Rolling and Forging

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Rolling and Forging

• Manufacturing Processes

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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

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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

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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

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Structure/Property Modification
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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

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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

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Typical Rolled Products
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Typical Rolled Products
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Rolling Process
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Rolling Process
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Rolling Process
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Rolling Process
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Rolling Process
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Example of a Hot Rolling Line
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Rolling Defects
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Shape Rolling

• Uses a series of specially shaped rolls to form a
  beam with a specific cross section (such as an
  I-beam)

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Ring Rolling

• Uses rolls to form a thick, small-diameter ring
  into a thin, larger-diameter ring

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Ring Rolling
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Thread Rolling

• Uses moving dies with grooves to form threads on
  cylindrical parts

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Thread Rolling
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Material Property Changes
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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

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Example of a Tube Rolling Mill
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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

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Calendering
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Calendering
Example of a calendered rubber sheet with two
layers Courtesy Cooper Tire
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Calendering of Rubber
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Coated Products
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Reinforced Materials
Coating on both sides of reinforcing material
coating material
spools
comb
reinforcing material
coating material
windup
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Reinforced Materials
Example of a polyester-reinforced rubber sheet
with fibers exposed Courtesy Cooper Tire
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Reinforced Materials
Example of a steel-belted rubber sheet with the
belt exposed Courtesy Cooper Tire
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Calender Control Systems
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Calendering Thickness Sensors
Emitter
X rays or beta radiation (electrons)
some radiation is blocked, depending on thickness
Detector
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Milling

• Squeezes material between rolls to mix or preheat
  it for further processes

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Forging

• Forging
• A deformation process in which the material is
  compressed between dies, using impact or gradual
  pressure to form the part

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Forging
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Example of a Forging Machine
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Example of a Forging Machine
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Working Temperature

• Hot Forging
• Material is above its recrystallization
  temperature
• Cold Forging
• Increased strength from strain hardening

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Forging

• Billet
• A piece of material with a square or circular
  cross section usually produced by a deformation
  process such as rolling or extrusion

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Open Die Forging

• Compresses the work between flat or nearly flat
  dies

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Open Die Forging
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Open Die Forging
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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

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Closed Die Forging

• Also called impression-die forging compresses
  the material into the shape of the die cavity

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Closed Die Forging
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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

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Roll Forging

• Uses grooved rolls to reduce thickness and
  increase length of round or flat bars

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Roll Forging
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Roll Forging
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Roll Forging
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Coining

• Uses dies to press fine detail into both sides of
  the workpiece

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Upsetting/Heading

• Decreases the length and increases the diameter
  of the workpiece often used to form heads on
  nails, bolts, etc.

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Orbital Forging

• Uses a die that moves in various directions to
  compress the workpiece

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Swaging

• Uses hammering dies to decrease the diameter of
  the part

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Swaging
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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

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Forging Defects
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Forging Machines
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Forging Machines
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Example of a Forging Machine
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Economics
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Summary

• Rolling and forging shape parts by deforming the
  material into the desired shape

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