Introduction to Manufacturing

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Introduction to Manufacturing

• Chapter 13 Rolling

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Rolling

• Process of reducing the thickness or changing the
  cross-section area of a long work piece by
  compressive forces.
• accounts for about 90 of all metals produced by
  metalworking processes.
• forging operations produce discrete parts, where
  rolling operations produce continuous products.

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Rolling
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Rolling Rolls
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Rolled Texture
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Unrolling and Straightening of Rolls (Maytag)
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Roll Loading
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Rolling Process

• Terminology (raw material)
• Bloom square cross section of at least 6" on the
  side. (sheets)
• Billets square cross section, smaller than
  bloom. (rod, pipe)
• Slab rectangular in shape, rolled into plates
  and sheet. (rails, I-beams)

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Rolling Mills

• Two-high
• primary roughing (cogging mills).
• Three-high
• primary roughing (reversing mill).
• Four High Cluster
• principal (small diameter) rolls lower the roll
  forces and power requirements, but must be
  supported in order to reduce deflection.

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Rolling Mills
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Rolling Mills

• Tandem Rolling
• strip is rolled continuously through a number of
  strands (set of rolls with its own separate
  housing and controls) to smaller gauges with each
  pass.
• Group of Strands train

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Roll Deflections

• Rolling forces cause deflection and roll
  flattening.
• Crown thicker in the center than the edges.
• Chamber thicker in the edges than center.
• Spreading increase of width after rolled.

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Roll Deflections

• Forces can be reduced by
• reducing friction.
• reducing contact area.
• smaller reductions per pass.
• rolling at elevated temperatures to reduce
  strength of material.

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Roll Materials

• Cast iron
• Cast steel
• Forged steel
• Aluminum Alloys

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Rolling Processes

• Flat-rolling
• hot or cold work (slabs, blooms, billets, or
  sheet metal).
• 3000 F for refractory alloys.
• 2300 F for alloy steels.
• 850 F for aluminum alloys.
• Pack Rolling two or more layers of metal rolled
  together (Al foil example)

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Flat-rolling (Cont.)

• Defects (P. 327)
• wavy edges
• zipper cracks
• edge cracks
• alligatoring

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Rolling Processes

• Shape Rolling (P. 331)
• structural shapes (I-beam, rails, etc.)
• requires specially designed rolls
• Ring Rolling (P. 332)
• ring (which is the part) placed between two
  rolls, to increase diameter.
• large rings for rockets, gearwheel rims, ball
  bearing and roller- bearing races, flanges,
  reinforcing rings for pipes, etc.

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Rolling Processes

• Thread rolling (P. 333)
• cold-forming process where threads are formed on
  round rods by use of flat reciprocating dies
  which pass the part between them.
• no material loss.
• no cutting through grain line flow improves
  strength.

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Rolling Processes

• Rotary Tube Piercing (P. 334)
• hot working process for making long, thick walled
  seamless tubing/pipe.
• round bar subjected to radial compressive forces
  causing tensile stresses toward the center of the
  bar.
• cavity forms from cyclic compressive stresses.