Chapter 3 - Rolling of metals

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Backup rolls •Therefore the rolling load P increases with the roll radius R 1/2 , depending on the contribution from the friction hill. • The rolling load also increases as the sheet entering the rolls becomes thinner (due to the term e Q ). • At one point, no further reduction in thickness can be achieved if the deformation resistance of the sheet is greater than the roll pressure. The rolls in contact with the sheet are both severely elastically deformed. • Small-diameter rolls which are properly stiffened against deflection by backup rolls can produce a greater reduction before roll flattening become significant and no further reduction of the sheet is possible. Example: the rolling of aluminium cooking foil. Roll diameter < 10 mm with as many as 18 backing rolls. Suranaree University of Technology Tapany Udomphol Jan-Mar 2007
• Frictional force is needed to pull the metal into the rolls and responsible for a large portion of the rolling load. • High friction results in high rolling load, a steep friction hill and great tendency for edge cracking. • The friction varies from point to point along the contact arc of the roll. However it is very difficult to measure this variation in µµµµ, all theory of rolling are forced to assume a constant coefficient of friction. • For cold-rolling with lubricants, µµµµ ~ 0.05 – 0.10. • For hot-rolling , µµµµ ~ 0.2 up to sticky condition. Suranaree University of Technology Tapany Udomphol Jan-Mar 2007
Page 1 and 2: Rolling of metals Subjects of inter
Page 3 and 4: www.world-aluminium.org Introductio
Page 5 and 6: Sheet rolling machines Rolled strip
Page 7 and 8: Rolls Mill rolls Mill rolls Suranar
Page 9 and 10: Typical arrangement of rollers for
Page 11 and 12: Typical arrangement of rollers for
Page 13 and 14: Different types of rolling processe
Page 15 and 16: Transverse rolling • Using circul
Page 17 and 18: Shaped rolling or section rolling A
Page 19 and 20: Simulation of ring rolling Simulati
Page 21 and 22: Powder rolling Metal powder is intr
Page 23 and 24: Thread rolling Cut thread and rolle
Page 25 and 26: Example for hot strip mill process
Page 27 and 28: Cold-rolling Cold rolling www.willi
Page 29 and 30: Cold-rolling Cold rolling • Cold
Page 31 and 32: h o Forces and geometrical relation
Page 33 and 34: • At only one point along the sur
Page 35 and 36: h o v o p A R N B h f Friction hill
Page 37 and 38: Therefore Free engagement will occu
Page 39 and 40: Problem with roll flattening When h
Page 41 and 42: Simplified analysis of rolling load
Page 43: 2) Normal friction situation In the
Page 47 and 48: 3) Sticky friction situation What w
Page 49 and 50: Relationship of µµµµ, rolling l
Page 51 and 52: Problems and defects in rolled prod
Page 53 and 54: Uniform thickness • Under high ro
Page 55 and 56: Flatness • The roll gap must be p
Page 57 and 58: • Hot mill can be provided with f
Page 59 and 60: Possible effects when rolls are ove
Page 61 and 62: • Edging can also be caused by in
Page 63 and 64: Rolling mill control • Modern con
Page 65 and 66: Rolling load P3 P2 P1 Situation whe
Page 67 and 68: Thickness measurement in continuous
Page 69 and 70: The stresses acting on an element o
Page 71 and 72: The forces acting in the vertical d
Page 73 and 74: The rolling load or total force P i
Page 75 and 76: Torque and power Torque is the meas
Page 77 and 78: The torque M T is equal to the tota
Page 79: References • Dieter, G.E., Mechan

Chapter 3 - Rolling of metals

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