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FORGING

FORGINGMODULE 3 UPSET FORGINGOpen Die forgingImpression/Closed Die forgingFlashless/ Precision forgingSTANDARD OPERATIONS AND CLASSIFICATIONS1. Upsetting2. Edging FulleringCrosssectionalareaoftheworkredu cesasmetalflowsoutward,awayfromcentre4. Drawing Piercing Metal flows around the die cavity as a moving die pierces the Bending: The metal is bent around a die/anvil. Roll FORGING Inthisprocess,thebarstockisreducedincros s-sectionorundergoeschangeincross-sectio nwhenitispassedthroughapairofgroovedroll smadeofdiesteel. Thisprocessservesastheinitialprocessings tepforforgingofpartssuchasconnectingrod, ROLLINGC oggingSuccessivelyreducingthethicknessof abarwithopendieforging Alsocalleddrawingout Reducingthethicknessofalongsectionofabar withoutexcessiveforcesormachiningForging betweentwoshapeddies FulleringandEdgingdistributematerialinto specificregionsoftheblank BlockingcreatesaroughshapePrecision FORGING Truecloseddieorflashlessforgingusespreci sevolumesofmaterialtocompletelyfillthedi ecavity Undersizeblankswillnotfillthecavity,over sizeblankswillcausehighpressuresandmayda magethedies Reducesthenumberofadditionaloperationsan dwastedmaterial Near-net-shapeforging(ornet-shape)DIE INSERTSSWAGINGR otaryswagingorradialforgingandTubeswagin g As

Roll forging In this process, the bar stock is reduced in cross-section or undergoes change in cross-section when it is passed through apair of grooved rolls made of die steel. This process serves as the initial processing step for forging of parts such as connecting rod, crank shaft etc.

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1 FORGINGMODULE 3 UPSET FORGINGOpen Die forgingImpression/Closed Die forgingFlashless/ Precision forgingSTANDARD OPERATIONS AND CLASSIFICATIONS1. Upsetting2. Edging FulleringCrosssectionalareaoftheworkredu cesasmetalflowsoutward,awayfromcentre4. Drawing Piercing Metal flows around the die cavity as a moving die pierces the Bending: The metal is bent around a die/anvil. Roll FORGING Inthisprocess,thebarstockisreducedincros s-sectionorundergoeschangeincross-sectio nwhenitispassedthroughapairofgroovedroll smadeofdiesteel. Thisprocessservesastheinitialprocessings tepforforgingofpartssuchasconnectingrod, ROLLINGC oggingSuccessivelyreducingthethicknessof abarwithopendieforging Alsocalleddrawingout Reducingthethicknessofalongsectionofabar withoutexcessiveforcesormachiningForging betweentwoshapeddies FulleringandEdgingdistributematerialinto specificregionsoftheblank BlockingcreatesaroughshapePrecision FORGING Truecloseddieorflashlessforgingusespreci sevolumesofmaterialtocompletelyfillthedi ecavity Undersizeblankswillnotfillthecavity,over sizeblankswillcausehighpressuresandmayda magethedies Reducesthenumberofadditionaloperationsan dwastedmaterial Near-net-shapeforging(ornet-shape)DIE INSERTSSWAGINGR otaryswagingorradialforgingandTubeswagin g Asolidrodortubeissubjectedtoradialimpact forcesbyreciprocatingdies(workpieceissta tionary)

2 Screwdriverbladesmadethisway Coiningisformintingcoinsandjewelry Completelycloseddiesandhighpressures(5-6 timesthestrengthofthematerial)toobtainfi nedetails Lubricantscannotbeusedsincetheyareincomp ressibleCOININGA nexampleofacoiningoperationtoproduceanim pressionoftheletterEDie Design Mustknowworkpiecematerialstrengthandduct ility,deformationrate,temperaturesensiti vity,frictionalcharacteristics Forgeabilityofmaterialsiscapabilitytound ergodeformationwithoutcracking Mustevaluateshape,size,andcomplexityofde sign Materialflowsinthedirectionofleastresist ance,whichiswhyintermediateshapesmayneed tobeformed Preshapingshouldpreventmaterialfromeasil yflowingintoflash,producefavorablegrainf lowpatterns,andminimizefrictionandwearat thedie-workpieceinterface Computerscanmodelandpredictmaterialflow Parting lines are usually at the largest cross section Flash specifications.

