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Rolling, Metal Forming @ W W W Presentation Transcript

  • 1.  
  • 2.
    • METAL FORMING
    • *Metals may be formed into useful shapes in two basic ways:
    • By plastic deformation processes in which the volume and mass of metal are conserved and the metal is displaced from one location to another.
    • By metal removal or machining processes in which material is removed in order to give it the required shape.
  • 3.
    • *Metal forming processes may be classified into only a few categories on the basis of the type of forces applied to the work-piece as it is formed into shape.
    • Direct-compression-type processes
    • Indirect-compression processes
    • Tension type processes
    • Bending processes
    • Shearing processes
  • 4.
    • ROLLING
    • The process of plastically deforming metal by passing it between the rolls is known as rolling.
    • The work is subjected to high compressive stresses from squeezing action of rolls.
    • The frictional force between metal and rolls is responsible for drawing the metal into the rolls.
    • Classification of Rolling Process
    • i) Hot Rolling
    • ii) Cold Rolling
  • 5.
    • Hot Rolling:
    • Hot working ---- above the re-crystallization temperature
    • It is employed where large reduction in cross-sectional area is required.
    • Used for bars, rods, rails etc.
    • 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 with good surface finish and increased mechanical strength.
  • 6.
    • ROLLED PRODUCTS
    • i) Bloom:
    • First breakdown product of ingots with a minimum cross-sectional area of 36 in 2 .
    • Generally, square in cross-section.
    • ii) Billet :
    • Further reduction of bloom by rolling results in a billet.
    • Cross-sectional area 1.5 in. X 1.5 in .
  • 7.
    • 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.
  • 8.
    • 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 .
  • 9.
    • Rolling Process:
    • In the process of rolling the billet is fed from one side into the rolls and reduces in thickness according to the section and gap between the rolls.
    • The reduction ratios have maximum allowable values for different metals beyond which reduction is not practicable in a single process.
    • Rolling sets in series may be employed.
    • ** There are fundamentally two types of rolls:
        • Supporting rolls
        • Driving rolls
    • ** the rolls must be rigid or the rolled material will have a loop like shape .
  • 10.
    • ROLLING MILLS:
    • A rolling mill is a machine or factory for shaping metal by passing it between a pair of work rolls .
    • 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 their speeds.
    • High forces are involved ------ large motors
    • Continuous mills ----- high initial investment
    • Rolling mills can be conventionally classified with respect to the number and arrangement of the rolls.
  • 11.
    • Classification of rolling mills:
        • Two-high mills
        • Two-high reversing mills
        • Three-high mills
        • Four-high mills
        • Cluster mills
        • Continuous mills
        • Planetary mills
  • 12.  
  • 13.  
  • 14.  
  • 15.
    • Rolling mill for plates and wires
  • 16.
    • Rolling mill with twin chamber reheating furnace
  • 17. 2 Hi Hot Rolling Mills for Ferrous/ Non-Ferrous Flats
  • 18. 3 high mill pinion housing, for steel rolling mill.
  • 19.  
  • 20. 4 Hi Cold Rolling Mill for Aluminium
  • 21. Multi-High Mills
  • 22. Cluster Mill
  • 23. Cluster Mill
  • 24. Continuous Rolling Mills
  • 25. Planetary Mill
  • 26. Slab Rolling
  • 27. Steel Ingots
  • 28. Rolled Shapes
  • 29. Rods
  • 30. Steel angles and channels
  • 31.
    • Two-high Mill:
    • The simplest and most common type.
    • Rolls of equals size are rotated in one direction.
    • The stock is returned to entrance, or rear, of the rolls for further reduction by hand carrying or by means of a platform which can be raised to pass the work above the rolls.
    • Improvement --- a two-high reversing mill, in which the work can be passed back and forth through the rolls by reversing their direction of rotation.
    • Three-high Mill:
    • It consists of an upper and lower driven roll and a middle roll which rotates by friction.
  • 32.
    • Four-high Mill:
    • Four rolls ---- two small rolls supported by large-diameter backup rolls.
    • ** Very thin sheet can be rolled to very close tolerance on a mill with small-diameter work rolls.
    • Cluster Mill:
    • E ach of the work rolls is supported by two backing rolls.
    • Continuous Mill:
    • high production
  • 33.
    • Planetary Mill:
    • It consists of a pair of heavy backing rolls surrounded by a large number of small planetary rolls.
    • The chief feature of this mill is that it hot reduces a slab directly to strip in one pass through the mill.
    • The overall reduction is the summation of a serious of small reductions by each pair of rolls in turn following each other in rapid succession.