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.
Vývoj
Elektrické svařování bylo vyvinuto s rozvojem elektroenergetického průmyslu na konci 19. století.
V roce 1885 objevil Rus H.H.Bernardos uhlíkový oblouk.
V roce 1887 vynalezl E.Thomson (ElihuThomson) odporové svařování pro svařování tenkých plechů.
Atthebeginningofthe20thcentury,manualarcweldinghasenteredthepracticalstage.Inthe1920s,theUnitedStatesmadeautomaticarcweldingmachines.
V roce 1930 Spojené státy vynalezly ponorné svařování.
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.
Metoda svařování
Metoda svařování se obvykle dělí na tři typy: tavné svařování, tlakové svařování a pájení podle teplotních a tlakových podmínek při svařování.
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. Arcstriking
(1)Swipemethod.Aligntheelectrodewiththeweldmentfirst.Thenlightlyscratchtheelectrodelikeamatchonthesurfaceoftheweldmenttoignitethearc,andthenquicklylifttheelectrodeby2to4mmandmakeitburnstably.
(2)Percussionmethod.Aligntheendoftheelectrodewiththeweldment,thenbendyourwristdownsothattheelectrodeslightlytouchestheweldment,andthenquicklylifttheelectrodeby2to4mm,andthenignitethearcandplaceyourwristflattokeepthearcburningsteadily.Thisarcstartingmethodwillnotscratchthesurfaceoftheweldment,andisnotlimitedbythesizeandshapeoftheweldmentsurface,soitisthemainarcstartingmethodusedintheweldingprocess.However,theoperationofthisarcignitionmethodisnoteasytomaster,anditisnecessarytoimprovetheproficiency.
Zadruhé, přeprava pásů
Transportationofstripsisthemostimportantlinkintheweldingprocess,whichdirectlyaffectstheappearanceandinternalqualityoftheweld.Afterthearcisignited,thereareseveralbasicmovementsoftheweldingrodonthenormaloperatingsurface:graduallyfeedinginthedirectionofthemoltenpool,graduallymovingintheweldingdirection,andswinginglaterally.
(1)Přímá metoda přepravy. Při použití tohoto způsobu přepravy svařovací tyče se svařovací tyč nenaklání do strany, ale pohybuje se lineárně podél směru svařování. Používá se pro ploché svařování drážky ve tvaru I, svařování první vrstvy vícevrstvého svařování nebo vícevrstvého svařování.
(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. Weldingseamend
(1)Circleendmethod:Whentheweldingrodmovestotheendoftheweldbead,usethemovementofthewristtomakeacircularmotion,Untilthearccraterisfilled,thenthearcisbroken.Thismethodissuitableforweldingofthickplates,andthereisadangerofburningthroughwhenusedforweldingofthinplates.
(2)Repeatedarcbreakingmethod:Whentheweldingrodismovedtotheendoftheweldbead,thearcisrepeatedlyextinguishedandtriggeredseveraltimesatthearccrateruntilthearccraterisfilled.Thismethodissuitableforthinplatesandhighcurrentwelding,butnotsuitableforalkalineelectrodes,otherwiseitwillproducepores.
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