制造工程与技术热加工英文joining-rocesses-and-e

成型技术基础ManufacturingEngineeringandTechnology--HotProcesses

制造工程与技术(热加工)制造冷加工与热加工特点热加工：Casting铸、

Forming锻、Welding焊、Heat

Processing热处理张大童、曹彪、黄珍媛PartⅤJoiningProcessesandEquipment

Joining:

Connectpartstogether.Joiningisanall-inclusiveterm(总称），coveringprocessessuchaswelding,brazing,soldering,adhesivebonding（胶接）,andmechanicalfastening.GivesomeexamplesofJoiningProcessesyouknown.Whyjoiningprocesses?Withoutjoining,therewouldnotbemodernindustry.BecauseproductsorpartswouldbeImpossibletomanufactureExpensiveDifficulttomaintenanceHardtogetdifferentpropertiesDifficulttotransportationjoiningprocessesclassificationSeeFig.V.3

Whatdifferencebetweenweldingandadhesivebonding,ormechanicalfastening?AdhesivebondingMechanicalfastening

JoiningProcessesweldingFusionBrazingandsolderingSolidstateChemicalElectricalElectricalChemicalMechanicalProcessselection:which’spreferred,whichnot?长征二号丙火箭8月发射卫星失利故障原因：二级飞行段二级游机Ⅲ分机与伺服机构连接部位失效造成，因为连接部位的可靠性存在薄弱环节。

ThechoiceofajoiningprocessdependsonTheapplicationThejointdesignThematerialsinvolvedTheshapesofthecomponentstobejoined,theirthicknesses,andtheirsizesOthers:thelocationofthejointwithintheproduct,componentnumbers,theoperatorskillrequired,costsandsoon.吴林教授：

1.制造技术的三个基本功能：成形、连接、改性；

2.古代焊接起源于中国，现代焊接发展于西方；

3.焊接已经逐渐从技术走向科学。

三种焊接原理还没有形成一个统一的科学理论；宏观、细观、界观、微观；还有若干自然现象：太空环境下材料的粘连，冰和肌肉的粘连等；各种新材料的连接，特别是陶瓷、高温材料、碳纤维、复合材料、异种材料等的连接问题有待于实现和发展。——焊接的问题基本上是一个材料界面的科学问题手艺技术科学§27Fusion-WeldingProcesses熔焊weldingFusionBrazingandsolderingSolidstateChemicalElectricalElectricalChemicalMechanicalShieldedMetal-ArcSubmergedArcPlasmaArcGasMetal-ArcFlux-CoredArcGasTungsten-ArcElectron-BeamLaser-BeamElectro-gasElectro-slagAtomicHydrogenetalTopicstoDiscussIntroductionOxyfuelGasweldingArc-WeldingProcesses:ConsumableelectrodeElectrodesArc-WeldingProcesses:NonConsumableProcessThermitWeldingElectronBeamWeldingLaserBeamWeldingCuttingWeldingSafety27.1IntroductionFusionwelding:Itisdefinedasthemeltingtogetherandcoalescingofmaterialsbymeansofheat.Heat(energy)isusuallysuppliedbychemicalorelectricalmeans.Fillermetals（填充金金属）mayormaynotbeused.Fillermetals:Metalsaddedtotheweldareaduringwelding.Autogenousweld（自熔焊焊缝）:FusionweldsmadewithouttheadditionoffillermetalsBasicprinciplesofeachprocessEquipmentAdvantagesandlimitationsCapabilitiesGeneralCharacteristicsofFusionWeldingProcesses27.2OxyfuelGasWelding—OFW气焊，氧氧乙炔焊焊weldingFusionBrazingandsolderingSolidstateChemicalElectricalElectricalChemicalMechanicalOxyfuelgasThermitOxyfuelGasWelding（氧燃气气焊接，，气焊））:Ageneraltermusedtodescribeanyweldingprocessthatusesafuelgascombinedwithoxygentoproduceaflame,whichisthesourceoftheheatthatisusedtomeltthemetalsatthejoint.Oxyacetylenewelding（氧乙炔炔焊）:Theprocessutilizestheheatgeneratedbythecombustionofacetylenegas(C2H2)inamixturewithoxygen.C2H2+O2→2CO+H2+heat(1/3ofthetotal)2CO+H2+1.5O2→2CO2+H2O+heat(2/3)Otherfuelgases??27.2.1TypesofflamesNeutralflame(中性焰））:Theratioofacetyleneandoxygenis1:1.It’swidelyusedforOFWofmostmaterials.Oxidizingflame（氧化焰焰）:Theratioissmallerthan1.It’sharmfulforsteelwelding,itcanbeusedfortheweldingofcopperandcopper-basedalloys.Reducingorcarburizingflame（还原焰焰或碳化化焰）:Theratioisbiggerthan1.It’’sforbrazing,soldering,andflame-hardeningbecauseofitslowertemperature27.2.2FillerMetals(填充金属属）andFlux（焊剂））Fillermetalsareusedtosupplyadditionalmaterialtotheweldzoneduringwelding.Theyareavailableasrodorwiremadeofmetalscompatiblewiththosetobewelded.Theseconsumablefillerrodsmaybebare,ortheymaybecoatedwithflux.Thepurposeoftheflux:①toremoveoxidesfromthesurfaces②togenerategaseousandslagshield③totakepartinthemetallurgicalreactions27.2.3WeldingpracticeandEquipmentWeldingTorch（焊炬））EquipmentOperation①Preparetheedgestobejoined,andestablishandmaintaintheirproperpositionbytheuseofclampsandfixtures;②Opentheacetylenevalve,andignitethegasatthetipofthetorch.Opentheoxygenvalve,andadjusttheflamefortheparticularoperation;③Position:Holdthetorchatabout450fromtheplaneoftheworkpiece,withtheinnerflameneartheworkpieceandthefillerrodatabout300-400;④Speed:Touchthefillerrodtothejointandcontrolitsmovementalongthejointlengthbyobservingtherateofmeltingandfillingofthejoint.Safety①Compressedgas:Exploding;②BurningBack;③Flame,heatandlightinjuring:goggleswithshadedlenses（带遮光光片的护护目镜））,faceshield（面罩））,gloves（手套））,protectiveclothing（防护服服）.ProcessCapabilitiesLowcostbutmoreheatinput;Mostferrousandnonferrousmetals(≤≤6mm)（黑色金属属有有色色金属））Manual:Portable（便携的的）,versatile（通用的的）,economicalforsimpleandlow-quantitywork;Forfabricationandrepairwork.27.3Arc-weldingprocess：Consumable-electrode(熔化极））weldingFusionBrazingandsolderingSolidstateChemicalElectricalElectricalChemicalMechanicalShieldedMetal-ArcSubmergedArcPlasmaArcGasMetal-ArcFlux-CoredArcGasTungsten-ArcElectron-BeamLaser-BeamElectro-gasElectro-slagAtomicHydrogenetalArc-weldingprocessWhatisarc?Whatkindofarccanbeusedforwelding?Anarcisproducedbetweenthetipoftheelectrodeandtheworkpiecetobewelded,bytheuseofanACoraDCpowersupply（电源））.Polarity（极性））forDC.(straightandreverse)正接反反接Arc-weldingprocessinvolveseitheraconsumableoranon-consumableelectrode.（熔化极极or非熔化极极）27.3.1ShieldedMetal-ArcWelding(SMAW)焊条电弧弧焊（手手工电弧弧焊）Weldingpractice①Theelectricarcisgeneratedbytouchingthetipofacoatedelectrode（焊条））againsttheworkpiece（工件））andthenwithdrawingitquicklytoadistancesufficienttomaintainthearc;②Theheatgeneratedmeltsaportionofthetipoftheelectrode,ofitscoating,andofthebasemetalintheimmediateareaofthearc;③Aweld（焊缝缝）formsafterthemoltenmetal,amixtureofthebasemetal,theelectrodemetal,andsubstancefromthecoatingontheelectrode,solidifiesintheweldarea.ShieldedMetal-ArcWelding----Arcbasemetal母材weldmetal焊缝electrode焊条，电极极coating涂层，药皮皮shieldinggas保护气体solidifiedslag凝固焊渣(27.4)ElectrodesIntroductionElectrodesareusedasconsumablesinSMAW.Theyaremadeupofweldingwire(core)andcoating.Electrodesareclassifiedaccordingtothestrengthofthedepositedweldmetal,thecurrent,andthetypeofcoating.Typicalcoatedelectrodedimensionsare150to460mminlengthand1.5to8mmindiameter.Asthethicknessofthesectionstobeweldedincreases,therequiredcurrentandelectrodediameteralsoincrease.Weldingwire(core)Actsasonepoleofthearcandfillermetal.ElectrodecoatingsElectrodesarecoatedwithclaylikematerialsthatincludesilicate（硅酸盐））binders（粘合剂））andpowderedmaterialssuchasoxides(氧化物）,carbonates（碳酸盐））,fluorides（氟化物））,metalalloys,andcellulose（纤维素））.Thecoating,whichisbrittleandparticipatesincomplexinteractionsduringwelding,hasthefollowingbasicfunctions:0~3Functionsofcoating①tostabilizethearc：toimprovemetaltransfermodeandweldcontour，toreducespatter;②tocontroltherateatwhichtheelectrodemelts;③togenerategasestoactasashieldagainstthesurroundingatmosphere—thegasesproducedarecarbondioxideandwatervapor(andcarbonmonoxideandhydrogeninsmallamounts);④toactasafluxtoⅰ.protecttheweldagainstformationofoxides,nitrides（氮化物）,andotherinclusions（夹杂）,andⅱ.withtheresultingslag,protectthemoltenweldpool;⑤toaddalloyingelementtotheweldzonetoenhancethepropertiesofthejoint—amongthem,deoxidizers（脱氧剂）,topreventtheweldfrombecomingbrittle.(1)牌号中的首首位字母E表示焊条。。(2)E之后的前两两位数字表表示熔敷金金属的最低低抗拉强度度值，单位位为9.8MPa。(3)E之后的第三三位数字表表示焊条适适用的焊接接位置，其其中0或1表示全位置置焊接，2表示平焊和和平角焊，，4表示立向下下焊。(4)E之后第四位位数字与第第三位数字字的组合表表示药皮类类型和焊接接电源的种种类。型号牌牌号E4303J422钛钙型E5015J507低氢钠型E5016J506低氢钾型Theprinciplesofelectrodeselection:①themetaltobewelded,②thepropertyoftheweld,③theworkingconditions,④theshapeandthicknessoftheworkpiece,⑤weldingposition,and⑥cost.ShieldedMetal-ArcWelding----equipmentelectrodeholder焊把，电极极夹cable电缆weldingmachine焊机powersource电源Figure27.5Schematicillustrationoftheshieldedmetal-arcweldingoperations(alsoknownasstickwelding,becausetheelectrodeisintheshapeofastick).Powersource:1.ThecurrentmaybeDCorAC(50A～300A).2.ThepolarityoftheDCcurrent:①straightpolarity:theworkpieceispositiveandtheelectrodenegative.Itproducesshallowpenetration,andisgoodforjointswithverywidegaps.②reversepolarity:Theelectrodeispositive.Deeperweldpenetrationispossible.3.TheACmethod:thearcpulsatesrapidly;thismethodissuitableforweldingthicksectionsandforusinglarge-diameterelectrodeatmaximumcurrents.Processcapabilities①Itissimple,portableandversatile(简单、灵活活、适应面面广）.Itiscommonlyusedingeneralconstruction（建筑）,inshipbuilding（造船）,onpipelines（管道）andformaintenance（维护）work.②Thecostofequipmentislow.③Itcanbeusedwithmostferrousandnonferrousmetals(3-19mm).Forthickerplate(slagremovedbeforenextpass)Fig27.6Adeepweldshowingthebuild-upsequenceofindividualweldsequence.27.3.2SubmergedArcWelding——SAW埋弧焊Processandequipment:Theweldarcisgeneratedbetweentheelectrodeandworkpiece,anditisshieldedbyagranularflux,consistingoflime（石灰石））,silica（硅酸盐））,manganeseoxide（氧化锰））,calciumfluoride(氟化钙）,andothercompounds.Thefluxisfedintotheweldzonebygravityflowthroughanozzle.reel盘wire-feed送丝contacttube导电嘴recovery回收hopper斗weldbacking焊接衬垫Functionoftheflux(unfusedflux):(焊剂）Thethicklayeroffluxcompletelycoversthemoltenmetal.ItpreventsspatterandsparksandsuppressestheintenseultravioletradiationandfumescharacteristicoftheSMAWprocess.Thefluxtakespartinthemetallurgicalreactionsathightemperature.Alloyingelementinfluxcanbeeffectivelytransfertotheweldmetaltoenhancethepropertiesofthejoint.Thefluxalsoactsasathermalinsulator,promotingdeeppenetrationofheatintotheworkpiece.Electrode:(焊丝，电极极）Theconsumableelectrodeisacoilofbareroundwire1.5mm-10mmindiameter.Itisfeedautomaticallythroughacontacttube（导电嘴））.ProcesscapabilitiesTheSAWprocessislimitedtoweldsinaflatorhorizontalpositionandhavingabackuppiece.Straightlongweldsandcircularweldscanbemade.Thequalityoftheweldisveryhigh,withgoodtoughness,ductility,anduniformityofproperties.Itprovidesveryhighweldingproductivity(I=300A～2000A),depositing4-10timestheamountofweldmetalperhourastheSMAWprocess;Itisusedtoweldavarietyofcarbonandalloysteelandstainlesssteelsheetorplate(﹥1mm),oftenatspeedsashighas5m/min.Typicalapplicationsincludethickplateweldingforshipbuildingandforpressurevessels.Multipleelectrode27.3.3GasMetal-ArcWelding(GMAW)熔化极气体体保护焊GasMetal-ArcweldingFusionBrazingandsolderingSolidstateChemicalElectricalElectricalChemicalMechanicalShieldedMetal-ArcSubmergedArcPlasmaArcGasMetal-ArcFlux-CoredArcGasTungsten-ArcElectron-BeamLaser-BeamElectro-gasElectro-slagAtomicHydrogenetalGasmetal-arcwelding(GMAW),developedinthe1950s,isformerlycalledmetalinert-gasweldingormetalactive-gaswelding(MIG/MAG)（熔化极惰性性气体保护护焊/活性）.Theweldarcisgeneratedbetweentheelectrodeandworkpiece.Theweldareaisshieldedeffectivelybyanatmosphereofargon,helium,carbondioxide,orvariousothergasmixtures.Theconsumablebarewireisfedautomaticallythroughanozzleintotheweldarc.Asanadditiontotheuseofinertshieldinggases,deoxidizers（脱氧剂））areusuallypresentintheelectrodemetalitself,inordertopreventoxidationofthemoltenweldpuddle（熔池）.(1)PrincipleSolidwire实芯焊丝Electrode电极Shieldinggas保护气Contacttube导电嘴Nozzle喷嘴Basemetal母材Fig.27.8SchematicillustrationofGMAWprocess(2)EquipmentPowersource电源Wirefeeder送丝机Gassupplysystem供气系统Fig.27.9EquipmentforGMAW(3)TypesofGMAWGas①Metalinert-gaswelding(MIG)熔化极惰性性气体保护护焊Shieldinggas:argon（氩气）,helium（氦）Itismainlyusedfortheweldingofstainlesssteelandnonferrousmetals（有色金属属）.②Metalactive-gaswelding(MAG)熔化极活性性气体保护护焊gasmixtures:Ar+O2orAr+CO2andmoreItismainlyusedfortheweldingofferrousmetals（黑色金属属）.③CO2,CO2+O2(CO2)二氧化碳焊焊接Itismainlyusedfortheweldingofferrousmetals.Current①DCelectrodeconnecttopositiveterminal②Pulsed(P-GMAW)averagecurrentdecreased脉冲熔化极极气体保护护焊③VariablePolarity(VP-GMAW)forweldingaluminumalloys变极性----PulsedCurrenttoimprovemetaltransfer(alsoarcstability)VariablePolarityCurrentforweldingAluminumanditsalloys(4)Metaltransfer(熔滴过渡））MetalcanbetransferredbythreemethodsintheGMAWprocess:spraytransfer(喷射过渡),globulartransfer(颗粒过渡））,andshort-circuitingtransfer(短路过渡).Thefactorsaffectingtransfermode:①weldingparameters，②thediameteroftheelectrode/wire,③electrodeextensionlength（焊丝干伸伸长）,and④thetypeofshieldinggas.①spraytransfer喷射过渡Smalldroplets（熔滴）ofmoltenmetalfromtheelectrodearetransferredtotheweldareaatarateofseveralhundreddropletspersecond.Thetransferisspatter-free（无飞溅）andverystable.HighDCcurrentandvoltagesandlarge-diameterelectrodesareused,withargonoranargon-richgasmixtureusedastheshieldinggas.