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BULK DEFORMATIONPROCESSESIN METALWORKING

@2002 ohn Wiley & Sons, Inc. M. P. Groover,"Fundamentals f ModernManufacturinq e'

BULKDEFORMATIONMetal orming perationshich ause ignificanthapechange y deformationn metal artswhose nitialis bulk ratherhansheeto Theseprocesses orkby stressing etal ufficientlycauseplasticlow ntodesired hapeo Performeds cold,warm, ndhotworking perations


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IMPORTANCEF BULKDEFORMATIONo In hotworking,ignificanthape hange anbeaccomplishedo Incoldworking,trengthanbe ncreaseduring hapechange

o Little r no waste someoperationsrenearnet shapeor netshapeprocesses. Theparts equireittle r no subsequent achining

FOURBASIC ULKDEFORMATIONPROCESSESi. Rolling slabor plates squeezedetween pposingrolls2. Forging work s squeezed ndshaped etweenopposingies3. Extrusion work ssqueezedhrough dieopening,therebyakingheshape f heopening4. Wireand bardrawing diameter f wireor bar s reducby pulling t through die opening l


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l . RollingDeformationrocessn whichwork hicknesss reducedby compressiveorces xerted y woopposingolls

Direction f work low-,--,------_>-

The roll ing rocess specifically,lat rolling)

THE ROLLSThe rotatingollsperformwo main unctions:o Pull hework nto hegapbetweenhemby rictionbetween ork-part nd ollso Simultaneouslyqueezehework o reduce rosssection

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TYPESOF ROLLINGo Bygeometry f work:. Flat olling used o reducehickness f a rectangularcross-section. Shape olling a squarecross-sections formed ntoashape uchas an l-beamo By emperaturef work:

. HotRolling mostcommondue o the argeamountofdeformationequired. Cold olling producesinished heetandplatestock

lntermediateolled om Final olled omStructuml hapesJ+fr*

7 Bars, rodsctSome f hesteel roducts ade na rollingmill


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A rollingmill or hot flatthe steelplate s seenas theglowingstripextendingdiagonally romthe lower eftcorner(photocourtesyof BethlehemSteelCompany)

VARIOUS ONFIGURATIONSFROLLING ILLS

(a)2-high ol l ingmil l ffis


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(b)3-high ol l ingmil l

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VARIOUS ONFIGURATIONSFROLLINMILLS

(c) our-highollingmill


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(d)(d)clustermill

VARIOUS ONFIGURATIONSF ROLLINMILLS

(e) andemoll ing i l l "$;")sf

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THREAD OLLINGBulkdeformation rocess sed o form hreads n cylindrical artsbythem between wo dieso Most mportant ommercial rocessor massproducing oltsando Performed y coldworking n hread ollingmachines

Advantages ver hreadcutting machining):. Higherproductionates. Bettermaterial tilization. Stronger hreads ue o work hardening. Better atigue esistance ue o compressivetressesntroduced "vrol l ing

THREADROLLING

Finishedpan,.,,'BMoving di

Thread olling ith latdies:(1)startof cycle, nd 2)endof cycle .'!t\\i\:i:,+-


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II.FORGINGDeformation rocess n whichwork s compressed etweentwo dieso Oldest f he metal orming perations,atingromabout 000BCo Components:ngine rankshafts,onnectingods, ears,aircraft tructuralomponents,et engineurbine artso Inaddition,asicmetalsndustriesse orgingoestablishgsicformof arge omponentshataresubsequentlyachinedoriq;final hape ndsize

CLASSIFICATIONF FORGINGOPERATIONSo Cold s.hot orging:. Hot or warm forging - mostcommon, ue o thesignificant eformation nd heneed o reducestrengthand ncrease uctility f workmetal. Cold forging - advantages increased trengthhatresultsromstrain ardeningo lmpact s.pressorging:. Forge hammer- appliesan impact oad. Forge press - appliesgradualpressure

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TYPESOF FORGING IESOpen-die forging - work is compressed etween wo flat dies,allowingmetal o flow aterally ithout onstraintlmpression-die forging - die surfacescontaina cavityorimpressionhat s impartedo workpart,hus constraining etalflow- f/ash s created

s. Fleshless forging - workpart s completely onstrained n dieand no excess lash s produced l.F

Lowar dis (9blionary)

1. OPEN.DIE ORGINGCompression f workpartwith cylindrical ross-sectionbetween wo flat dieso Similar o compressionesto Deformation perationeduces eight nd ncreases

diameterof worko Commonnames ncludeupsetting r upsef orging


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2. IMPRESSION.DIEORGINGCompression f workpartby dieswith nverseof desiredpartshapeo Flash s formedby metal hat lowsbeyonddie cavity ntosmallgapbetweendie plateso Flash must be later rimmed rom part,but t servesan importantfunctionduringcompression:. As flash orms, riction esistscontinuedmetal low ntogap,constrainingmaterialo fill die cavity. In hot forging,metal low s further estricted y coolingagainstdie

platesl " Ft t " .*"mffi ffix:i'""i,jig#;;__*ap between ie plates

IMPRESSION.DIEORGINGADVANTAGESNDLIMITATIONSo Advantagesomparedo machiningromsolid tock:. Higher roductionates. Conservationf metal lesswaste). Greater trength. Favorablerain rientationn hemetalo Limitations:. Notcapable f closeolerances. Machiningften equiredo achieve ccuraciesand eatures eeded,uchas holes,hreads, ndmating urfaceshat it withother omponents ffii


