Briefintroduction
Electricweldingisakindofweldingoperationthatusesweldingrodstomelttheplaceswheremetalpartsneedtobeconnectedthrougharchightemperature.Itsworkingprincipleis:throughthecommonlyused220Vor380Vvoltage,thetransformerintheelectricweldingmachinereducesthevoltage,enhancesthecurrent,andcausestheelectricenergytogeneratehugearcheattomelttheweldingrodandthesteel,andthemeltingoftheweldingrodmakesthefusionbetweenthesteelhigher.Arcweldingisthemostwidelyusedweldingmethod,includingmanualarcwelding,submergedarcwelding,tungstengasshieldedarcwelding,plasmaarcwelding,moltenelectrodegasshieldedweldingandsoon.Becausearcweldingusesapowersource,thehigh-temperaturearcgeneratedbyitispronetofireandexplosion,andthedangerIisgreater.
Electricweldingisaneconomical,applicableandtechnologicallyadvancedmethodinmaterialconnectionprocessing.Almostanytwokindsofmetalmaterialscanbeweldedbyelectricwelding,andsomemetalmaterialsandnon-metalmaterialscanbewelded;smallpiecescanbecombinedtomakelarge,economicalandreasonablestructures;differentpartsofthestructurecanbeuseddifferently.High-performancematerialsgivefullplaytothecharacteristicsofvariousmaterials;electricweldmentshavethecharacteristicsofgoodairtightnessandlightweight;electricweldingcanalsorealizetheweldingofultra-thinandultra-finematerials.
Развитие
Електрическото заваряване е разработено с развитието на електроенергийната индустрия в края на 19-ти век.
През 1885 г. руснакът Х. Х. Бернардос открива въглеродната дъга.
През 1887 г. E.Thomson (ElihuThomson) изобретява електросъпротивително заваряване за заваряване на тънки плочи.
Atthebeginningofthe20thcentury,manualarcweldinghasenteredthepracticalstage.Inthe1920s,theUnitedStatesmadeautomaticarcweldingmachines.
През 1930 г. Съединените щати изобретяват заваряване с дървесина под флюс.
Inthe1940sandearly1950s,tungstenandmoltenmetalinertgasshieldedwelding,aswellascarbondioxidegasshieldedwelding,cameoutintheUnitedStatesandtheSovietUniononeafteranother,whichpromotedtheapplicationanddevelopmentofgasshieldedarcwelding.
In1951,theSovietUnioninventedelectroslagwelding,whichbecameanefficientweldingmethodforlargethicknessweldments.
Inthe1950s,ultrasonicwelding,frictionweldinganddiffusionweldingcameoutintheUnitedStatesandtheSovietUniononeafteranother.Plasmaarcwelding,electronbeamweldingandlaserweldingthatappearedinthelate1950sand1960smarkedthedevelopmentofhigh-powerdensityfusionwelding,whichmadeitpossibletoweldmanymaterialsandstructuresthatweredifficulttoweldbyothermethods.
Currently,electricweldinghasbeenwidelyusedinmachinery,electronics,construction,shipbuilding,aerospace,aviation,energyandotherindustrialsectors.Theweightofelectricweldedsteelstructuresaccountsforabout45%oftheworld'ssteeloutput.Theproportionofaluminumandaluminumalloyweldedstructuresisalsoincreasing.Lookingforwardtothefuture,ontheonehand,newweldingmethods,weldingequipmentandweldingmaterialswillbefurtherdeveloped,weldingprocessperformanceandweldingqualitywillbeimprovedandimproved;ontheotherhand,thelevelofmechanizationandautomationoftheweldingprocesswillbefurtherimproved,weldingrobotsandweldingrobotswillbefurtherdeveloped.Weldingrobotswillbefurtherpromoted.
Метод на заваряване
Методът на заваряване обикновено се разделя на три вида: заваряване чрез стопяване, заваряване под налягане и спояване според условията на нагряване и налягане по време на заваряване.
