氧乙炔-切割和焊接-Oxyfuel-Cutting-and-Welding課件

OxyfuelCutting

andWeldingOxyfuel:theprocessofcombiningpureoxygenwithacombustiblefuelgastoproduceaflameCanbeusedforwelding,brazing,cutting,andheatingmetalsOxygen&fuelgasesarestoredunderpressureincylindersandarereleasedasindividualgasesthroughvalves,regulators,andhoses.MixedastheyflowthroughtorchassembliesBurnastheyaredischargedthroughspecialtipsFuelgases:Propane,naturalgas,propylene&acetyleneVaryintheirchemicalcompositionReactwiththemetalindifferentwaysFactorstoconsiderinselectingagas:Availability&costWeldingprocessoroperationtobeperformedThicknessofmetal&typeofweldedjointtobeproducedPhysicalpropertiesofmetalsChemicalpropertiesofmetalsPropane(C3H)Suppliedinaliquidformunderpositivepressure,whichvarieswithtemperatureMostoxyfuelcuttingtorchescanuseLPgas,butspecialhosesandcuttingtipsarerequired.ReadilyavailableinmostareasDuetocost,propanecuttingisheavilyusedinthemetalrecyclingindustry.Propylene(C3H6)Hasbeenusedforapproximately30yearsStableinbothliquidandgasstatesEconomicalProduceslittleslagHasahighheatvalueDoesnothavethewithdrawalpressurelimitationsthatarenecessarywithacetyleneApproximately5%propylene,87%propane&tracesofothergasesAcetylene(C2H2)MostwidelyusedfuelgasforweldingandcuttingapplicationsProducesacleanweldandacontrollableflameLessstableandmoreexpensivethanotherfuelgasesPerformsmostfunctionswellandiswidelyavailableCompressedNaturalGas(CH4)Adaptableforcutting,soldering,brazing,andpreheatingAwatersealorblowbackvalvetopreventbackfiringintothegassupplylinemustprotectthenaturalgassource.FactsAboutOxygen(O2)Odorless,colorless,tasteless&heavierthanairMakesupabout20%oftheatmosphereWillnotburnbyitselfProducedcommerciallybycausingairtoliquefyCompressedintosteelcylindersat1,800to2,400poundsperin2(psi)SupportscombustionandisexplosiveifhandledimproperlyCylindersizes=80to244ft3FactsAboutAcetylene(C2H2)Colorless,buthasaverydistinctodorHighlycombustibleCylindersizes=60to300ft3CylindercontainsaporoussubstancesaturatedwithliquidacetoneAcetyleneispumpedintothecylinder,displacingsomeoftheacetoneNotunderextremelyhighpressureFullcylinderispressurizedtoapproximately250psiMaynotbewithdrawnataratehigherthan

15psiFunctionsofOxyfuelHeat Oxyfuelcuttingofmildcarbonsteelheatsthemetaltorekindlingtemperature(1,400oFto1,800oF),thenoxidizesandblowstheslagfromthecutwithastreamofpureoxygen.Oxyfuelweldingfusestwopiecesofmetalbyheatingthemtothemeltingpointwithacombustiblemixtureofoxygenandfuelgas.CanbedonewithorwithouttheuseofaweldingrodBrazing:thejoiningofmetalsbyaddingbronzefillerSoftandhardsolders(lead&silveralloys)arethefillermaterialsusedinsoldering.Theoxyfuelflameisalsousedtobend,shape,preheat,stressrelieve,post-heat&tempermetal.AssemblyoftheOxyfuelRigSecuretheoxygenandfuelgascylinderstoawall,aspecialcylindercart,oraspecialrackiftransportedtojobsitesinatruck.Removethevalveprotectioncapsandwipeoffanydirtaccumulationwithaclean,drycloth(freefromoilorgrease).Slightlyopen(crack)bothcylinderstomakesuretheydonotstickandtoblowoutanydirtordustlodgedinthevalve.Closethevalves.Checkallvalves,connections,andsoftplugsforleakswithmildsoapywaterandacleanbrush.Attachtheregulatorstothecylinderspointingtowardtheskytopreventsomeonefromgettinginfrontoftheregulator.Theregulators,safetycheckvalves,andhosesshouldbetightenedsecurelywithawrench.Do

Notuseawrenchtoattachtheweldingtiporcuttingattachmenttothetorch.OxyfuelEquipmentDesignedwithseveralbuilt-insafetyprecautions:Oxygenhosesareusuallygreen.Fuelgashosesarered.Alloxygenconnectionsandcylindershaveright-handthreads.Allfuelgasconnectionsandcylindershaveleft-handthreads.Fuelgasfittingshavea“V”notchcutaroundthetheoutsideoftheconnectors.Oxygenfittingsandconnectorsaresmooth.Cylinders:

