1. Rolling of Metals

2. Introduction This chapter describes Flat rolling Shape rolling
Rolling Mills
Production of seamless tubing & pipe
Defects in rolled products

3. Introduction
The Process of Plastically deforming metal / alloy by passing it between rolls is known as ROLLING.
Rolling done either at Hot or cold.
The metal is drawn into the opening between the rolls by frictional forces.
Work piece is subjected to high compressive forces due to squeezing action of rolls, resulting in reduced area of cross-section and increased length.

4. Cold Rolling
Hot Rolling

5. TERMINOLOGY

6. TERMINOLOGY Contd.,
Angle of contact or Angle of bite – The Angle subtended at the centre of the roll by arc AB ( Metal in contact with the roll)
Rolling Pass – The feeding of material between the rolls once
Rolling mill – Consists of rolls , bearings& Housings and Drive for applying power to rolls

7. Flat Rolling Process
Flat
Flat Rolling Process
Rolling Process

8. 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

9. GEOMETRY OF ROLLING

10. GEOMETRY OF ROLLING

11. h0-hf = µ2R The angle of bite α can be expressed as; tan α = α = L/R
The length of contact, L=̃ sqrt{R(ho-hf)}
h0 is the strip thickness at start and R is the roll radius
h0-hf = µ2R
(2)

12. Schematic Illustration of Various Roll arrangements

13. Schematic Illustration of various roll arrangements : (a) two-high; (b) three-high; (c) four-high; (d) cluster mill

15. Shape-Rolling Operations
Various shapes can be produced by shape rolling
Bars
Channels
I-beams
Railroad rails
Roll-pass design requires considerable experience in order to avoid external and internal defects

16. Stages in Shape Rolling of an H-section part
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.

17. 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
Various shapes can be produced by shaped rolls
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

18. 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

19. Thread Rolling Cold-forming process
Straight or tapered threads are formed on round rods by passing the pipe though dies
Typical products include
Screws
Bolts

20. 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

22. Defects in Rolled Plates & Sheets
Undesirable
Degrade surface appearance
Adversely affect the strength
Sheet metal defects include:
Scale, Rust, Scratches, Gouges, Pits, & Cracks
May be caused by impurities and inclusions
Wavy edges – result of roll bending
Alligatoring – complex phenomenon