Fusionweldingisamethodinwhichthemetalatthejointoftheweldmentisheatedtoamoltenstateduringtheweldingprocess,andtheweldingisgenerallycompletedwithoutpressure.Duringfusionwelding,theheatsourcequicklymeltsthemetalatthejointoftheweldmentandthefillermetaladdedwhennecessarytoformamoltenpool.Themoltenpoolextendswiththemovementoftheheatsourceandformsaweldaftercooling.Fusionweldingusingelectricenergycanbedividedintoarcwelding,electroslagwelding,electronbeamweldingandlaserweldingaccordingtodifferentelectricheatingmethods.Fusionweldinghasawiderangeofapplications,andismostcommonlyusedinvariousweldingmethods,especiallyarcwelding.
Pressureweldingisaweldingmethodinwhichweldmentsarejoinedtogetherunderpressure(withorwithoutheating).Generally,nofillermetalisaddedduringthepressureweldingprocess.Pressureweldingcanbedividedintoresistancewelding,highfrequencywelding,diffusionwelding,frictionwelding,ultrasonicwelding,etc.accordingtodifferentweldingmechanisms.Amongthem,resistanceweldingisthemostwidelyused.Mostpressureweldingmethodsdonothaveameltingprocess,anddonothavetheproblemsofburningofbeneficialalloyelementsandimmersionofharmfulelementsintotheweldlikefusionwelding.However,theweldingconditionsofpressureweldingareharshandtheapplicationareaisnarrow.
Brazingisaweldingmethodthatusesamaterialwithalowermeltingpointthantheweldment(brazingfillermetal)toadheretheweldmentafterbeingmelted,andthenconnecttheweldmentseamstogetheraftercooling.
Basicoperation
Theweldingoperationisobservedandcarriedoutunderthemask.Duetotheunclearvisionandpoorworkingconditions,toensuretheweldingquality,notonlyarelativelyskilledoperationtechnique,butalsoahighdegreeofconcentrationshouldberequired.
Beforewelding,cleanthesurfacewithin20mmonbothsidesofthejointoftheworkpiece(suchasremovingrust,oil,andmoisture),andexposetheendmetaloftheelectrodecoreforshort-circuitarcignition.Therearetwotypesofarcignitionmethods:percussionmethodandwipingmethod.Thewipingmethodiseasiertomasterandissuitableforbeginnerstooperatethearc.
1. Удар с дъга
(1)Swipemethod.Aligntheelectrodewiththeweldmentfirst.Thenlightlyscratchtheelectrodelikeamatchonthesurfaceoftheweldmenttoignitethearc,andthenquicklylifttheelectrodeby2to4mmandmakeitburnstably.
(2)Percussionmethod.Aligntheendoftheelectrodewiththeweldment,thenbendyourwristdownsothattheelectrodeslightlytouchestheweldment,andthenquicklylifttheelectrodeby2to4mm,andthenignitethearcandplaceyourwristflattokeepthearcburningsteadily.Thisarcstartingmethodwillnotscratchthesurfaceoftheweldment,andisnotlimitedbythesizeandshapeoftheweldmentsurface,soitisthemainarcstartingmethodusedintheweldingprocess.However,theoperationofthisarcignitionmethodisnoteasytomaster,anditisnecessarytoimprovetheproficiency.
Второ, транспортиране на ленти
Transportationofstripsisthemostimportantlinkintheweldingprocess,whichdirectlyaffectstheappearanceandinternalqualityoftheweld.Afterthearcisignited,thereareseveralbasicmovementsoftheweldingrodonthenormaloperatingsurface:graduallyfeedinginthedirectionofthemoltenpool,graduallymovingintheweldingdirection,andswinginglaterally.
(1)Метод на праволинейно транспортиране. Когато се използва този метод за транспортиране на заваръчния прът, заваръчният прът не се люлее странично, а се движи праволинейно по посока на заваряването. Той се използва меко за челно плоско заваряване на I-образен жлеб, заваряване на първи слой на многослойно заваряване или многослойно многопроходно заваряване.
(2)Straight-linereciprocatingtransportationmethod.Whenusingthismethodoftransportingtheweldingrod,theendoftheweldingrodswingsbackandforthalongthelongitudinaldirectionoftheweldingseam.Itischaracterizedbyfastweldingspeed,narrowweldingseamandfastheatdissipation.Itissuitableforthefirstlayerweldingofmulti-layerweldingwithlargegapsbetweenthinplatesandjoints.
