Foundry Sands and Coatings | Zircon Industry Association

Why is zircon used for casting in foundries?

The following properties make zircon an excellent material for sand casting, investment casting, and die casting:

Low acidity: its pH varies between neutral to slightly acid
Clean and round grains allow the material to be easily bonded together
Consistent fineness and ability to form fine grains
High ability to bind with all organic and inorganic sand binders
Low thermal expansion coefficient and high spatial stability at increased temperatures
High melting point (2,100 – 2,300℃)
Low thermal conductivity
Chemical stability at high temperatures
Low wettability by molten metal
Good recyclability

The advantages of using zircon sand and zircon flour in these foundry processes are:

Zircon’s low wettability, consistent grain fineness and ability to form fine grains allows the creation of high precision castings with good surface finish, prevents the mineral from sticking to the cast metal and avoids metal penetration into the mould
Its high thermal conductivity allows higher cooling rates than other mould materials, which also results in a better surface finish
The higher dimensional accuracy and better surface finish achieved through the use of zircon minimises post-casting operations such as machining and cleaning of the cast part
Zircon’s low wettability by molten metal increases the recoverable sand and hence the recyclability of the material
Its chemical stability ensures uniform results when using recycled sand