MProcesses 12 Rolling

7/29/2019 MProcesses 12 Rolling

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Rolling and Forging

Manufacturing

Processes


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Outline

Temperature

RollingFlat Rolling

Shape Rolling OperationsThread Rolling

Seamless Tubing and Pipe

Rolling Nonmetallic Materials

ForgingOpen-Die ForgingClosed-Die Forging

Roll Forging

Heading

Rotary SwagingForging Machines

Dies

Economics


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Rolling and Forging

Rolling

The thickness of a slab of a

slab or plate is reduced bycylindrical rolls which rotate topull the material between themand compress it

Forging

A workpiece is compressed

between opposing dies so thatthe material is forced into thedie shape


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Temperature in Metal

FormingCold working (room temperature

or slightly higher)

Warm working (30% - 50% of themelting temperature)

Hot working (50% - 75% of themelting temperature)

Isothermal formingTools are preheated to preventsurface cooling during forming


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Structure/Property

Modification


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Cold Working

Advantages

- No heating required

- Better surface finish- Better dimensional accuracy

- Parts are interchangeable

- Better strength, fatigue andwear properties

- Directional properties can beimparted

- Minimal contaminationproblems


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Cold Working

Disadvantages

- Higher forces required

- More powerful equipmentrequired

- Less ductility is available

- Surfaces must be clean- Intermediate anneals may be

needed to restore ductility

- Directional properties may be

detrimental- May produce undesirable

residual stresses


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Typical Rolled Products


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Typical Rolled Products


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Rolling Process


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Rolling Process


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Rolling Process


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Rolling Process


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Rolling Process


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Example of a Hot

Rolling Line


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Rolling Defects


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Shape Rolling

Uses a series of specially shaped

rolls to form a beam with a specific

cross section (such as an I-beam)


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Ring Rolling

Uses rolls to form a thick, small-

diameter ring into a thin, larger-

diameter ring


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Ring Rolling


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Thread Rolling

Uses moving dies with grooves to

form threads on cylindrical parts


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Thread Rolling


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Material Property

Changes


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Roll Piercing

Uses compressive stresses on a

cylindrical part to cause tensile

forces at the interior, creating ahole to form a thick-walled tube


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Example of a Tube

Rolling Mill


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Rolling Nonmetallic

Materials- Paper

- Plastic sheets

- Rubber products

- Reinforced fabric

Calendering

Passes material through a

series of gaps between rolls to

form a thin sheet


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Calendering


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Calendering

Example of a calendered rubber sheet with twolayers

Courtesy Cooper Tire


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Calendering of Rubber


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Coated Products


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Reinforced Materials

spools

reinforcing

material

windup

coating

material

Coating on both sides of

reinforcing material

comb

coating

material


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Example of a polyester-reinforced rubber sheet withfibers exposed



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Example of a steel-belted rubber sheet with the beltexposed



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Calender Control

Systems


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Calendering Thickness

Sensors

X rays or beta

radiation (electrons)

Detector

Emitter

some radiation is

blocked, depending

on thickness


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Milling

Squeezes material between rolls to

mix or preheat it for further

processes


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Forging

ForgingA deformation process in which

the material is compressed

between dies, using impact orgradual pressure to form the

part


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Forging


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Example of a Forging

Machine


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Machine


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Working Temperature

Hot Forging

Material is above its

recrystallization temperature

Cold Forging

Increased strength from strainhardening


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Forging

Billet

A piece of material with a square or circular cross

section; usually produced by a deformation process

such as rolling or extrusion


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Open Die Forging

Compresses the work between flat or

nearly flat dies


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Open Die Forging


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Open Die Forging


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Open Die Forging

Advantages

Simple, inexpensive dies; wide

range of sizes; good strength

Limitations

Simple shapes only; difficult tohold close tolerances;

machining necessary; low

production rate; poor utilizationof material; high skill required


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Closed Die Forging

Also called impression-die forging;

compresses the material into the

shape of the die cavity


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Closed Die Forging


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Closed Die Forging

Advantages

Good utilization of material;

better properties than open dieforging; good dimensional

accuracy; high production rate;

good reproducibility

Limitations

High die cost for smallquantities; machining often

necessary


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Roll Forging

Uses grooved rolls to reduce

thickness and increase length of

round or flat bars


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Roll Forging


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Roll Forging


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Roll Forging


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Coining

Uses dies to press fine detail into

both sides of the workpiece


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Upsetting/Heading

Decreases the length and increases

the diameter of the workpiece;

often used to form heads on nails,

bolts, etc.


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Orbital Forging

Uses a die that moves in various

directions to compress the

workpiece


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Swaging

Uses hammering dies to decrease

the diameter of the part


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Swaging


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Forging Dies and Die

InsertsSeparate inserts may be used for

forging complex shapes; this may

be less expensive than a complexsingle-piece die


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Forging Defects


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Forging Machines


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Forging Machines


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Machine


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Economics


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Summary

Rolling and forging shape parts

by deforming the material into

the desired shape


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MProcesses 12 Rolling

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