②globulartransfer颗粒过渡Inglobulartransfer,carbon-dioxide-richgasesareutilized,andglobules(小球）propelledbytheforcesoftheelectricarctransferthemetal,withconsiderablespatter（飞溅）.Highweldingcurrentsareused.Theymakepossiblegreaterweldpenetration（熔深））andweldingspeedthanareachievedinspraytransfer.Heaviersectionsarecommonlyjoinedbythismethod.③short-circuitingtransfer短路过渡渡Inshort-circuiting,themetalistransferredinindividualdroplets（熔滴））,morethan50persecond,astheelectrodetiptouchesthemoltenweldmetalandshort-circuits.Lowcurrentsandvoltagesareutilized,withcarbon-dioxide-richgasesandwithelectrodesmadeofsmall-diameterwire.Thismethodissuitableonlyforthinsheetsandsections(≤6mm),otherwiseincompletefusionmayoccur.Processcapabilities①Theprocessisversatile,rapid,andeconomical.TheweldingproductivityisdoublethatoftheSMAWprocess.②Itissuitableforweldingavarietyofferrousandnonferrousmetals（各种黑黑色金属属和有色色金属））andisusedextensivelyinthemetal-fabricationindustry.③Lowerdistortion（变形））andslag（溶渣））.④Itcaneasilybeautomatedandlendsitselfreadilytoroboticsandtoflexiblemanufacturingsystem.27.3.4Flux-CoredArcWelding(FCAW)药芯焊丝丝弧焊Theflux-coredarcweldingprocessissimilartogasmetal-arcwelding,withtheexceptionthattheelectrodeistubular（管状的的）inshapeandisfilledwithflux.Figure27.10Schematicillustrationoftheflux-coredarc-weldingprocess.Thisoperationissimilartogasmetal-arcwelding,showinginFig.27.8.Flux-coredwire:Theflux-coredelectrodesareprovidedinlongcoiledlengths.Theyareusually0.5mm-4mmindiameter,withdifferentcross-section.Coredelectrodesproduceamorestablearc,improveweldcontour,andproducebettermechanicalpropertiesoftheweldmetal.Themainpurposeofusingflux-coredelectrode：toimprovethetransitioncoefficientofalloyingelementsbyadjustingtheircontentinfluxcore,thusproducingbettermechanicalpropertiesoftheweldmetal;towelddifferentkindsofmetalsbyadjustingtheformulaofflux（药芯配配方）.Whatisdifferentwiththechangeofelectrode?AdvancesinthemanufactureofelectrodesforFCAWandinthechemistryofthefluxhavemadethisprocessthefastestgrowinginweldingProcesscapabilities①theflux-coredarc-weldingprocesscombinestheversatility（多功能性性）ofSMAWwiththecontinuousandautomaticelectrode-feedingfeatureofGMAW.②Itissuitableforweldingavarietyofjoints,mainlyonsteels,stainlesssteels,andnickelalloys.③It’ssuitableforthejoiningofsectionsofallthicknesses.?(usuallythicker,butthinsheetnowwithsmallerdiameterelectrodes)④Itcaneasilybeautomatedandisreadilyadaptabletoroboticsandtoflexiblemanufacturingsystem.27.3.5ElectrogasWelding—EGW（气电焊焊）Weldthicknessrangesfrom12mm-75mmWeldinginonepassFigure27.11Schematicillustrationoftheelectrogasweldingprocess.Source:AmericanWeldingSociety.27.3.6ElectroslagWelding——ESW（电渣焊焊）Workpiecethicknessesrangefrom50mmtomorethan900mm.WeldinginonepassFigure27.12Equipmentusedforelectroslagweldingoperations.Source:AmericanWeldingSociety.27.5Arc-weldingprocesses:Nonconsumable-electrode(非熔化极极）Unlikethearc-weldingprocessesthatuseconsumableelectrodes,nonconsumable-electrodeprocessestypicallyuseatungstenelectrode（钨电极极）.Asonepoleofthearc,itgeneratestheheatrequiredforwelding.Ashieldinggasissuppliedfromanexternalsource.27.5.1GasTungsten-ArcWelding(GTAW)（钨极气气体保护护焊）tungsteninertgaswelding(TIG)(钨极惰性性气体保保护焊，，钨极氩氩弧焊））InGTAW,thefillermetalissuppliedfromafillerwire.Thefillermetalsaresimilartothemetaltobewelded,andfluxisnotused.WeldingwithGTAWmaybedonewithoutfillermetals.Theshieldinggasisusuallyargonorhelium(oramixtureofthetwo).Becausethetungstenelectrodeisnotconsumedinthisoperation,aconstantandstablearcgapismaintainedataconstantcurrentlevel.Electricalconductor电导体;tungstenelectrode钨电极;Shieldinggas保护气体;Gaspassage气体通道;Fillerwire填充焊丝，，焊丝;Basemetal基体金属，，母材;Moltenweldmetal熔化的焊接接金属，熔熔池金属;Solidifiedweldmetal凝固焊缝金金属，焊缝缝Figure27.13Thegastungsten-arcweldingprocess,formerlyknownasTIG(fortungsteninertgas)welding.Tungstenelectrode:Thorium（钍）,cerium（铈）orzirconium（锆）maybeusedinthetungstenelectrodes,toimprovetheirelectronemissioncharacteristics.ContaminationofthetungstenelectrodeContamination（污染）ofthetungstenelectrodebythemoltenmetalcanbeasignificantproblem,particularlyincriticalapplications,becauseitcancausediscontinuitiesintheweld.Contactoftheelectrodewiththemoltenmetalpoolshouldbeavoided.Howtoinfluencetheweld？PowersupplyDependingonthemetalstobewelded,thepowersupplyiseitherDC(includepulsed-DC)orAC.Ingeneral,ACispreferredforaluminumandmagnesium,becausethecleaningactionofACremovesoxideandimprovestheweldquality.Figure27.14Equipmentforgastungsten-arcweldingoperations.ProcessCapabilities:①Theprocesshasbetterarcstability,andisespeciallysuitableforthinmetals(normally≤4mm);②Itprovidesweldswithhighqualityandsurfacefinish;③Itcanbeusedinallweldingposition;④Itisusedforawidevarietyofmetalsandapplications,particularlyaluminum,magnesium,titaniumandtherefractorymetals(难熔熔金金属属））;⑤ThecostoftheinertgasmakesthisprocessmoreexpensivethanSMAW.?27.5.2Plasma-ArcWelding(PAW)（等等离离子子弧弧焊焊））InPAW,aconcentratedplasmaarc(压缩缩等等离离子子弧弧)isproducedandisaimedattheweldarea.Thearcisstableandreachestemperaturesashighas33000℃℃.Aplasmaisionizedhotgas(完全全电电离离了了的的气气体体),composedofnearlyequalnumbersofelectronsandions.Whenafillermetalisused,itisfedintothearc,asisdoneinGTAW.Arcandweld-zoneshieldingissuppliedbyargon,helium,ormixtures.Howtoconcentratethearc?plasmagas(离子子气气);shieldinggas(保护护气气);powersupply(电源源)Figure27.15Twotypesofplasma-arcweldingprocesses:(a)transferred,(b)nontransferred.Deepandnarrowweldscanbemadebythisprocessathighweldingspeeds.TherearetwomethodsofPAW:①transferred-arcmethod:(转移电电弧））Theworkpiecebeingweldedispartoftheelectricalcircuit,thearctransfersfromtheelectrodetotheworkpiece.Itismainlyusedforweldingandcuttingofmetals.②nontransferredmethod:(非转移移电弧弧）Thearcoccursbetweentheelectrodeandthenozzle,workpieceisnotlinkedintothecircuit,andtheheatiscarriedtotheworkpiecebytheplasmagas.Itismainlyusedforweldingandcuttingofnonmetals.Keyholetechnique(小孔型型等离离子弧弧焊)ProcessCapabilities:①PAWhashigherenergyconcentration(andsopermitsdeeperandnarrowwelds),betterarcstability,lessthermaldistortion,andhigherweldingspeeds.Ithashigherproductivity;②Withkeyholetechnique,itcanpenetratecompletelythroughthejointofthicknessesasmuchas20mmforsomeTiandAlalloysEffectiveheatinweldingCarbon(electrode)arcGasmetalarcSubmergedarc27.6ThermitWelding（热剂焊焊/铝热焊焊）27.7Electron-BeamWelding(EBW)电子束束焊InEBW,heatisgeneratedbyhigh-velocitynarrow-beamelectrons.Thekineticenergyoftheelectronsisconvertedintoheatastheystriketheworkpiece.Thisprocessrequiresspecialequipmenttofocusthebeamontheworkpieceinavacuum;thehigherthevacuum,themorethebeampenetratesandthegreaterthedepth-to-widthratio.Generally,noshieldinggas,flux,orfillermetalisrequired.Electrongun:ElectronsareacceleratedandfocusedProcessCapabilities:AlmostanymetalcanbeweldedbyEBW(theweldqualityishighduetothevacuum).Theprocesshasthecapabilityofmakinghigh-qualityweldsthatarealmostparallel-sided,deepandnarrow,andhavesmallheat-affectedzones（热影影响区区）.Distortion（变形形）andshrinkage（收缩缩）intheweldareaisminimal.Depth-to-widthratios（深宽宽比））rangebetween10to30.Theintenseenergyisalsocapableofproducingkeyholesintheworkpiece,andworkpiecethicknessescanrangefromfoil(箔，薄薄片）upto150mm.Typicalapplicationsincludetheweldingofaircraft,missile,nuclear,andelectroniccomponentsandofgearsandshaftsfortheautomotiveindustry.(importantparts)EBWequipmentgeneratesx-rays;hence,propermonitoringandperiodicmaintenanceareessential.27.8Laser-BeamWelding(LBW)激光焊焊LBWutilizesahigh-powerlaserbeamasthesourceofheat,toproduceafusionweld.Thelaserbeamcanbefocusedontoaverysmallarea,ithashighenergydensityand,therefore,deep-penetratingcapability.Thisprocessisparticularlysuitableforweldingdeepandnarrowjoints,withdepth-to-widthratiosrangefrom4to10.Thelaserbeammaybepulsedforapplicationssuchasspotweldingofthinmaterials.Continuousmulti-kWlasersystemsareusedfordeepweldsonthicksections.Figure27.16Comparisonofthesizeofweldbeadsin(a)electron-beamorlaser-beamweldingtothatin(b)conventional(tungsten-arc)welding.Source:AmericanWeldingSociety,WeldingHandbook(8thed.),1991.ComparisonofLaser-BeamandTungsten-ArcWeldingProcessCapabilities:①LBWproducesweldsofgoodquality,withminimumshrinkageanddistortion.Laserweldshavegoodstrengthandaregenerallyductileandfreeofporosity;②Itisparticularlyeffectiveonthinworkpiece;itcanbeautomatedtoweldthematerialswiththicknessesofupto25mm.Weldingspeedsrangefrom2.5m/mintoashighas80m/minforthinmetals;③Typicalmetalsandalloysweldedincludealuminum,titanium,ferrousmetals,copper,superalloys（高温温合金金）,andtherefractorymetals（难熔熔金属属）.ThemajoradvantagesofLBWoverEBW:Avacuumisnotrequired,andsothebeamcanbetransmittedthroughair.Laserbeamscanbeshaped,manipulated,andfocusedoptically,sotheprocesscaneasilybeautomated.Thebeamsdonotgeneratex-rays(asopposedtoEBW)Thequalityoftheweldisbetter,withlesstendencyforincompletefusion,spatter,andporosityandwithlessdistortion.Safetyconsideration：Laserbeamisinvisible,butwithhighenergy.Thelasercanbereflectedbythematerialsurface,especiallythesolid-state(YAG)lasers.Keepyoureyesandskinfromthehazards.27.9Cutting切割27.9.1OxyfuelGasCutting可燃气气体切切割,火焰切切割27.9.2ArcCutting电弧切切割Aircarbon-arccutting碳弧切切割Plasma-arccutting等离子子切割割27.9.3LaserBeamCutting激光切切割27.9.4WaterJetCutting水射流流切割割27.9.5MechanicalCutting机械切切割Figure27.18(a)Flamecuttingofsteelplatewithanoxyacetylenetorch,andacross-sectionofthetorchnozzle.