Rolling of Metals
Download
1 / 22

Chapter 13 - PowerPoint PPT Presentation


  • 201 Views
  • Uploaded on

Rolling of Metals. Chapter 13. Introduction. This chapter describes Flat rolling Shape rolling Production of seamless tubing & pipe Rolling – process of reducing the thickness of a long work piece Plates – having thickness greater than 6mm Sheets – generally less than 6mm thick.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Chapter 13' - Leo


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Chapter 13

Rolling of Metals

Chapter 13


Chapter 13

Introduction

  • This chapter describes

    • Flat rolling

    • Shape rolling

    • Production of seamless tubing & pipe

  • Rolling – process of reducing the thickness of a long work piece

  • Plates – having thickness greater than 6mm

  • Sheets – generally less than 6mm thick


Chapter 13

Flat Rolling

Flat Rolling Process


Flat rolling process
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


Frictional forces
Frictional Forces

Friction Forces acting on strip forces

  • Max Draft

  • h0-hf = µ2R

    Roll Force

  • F= W0.L.Yavg

  • L=̃ sqrt{R(ho-hf)}


Flat rolling practice
Flat-Rolling Practice

  • 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

  • Continuous Casting

    • Is replacing traditional methods

    • Faster & better

      Product of the first hot-rolling operation - Bloom or slab

    • Square cross section of 150mm (6in) on one side

    • Processed father by shape rolling

      • I-beams

      • Railroad rails


Flat rolling practice con t
Flat-Rolling Practice Con’t

  • 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

  • Pack rolling – when two or more layers of metal are rolled together

Changes in grain structure during hot-rolling


Defects in rolled plates sheets
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


Other characteristics
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 roughness

    • 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



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


Shape rolling operations
Shape-Rolling Operations two-high; (b) three-high; (c) four-high; (d) cluster mill

  • 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


Chapter 13

Stages in two-high; (b) three-high; (c) four-high; (d) cluster millShape Rolling of an H-section part. Various other structural sections such as channels and I-beams, are rolled by this kind of process.


Ring rolling
Ring Rolling two-high; (b) three-high; (c) four-high; (d) cluster mill

  • 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


Ring rolling1
RING ROLLING two-high; (b) three-high; (c) four-high; (d) cluster mill

(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


Thread rolling
Thread Rolling two-high; (b) three-high; (c) four-high; (d) cluster mill

  • Cold-forming process

  • Straight or tapered threads are formed on round rods by passing the pipe though dies

  • Typical products include

    • Screws

    • Bolts


Thread rolling con t
Thread Rolling Con’t two-high; (b) three-high; (c) four-high; (d) cluster mill

  • Threads are rolled in the soft condition

  • Threads may then be heat treated, and subjected to final machining or grinding

  • Uncommon or special-purpose threads are machined


Production of seamless pipe tubing
Production of Seamless Pipe & Tubing two-high; (b) three-high; (c) four-high; (d) cluster mill

  • 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


Continuous casting integrated mills minimills
Continuous Casting & Integrated Mills & Minimills two-high; (b) three-high; (c) four-high; (d) cluster mill

  • Continuous casting

    • Advantages

      • Highly automated

      • Reduces product cost

      • Companies are converting over to this type of casting


Continuous casting integrated mills minimills con t
Continuous Casting & Integrated Mills & Minimills Con’t two-high; (b) three-high; (c) four-high; (d) cluster mill

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


Chapter 13
Spray Casting two-high; (b) three-high; (c) four-high; (d) cluster mill : In spray casting the molten metal is sprayed over a rotating mandrel to produce seamless tubing and pipe


The end

THE END two-high; (b) three-high; (c) four-high; (d) cluster mill