TwoRegulators:

TwosetsTwostageregulatorsarethesafesttouse.Hoses:Color-coded&specificallydesignedbasedonuseTypeR:designedspecificallyforacetyleneuseTypeT:approvedforallfuelgasesSafetyCheckValves:TwosetsrecommendedAttachbetweenregulatorsandhosesandbetweenhosesandtorchtopreventreverseflowofthegasesandflamethatcouldcausehosefires,regulatorruptures,andcylinderfiresTorchHandle:RegulatedbytwovalvesOftenequippedwithinternalreverseflowcheckvalvesCuttingAttachment:RegulatedbypreheatoxygencontrolvalveOperatedbydepressingthecuttingoxygenleverTorchButtCuttingAttachmentCuttingTips:3to8preheatorificesand1oxygen-cuttingorificeDrillsizedeterminestipsizePropanetipisa2-piecetipwithatleast6preheatorificesWeldingTip:1orificeforgasmixtureSizeisdeterminedbydrillsizeoforificeSafetyPrecautionsKeepoilandgreaseawayfromallpartsoftheoxyfuelapparatus.Securethecylindersinanuprightpositionsotheycannotbeoverturned.Facetheregulatorgaugestowardtheskymakingitimpossibletostandinfrontofthem.Storeanduseoxyfuelunitsinwellventilatedareasadequatelyseparatedfromotheractivities.AcetylenepressureinthelinesshouldNEVERexceed15psi.Opentheacetylenecylindervalve?to?turns;ifitisthewheeltype,openalltheway.Useanapprovedsparklightertolightthetorch;neverusematchesorcigarettelighters.NEVERuseoxygentooperatepneumatictools,blowoutlines,inflatetires,ordustoffclothing.NEVERhangclothingoncylinders,runningtheriskofsaturatingthemwithoxygenandacetylene.DO

NOTconvertanacetyleneregulatortoanoxygenregulatororviceversa.Slowlyopentheoxygencylindervalvetopreventasuddensurgeofpressure.Releaseorloosentheregulatoradjustingscrewbeforeopeningacylindervalve.DO

NOTwalkwithalightedtorchorlaydownalightedtorch.PurgehosesbeforeattachingthetorchRepairhoseswithproperhosesplices,notfrictiontape.NEVERusealeakinghose.Testforleakswithsoapandwater,notmatches.Ifvalvesoncylindersarefaultyortootight,notifythesupplier;undueforcewouldbedangerous.Keepafireextinguisherhandyatalltimes.Dressproperlyandweareyeprotection.Preventheatandsparksfromgettingtocylindersandhoses.DO

NOTstrikeanarconacylinderorhitacylinderwithametalobject.NEVERuseacylinderasagroundinanelectricalcircuit.NEVERguess;getthecorrectinformationfromaqualifiedperson.Mark,isolate,orotherwisedesignateemptycylinders.Oxygenandfuelgascylinders(eitherfullorempty)MUSTbestoredseparatelyinaccordancewithsafetyandfirecodes.Set-UpProcedurefor

OxyfuelTorchNozzleChecktorchbodyforclosedvalves.Checkregulatorforlooseregulatoradjustingscrew.Openacetylenecylindervalve?to?turn(wheel-typevalvesoneturn)maximum.Turnacetyleneregulatoradjustingscrewtodesiredworkingpressure.Openoxygencylindervalvecompletely.Turnoxygenregulatoradjustingscrewtodesiredworkingpressure.Crackacetylenetorchvalveandlightthetorch,openacetylenetorchvalveuntilsootdisappears.Openoxygentorchvalvetoadjusttoneutralflame;noacetylenefeatherandsharpinnerconeWhenwelding,theratioofoxygentoacetyleneisapproximately1:1.Oxygenandacetylenesettingswillvarydependingontheattachmenttipandthicknessofmetaltocutorweld.TypesofOxyfuelFlamesShutdownProcedure

forTorchNozzleTurnoffacetylenevalveontorchbutt.NEVERturnoffoxygenfirst.Turnoffoxygenvalveontorchbutt.Closeacetylenecylindervalve.Bleedacetylenehosebyopeningacetylenetorchvalve;closevalve.Backacetyleneregulatoradjustingscrewuntilloose.Closeoxygencylindervalve.Bleedoxygenhosebyopeningoxygentorchvalve;closevalve.Backoxygenregulatoradjustingscrewuntilloose.Recheckvalvesforclosure,rolluphoses.Ifrigisnottobeusedforsometime, removetheregulatorsandputthe safetycapsbackonthecylinders.

