4. TOPICS
Rolling
Types of Rolling
Flate Rolling
Shapes rolling
Ring rolling
Rolling mill
5. Rolling (metalworking)
Rolling…… process of reducing the
thickness of a long work piece.
OR
The process of plastically deforming metal by
passing it between the rolls is known as rolling.
6. • Rolling….. Is widely used to convert steel
ingots into blooms, billets, and slabs, and
subsequently into plates, sheets and strips.
Rods
8. Rolling Process
Rolls transfer energy to the strip through friction. As the
strip is dragged by the rolls into the gap between them, it
decreases in thickness while passing from the entrance
to the exit. Meanwhile its speed gradually increases from
the entrance to the exit.
V0 = input velocity
Vf = final or output
velocity
R = roll radius
hb = back height
hf = output or final
thickness
11. Hot rolling
Hot working ---- above the re-crystallization
temperature.
It is employed where large reduction in cross-
sectional area is required.
Used for to produce bars, rods, rails etc.
12. Advantages:
Machanical strength is increase.
Porosity is reduce.
Dis-Advantages:
Poor surface finish.
Loss of precise dimension.
13. Cold rolling
Cold working ---- below the re-
crystallization temperature.
Employed for finishing the metal to
given specification of sizes and surface
quality.
Produces sheets, strips and foils.
15. Re-crystallization
Re-crystallization is a process by which
deformed grains are replaced by a new set of
undeformed grains.
Re-crystallization temperature can be defined
as the temperature at which destroyed grains
of a crystal structure are replaced by the new
strain grains
16. → Solvent added (clear) to compound (orange) → Solvent
heated to give saturated compound solution (orange) →
Saturated compound solution (orange) allowed to cool over time
to give crystals (orange) and a saturated solution (pale-orange
18. Flat Rolling Process
Metal strip enters the roll gap
The strip is reduced in size by the
metal rolls
The velocity of the strip is increased
the metal strip is reduced in size
Factors affecting Rolling Process
Frictional Forces
Roll Force and Power
Requirement
19. Flat Rolling
Hot rolling
The initial break down of an ingot
Continuously cast slab
Structure may be brittle
Converts the cast structure to a wrought structure
Finer grains
Enhanced ductility
Reduction in defects
Product of the first hot-rolling operation - Bloom or slab
Square cross section of 150mm (6in) on one side
Processed further by shape rolling
I-beams
Railroad rails
20. Flat-Rolling
Billets – smaller than blooms and rolled into bars and rods
Cold rolling
carried out at room temperature
Produces sheet and strip metal
Better surface finish – less scale.
Changes in grain structure during hot-rolling
21. Defects in Rolled Plates & Sheets
Undesirable
Degrade surface appearance
Adversely affect the strength
Sheet metal defects include:
Scale, Rust, Scratches, Pits, & Cracks
May be caused by impurities and inclusions
Wavy edges – result of roll bending
22. Other Characteristics
Residual stresses – produces:
Compressive residual stresses on the surfaces
Tensile stresses in the middle
Tolerances
Cold-rolled sheets: (+/- ) 0.1mm – 0.35mm
Tolerances much greater for hot-rolled plates
Surface finish
Cold rolling can produce a very fine finish
Hot rolling & sand have the same range of surface finish
Gauge numbers – the thickness of a sheet is identified by a
gauge number
24. Shape-Rolling
Structural shape rolling, also known as shape rolling and
profile rolling.
It is a metal forming process where structural shapes are passed
through rollers to bend or deform the workpiece to a desired
shape while maintaining a constant cross-section.
Structural shapes that can be rolled include:
1) I-beams
2) H-beams
3) T-beams
4) U-beams
5) channels
6) railroad rails
7) pipes
25. Stages in Shape Rolling of an H-section part. Various other
structural sections such as channels and I-beams, are rolled by
this kind of process.
26. Production of Seamless Pipe & Tubing
Rotary tube piercing (Mannesmann process)
Hot-working process
Produces long thick-walled seamless pipe
Carried out by using an arrangement of rotating rolls
Tensile stresses develop at the center of the bar when it is subjected to compressive forces
27. Ring Rolling
A thick ring is expanded into a large diameter ring
The ring is placed between the two rolls
One of which is driven
The thickness is reduced by bringing the rolls together
The ring shaped blank my be produced by:
Cutting from plate
Piercing
Cutting from a thick walled pipe
Typical applications of ring rolling:
Large rings for rockets
Gearwheel rims
Ball-bearing and roller-bearing races
Can be carried out at room temperature
Has short production time
Close dimensional tolerances
28. RING ROLLING
(a) Schematic illustration
of Ring-rolling
operation. Thickness
reduction results in an
increase in the part
diameter.
(b) Examples of cross-
sections that can be
formed by ring-rolling
29. ROLLING MILLS:
A rolling mill consists basically of rolls, bearings, a housing
for containing these parts, and a drive for applying power to
the rolls and controlling there speeds.
Rolling mills can be conventionally classified with respect to
the number and arrangement of the rolls.
Classification of rolling mills:
i) Two-high mills
ii) Tow-high reversing mills
iii) Three-high mills
iv) Four-high mills
v) Cluster mills
vi) Continuous mills
vii) Planetary mills
30. Schematic Illustration of various roll arrangements : (a) two-
high; (b) three-high; (c) four-high; (d) cluster mill
31. Continuous Casting & Integrated Mills & Minimills
Continuous casting
Advantages
Highly automated
Reduces product cost
Companies are converting over to this type of casting
32. Continuous Casting & Integrated Mills & Minimills Con’t
Integrated Mills utilize everything from the production of hot metal to the casting
and rolling of the finished product
Minimills
Scrap metal is melted
Cast continuously
Rolled directly into specific lines of products
Each minimill produces one kind of rolled product
Rod
Bar
Structural steel
33. ROLLED PRODUCTS
i) Bloom:
First breakdown product of ingots with a minimum
cross-sectional area of 36 in2.
Generally, square in cross-scetion.
ii) Billet:
Further reduction of bloom by rolling results in a billet.
Cross-sectional area 1.5 in. X 1.5 in.
iii) Slab:
A hot rolled ingot with a width to thickness ratio of 2:1
at least.
Cross-sectional area over 16 sq. in.
**Blooms, billets and slabs are known as semi-finished products
because they are subsequently formed into other mill products.
34. iv) Plate:
It has thickness greater than ¼ in.
v) Sheet and Strip:
Generally have thickness lesser than ¼ in.
vi) Foil:
Thickness is very small just as 0.002 in.
* Billets and other unfinished rollings are further rolled to
I-sections, T-sections, Angles, Channels, Girders etc.