Centrifugal casting is a casting technique that is typically used to cast thin-walled cylinders. It is noted for the high quality of the results attainable, particularly for precise control of their metallurgy and crystal structure. Unlike most other casting techniques, centrifugal casting is chiefly used to manufacture stock materials in standard sizes for further machining, rather than shaped parts tailored to a particular end-use.
In centrifugal casting, a permanent mold is rotated continuously about its axis at high speeds (300 to 3000 rpm) as the molten metal is poured. The molten metal is centrifugally thrown towards the inside mold wall, where it solidifies after cooling. The casting is usually a fine-grained casting with a very fine-grained outer diameter, owing to chilling against the mould surface. Impurities and inclusions are thrown to the surface of the inside diameter, which can be machined away.
Features of centrifugal casting are as follows:
- castings can be made in almost any length, thickness and diameter;
- different wall thicknesses can be produced from the same size mold;
- eliminates the need for cores;
- resistant to atmospheric corrosion, a typical situation with pipes;
- mechanical properties of centrifugal castings are excellent;
- only cylindrical shapes can be produced with this process;
- size limits are up to 3 m (10 feet) diameter and 15 m (50 feet) length;
- wall thickness range from 2.5 mm to 125 mm (0.1 – 5.0 in);
- tolerance limit: on the OD can be 2.5 mm (0.1 in) on the ID can be 3.8 mm (0.15 in);
- surface finish ranges from 2.5 mm to 12.5 mm (0.1 – 0.5 in).