NEVERleaveequipmentunder pressure24hoursaday.CuttingMetalsMetaltobecutshouldbeclean,markedwithapunchorsoapstone,andplacedinasuitablepositionforcutting.DO

NOTcutoveraconcretefloor.Useacontainerorspecialcuttingtabledevicetocatchthemoltenmetal.Oxyfuelcuttingislimitedtoferrousmetals.Steelswithahightungstenorchromiumcontentorstainlesssteelcannotbecutwithoxyfuel.Castironismoredifficulttocutthansteel.AnexcessfuelflameisusedMoreoxygenpressureisneededStepstoFollowinMakingaCutHoldblowpipeperpendiculartosurfaceofmetalunlessbevelsaretobecutHoldtheflameinnerconeabout1/16to1/8inchabovetheplate.ProperdistanceawayfromplatewillpreventmetalfromstickingtothetipHoldtipsothattwopreheatholesareinlinewiththecutHoldtorchatedgeofmetaluntilmetalbeginstomeltTopoftorchmaybeslantedtowardthecut&changedtoaverticalpositionascutprogressesPressdownslowlyonthecuttingoxygenleveruntilcuttingvalveiscompletelyopenWhenthecutisthroughthemetal,movetorchalongmarkTilttorchtiptowarddirectionofcutonthinmetalItshouldbeheldinaverticalpositiononthickmetalMovetorchslowlyalongsurfaceoroxygenstreamwillnotpasscompletelythroughthickmetalTorestartthecut,releasecuttingleverandreheatmetalagainbeforepressingcuttinglevelLosingthecutmaycauseirregularedges.Whenbevelingplateedgesorcuttingatanangle,leanthetipatthedesiredangleandholdthetorchparalleltothework.CorrectCutNoticethatthetopedgeissquareandthatthedraglinesshowaslightcurve.OxygenPressureTooLowProducesacutwithroughsurface,makesitdifficulttoholdcutandresultsinslowspeedwithtoomuchlag.SpeedTooFastProducesaroughcutwithpronounceddraglineverysimilartotoolowoxygenpressure.OxygenPressureTooHighProducesaroughsurface,meltsdowntopedgeandwastesoxygen.TooMuchAcetyleneinPreheatsReducescuttingspeedapproximately25%.Formscarbondepositsoncutsurfaceandwastesacetylene.CorrectCutHerethefactorsoftipsize,pressuresandspeedarecorrect…resultsinsquaretopedgeanduniformnarrowkerf.PreheatsTooHeavyTopedgeismelteddown,kerfirregularandexcessgasisconsumedbythepreheatflame.PreheatsTooSmallWastestimeasmaximumspeedcannotbeobtained.Lowcuttingspeedresultsingougesatbottomedgeofcut.OversizeTipProducesakerfwhichistoowide,causingnotonlyawasteofplatebutalsoawasteofbothgases.UndersizeTipInefficientcutbecausepiecewillnotdropwhenendisreachedasslaghasnotclearedthekerfandcuttingtimewillbeexcessive.StepstoFollowWhenPiercingHolesHoldblowpipetipperpendiculartothesurfaceuntilaspotonthesurfacebeginstomeltRaisetorchuntiltipisabout1/2”fromthesurfaceandslowlypresstheleverastorchisraisedMovetiptoonesideoftheheatedareasothattheslagcanbeblownoutMoveinnerconewithinabout1/8”fromthesurfaceandmakethecutontheinsideedgeoftheholeTofacilitatethecuttingofaholeinthickmetal,drillahole1/4”indiameterorlargerandstartthepiercinginthishole.CareofOxyfuelTipsTipsfrequentlybecomespatteredwithmetalorothermaterialsthatmaycauseinferiorwork.Tocleantips:Rubemerycloth,steelwool,orthefileonatipcleanertocleanandsquarethetippoint.Insertthecorrectsizecleanerintoeachorifice.Pushinandpullout;donottwistorbendthecleaner.Openoxygenslightlyduringthisproceduretoblowoutforeignparticles.Careshouldbetakennottodamagethethreadsandseatsofthetips.PreparingMetalforWeldingFreethemetalfromoil,paint,grease,dirt,rust,andotherforeignmaterial.Heatthemetalwiththetorch,andthencleanwithawirebrush.Thickmetalshouldbebeveledwithagrinderortorch.Aligntheplatestobeweldedandtackweldthemtopreventwarping.ProperWeldingTipPositionsTheblowpipecanbeheldlikeahammerwhenstandingorlikeapencilwhensitting.Thetipandweldingrodshouldbeheldata45oangletotheworksurface.Theinnerconeflameshouldbe1/16”to1/8”abovethemetal.Preheatingthemetalisveryimportantinmakingasuccessfulweld;therefore,theflameshouldbemovedinthedirectionoftheweld,andtheconeshouldstayinsidethepuddle.OxyfuelWeldingProceduresOneofthemostimportantstepsinlearningtoweldwithoxyfuelistocarryamoltenpuddleofmetalalongthelineorseamofpartstobejoined.Forming&runningthebead:Flameheldatstartingpointuntilabrightroundpool(1/4”to3/8”indiameter)isformedWeldingspeedshouldbeadaptedtomaintainauniformpuddlewidth.Innerconeheld1/16”to1/8”abovesurfaceSlowspeed:flameburnsaholethroughthemetalFastspeed:beadwillbeirregularandnarrowMostcommonmovementpatternforfusionweldingisthecircularmotionZigzagmotionisbestwhenusingafillerrodTorchshouldbeheldatabout45otothesurfaceWeldingrodshouldbeheldat45o,butslantedawayfromthetorchtipRoddiametershouldbeequaltothethicknessofthemetalTorchmaybeheldsotipispointedindirectionofweld(forehandwelding)ortippointedtowardweld(backhandwelding)TypesofWeldedJointsMostareeitherbuttjointsorfilletjointsButtwelding:Twopiecesofmetalarebuttedtogetherandwelded,withorwithoutbevelingFilletwelding:MetalpiecesarejoinedtogetherforminganangleWeldingCastIronUsuallydonewithabronzerod,unlessthecolorofthebasemetalmustbematchedCastironrodsrequirehigherpreheatingthanbronzerods.Practiceprocedureforweldingcastiron:Selectthecorrectflux.Cleanandbeveltheedgesofthestock.Usea3/16”rodwithaneutralflameandtacktheendstogether.Heattherodtiptoared-coloredheatanddipitintheflux,thendipthetipintothemoltenpuddleofcastiron.Weldinthesamemannerasfusionweldingonmildsteel.Dipthehottipoftherodinfluxfromtimetotime.Ifbubblesappear,addmoreflux.PracticeProcedureforBrazeWelding:DoesnotrequireextremelyhighweldingtemperatureCleansurfacetobeweldedBevelandalignedgesofthemetalUseneutralflameandheattheendoftherodanddipintothefluxHeattheareatobeweldedtoadullredandtackendsApplyfluxfromrodonheatedarea,thenpassrodintoflameanddepositasmallamountofbronzeattheintervalsuntiltheweldiscomplete.Addfluxfromtimetotime.HardsurfacingApplicationofanallalloymaterialtoanothermetalforthepurposeofreducingwearProcedure:Thoroughlycleanthemetalbeforeapplyingalloy.Placethematerialtobehardsurfacedinaflatposition.Heatasmallsectionoftheareawithanexcessacetyleneflameuntilthemetalbeginstosweat.Touchthetipofthealloyrodtothesurfaceandmeltenoughoftherodtoformanalloycover1/16”thickandadesirablewidthwithoutheatingthebasemetaltoameltingpoint.Maintainthehardsurfacingtemperatureinfrontofthepathonthehardmetal.Addjustenoughrodtothemetaltomaintainauniformthicknessandwidth.Hardsurfacedmetalshouldbeallowedtocoolslowly.Drylimeservesasagoodcoverforcoolingmetal.Besuretofollowrecommendationsofthemanufacturerofthehardsurfacingrods.AmericanWelding

