The document discusses the rolling process used in mechanical engineering. It begins with introductions and terminology for rolling. It then covers classifications of rolling mills like two high, three high, and four high mills. The types of rolling processes discussed include conventional, transverse, shaped, ring, powder, and thread rolling. Hot and cold rolling are also covered. Key aspects of the rolling process like roll bite condition and common rolling defects are defined. The document concludes with potential problems in rolling and sample multiple choice questions.

1. ROLLING PROCESS
DEPARTMENT OF MECHANICAL ENGINEERING,
ATRIA INSTITUTE OF TECHNOLOGY, BANGALORE
TEJAS RAO.N - 1AT19ME040
MANOJ JAIN - 1AT18ME029
NAGAPPA - 1AT20ME401
L SUNDAR - 1AT19ME018
COURSE COORDINATOR :
Pf. ANJAN KUMAR D
Asst. Professor, Dept. of ME, Atria I T,
Bangalore

2. CONTENT
 INTRODUCTION
 TERMINOLOGY
 CLASSIFICATION OF ROLLING MILLS.
 TYPES OF ROLLING PROCESS
 ROLL BITE CONDITION
 ROLLING DEFECTS
 PROBLEMS
 MCQ’s

3. INTRODUCTION
•Definition of Rolling : The process
of plastically deforming metal by
passing it between rolls.
• Rolling is the most widely used
forming process, which provides high
production and close control of final
product.
• Due to the frictional forces the metal is drawn into
the opening.
• Metal Changes its shape due to high compressive
forces.
• Both hot(for drastic shape changing) and cold
rolling(for finishing) process are there.
• From the start ingot- blooms- billet- slaps which are
further rolled into plat, sharp, rod, bar, pipe, rails.

4. TERMINOLOGY
INGOT-A Moldinwhichmetal istocastorablockof steelor
othermetal, typicallyoblonginshape.
SEMI FINISHED PRODUCTS
BLOOM-The productoffirst breakdownofingot.
BILLET-Theproductobtainedfromafurther
reductionbyhotrolling.
SLAB-Thehotrolledingot.
MILLPRODUCTS
PLATE-Theproduct withthickness>6mm.
SHEET-Theproductwithathickness<6mmand
width>600mm.
STRIP-Theproductwithathickness<6mmandwidth<600mm.

5. TERMINOLOGY

6. TERMINOLOGY

7. MILL ROLLS(Pairsofrollaregrouped)

8. CLASSIFICATION OF ROLLING
MILLS
Classifications based on number of rolls.
 Two high rolling mills
 Three high rolling mills
 Four high rolling mills
 Multi roll rolling mills
 Sendzimir mill
 Universal rolling mill
 Planetary rolling mill
 Continuous rolling mill

9. TWO HIGH ROLLING
MILLS(SINGLE DIRECTION)
 Constant direction rolling
 Upper rolls is moveable one to set the distance.
 For single step reduction it is better one.
 If successive reduction is need we have
to change the distance for each operations

10. TWO HIGH ROLLING
MILLS(BOTH DIRECTION)
 For successive reduction this is better than single direction
rolling.
 We can set a different distance for each direction.
 Two high reversing mills are often used for the first rolling of an
ingot into blooms

11. THREE HIGH ROLLING MILLS
 Three rolls with constant direction of rotation are arranged
in a single vertical plane.
 Lifting table used to rise or lower the metal after each
pass.
 Both top and bottom rolls are driver rolls.

12. FOUR HIGH ROLLING MILLS
 The bending of the roller is less if the diameter of the roller is high.
At the same time the power consumption and force P value also very
high for big diameter rollers.
 To over come this problem small Diameter rollers with larger
diameter back up rollers are used. This can be used for both
directions.

13. MULTIPLE ROLE MILLS
 In four high rolling the diameter of the back up rolls can not be
greater that 2 to 3 times that of the work rolls.
 By reducing the work roll diameter will produce bending effect
on the back up rolls.
 So in multiple roll mills a cluster of 6, 12, 20 rolls are used to
manufacturing strips. Form 0.001mm thick and 2000 mm wide.

