CENTRIFUGAL CASTING

CENTRIFUGAL CASTING:
In this process, the mould is rotated rapidly about its central axis as the metal is poured into it. Because of the centrifugal force, a continuous pressure will be acting on the metal as it solidifies. The slag, oxides and other inclusions being lighter, get separated from the metal and segregate towards the center. This process is normally used for the making of hollow pipes, tubes, hollow bushes, etc., which are axisymmetric with a concentric hole. Since the metal is always pushed outward because of the centrifugal force, no core needs to be used for making the concentric hole. The mould can be rotated about a vertical, horizontal or an inclined axis or about its horizontal and vertical axes simultaneously. The length and outside diameter are fixed by the mould cavity dimensions while the inside diameter is determined by the amount of molten metal poured into the mould.
There are three types of centrifugal casting.
a) True centrifugal casting
b) Semi centrifugal casting
c) Centrifuging
a) True centrifugal casting:
- Hollow pipes, tubes, hollow bushes – axi-symmetric with concentric holes
- Axis of rotation – horizontal, vertical or any angle.
- Sand moulds/ metal moulds
- Water cooling
Adv: superior mechanical properties
Directional solidification
No cores
No gates and runners
Limitation: - only for axi-symmetric concentric holes
- Expensive
b) Semi-centrifugal casting:
- More complicated- axi-symmetric jobs
- Vertical
c) Centrifuging:
- Not axi-symmetrical jobs
- Small jobs of any shape – joined by radial runners with a central sprue on revolving table.