SocietyCertificationTheAmericanWeldingSociety(AWS)istheprofessionalorganizationresponsibleforsettingstandardsforthecertificationofweldors.1ststepinbecomingahighlyskilledcraftsmanistocertifyasanEntryLevelWeldorCertificationprocessforEntryLevelWeldorconsistsof:APracticalKnowledgeTest:Welding/cuttingtheoryWelding/cuttinginspection&testingSkill-relatedvocabularyMetalidentificationWeldingvariablesElectricalfundamentalsWeldingsymbolinterpretationFabricationprinciples&practicesSafetyRequiresaminimumpassinggradeof75%,withaminimumscoreof90%onsafety-relatedquestionsAPerformanceTest:ReadingweldingsymbolsFollowingwrittenproceduresCuttingpartstoproperspecificationsFittingpartscorrectlyPerformingspecificweldingtechniquesPreparetestcouponbyoxyfuel(OFC)andplasma-arccutting(PAC)IncludesbothcuttingstraightlinesandpiercingholesCheckingforCylinderLeaksStandardacetylenecylindercontainsfrom90to154ft3,storedinaporousfillersaturatedwithacetoneCylindersarefilledunderpressureandmaydevelopleaksaroundthevalvestemorinthe“softplugs”Anacetylenecylinderleakingforanentireweekendintoaclosedfacilitycanbecomeatragedyofsignificantproportions.Sparksfromelectricalswitchesorpilotlightsonforced-airheaterscanprovidethenecessaryignitionsource.