(3)Zigzagstripingmethod.Whenusingthismethodoftransportingtheweldingrod,theendoftheweldingrodcontinuouslyswingsandmovesforwardinazigzagshape,andstopsforawhileonbothsides.Thepurposeofswingistocontroltheflowofmoltenmetalandobtainthenecessaryweldwidthtoobtainbetterweldformation.Thisstriptransportationmethodiswidelyusedinproduction,andismostlyusedforweldingofthicksteelplates,buttjointsofflatwelding,overheadwelding,verticalwelding,andverticalweldingfilletjoints.
(4)Crescent-shapedtransportationmethod.Whenusingthismethodoftransportingtheweldingrod,theendoftheweldingrodswingsleftandrightinacrescentshapealongtheweldingdirection.Theswingspeedshouldbedeterminedaccordingtothepositionoftheweld,thejointform,thewidthoftheweldandthevalueoftheweldingcurrent.Atthesametime,itisnecessarytostayonbothsidesofthejointforawhile,thisistomaketheedgeoftheweldhaveenoughpenetrationtopreventundercut.Thecharacteristicsofthisstriptransportationmethodarethatthemetalmeltswell,ithasalongholdingtime,thegasiseasytoprecipitate,andtheslagisalsoeasytofloatonthesurfaceoftheweld.Thequalityoftheweldishigh,buttheresidualtemperatureoftheweldedweldisrelativelyhigh..Theapplicationrangeofthismethodofstriptransportisbasicallythesameasthatofthezigzagstripmethod.
(5)Triangulartransportationmethod.Whenusingthiskindoftransportmethodforwelding,theendoftheelectrodemakesacontinuoustriangularmovementandmovesforwardcontinuously.Accordingtothedifferentswingforms,itcanbedividedintotwotypes:obliquetriangleandregulartriangle.TheobliquetrianglestripmethodissuitableforweldingflatweldingandoverheadweldingT-jointweldsandgroovedtransversewelds.Itsadvantageisthatitcanbeborrowed.Theswingoftheweldingrodcontrolsthemoltenmetalandpromotesagoodweldformation.TheequilateraltriangletransportationmethodisonlysuitableforverticalweldingofgroovedbuttjointsandT-shapedjointwelds.Thecharacteristicisthatitcanweldathickerweldsectionatatime,andtheweldisnoteasytoproducedefectssuchasslaginclusion,whichisbeneficialtoimproveproductionefficient.
(6)Thecircle-shapedmovementmethod.Whenusingthistransportmethodforwelding.Theendoftheelectrodecontinuouslymovesinastraightcircleoranobliquecircle,andmovesforwardcontinuously.Thestraightcircle-shapedstripmethodissuitableforweldingflatweldsofthickerweldments.Itsadvantagesarethatthemoltenpoolhasalongtimeandthetemperatureofthemoltenpoolmetalishigh,whichisconducivetotheprecipitationofoxygen,nitrogenandothergasesdissolvedinthemoltenpool.Theslagfloatsup.Theobliquecircle-shapedstripmethodissuitableforthehorizontalandverticalT-jointweldsandthehorizontalweldsofbuttjoints.Itsadvantageistohelpcontrolthemoltenmetalfromtheinfluenceofgravitytocausethephenomenonofdownwardflow,whichisbeneficialtotheformationoftheweld.
3.Заваръчен шев
(1)Circleendmethod:Whentheweldingrodmovestotheendoftheweldbead,usethemovementofthewristtomakeacircularmotion,Untilthearccraterisfilled,thenthearcisbroken.Thismethodissuitableforweldingofthickplates,andthereisadangerofburningthroughwhenusedforweldingofthinplates.
(2)Repeatedarcbreakingmethod:Whentheweldingrodismovedtotheendoftheweldbead,thearcisrepeatedlyextinguishedandtriggeredseveraltimesatthearccrateruntilthearccraterisfilled.Thismethodissuitableforthinplatesandhighcurrentwelding,butnotsuitableforalkalineelectrodes,otherwiseitwillproducepores.
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