M
ention centrifugal casting to someone in the metalcasting industry, and you might hear something like, “Oh, yeah. Pipes.” Considering the mass production of ductile
iron pipe, the direct association is hardly unwar- ranted. But with recent advances in technology
and design capabilities, the process is far from a one-trick pony. It has the potential to be used in broader applications to produce components with intricate outer shapes and can include casting two diff erent alloys to obtain diff erent properties on the outer diameter compared to the inner diameter. T e process lends itself to increased automation and data recording procedures to streamline the manufacturing process.
Process & Methods Centrifugal casting involves pouring molten metal into a rotating perma-
nent mold or die (as shown in Fig. 1) spun around its center axis. By flowing molten metal into these dynamic molds, metalcasters use centrifugal force to produce components with attributes often unattainable via traditional casting methods. The spinning axis of the casting machine can be oriented vertically or horizontally.
Vertical machines, with the
addition of gravity’s downward pull, produce castings that are slightly thicker at the bottom, while horizontal machines produce high uniformity throughout the castings. There are three primary methods
for centrifugal casting: • True Centrifugal Casting: T is
• Semicentrifugal Casting: Similar to true centrifugal cast- ing, this process incorporates more complex molds and cores to produce hollow sections. Because the mold spins on its vertical axis, centrifugal force pushes the molten metal to the mold’s outer edge, which helps feed the cast- ing. However, with the introduc- tion of cores, solidifi cation can also progress from the core faces inward, which introduces the possibility of void defects. Gear blanks, pulley sheaves, wheels and impellers are commonly produced with a semicentrifugal casting process.
method features an outer cylindri- cal mold with no cores and is used primarily for cylindrical or ring- shaped castings. T e molten metal is pushed to the mold wall via centrifugal force and held there while the mold acts as a chill, allowing for strong directional solidifi cation. No gates, risers or sprues are needed, meaning yield can approach 100%.
• Centrifuge Centrifugal Casting: T e process with the most design versatility, centrifuge centrifugal casting features mold cavities arranged around a center axis of rotation, similar to spokes on a wheel. T is arrangement allows for the production of multiple cast- ings in a variety of confi gurations, making it an ideal process to create valve bodies, plugs and yokes. Centrifugal casting machines
Fig. 1. In a vertical centrifugal casting machine, molten metal is poured into a rotating mold and pushed to the outer edge of the mold cavities by centrifugal force.
are identifi ed primarily by the axis of rotation. T e large majority of machines are either horizontal or
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