(b)Cross-sectionofaflame-cutplateshowingdraglines.27.10WeldingSafetyTherearecertainhazardsinweldingandcutting.Safetyconsiderationsandmethodsshouldbetaken.①SurroundingsBecauseoftheheatsources,suchasopenflames,arcs,sparksandhotmetal,usedinweldingandrelatedoperations,fireandexplosionhazardsarealwayspresentintheworkarea.Thusweldingprocessesshouldbecarriedoutawayfromallcombustiblematerials,includingflammablefluids,vapors,gases,fuel,wood,andtextiles.20101115上海高高层大大火，，58人死亡亡，电焊工无特特种作作业人人员资资格证证，严严重违违反操操作规规程，，引发发大火火后逃逃离现现场；；事故故现场场违规规使用用大量量尼龙网网、聚聚氨酯酯泡沫沫等易燃材材料，导导致大火火迅速蔓蔓延。②PersonalDangerFiresandexplosionscancauseseriousinjuryandevenfatality.Protectionoftheoperator’seyes,face,andbodyagainstsparks,spatter,andinfraredandultravioletradiationisessential.Safetyequipmentandprotectiveclothingshouldbeused.③NoiseandShock(噪音与电电击）Excessiveandprolongednoisegeneratedbyweldingorcuttingoperationscancausetemporaryorpermanenthearingloss.Earprotectiondevicesshouldbeused.Weldingthatuseselectricitypresentshazards.④FumesManyweldingprocessesemitfumesandgases.Someofthesefumesandgasesaretoxicandcanbehazardoustohealth.Someimportantfactorstobeconsideredare:thenatureofthefumesandthegasesevolvedduringwelding;theproperdisposalofusedelectrodes,fluxesandslag;andtheproperhandlinganddisposalofsomeofthehighlytoxicchemicalsusedinsurfacepreparationpriortowelding.SummaryOxyfuelgas,arc,andhigh-energy-beamweldingareamongthemostcommonlyusedjoiningoperations.Gasweldinguseschemicalenergy;tosupplythenecessaryheat,arcandhigh-energy-beamweldinguseelectricalenergyinstead.Inalltheseprocesses,heatisusedtobringthejointbeingweldedtoaliquidstate.Shieldinggasareusedtoprotectthemoltenweldpoolandtheweldareaagainstoxidation.Fillerrodsmayormaynotbeusedinoxyfuelgasandarcweldingtofilltheweldarea.Theselectionofaweldingprocessforaparticularoperationdependsontheworkpiecematerial,onitsthicknessandsize,onitsshapecomplexity,onthetypeofjoint,onthestrengthrequired,andonthechangeinproductappearancecausedbywelding.Avarietyofweldingequipmentisavailable,muchofwhichisnowcomputercontrolledwithprogrammablefeatures.Thecuttingofmetalsalsocanbedonebyprocesses,theprinciplesofwhicharebasedonoxyfuelgasandarcwelding.Thecuttingofsteelsoccursmainlythroughoxidation(burning).Thehighesttemperaturesforcuttingareobtainedbyplasma-arccutting.TrendsAmajortrendinweldingistheautomationofweldingprocesses,doneinordertocontrolprocessvariablesaccuratelyandrepeatedly(stability)andtoreducetheneedforskilledlabor.(protection)Computercontrolsandprogrammablerobotsarebeingusedextensivelyformanyweldingoperations.Thesedevelopmentsarebeingfurtherenhancedbytheuseofappropriatesensorstotracktheweldjoint.Theymonitortheconditionsduringweldingand,withfeedbackcontrols,maketheadjustmentsnecessarytomaintainweldqualityandintegrity.Theflux-coredarc-weldingprocesshasadvancedfarbeyondgasmetal-arcweldinginreplacingshielded-metal-arcwelding.Pulsed-arcgasmetal-arcweldingisgainingwideusageforthinferrousandnonferrousmetals.Laser-beamweldingofflatsheetmetalfora