casting Sand: Some
casting sands are oil bonded and foundry mix sand. This is a mixing of oil,
resin and sharp fine silica sand. Such a mix can be utilized in sand casting of
all varieties of metals. Some casting sands consist of 20 percent more oil and
resin as compared to other brands. The objective is to ascertain the best mix
for maximum green power and the best finish for the surface, that is possible.

The oil bonded sand is a
substitute for water bonded green sands to be used for casting sand. The
advantage over traditional, older sands is that as water is absent, the sand
does not steam like the traditional sands. This sand is more secure to use than
green sand. The reason is that potentially explosive quantities of steam are
not generated. Due to this dearth of steam generation and the smooth texture of
the sand, the oil bonded sand results in a smoother surface finish. The novice
can use these sands and get professional results.

Use of casting sand: The same techniques, patterns and tools that are used for
water bonded sands can be used for oil bonded casting sands. As the sand has
better adhesive properties, there are fewer hassles with loose sand in the
impression. The difference is that water cannot be used to manage loose
sections. However, as the self adhesion is better, there are fewer problems of
crumbling.

When the oil comes in contact with
molten metal, it does not burn. When the castings are being shaken out, it is
advisable to take off the sand that is burned. This sand that is burned can
then be mixed again in the pile of fresh sand. It reabsorbs oil and works very well.
After repeated use of this sand, the oil gets depleted. In this case , around
30W of non-detergent motor oil can be used to reload the sand with oil.

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Tags: casters, casting sand, combustion, degas, flask, flasks, foundry sand, green sand, metals, mix sand, molding sand, molten metal, organic vapors, proportions, ratios, resin, sand casting, sea coal, silica sand, surface finish

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