3 Flash clearance should be 3% of maximum FORGING thickness Land that is 2-5 times flash thickness, then a larger gutter that does not restrict flash flow Draft angles are needed (7-10 deginternal, 3-5 external) Avoid small radii Avoid sharp corners Inserts can be used Diematerialsmusthavestrengthandtoughness atelevatedtemperatures,hardenability,res istancetomechanicalandthermalshock,wearr esistance Dieselectionbasedonsize,requiredproperti es,forgingtemperature,operationtype,cost ,andproductionquantities Commondiematerialsaretoolanddiesteelswit hchromium,nickel,molybdenum,andvanadium Diesareforgedfromcastings,andthenmachine dandfinishedasneeded,oftenwithheattreatm enttoincreasehardnessandwearresistance Lubricantsactasthermalbarriersforhotwork pieceandcoolerdies,improvemetalflow,anda repartingagentsDie Failure Causes Improperdesign Defectivematerial Improperheattreatmentandfinishingoperati ons Overheatingandcrackscausedbytemperaturec ycling usuallypreheatdiesto1500-2500degreesCels ius Excessivewear chippingorcrackingfromimpactforces(canbe repairedbyweldingorlasermetaldeposition) Overloading Misuseorimproperhandling failuretoremoveaforgedpartbeforeinsertin ganewblankTypes of FORGING Machine Work Restricted Machines (Energy or Load Limited) Hammers Gravity drop hammers Power hammers Counterblow hammers Friction Screw Presses Hydraulic Presses Stroke Limited (Restricted) Machines Mechanical pressesDIFFERENT TYPES OF DROP HAMMERSM echanical board hammerItisastrokerestrictedmachine.

4 Repeatedlytheboard(weight)israisedbyroll sandisdroppedonthedie. Hammer (Power Hammer) Range: 5 kNto 200 kN It uses steam in a piston and cylinder arrangement. It has greater FORGING capacity. It can produce forgings ranging from a few kgsto several tonnes. Preferred in closed die forgingFORGING MACHINESH ydraulic pressIt is a load restricted machine. It has more of squeezing action than hammering action. Hence dies can be smaller and have longer life than with a hammer. Hydraulic pressFeatures of Hydraulic Press Full press load is available during the full stroke of the ram. Ram velocity can be controlled and varied during the stroke. It is a slow speed machine and hence has longer contact time and hence higher die temperatures. The slow squeezing action gives close tolerance on forgings. Initial cost is higher compared to hammers.

5 Mechanicalpresswithaneccentricdrive; -joint pressScrew pressRACK AND PINION PRESSCRANK PRESSG ravity drop hammerForgingHammers GravityDropHammers dropforgingwithafreefallingram;energybas edonproductofram sweightanddropheightRamweightsof180-4500 kg(400-10000lbs) PowerDropHammers downstrokeisacceleratedbysteam,air,orhyd raulicpressureRamweightsof225-22500kg CounterblowHammers tworamsthatapproacheachotherhorizontally orvertically(partmayberotatedbetweensucc essiveblows);operateathighspeedswithless vibrationstransmitted verylargecapacitypossible HighEnergyRateMachines ramacceleratedbyaninertgasathighpressure ;veryhighspeedsbutproblemswithmaintenanc e,diebreakage,andsafetyFORGING HAMMERSM echanical PressesMechanicalPresses crankoreccentricshaftdriven,orknuckle-jo intforveryhighforces; (300-14000tons) Higherproductionratesthanhammers lessblowsMoreprecisethanhammers movingdieplateguidedbyslidewaysorcolumns Hydraulic PressesHydraulicPresses constantspeeds,loadlimited,longerprocess ingtimes,higherinitialcostthanmechanical pressesbutrequirelessmaintenance125MN(14 000tons)opendie,450MN(50000tons)closeddi eFriction Screw Presses ScrewPresses flywheeldriven,energylimited(ifdiesdonot completelyclose,cyclerepeats) Smallproductionruns,highprecision (160-31500tons) FORGING DEFECTSThe different types of defects, occurring in the FORGING operations are as follows: die filling.

6 Misalignment. laps. FORGING penetration-should forge on the press. differences resulting in pronounced property variation. shortness, due to high sulphurconcentration in steel and nickel. , ,inupsettingforging, ,duetotemperaturedifferentialbetweensurf aceandcenter, , EXTRUSIONCOLD EXTRUSIONF orward or direct extrusionBackward or indirect extrusionHooker ExtrusionHydrostatic extrusionImpact extrusionExtrusionisaplasticdeformationp rocessinwhichablockofmetal(billet)isforc edtoflowbycompressionthroughthedieopenin gofasmallercross-sectionalareathanthatof theoriginalbilletExtrusion is an indirect-compression processDefinition and principle of DIRECT extrusion 1. DIRECT EXTRUSION2. INDIRECT EXTRUSIONINDIRECT EXTRUSIONI nindirectextrusion,thedieatthefrontendof thehollowstemmovesrelativetothecontainer , ,thisprocessischaracterizedbytheabsenceo ffrictionbetweenthebilletsurfaceandtheco ntainer, EXTRUSION_ColdExtrusion ForwardLATERAL EXTRUSIONHOOKER EXTRUSIONCold Extrusion_ ,reductionincrosssection,extrusionspeed, billettemperature, dieconfigurations:(a)diefornonferrousmet als;(b)dieforferrousmetals.