14. SENDZIMIR MILLS
 Modified cluster mill
 For thin sheets
 1 to 5 micron

16. UNIVERSAL ROLLING MILLS
 Metal reduction occurs in both horizontal and vertical rolls.
 Vertical rolls are mounted either one side or both sides
 Horizontal rolls may be either two, three or four high arrangement.
 Used for roll wide strips, sheets, plates and slabs that requires both
rolling edges and also for rolling of H sections.

17. PLANTERY ROLLING MILLS
 Consist of a pair of heavy backing rolls surrounded by a large number of
planetary rolls.
 Each planetary roll gives an almost constant reduction to the slab as it sweeps out
a circular path between the backing rolls and the slab.
 As each pair of planetary rolls ceases to have contact with the work piece, another pair
of rolls makes contact and repeat that reduction.
 The overall reduction is the summation of a series of small reductions by each pair of
rolls .Therefore, the planetary mill can hot reduces a slab directly to strip in
one pass through the mill.

18. CONTINUOUS ROLLING MILLS
 Arrangement is similar to two- high rolling mill.
 Here the metal work piece passes from one roll pass to
another and we get continuous reduction in size.
 Used for mass production

19. TYPES OF ROLLING PROCESS
 Conventional rolling
 Transverse rolling
 Shaped rolling or section rolling
 Ring rolling
 Powder rolling
 Continuous casting and hot rolling
 Thread rolling
 Hot rolling and cold rolling

20. CONVENTIONAL ROLLING
 The objective is to decrease the thickness of the metal with an increase in length and
with little increase in width.
 The material in the centre of the sheet is constrained in the z direction (across the
width of the sheet) and the constraints of undeformed shoulders of material on each
sideof the rolls prevent extension of the sheet in the width direction.
 This condition is known as plane strain. The material therefore gets longer and not
wider.
 Otherwise we would need the width of a football pitch to roll down a steel ingot to
make tin plate!

21. TRANSVERSE ROLLING
 Using circular wedge rolls.
 Heated bar is cropped to length and fed in transversely
between rolls.
 Rolls are revolved in one direction.

22. SHAPED OR SECTIONAL ROLL
 •A special type of cold rolling in which flat slap is progressively bent into
complex shapes by passing it through a series of driven rolls.
 •No appreciable change in the thickness of the metal during this process.
 •Suitable for producing moulded sections such as irregular shaped
channels and trim.

23. RING ROLL
 Seamless (i.e., without a joint) rings find wide application in industry.
 The inner and outer races of ball and roller bearings, steel tyres for railway
wheel are some such applications.
 These rings are made by a special rolling process called ring rolling.
 Ring rolls are used for tube rolling, ring rolling.
 Ring rolls are made of spheroidized graphite bainitic and pearlitic matrix or
alloy cast steel base.
 cantilever roll tube roll universal roll

24. POWDER ROLLING
CONTINUOUS CASTINGAND
HOT ROLLING
 Metal powder is introduced between the rolls and compacted into a ‘green strip’, which
is subsequently sintered and subjected to further hot working and/or cold working and
annealing cycles.
•Metal is melted, cast and hot rolled
continuously through a series of rolling mills
within the same process.
• Usually for steel sheet production.

25. THREAD ROLLING
 Dies are pressed against the surface of cylindrical blank. As the blank rolls against the in-feeding
die faces, the material is displaced to form the roots of the thread, and the displaced material flows
radially outward to form the thread's crest.
 A blank is fed between two grooved die plates to form the threads.
 The thread is formed by the axial flow of material in the work piece. The grain structure of the
material is not cut, but is distorted to follow the thread form.
 Rolled threads are produced in a single pass at speeds far in excess of those used to cut threads.
 The resultant thread is very much stronger than a cut thread. It has a greater resistance to
mechanical stress and an increase in fatigue strength. Also the surface is burnished and work
hardened.

26. HOT ROLLING
 The first hot-working operation for most steel products is done on the primary
roughing mill
 These mills are normally two-high reversing mills with 0.6-1.4 m diameter
rolls (designated by size).
 The objective is to breakdown the cast ingot into blooms or slabs for
subsequent finishing into bars, plate or sheet.

