The production of seamless forged
rings is often performed by a process called ring rolling
on rolling mills. These mills vary in size to produce
rings with outside diameters of just a few inches to over
300" and in weights from a single pound up to over
The process starts with a circular
preform of metal that has been previously upset and pierced
(using the open die forging process) to form a hollow
"donut". This donut is heated above the recrystallization
temperature and placed over the idler or mandrel roll.
This idler roll then moves under pressure toward a drive
roll that continuously rotates to reduce the wall thickness,
thereby increasing the diameters (I.D. and O.D.) of the
Seamless rings can be produced
in configurations ranging from flat, washer-like parts
to tall, cylindrical shapes, with heights ranging from
less than an inch to more than 9 feet. Wall thickness
to height ratios of rings typically range from 1:16 up
to 16:1, although greater proportions can be achieved
with special processing. The simplest, and most commonly
used shape is a rectangular cross-section ring, but shaped
tooling can be used to produce seamless rolled rings in
complex, custom shapes with contours on the inside and/or
The Seamless Rolled Ring Forging
Producing a ring "preform"
by the open die forging process:
Starting stock cut to size by weight is first
rounded, then upset to achieve structural integrity
and directional grain flow.
Work piece is punched,
then pierced to achieve starting "donut"
shape needed for ring rolling process.
Completed preform ready
for placement on ring mill for rolling.
Rolled ring forging process:
Ring rolling process
begins with the idler roll applying pressure
to the preform against the drive roll.
Ring diameters are
increased as the continuous pressure reduces
the wall thickness. The axial rolls control
the height of the ring as it is being rolled.
The process continues
until the desired size is achieved.