Tuesday, April 5, 2011

CrazyEngineers Forum - Mechanical & Civil Engineering

CrazyEngineers Forum - Mechanical & Civil Engineering

Types of Molding sands

Posted: 05 Apr 2011 09:37 AM PDT

There are a different types of molding sands which are used in a foundry shop. I am mentioning the basic or the most common of them. There may be a lot more development now please correct or update my knowledge if I am wrong.

Green sand:
It is called green sand because of its water content. However it is color is black, remember that. It is a wet sand used for molding and contains about 20-30% clay and 8 % water by part. If we can maintain the amount of clay then we can easily maintain the flow-ability of sand. We can maintain its porosity.

Dry sand:
If we dry the green sand mentioned above, then we get dry sand. the physical composition remains same, except for water content.

Facing sand:
This sand comes in contact with direct contact of molten metal hence it is subjected to severest conditions. the basic composition is silica sand and clay but we do not use already used sand. We have to use fresh silica sand for preparing facing sand.
if we mix 1 part of the mentioned sand in 6-8 parts of normal molding sand then we can produce a facing sand.

Backing sand:
We can use old and repeatedly used sand for this purpose as this only contributes to support the mold. No need to waste fresh sand for it.

System sand:
We use this sand in mechanical foundries where we do molding with the aid of machines. we fill whole container with this sand and in this case we do not use facing sand.

Parting sand:
This is used so that the green sand should not stick to the pattern
Eg: We used Bentonite powder during our practicles

Core sand:
This is also called as oil sand. We can make this sand if we mix the normal silica sand with Linseed oil or any other oil like mineral oil or resin etc.
It is used to form the core.
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