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MetalForming
3Forging of Metals)orging of Metals)
Assoc Prof Zainal Abidin Ahmad
FKM UTM
LectureOutline
1. Introduction
2. Forgingoperations
3. Classificationofforgingprocesses
4. Closedandopendieforgingprocess
5. Effectofforgingonmicrostructure
6. Otherforgingrelatedprocesses
Swaging
Rollforging
7. Typicalforgingdefects20-Aug-08 Assoc Prof Zainal Abidin Ahmad 2
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1.Introduction
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Introduction Typicalforgedproductsaresuchasgears,
connectingrods,bolts
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Landing-gear components for the C5A andC5B transport aircraft, made by forging
Steps involved in forging a bevel gearwith a shaft.
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2.OutlineofForgingandRelated
Operations
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ForgingOperations
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ForgingOperations
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ForgingOperations
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3.Classificationsofforgingprocesses
Byequipment
Forginghammerordrophammer
Pressforging
Byprocess
Opendieforging
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Forgingmachines
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Hammerandpressforging
processes Forginghammers
Boardhammer
Powerhammer
Forgingpresses
Mechanicalpress
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Boardhammer
forging
hammer
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Forginghammerordrophammer
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Exampleof
forging
hammerordrop
hammer
suppliedbythe
blowisequalto
thepotential
energyduetothe
weightof
the
ram
andtheheightof
thefall
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Powerhammer
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Hydraulicpress
forging
Usingahydraulicpressor
metal,therefore,givescontinuous
formingataslowerrate.
Providesdeeperpenetration
Betterproperties(more
Equipmentisexpensive
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A general view of a 445MN (50,000 ton)hydraulic press. Source:Wyman-GordonCompany.
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Mechanicalpressmachine
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Mechanical press with an eccentric drive;the eccentric shaft can be replaced by acrankshaft to give the up-and-down motionto the ram
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PrinciplesofVariousForgingMachines(cont.)
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Schematic illustration of the principles of various forging machines.(c) Knuckle-joint press. (d) Screw press. (e) Gravity drop hammer.
Typicalvaluesofvelocityforvariousforging
machines
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4.Closedandopendieforging
processes
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Opendie
forging
Opendieforgingiscarried
outbetweenflatdiesor
diesofverysimpleshapes
Theprocessisusedfor
mostlylargeobjectsor
whenthenumberofparts
producedissmall
Opendie
forging
is
often
usedtopreform the
workpieceforcloseddie
forging20-Aug-08 Assoc Prof Zainal Abidin Ahmad 24
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Upsetting
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Figure 14.4 (a) Solid cylindrical billet upset between two flat dies. (b) Uniform deformation of thebillet without friction. (c) Deformation with friction. Note barreling of the billet caused by frictionforces at the billet-die interfaces.
Cogging
Figure 14.5 Twoviews of a cogging
rectangular bar.Blacksmiths use thisprocess to reduce thethickness of bars byhammering the parton an anvil. Note thebarreling of theworkpiece.
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ImpressionDie&ClosedDieForging
Fullerin &ed in areusedtodistributethe
material
Fullering materialisdistributedawayfroman
area
Edging materialisgatheredintoanarea
oc ng roug s ap ngo epar
Impressiondies
give
the
part
its
final
shape
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Closeddie
forging
(impression
die
forging)
Theworkpieceisdeformed
betweentwodiehalveswhichcarry
the im ressions of the desired final
shape.
Theworkpieceisdeformedunder
highpressureinaclosedcavity
Normallyusedforsmaller
components
Theprocess
provide
precision
forgingwithclosedimensional
tolerance
Closeddiesareexpensive
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5.Effectofforgingonmicrostructure
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6. Other forging related process -Coining Closed-die forging process Used for minting coins, medallions, & jewelry
Can be used to improve surface finish
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Other forging related process -Heading/Upset
Forging
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(a) Heading operation, to form heads on fasteners such as nails andrivets. (b) Sequence of operations to produce a bolt head by heading.
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Other forging related process RollForging
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Two examples of the roll-forging operation, also known ascross-
rolling. Tapered leaf springs and knives can be made by this process..
Other forging related process -ProductionofBearingBlanks
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(a) Production of steel balls by the skew-rolling process. (b)Production of steel balls by upsetting a cylindrical blank. Notethe formation of flash. The balls made by these processes aresubsequently ground and polished for use in ball bearings (seeSections 25.6 and 25.10).
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Other forging related process -Swaging
(a) Schematic
rotary-swagingprocess. (b)Forming internalprofiles on a tubularworkpiece byswaging. (c) A die-closing typeswaging machine,
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s ow ng ormng oa stepped shaft. (d)
Typical parts madeby swaging.
Swaging
of
Tubes
With
and
Without
a
Mandrel
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(a) Swaging of tubes without a mandrel; not the increase in wall thickness inthe die gap. (b) Swaging with a mandrel; note that the final wall thickness ofthe tube depends on the mandrel diameter. (c) Examples of cross-sections oftubes produced by swaging on shaped mandrels. Rifling (spiral grooves) insmall gun barrels can be made by this process.
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ClassificationofMetalsinDecreasingOrder
ofForgeablilty
TABLE 14.3
Metal or alloy Approximate range of hot
Aluminum alloysMagnesium alloysCopper alloysCarbon and lowalloy steelsMartensitic stainless steelsAustenitic stainless steels
Titanium alloysIron-base superalloys
40055025035060090085011501100125011001250700950
10501180
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Cobalt-base superalloysTantalum alloys
Molybdenum alloysNickel-base superalloysTungsten alloys
1180125010501350
115013501050120012001300
7.
Defects
in
Forged
Parts
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Examples of defects in forged parts. (a) Labs formed by web buckling duringforging; web thickness should be increased to avoid this problem. (b) Internaldefects caused by oversized billet; die cavities are filled prematurely, and thematerial at the center flows past the filled regions as the dies close.
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RelativeUnitCostsofaSmallConnecting
Rod
Relative unit costs of asmall connecting rodmade by various forgingand casting processes.Note that, for largequantities, forging ismore economical. Sandcasting is the moreeconomical process for
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,pieces.
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