27. COLD ROLLING
 Cold rolling is carried out under recrystallisation temperature and
introduces work hardening.
 The starting material for cold-rolled steel sheet is pickled hot-rolled breakdown coil
from the continuous hot-strip mill.
 Cold rolling provide products with superior surface finish (due to low temperature
no oxide scales)
 Better dimensional tolerances compared with hot-rolled products due to less thermal
expansion.
 Cold-rolled nonferrous sheet may be produced from hot-rolled strip, or in the case of
certain copper alloys.

28. ROLL BITE CONDITION
 The metal contact each of the roller along the arc(AB), which is
known as the “flat strip” arc of contact.
 This arc corresponds to the central angle “α” called angle of contact
or Bite.

29. ROLLING DEFECTS
Two types ,
 1. Surface defects
 2. Structural defects.
SURFACE DEFECTS
 Surface defects include rusting and scaling,
surface scratches, surface cracks.

30. ROLLING DEFECTS
STRUCTRUAL DEFECTS
These defects include the following:
(i) Wavy edges
(ii) Zipper cracks
(iii) Edge cracks
(iv) Centre split
(v) Alligatoring
(vi) Folds

31. ROLLING DEFECTS
 Wavy edges and zipper cracks:
 These defects are caused due to bending of rolls under the rolling pressure.
 This causes tensile stress in the centre and compressive stress in the edges. The former
causes zipper cracks in the centre and the latter causes wavy edges.
 Remedy for zipper cracks and wavy edges lies in provide a “camber” to the rolls. They
are made slightly convex in the central portion to offset the effect of deflection under
rolling loads.
 Edgecracks and centre split:
 These defects are caused due to non homogeneous plastic deformation of metal across
the width.
 As the work piece passes through the rolls, under the rolling pressure its height
decreases while its length increases.

32. ROLLING DEFECTS
 Alligatoring:
 rupture of material along the length into an upper half and a lower half
resembling the open mouth of an alligator.
 Folds:
 This defect is encountered when the reduction per pass is very low.

33. PROBLEMS

34. PROBLEMS

35. MCQ’s
 1. The earing defect in the rolling of the work piece is not caused by
_________
a) too high speed
b) low clearance between the roll and workpiece
c) blank holding
d) material dependent
 2. The roll separating force between the rolling rolls will increase if
_____________
a) roll diameter increases
b) roll diameter decreases
c) number of rolls increases
d) number of rolls decreases
 3. The roll separating force between the rolls can be decreased by
lowering the friction between the workpiece and the rolls.
a) True
b) False

36. MCQ’s
 4. Appling the back tension on workpiece will shift the neutral point
towards ____________
a) exit of roll
b) entrance of roll
c) does not shift
d) depends upon the magnitude of the force
 5. If the coefficient of friction of material with the roll is 0.2, find the
angle of a bite?
a) 11.3 degree
b) 16.25 degrees
c) 21.02 degrees
d) 71.29 degrees
 6. The arc of contact between the roll and the workpiece is circular in
geometry, and its radius is smaller than the roll radius.
a) True
b) False

37. MCQ’s
 7. The sheet has an initial thickness of 30 mm with roll diameter of
300 mm and coefficient of friction equal to 0.2. Find the final
thickness of the sample in case maximum reduction is carried out in a
single pass?
a) 12 mm
b) 18 mm
c) 24 mm
d) 30 mm
 8. Find the coefficient of friction of the roll having diameter 100 mm
and the maximum possible reduction is 1 mm?
a) 0.01
b) 0.1
c) 0.5
d) 1

38. MCQ’s
 9. The position of the neutral point in rolling does not depend upon
__________
a) diameter of roll
b) percentage of reduction
c) coefficient of friction
d) composition of material
 10. Find the angle of contact for an arc on a roll having the maximum
reduction equal to 2 mm and roll diameter 800 mm?
a) 2.86 degrees
b) 4.28 degrees
c) 82.2 degrees
d) 54 degrees

39. THANK YOU