7 (c)dieforaTdieforaT-shapedextrusionmadeo fhot-workdiesteelandusedwithmoltenglassa salubricantExtrusions and examples of products made by sectioning off extrusionsExtrusion ratio,foxAAr ExtrusionDefectsa)Centre-burst:internalc rackduetoexcessivetensilestressatthecent repossiblybecauseofhighdieangle, ) ) ForceForce,F,dependson: Strengthofbilletmaterial ExtrusionRatio,R,Ao/Af Frictionbetweenbilletandchamber&diesurfa ces Processvariables:temperature,velocityF = A0k ln(A0/Af)TheExtrusionconstant,k, Flow in Extrusion Influences quality & mechanical properties of extruded product Material flows longitudinally Elongated grain structureTypesofmetalflowinextrudingwith squaredies.(a)Flowpatternobtainedatlowfr ictionorinindirectextrusion.(b)Patternob tainedwithhighfrictionatthebillet chamberinterfaces.(c) ,observedinmetalswhosestrengthincreasesr apidlywithdecreasingtemperature,leadstoa defectknownaspipe(orextrusion)defect.

8 Usehighertemperaturestoimproveductility& metalflow Cancauseexcessivediewear,resultofabrasio nfromsurfaceoxides Canhavenonuniformdeformationcausedbycool ingsurfacesofbilletanddie Improvebypreheatingdie Surfaceoxidesonproductmaybeundesirablewh engoodsurfacefinishisimportant Canpreventextrusionofsurfaceoxidesbymaki ngthediameterofthedummyblockalittlesmall erthanthecontainer;thiskeepsathinshell( skull )ofoxidesinthecontainerHOT EXTRUSIONE xtrusionofaseamlesstube(a)usinganinterna lmandrelthatmovesindependentlyoftheram.( Analternativearrangementhasthemandrelint egralwiththeram.)(b) : Materialflowduringextrusion Surfacefinish&integrity Productquality ExtrusionforcesGlassisexcellentlubricant for: Steels Stainlesssteels High-temperaturemetals&alloysGlassapplie daspowdertobilletsurfaceorInsertglasspad atdieentrance;whenheated,meltedglasslubr icatesdiesurfaceColdExtrusion Usesslugscutfromcoldfinishedorhotrolledb ars,wire,orplates Smallerslugs( )aresheared.

9 Endssquaredifnecessary Largerslugsaremachinedtospecificlengths Stressesontooldiesareveryhigh Lubricationiscritical,especiallywithstee ls Applyphosphate-conversioncoatingonworkpi ece,conversioncoatingonworkpiece,followe dbysoaporwaxCold ExtrusionForce = F = AoiscrosssectionalareaofblankYavgisavera geflowstressofmetal istruestrainthatpieceundergoes=ln(Ao/Af) DRAWINGD rawing Changingthecross-sectionalareaorshapeofa solidrod,wire,ortubingbypullingitthrough adie Rodisthetermforlargercrosssections,wiref orsmaller Typicalproducts:Electricalwiring,Cable,T ension-loadedstructuralmembers,Weldingel ectrodes,Springs,Paperclips,Bicyclewheel spokes, (chromiumplated)andcarbides(titaniumnitr idecoated),diamondforfinewireDrawingPara meters Parametersincludedieangle(a),reductionin crosssectionalarea,drawingspeed,temperat ure,andlubrication Foracertainreductionindiameterandfrictio nconditions,thereisanoptimumdieangle Yavgisaveragetruestressofthematerialinth ediegap Dieangleistypically6-15degrees Maximumreductionperpassis63%,butmorethan 45%cancauselubricantbreakdownandsurface- finishdeterioration Thesmallertheinitialarea,thesmallerthere ductionperpasspercentagethatistypicallyu sed Intermediateannealingmaybeneededbetweenp assesIndrawing,thecrosssectionofalongrod orwireisreducedorchangedbypulling(hencet hetermdrawing)

10 ItthroughadiecalledadrawdieDrawingVariou sShapes Drawingflatstrips(ironing)isusedinmaking beveragecans Bundledrawingisusedtosimultaneouslydrawt housandsofwireswithfinalpolygonalcrossse ctionalshapesTubeDrawing:Drawingcanbeuse dtoreducethediameterorwallthicknessofsea mlesstubesandpipes, , (whichhasbeenmadebyotherprocesses). ( )arepossibleinwiredrawingContinuous drawing of wire Wiredrawingisdoneoncontinuousdrawingmach inesthatconsistofmultipledrawdies,separa tedbyaccumulatingdrumsbetweenthedies. Eachdrum,calledacapstan,ismotordriventop rovidetheproperpullforcetodrawthewiresto ckthroughtheupstreamdie. Italsomaintainsamodesttensiononthewireas itproceedstothenextdrawdieintheseries. Eachdieprovidesacertainamountofreduction inthewire,sothatthedesiredtotalreduction isachievedbytheseries. Dependingonthemetaltobeprocessedandtheto talreduction,annealingofthewireissometim esrequiredbetweengroupsofdiesintheseries .


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