MOULDING SAND: PROPERTIES AND TYPES OF MOULDING SAND
The Moulding sand is also known as foundries sand, this sand is commonly used for making moulds. Natural sand located on the bed and banks of rivers gives a larger source, although high-quality silica sand is also mined.
The sand is chemically Si02, silicon dioxide in a granular manner. Ordinary river sand contains a percentage of clay, moisture, non-metallic impurities and traces of magnesium and calcium salts besides silica grains. After appropriate treatment, this sand is used to make a mould.
Types of Moulding Sand
Following are the 8 different types of moulding sands:
- Dry sand
- Loam sand
- Facing sand
- Backing sand
- System sand
- Parting sand
- Core sand
1. Green Sand
Green sand is a sand or sandstone which has a greenish colour. it is a mixture of silica sand with 18 to 30% clay, having total water of 6 to 8%. It is soft, light and porous with clay and water furnishing the bond for green sand.
In green sand, It is slightly wet when squeezed by hand. It has the ability to maintain the shape and impression given to it under the pressure. The green sand can be easily available and it has a low cost. The mould that is prepared in this sand is called green sand mould. It is commonly used for the production of ferrous and non-ferrous castings.
2. Dry Sand
The Green sand that has been dried or backed after the mould is made is called dry sand. They are suitable for large castings. Moulds prepared in dry sand are known as dry sand moulds. If we talk about the physical composition of dry sand, it is similar to green sand except for water.
3. Loam Sand
The Loam sand with 50% of clay is called loam sand. They are also suitable for large castings. It is a mixture of sand and clay and water is present in such a quantity that it forms a thin plastic paste. In these types of sand, moulding patterns are not used.
4. Facing Sand
It forms the face of the mould. The facing sand is used directly next to the patterned surface and comes into direct contact with the molten metal when the molten metal is poured into the mould. It has high strength and refractivity as it comes in contact with molten metal. It is made of clay and silica sand in addition to unused sand.