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MEM560MEM560Topic 3 (a): Metal Forming andTopic 3 (a): Metal Forming andShaping ProcessesShaping Processes

Rahani Abdul RahmanCo-ordinator: PM Yusof Mohd

FKM

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Topic 3Topic 33.1 Classification3.2 Open-die forging3.3 Impression-die forging and closed-die

forging3.5 Drawing3.6 Rolling

-----------------------------------------------------------3.7 Sheet-metal Working Process3.8 Process Design and Capabilities

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Metal forming;

- Process of deforming / displacing the metal

- Forming certain shape/design

To produce given shape

To improve properties (material distribution grains & impurities)

By nature, plastic deformation; Beneficial effect to its mechanical properties

Normal : large amount of mechanical force or heating) then a small force

Slip & twinning at solid state

Creation of fiber flow line

at flow direction , higher resistance on force across them

- Metal flow in certain direction type of process

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Primary shaping : casting, powder metallurgy (well define final shape)

Metal forming : extrusion, rolling, forging (shaped via plastic deformation)

Material removing : sawing, turning, milling, grinding

Joining/assembly

Metallurgical (weld, brazing, diffusion bonding)

Mechanical (rivet, bolt & nuts)

Metal treatment : het-treatment, anodizing, surface hardening

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3.1 Classification3.1 Classification

Forming = reshaping of material : deformed (via tensional load, compression, shear,tensile, bending or combinations). Example? Classification of deformation = bulk or sheet Kinematics of deformation = metal flow (shape, velocities, stress, strain) Limits of deformation = internal material failures or surface condition. Forces & capacity = varied Forming classification

i. Hot working at high temperature @ above re-crystallization temperature, notreaching strain hardening - extrusion, forging & rolling. -

crystallization temperature - stamping & drawingiii. Bulk (massive) forming massive increase ofsurface/volumeratio and shape. Large

ratio ofplastic/elastic strainiv. Sheet forming little change on cross sectional area, significant in shape, comparative

and spring back properties.

v. recrystallization Tvi. T ranges

(Hot work 0.5-0.75 of melt temp)

(Warm work 0.3 0.6 melt temp)

(Cold work

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Major Processing Methods for Metal

WroughtProcessing

Rolling

Extrusion

Joining

Welding

Brazing

Casting Powdermetallurgy

Hot isostaticprocessing

Rapidsolidification

primaryshaping

processes

Casting

Blooms Billets Slabs

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Forging

Stamping

Forming

Stamping

Soldering

Metal

formingprocesses

Expensive equipmentLarge forcesLarge capitalLarge number of partsFast production rateNear net-shaping

Structuralmills

Rail mills Bar mills Rod millsSeamlesspipes &

tubes millsSkelp mills Plate mills

Hot-stripmills

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Forging

Drop

Open die

Impression

die

forging

forging

hot forging

forging

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Open die forging (smithOpen die forging (smithforging)forging)Forging

Process by which metal is heated and is shaped by plastic deformation bysuitably applying compressive force. Commonly using compressive force i.epower hammer or a press sample: kerisor ingots.

Advantage

refines the grain structureand improves physical propertiesof the metal.

Grain flow is the direction of the pattern that the crystals take during plastic.

Physical properties (such as strength, ductility and toughness) are muchbetter in a forging than in the base metal, which has, crystals randomlyoriented.

consistent from piece to piece, without any of the porosity, voids, inclusions

and other defects i.e less machining required.Open die forgings/hand forgings

Due to repeated blows in an open die, where the operator manipulates thework piece in the die.

The finished product is a rough approximation of the die. This is what atraditional blacksmith does, and is an old manufacturing process.

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Impression die forging and closedImpression die forging and closed--die forgingdie forging The word impression means close resemblance to the die :

precision forgings.

Closed die : used of mould to form the shape attached to an anvil.

Some with multi-directional flow to fill into cavities

Contact : of hammer to material very short (milliseconds).

Advantages

Cost effective as volume of production increase

Greater strength (~ 20% higher strength-to-weight ratio)

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ConsiderationsConsiderations -- tolerancestolerances

Dimension tolerances -0.3 % of the dimension, rounded offto the next higher 0.5 mm (0.020 in).

Die wear tolerances- lateral tolerances (parallel to theparting plane) : around +0.2 % for Copper alloys to

+0.5 % for Aluminum and Steel.-

closing, and range from 1 mm (0.040 inch) for smallforgings, die projection area < 150 cm2 (23 in2), to 6.25mm (0.25 inch) for large forgings, die projection area >

6500 cm2

(100 in2

). Die match tolerances :to allow for shift in the upper die

with respect to the lower die. Flash tolerance :amount of acceptable flash after the

trimming operation.

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ExtrusionExtrusion (I(I--beam, pipe, tubing, tee, zee, bar, angle)beam, pipe, tubing, tee, zee, bar, angle)Extrusion

a process used to create parts/objects with a fixed cross-sectional profile.

Raw material is pushed/drawn through a die of the desired cross-section.

Advantages

Ability to create very complex cross-sections (+/-0.002?)

Process suits to material that are brittle due to application of compressive andshear stresses.

Excellent surface finishDisadvantage

Surface cracking due to temperature, friction, or high speed being or atlower temperatures if the extruded product temporarily sticks to the die.

Pipe - A flow pattern that draws the surface oxides and impurities to thecenter of the product due to high friction or cooling of the outer regions ofthe billet.

Internal cracking due to a state of hydrostatic tensile stress at the centerlinein the deformation zone in the die.

Processes

Hot extrusion work hardening

Cold extrusion cold working (higher strength)

Warm extrusion below re-crystaline temperatureTopic 3 10

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DrawingDrawing Cold working process

Usage of tensile force to stretch metal

Too slow : wrinkle

Too fast : break & thin

Stretch effect of the rollers

Pull effect draw of canister (hydroforming)

raw

heet

metal

,

tube

&

wire

Plastic

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RollingRolling

Hot Rolling Mill

Hot rolling is a hot working metalworking process where large piecesof metal, such as slabs or billets, are heated above theirrecrystallization temperature and then deformed between rollers toform thinner cross sections. Hot rolling produces thinner crosssections than cold rolling processes with the same number of stages.Hot rolling, due to recrystallization, will reduce the average grain sizeo a me a w e ma n a n ng an equ axe m cros ruc ure w ere as corolling will produce a hardened microstructure.

Cold Rolling Mill

Cold rolling is a metalworking process in which metal is deformed bypassing it through rollers at a temperature below its recrystallizationtemperature. Cold rolling increases the yield strength and hardness ofa metal by introducing defects into the metal's crystal structure. Thesedefects prevent further slip and can reduce the grain size of the metal,resulting in Hall-Petch hardening.

Cold rolling is most often used to decrease the thickness of plate andsheet metal.

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