Rolling

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Rolling And Extrusion
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• Rolling Process
• Points
• Significant shape change
• Capital intensive
• Large volume
• Usually hot worked (isotropic)
• Oxide scale
• Tolerances difficult to hold

Can be followed by cold rolling to improve
tolerances and directional properties
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Rolling Products
Billet Blooms (gt 6 x 6)
Slab Ingots Billets (gt 1.5 x 1.5)
Slab (gt 10 x 1.5)
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vr
Rolling Model
R
q
p
vo
vf
to
tf
L

• Assumptions
• Infinite sheet
• Uniform, perfectly rigid rollers
• Constant material volume to wo Lo tf wf Lf
  rate (to wo vo tf wf vf )
• where Lo initial plate length Lf
  final plate length

vr
R roller radiusp roll pressure L
contact lengthq contact angle vr roll speed
to initial plate thickness tf final plate
thickness vo plate entry speedVf plate exit
speed
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Rolling Model
Define draft d to - tf Draft limit
dmax m2R m 0.1 cold m 0.2
warm m 0.4 1.0 hot Define forward slip
s (vf vr)/vr Does it make sense that vr
lt vf?
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Rolling Model stress, strain, force, power
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Other rolling configurations
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Example 21.1 in text
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• Extrusion
• Limitation requires uniform cross-section vs
  length
• Advantages
• Variety of shapes
• Control mechanical properties in cold and warm
  extrusion
• Little wasted material
• Good tolerances
• Types Direct extrusion and indirect extrusion

Less friction!
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Extrusion Model

• Assumptions
• Circular cross-section
• Uniform stress distribution

p ram pressure L remaining billet
lengthDo chamber diameter Df extrudate
diameter
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Extrusion Model stress and strain
Ao billet (chamber) area Af extrudate area
a 0.81.2 b 1.5
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Extrusion Model stress and strain
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Extrusion Model non-circular sections
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Extrusion Model forces and power
Ram force F pAo Power P Fv
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Rolling and Extrusion
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