0. Introduction to Manufacturing
Chapter 13: Rolling

1. 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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2. Rolling
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3. Rolling Rolls
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4. Rolled Texture
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5. Unrolling and Straightening of Rolls (Maytag)
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6. Roll Loading
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7. 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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8. Rolling Mills Two-high Three-high Four High & Cluster
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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9. Rolling Mills
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10. 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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11. 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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12. 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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13. Roll Materials Cast iron Cast steel Forged steel Aluminum Alloys
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14. 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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15. Flat-rolling (Cont.) Defects (P. 327) wavy edges zipper cracks
edge cracks
alligatoring
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16. Rolling Processes Shape Rolling (P. 331) Ring Rolling (P. 332)
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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17. 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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18. 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.
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