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3. FLASHLESSORGINGCompression f work n punchand die oolingwhosecavitydoesallowfor flasho Startingworkpart olumemustequaldie cavity olumewithinveryclose oleranceo Process ontrolmoredemandingha n mpression-dieorgingo Bestsuited o partgeometrieshatare simpleand symmetricalo Often classified as a precisionforgingprocess

Flashless orging:(i ) just before nitial ontactwith workpiece,(2 ) partial ompression, nd(3) finalpunchand die closure

FORGTNGAMMERSDROPHAMMERS)o Apply an impact oadagainstworkpart - two types:. Gravitydrophammers impactenergy romfallingweightof aram

. Powerdrop hammers acceleratehe ram by pressurized ir orsteamo Disadvantage:mpactenergy ransmittedhrough nvil nto loorofbui ldingo Mostcommonly se d or impression-d ieorging

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FORGING RESSESo Apply radual ressureo accomplishompressionoperation types:. Mechanical resses converts otation f drivemotorinto inearmotion f ram. Hydraulic resses hydraulic istonactuates am. Screwpresses screwmechanism rives am

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III.EXTRUSIONCompressionormingprocessn which he work metal s forced o flowthrough die opening o produce desired ross-sectionalhapeo Process s similar o squeezingoothpaste utof a toothpasteuo eo In general, xtrusions used o produceon gpartsof uniform ross-sectionso Two basic ypes of extrusion:. Directextrusion Rem. lndirect xtrusion ?

Wht;.u * ,irect xtrusion


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COMMENTS N DIRECT XTRUSIONo Also called forward extrusiono As ram approaches ie opening, smallportion f bil let emains hatcannotbe forced hrough ie openingo This extraportion,called he butt, mustbe separated rom extrudedproduct y cutting t ust beyond he dieexito Starting illet rosssection sually ound,but inalshape s determibydie opening

otl c E(a) Directextrusion o producea hollowor semi-hollow ross-section;b)hollowand (c )semi-hollowross- ections ,.-:,,1rfrf-N

COMMENTS N INDIRECT XTRUSIONo Also called backwardextrusionandeverse extrusiono Limitations f indirect xtrusion re mposed y he ower igidity fhollow am and difficultyn supporting xtruded roduct s it exitsdie

lndirectextrusion o oroduce(a) a solid cross-section nd (b) a hollowcross-section


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GENERAL DVANTAGESFEXTRUSIONo Varietyof shapespossible, speciallyn hotextrusion. Limitation:ar t ross-sectionust euniformhroughoutlengtho Grain tructure ndstrength nhancedn coldandwarmextrusiono Closeolerancesossible,speciallyncoldextrusiono In someoperations,ittle r nowasteof material

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HOTVS. COLDEXTRUSIONo Hotextrusion priorheating f billet o above tsrecrystalzationemperatue. This educes trength nd ncreases uctility f themetal,permitting oresize eductionsnd morecomplex hapeso Coldextrusion generally sed o produce iscrete

parts. The term mpactextrusions used o indicate ighspeed oldextrusion! :l i,:::::::::::::


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A complex xtrudedross-sectionora heatsink(photo ourtesy f Aluminum ompany f America).__*ffi

IV.WIREANDBAR DRAWINGCross-section f a bar, od,or wire s reduced y pull ing t through dieopeningo Similar o extrusion x ceptwork spulled hrough ie n drawing it spushed hrough n extrusion)o Although rawingapplies ensile tress, ompression lsoplaysasignificantolesincemetal s squeezed s it passes hrough ieopening

Figure19.41 Drawing f bar, od,or wire . s i

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WIREDRAWING S.BARDRAWINGo Difference etween ardrawing ndwiredrawingsstocksize. Bar drawing largediameter ar androdstock. Wiredrawing smalldiameter tock wire sizesdown o0.03mm(0.001n.)arepossibleo Althoughhemechanicsre hesame,hemethods,quipment,ndeven erminologyre

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DRAWING RACTICE NDPRODUCTSo Drawing ractice:. Usually erformedscoldworking. Most requently sed or roundcross-sectionso Products:. Wire'. lectricalwire;wire stock or fences, oat hangers, ndshopping arts. Rodsfock or nails,screws, ivets, nd springs. Bar sfock metalbars or machining,orging, ndotherprocesses

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WIREDRAWINGo Continuous rawingmachines onsisting f multiple raw dies(typically Io 12)separated y accumulatingrums. Eachdrum (capsfan)providesproper orce o draw wire stockthroughupstream ie. Eachdie provides small eduction,o desired otal eductionsachieved y the series. Annealing ometimes equired etween ies

BAR DRAWINGo Accomplisheds a smg/e-draftperationthe stockispulledhrough nedieopeningo Beginningtock as arge iameternd sa straightcylindero Thisnecessitatesbatch ypeoperation

:.ll\i.!:!::+::r:l38:':Hydraulically perateddraw bench or drawingmetalbars


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