Centrifugal casting

Centrifugal casting is a method of casting parts having axial symmetry. The method involves pouring molten metal into a cylindrical mold spinning about its axis of symmetry.
The mold is kept rotating till the metal has solidified.
As the mold material steels, Cast irons, Graphite or sand may be used.
The rotation speed of centrifugal mold is commonly about 1000 RPM (may vary from 250 RPM to 3600 RPM).
A centrifugal casting machine is schematically presented in the picture:


Centrifugal casting is carried out as follows:

• The mold wall is coated by a refractory ceramic coating (applying ceramic slurry, spinning, drying and baking).

• Starting rotation of the mold at a predetermined speed.

• Pouring a molten metal directly into the mold (no gating system is employed).

• The mold is stopped after the casting has solidified.

• Extraction of the casting from the mold.

The casting solidifies from the outside fed by the inner liquid metal.
Non-metallic and slag inclusions and gas bubbles being less dense than the melt are forced to the inner surface of the casting by the centrifugal forces. This impure zone is then removed by machining.
Resulted structure of the centrifugal castings is sound.
Centrifugal casting technology is widely used for manufacturing of iron pipes, bushings, wheels, pulleys bi-metal steel-bronze bearings and other parts possessing axial symmetry.