SME2713 Metal Forming - 3_2

7/28/2019 SME2713 Metal Forming - 3_2

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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

20-Aug-08 Assoc Prof Zainal Abidin Ahmad 3

Introduction Typicalforgedproductsaresuchasgears,

connectingrods,bolts


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


ForgingOperations



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ForgingOperations


ForgingOperations



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3.Classificationsofforgingprocesses

Byequipment

Forginghammerordrophammer

Pressforging

Byprocess

Opendieforging


Forgingmachines



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Hammerandpressforging

processes Forginghammers

Boardhammer

Powerhammer

Forgingpresses

Mechanicalpress


Boardhammer

forging

hammer



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Forginghammerordrophammer


Exampleof

forging

hammerordrop

hammer

suppliedbythe

blowisequalto

thepotential

energyduetothe

weightof

the

ram

andtheheightof

thefall



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Powerhammer


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



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.)


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


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


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


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


Other forging related process -Heading/Upset

Forging


(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


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


(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,


s ow ng ormng oa stepped shaft. (d)

Typical parts madeby swaging.

Swaging

of

Tubes

With

and

Without

a

Mandrel


(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


Cobalt-base superalloysTantalum alloys

Molybdenum alloysNickel-base superalloysTungsten alloys

1180125010501350

115013501050120012001300

7.

Defects

in

Forged

Parts


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


,pieces.

SME2713 Metal Forming - 3_2

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