Rolling and Forging
Manufacturing
Processes
Outline
Temperature
Rolling
Flat Rolling
Shape Rolling Operations
Thread Rolling
Seamless Tubing and Pipe
Rolling Nonmetallic Materials
Forging
Open-Die Forging
Closed-Die Forging
Roll Forging
Heading
Rotary Swaging
Forging Machines
Dies
Economics
Rolling and Forging
Rolling
The thickness of a slab of a
slab or plate is reduced by
cylindrical rolls which rotate to
pull the material between them
and compress it
Forging
A workpiece is compressed
between opposing dies so that
the material is forced into the
die shape
Temperature in Metal
Forming
Cold working (room temperature
or slightly higher)
Warm working (30% - 50% of the
melting temperature)
Hot working (50% - 75% of the
melting temperature)
Isothermal forming
Tools are preheated to prevent
surface cooling during forming
Structure/Property
Modification
Cold Working
Advantages
- No heating required
- Better surface finish
- Better dimensional accuracy
- Parts are interchangeable
- Better strength, fatigue and
wear properties
- Directional properties can be
imparted
- Minimal contamination
problems
Cold Working
Disadvantages
- Higher forces required
- More powerful equipment
required
- Less ductility is available
- Surfaces must be clean
- Intermediate anneals may be
needed to restore ductility
- Directional properties may be
detrimental
- May produce undesirable
residual stresses
Typical Rolled Products
Typical Rolled Products
Rolling Process
Rolling Process
Rolling Process
Rolling Process
Rolling Process
Example of a Hot
Rolling Line
Rolling Defects
Shape Rolling
Uses a series of specially shaped
rolls to form a beam with a specific
cross section (such as an I-beam)
Ring Rolling
Uses rolls to form a thick, smalldiameter ring into a thin, largerdiameter ring
Ring Rolling
Thread Rolling
Uses moving dies with grooves to
form threads on cylindrical parts
Thread Rolling
Material Property
Changes
Roll Piercing
Uses compressive stresses on a
cylindrical part to cause tensile
forces at the interior, creating a
hole to form a thick-walled tube
Example of a Tube
Rolling Mill
Rolling Nonmetallic
Materials
-
Paper
Plastic sheets
Rubber products
Reinforced fabric
Calendering
Passes material through a
series of gaps between rolls to
form a thin sheet
Calendering
Calendering
Example of a calendered rubber sheet with two
layers
Courtesy Cooper Tire
Calendering of Rubber
Coated Products
Reinforced Materials
Coating on both sides of
reinforcing material
spools
comb
reinforcing
material
coating
material
windup
coating
material
Reinforced Materials
Example of a polyester-reinforced rubber sheet with
fibers exposed
Courtesy Cooper Tire
Reinforced Materials
Example of a steel-belted rubber sheet with the belt
exposed
Courtesy Cooper Tire
Calender Control
Systems
Calendering Thickness
Sensors
Emitter
X rays or beta
radiation (electrons)
some radiation is
blocked, depending
on thickness
Detector
Milling
Squeezes material between rolls to
mix or preheat it for further
processes
Forging
Forging
A deformation process in which
the material is compressed
between dies, using impact or
gradual pressure to form the
part
Forging
Example of a Forging
Machine
Example of a Forging
Machine
Working Temperature
Hot Forging
Material is above its
recrystallization temperature
Cold Forging
Increased strength from strain
hardening
Forging
Billet
A piece of material with a square or circular cross
section; usually produced by a deformation process
such as rolling or extrusion
Open Die Forging
Compresses the work between flat or
nearly flat dies
Open Die Forging
Open Die Forging
Open Die Forging
Advantages
Simple, inexpensive dies; wide
range of sizes; good strength
Limitations
Simple shapes only; difficult to
hold close tolerances;
machining necessary; low
production rate; poor utilization
of material; high skill required
Closed Die Forging
Also called impression-die forging;
compresses the material into the
shape of the die cavity
Closed Die Forging
Closed Die Forging
Advantages
Good utilization of material;
better properties than open die
forging; good dimensional
accuracy; high production rate;
good reproducibility
Limitations
High die cost for small
quantities; machining often
necessary
Roll Forging
Uses grooved rolls to reduce
thickness and increase length of
round or flat bars
Roll Forging
Roll Forging
Roll Forging
Coining
Uses dies to press fine detail into
both sides of the workpiece
Upsetting/Heading
Decreases the length and increases
the diameter of the workpiece;
often used to form heads on nails,
bolts, etc.
Orbital Forging
Uses a die that moves in various
directions to compress the
workpiece
Swaging
Uses hammering dies to decrease
the diameter of the part
Swaging
Forging Dies and Die
Inserts
Separate inserts may be used for
forging complex shapes; this may
be less expensive than a complex
single-piece die
Forging Defects
Forging Machines
Forging Machines
Example of a Forging
Machine
Economics
Summary
Rolling and forging shape parts
by deforming the material into
the desired shape