Centrifugal Casting & its types (True Centrifugal Casting, Semi Centrifugal Casting & Centrifuge Casting)
Centrifugal Casting:
Centrifugal casting uses a permanent mold that is rotated
about its axis at a speed between 300 to 3000 rpm as the molten metal is
poured. Centrifugal forces cause the metal to be pushed out towards the mold
walls, where it solidifies after cooling. Parts cast in this method have a fine
grain microstructure, which is resistant to atmospheric corrosion.
Advantages:
•Suitable for all casting metals & alloys
•Used for large castings.
•Fly wheels, hollow cylindrical castings.
•Good mechanical properties of the products.
Disadvantages:
•Not suitable for intricate castings
•High manufacturing cost.
Centrifugal casting can be classified into three general types:
•True centrifugal casting
•Semi-centrifugal casting
•Centrifuging casting.
True centrifugal casting:
Molten metal is poured into a rotating mould. The axis of
rotation may be horizontal, vertical or inclined at any suitable angle between
0-90°. Moulds are made with steel, iron or graphite and may be coated with
refractory lining for increases life of mould. Mould surfaces can be
shaped so that pipes with various outer shapes, including square or polygonal can be cast. Inner surface of the
casting remains cylindrical, because molten metal is uniformly distributed by centrifugal forces. Most of the impurities
and inclusions are closer to the inner diameter and can be machined away.
Advantages:
•Quick and economical than other methods.
•Risers, feed heads, cores are eliminated.
•Ferrous and non-ferrous metals can be cast
•Good surface finish.
Disadvantages:
•Mechanical composition of alloys are not uniform.
•Mechanical properties of centrifugal castings are superior
to sand castings but gravity segregation is encountered in some alloys.
•Good for production of cylindrical parts only.
Applications:
Pipes, bushings, gears, flywheels.
Semi centrifugal casting:
It is also known as profited centrifugal casting. It is
nearly to true centrifugal casting with only difference is central core is used
in the inner surface. The particular shape of casting is produced by mouldand
core shapes not only by a centrifugal force. The axis of spin is always
vertical. This method is used to cast parts with rotational symmetry.
Limitations:
•Rotational speed is less compare to the true centrifugal
process.
•This process is used only for symmetrical parts.
•Yield value is less
when compare to the true centrifugal process
Applications:
•It is used for making Gears, Fly wheels and Track Wheels etc.
Centrifuge casting:
In this type of casting several casting cavities are located
around the outer portion of the mould. The metal is fed to these cavities by
radial gates from centre either single or stack can be used. The cavities are
filled under pressure from centrifugal force of metal as the mould is rotated.
It is also known as pressure casting.
Advantages:
•Irregular shapes can be cast [ like bearing caps, small
brackets.]
•Dental profession use this process for casting gold inlays.
Disadvantages:
•This type of casting is possible only in vertical direction.
Applications:
•Bearing caps,Lamp Bracket etc.
END
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