2. 13.5 Centrifugal Casting
• Inertial forces due to spinning distribute the
molten metal into the mold cavity
• True centrifugal casting
– Dry-sand, graphite or metal mold can be rotated
horizontally or vertically
– Exterior profile of final product is normally round
• Gun barrels, pipes, tubes
– Interior of the casting is round or cylindrical
– If the mold is rotated vertically, the inner surfaces
will be parabolic
– Final product has a strong, dense exterior with all
of the lighter impurities on the inner surface.
3. Centrifugal Casting (Horizontal)
• Specialized equipment
• Expensive for large castings
• Long service life
• No sprues, gates, or risers
Figure 13-8 (Left) Schematic
representation of a horizontal
centrifugal casting machine.
(Courtesy of American Cast Iron Pipe
Company, Birmingham, AL.)
4. Centrifugal Casting (Vertical)
Figure 13-9
(Above) Vertical
centrifugal casting,
showing the effect
of rotational speed
on the shape of the
inner surface.
Parabaloid A
results from fast
spinning whereas
slower spinning
will produce
parabaloid B.
6. Centrifugal Casting
first suggested in the early 1800s
centrifugal-casting process utilizes inertial forces
Rotation force distribute the molten metal into the mold cavities
Centrifugal casting refers to several casting methods in which the mold
is rotated at high speed so that centrifugal force distributes the molten
metal to the outer regions of the die cavity
three types of centrifugal casting
true centrifugal casting
semi centrifugal casting
centrifuging.
7. True Centrifugal Casting
• In true centrifugal casting, molten metal is poured into a rotating mold to
produce a tubular part
• In true centrifugal casting, hollow cylindrical parts (such as pipes, gun
barrels, bushings, engine-cylinder liners, bearing rings with or without
flanges, and street lampposts) are produced by the technique
• The axis of rotation is usually horizontal, but can be vertical for short work
pieces
• The high-speed rotation results in centrifugal forces that cause the metal to
take the shape of the mold cavity.
• Molds are made of steel, iron, or graphite and may be coated with a
refractory lining to increase mold life.
• The mold surfaces can be shaped so that pipes with various external
designs can be cast.
• The inner surface of the casting remains cylindrical, because the molten
metal is distributed uniformly by the centrifugal forces.
• because of density differences, lighter elements (such as dross, impurities,
and pieces of the refractory lining) tend to collect on the inner surface of
the casting.
• Consequently, the properties of the casting can vary throughout its
thickness.
8. • Cylindrical parts ranging from 13 mm to 3 m in diameter and 16 m long can
be cast centrifugally with wall thicknesses ranging from 6 to 125 mm.
• The pressure generated by the centrifugal force is high;
• high pressure is necessary for casting thick-walled parts
• Castings with good quality, dimensional accuracy, and external surface
detail are produced by this process.
(a) Schematic illustration of the centrifugal-casting process. Pipes, cylinder liners, and
similarly shaped parts can be cast with this process. (b) Side view of the machine
9. Semicentrifugal Casting.
• This method is used to cast parts with rotational symmetry, such as a wheel
with spokes.
(a) Schematic illustration of the semicentrifugal casting process. Wheels with spokes can be
cast by this process. (b) Schematic illustration of casting by centrifuging. The molds are placed
at the periphery of the machine, and the molten metal is forced into the molds by centrifugal
force.
10. • centrifugal force is used to produce solid castings, rather than tubular parts
• the molds are designed with risers at the center to supply feed metal
• Density of metal in the final casting is greater in the outer sections than at
the center of rotation
• The process is often used on parts in which the center of the casting is
machined away, thus eliminating the portion of the casting where the
quality is lowest.
• Wheels and pulleys are examples of castings that can be made by this
process
Centrifuging
• In centrifuging (also called centrifuge casting), mold cavities of any shape
are placed at a certain distance from the axis of rotation.
• The molten metal is poured from the center and is forced into the mold by
centrifugal forces
• The properties of the castings can vary by distance from the axis of rotation,
as in true centrifugal casting.
