consists of a number of processes in which the centrifugal
force set up by the rotation of a part of the casting installation
is utilized to shape the casting, fill the mold, and help
solidify and strengthen the metal. There is a difference between
Vertical centrifugal casting (Fig.1) and horizontal centrifugal
casting. The first mentioned process is essentially a pressure-casting
technique employing rotation about a vertical axis. It produces
good filling of the mold, high dimensional accuracy, and a
high strength dense structure of the casting metal. This method
is used for casting of components that are too difficult to
produce satisfactorily by static casting methods because their
sections are too thin or for other reasons: e.g., gears, piston
rings, impellers, propellers, bushings and railway wheels.
Horizontal centrifugal casting is used mainly for making long
hollow castings, such as pipes, gun barrels, sleeves, etc.
mold rotates at high speed about a horizontal axis, the molten
metal being fed into the interior of the mold and distributed
around it by centrifugal action. Rotation is continued until
solidification is complete. The external diameter of the casting
corresponds to the internal diameter of the mold. The internal
diameter of the casting can, however, be varied by appropriately
proportioning the amount and feed rate of the casting metal.
An advantage of the centrifugal process is that it produces
a sounder and more uniform casting than static means. The
mold is usually made of steel or cast iron. Non-metallic linings
may be used.
important application of horizontal centrifugal casting is
the manufacture of pipes, especially cast-iron pipes. It provides
an economical method capable of an advanced degree of mechanization.
The two main methods of centrifugal casting are : In a water-cooled
mold by the Briede-de Lavaud process (Fig.2) and in a sand
lined mold by Moore’s process (Fig.3). For the manufacture
of spigot pipes, a sand core is inserted at the end of the
mold and is subsequently destroyed when the pipe is demolded.
The first mentioned method employs a slightly inclined mold
which can move longitudinally.
molten iron is introduced into the mold through a long duct
from a tilting ladle containing the correct amount of casting
metal to form the pipe. When the mold has reached a certain
speed of rotation, the molten iron is admitted to it, and
mold is moved slowly forwards (Fig.2) while the feed duct
remains stationary, so that uniform distribution of the metal
along the mold is achieved. Moore’s method uses a rotating
mold with a sand lining, which protects the metal shell of
the mold so that water cooling is not necessary. The sand
itself is applied to the mold wall and compacted by centrifugal
action. The inlet duct is short because, with a sand lining,
solidification of the casting takes a relatively long time
(no rapid cooling); proper filling of the mold is thus ensured.
This process has the advantage of not requiring a wide range
of molds of different diameters, since any desired pipe diameter
can be produced simply by varying the thickness of the sand
are also used for the production of composite castings. Centrifugal
casting as are categorized into Centrifugal Casting, Semi-Centrifugal
Casting and Centrifuging. In centrifugal casting, a permanent
mold is rotated 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 grain casting with
a very fine-grained outer diameter, which is resistant to
atmospheric corrosion, a typical situation with pipes. The
inside diameter has more impurities and inclusions, which
can be machined away. Only cylindrical shapes can be produced
with this process. Size limits are upto 3 m (10 feet) diameter
and 15 m (50 feet) length. Wall thickness can be 2.5 mm to
125 mm (0.1 - 5.0 in). The tolerances that can be held on
the outer diameter can be as good as 2.5 mm (0.1 in) and on
the ID can be 3.8 mm (0.15 in). The surface finish ranges
from 2.5 mm to 12.5 mm (0.1 - 0.5 in) rms. Typical materials
that can be cast with this process are iron, steel, stainless
steels, and alloys of aluminum, copper and nickel.
materials can be cast by introducing a second material during
the process. Typical parts made by this process are pipes,
boilers, pressure vessels, flywheels, cylinder liners and
other parts that are axi-symmetric. In Semi-Centrifugal Casting,
the molds used can be permanent or expendable, can be stacked
as necessary. The rotational speeds are lower than those used
in centrifugal casting. The center axis of the part has inclusion
defects as well as porosity and thus is suitable only for
parts where this can be machined away. This process is used
for making wheels, nozzles and similar parts where the axis
of the part is removed by subsequent machining. Centrifuging
is used for forcing metal from a central axis of the equipment
into individual mold cavities that are placed on the circumference.
This provides a means of increasing the filling pressure within
each mold and allows for reproduction of intricate details.
This method is often used for the pouring of investment casting