NC#State#UniversityDepartment)of)Materials)Science)and)Engineering 1

MSE#440/540:#Processing#of#Metallic#Materials

Instructors:)Yuntian)ZhuOffice:)308)RBIIPh:)513D0559ytzhu@ncsu.edu

Lecture)9:)Forging

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Forging

Deformation-process-in-which-work-is-compressed-

between-two-dies--

• Oldest-of-the-metal-forming-operations

– Dates-from-about 5000-B-C-

• Products:-engine-crankshafts,-connecting-rods,-gears,-

aircraft-structural-components,-jet-engine-turbine-parts--

– Also,-basic-metals-industries-use-forging-to-establish-basic-

shape-of-large-parts-that-are-subsequently-machined-to-final-

geometry-and-size---

http://www.youtube.com/watch?v=Fa0FVYxbVWk (Axe,-5.5-min)

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Classification+of+Forging+Operations

• Cold+vs.+hot+forging:++– Hot+or+warm+forging+– advantage:+reduction+in++strength+and+increase+in+ductility+of+work+metal++

– Cold+forging+– advantage:+increased+strength+due+to+strain+hardening+

• Impact+vs.+press+forging:– Forge+hammer+@ applies+an+impact+force+– Forge+press+@ applies+gradual+force+

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Types&of&Forging&Operations• Open2die&forging&2 work&is&compressed&between&two&flat&dies,&allowing&metal&to&flow&laterally&with&minimum&constraint

• Impression2die&forging&2 die&contains&cavity&or&impression&that&is&imparted&to&workpart– Metal&flow&is&constrained&so&that&flash&is&created&

• Flashless&forging&(closed&die&forging)&2 workpart&is&completely&constrained&in&die

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Open%Die(Forging(

Compression(of(workpart(between(two(flat(dies((– Deformation(operation(reduces(height(and(increases(diameter(of(work((

– Also(called(upsetting or(upset)forging)(decrease(in(height,(increase(in(diameter)

https://mail.google.com/mail/u/0/?shva=1#inbox/15ee3788482e1e36?projector=1(Autoparts,(3(min)(

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• (1)%Start%of%process%with%workpiece%at%its%original%length%and%diameter,%(2)%partial%compression,%and%(3)%final%size

Open>Die%Forging%with%No%Friction

hholn=!True%strain:%

Quiz:%What%is%engineering%strain?

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Actual'deformation'of'a'cylindrical'workpart'in'open4die'forging,'showing'pronounced'barreling:'(1)'start'of'process,'(2)'partial'deformation,'and'(3)'final'shape

Open4Die'Forging'with'Friction

!! = !!!!!! , !! = 1+ !.!!"! , !! = ! !! !!!

! = ! ℎ!

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Impression*Die,ForgingCompression,of,workpart,by,dies• Flash,is,formed,by,metal,that,flows,beyond,die,cavity,into,small,gap,between,die,plates,

• Flash,must,be,later,trimmed,,but,it,serves,an,important,function,during,compression:– As,flash,forms,,friction,resists,continued,metal,flow,into,gap,,constraining,metal,to,fill,die,cavity,,

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Impression*Die,Forging,Practice

• Several,forming,steps,are,often,required– With,separate,die,cavities,for,each,step,,• Beginning,steps,redistribute,metal,for,more,uniform,deformation,and,desired,metallurgical,structure,in,subsequent,steps,• Final,steps,bring,the,part,to,final,geometry,,

http://www.youtube.com/watch?v=mySkT0Gw_X0 (1,min),

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Advantages*and*Limitations*of*Impression3Die*Forging

• Advantages*compared*to*machining*from*solid*stock:– Higher*production*rates– Less*waste*of*metal– Greater*strength– Favorable*grain*orientation*in*the*metal

• Limitations:– Not*capable*of*close*tolerances– Machining*is*often*required*to*achieve*accuracies*and*features*needed

Quiz:*why*forging*improve*the*strength?

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Flashless'(closed'die)'Forging

Compression'of'work'in'punch'and'die'tooling'whose'cavity'does'not'allow'for'flash

• Starting'work'volume'must'equal'die'cavity'volume'within'very'close'tolerance''

• Process'control'more'demanding'than'impression?die'forging''

• Best'suited'to'part'geometries'that'are'simple'and'symmetrical''

• Often'classified'as'a'precision)forging process

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• (1)%Just%before%contact%with%workpiece,%(2)%partial%compression,%and%(3)%final%punch%and%die%closure

Flashless%Forging%(Closed%Die%Forging)

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• Upset'forging'to'form'a'head'on'a'bolt'or'similar'hardware'item:'(1)'wire'stock'is'fed'to'stop,'(2)'gripping'dies'close'on'stock'and'stop'retracts,'(3)'punch'moves'forward,'(4)'bottoms'to'form'the'head

Upset'Forging

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• Examples*of*heading*operations:*(a)**heading*a*nail*using*open*dies,*(b)*round*head*formed*by*punch,*(c)*and*(d)*two*common*head*styles*for*screws*formed*by*die,*(e)*carriage*bolt*head*formed*by*punch*and*die

Heading*(Upset*Forging)

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Swaging'

Accomplished'by'rotating'dies'that'hammer'a'workpiece'radially'inward'to'taper'it'as'the'piece'is'fed'into'the'dies''

• Used'to'reduce'diameter'of'tube'or'solid'rod'stock

• Mandrel'sometimes'required'to'control'shape'and'size'of'internal'diameter'of'tubular'parts''

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• Swaging(process(to(reduce(solid(rod(stock4(dies(rotate(as(they(hammer(the(work((

• In(radial(forging,(workpiece(rotates(while(dies(remain(in(a(fixed(orientation(as(they(hammer(the(work((

Swaging(and(Radial(Forging

https://www.youtube.com/watch?v=LFly3VRqjiE (cartoon,(1.12(min)

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HW#assignment

• Reading#assignment:#Chapters#13

• Review#Questions:#13.10,#13.11,#13.12,#13.14,#

• Problems:#13.10,#13.12,#13.14

Department#of#Materials#Science#and#Engineering 17