The cores are defined as sand bodies used to form the hollow portions or cavities of desired shape and size in the casting. Thus the sand used for making these cores is called core sand. It is sometimes called oil sand. It is the silica sand mixed with linseed oil or any other oil as binder.
Types of Moulding Sands :
1: Green sand :
The sand in its natural or moist state is called green sand. It is also called tempered sand. It is a mixture of sand with 20 to 30 percent clay, having total amount of water from 6 to 10 percent. The mould prepared with this sand is called green sand mould, which is used for small size casting of ferrous and non-ferrous metals.
2: Dry Sand :
The green sand moulds when baked or dried before pouring the molten metal are called dry sand moulds. The sand of this condition is called dry sand. The dry sand moulds have greater strength, rigidity and thermal stability. These moulds used for large and heavy casting.
3: Loam Sand :
A mixture of 50 percent sand grains and 50 percent clay is called loam sand. It is used for loam moulds of large Grey iron casting.
4: Facing Sand :
A sand which is used before pouring the molten metal, on the surface is called facing sand. It is specially prepared sand from silica sand and clay.
5: Backing or Floor Sand :
A sand used to back up the facing sand and not used next to the pattern is called backing sand. The sand which have been repeatedly used may be employed for this purpose. It is also known as black sand due to its color.
6: System Sand :
A sand employed in mechanical sand preparation and handling system is called system sand. This sand has high strength, permeability and refractoriness.
7: Parting Sand :
A sand employed on the faces of the pattern before the moulding is called parting sand. The parting sand consists of dried silica sand, sea sand or burnt sand.
8: Core Sand :