电弧焊基础Arc welding foundation.docx
- 文档编号:18527134
- 上传时间:2023-08-19
- 格式:DOCX
- 页数:7
- 大小:19.09KB
电弧焊基础Arc welding foundation.docx
《电弧焊基础Arc welding foundation.docx》由会员分享,可在线阅读,更多相关《电弧焊基础Arc welding foundation.docx(7页珍藏版)》请在冰点文库上搜索。
电弧焊基础Arcweldingfoundation
电弧焊基础(Arcweldingfoundation)
A,1inthecathodeconductivecharacteristicsofcathodefunctions:
acceptpositiveionsandemissioncathodeelectronicinstitutions:
thethermionicemissionofcathodesurface,fieldemission,thermalionizationcollisionlocalplasmaemissioncathode.Hotcathode(tungsten,carbon,etc.):
hotemissioncoldcathode(iron,aluminum,etc.):
electricfieldemissioncollisionemissionplasmacausedthethermalpowertoleave.
Theelectricconductioncharacteristicofthearccolumnisdisorganizedandtheaveragekineticenergyisincreased,resultinginhightemperature.Themolecules,theatoms,willgenerateathermoelectricshock,formingaplasma.Thenarccolumniselectricallyneutral(theunitvolumeispositiveandnegativewithpointparticles
Thechargedparticlesaredirectedtomoveandareessentiallyfreefromtherepulsiveactionofthespaceelectricfield,sotheycantransmitalargecurrentunderlowvoltageconditions.Narccolumnlengthisarclength,arccolumnlength
Voltagedropbecomestheelectricfieldintensityofarccolumn.Theintensityofelectricfieldinthearccolumnislow:
usuallyonly5~10v/cm.
Theroleofanodesintheconductivecharacteristicofthe3anodearea:
toaccepttheelectronandprovidethepositiveiontothearccolumn.Theproductionmechanismofpositiveions:
?
Ionizationundertheactionoftheanodefield:
inthecaseofsmallcurrent,thethermalpowerisdifficulttogetout.Formingananodepressuredrop?
Electronkineticenergy?
Collisionionization?
Untiltheanodevoltageisstable.?
Thermoelectriccurrentintheanodearea:
inthecaseoflargecurrent,theanodepressuredropisapproximatelyzero,andthemetalevaporatesduetohighelectrodetemperature.Thermalionization?
Doesthecurrentnotformananodewhenitislargeenough?
Theanodepressuredropisalsorelatedtotheelectrodematerialcharacteristics,thethermalconductivityisgoodandtheanodepressuredrops.
2.Theformingconditionsofcathodespots:
1)theconditionsofemissionelectron(fieldemissionandthermalemission)2)thearccolumnenergydissipationisminimizedbythispoint.Thecharacteristicsofcathodespots:
1)thehotcathodeisinthecaseofsmallcurrent,whilethecoldcathodespotsthecathodespotinthelargercurrent.2)toremoveoxidefilm:
cathodeartifacts,automaticsearchforoxidefilm(small)workfunction3)blockdroptransition:
spotpressure(includingmetalcationssteamflowreactionforceandimpactforce),thedconmeltingpolarhinderthedroplettransitionduringwelding.4)adhesioncharacteristics:
accordingtotheminimumprincipleof
Theconditionoftheanodespot:
?
Isthereanymetalevaporationatthatpoint?
Thearccolumnatthispointconsumesthelowestenergy
Characteristicsofanodespots:
?
Currentdensitylessthancathodespot?
Findpuremetal,donothavetheroleofoxidationfilm?
Adhesion?
Becausethespotpressureissmall,theresistancetothemeltdropissmall.
theweldingarcforceconcretecanbedividedintothree:
thecontraction(electromagneticforce)arcarcstaticpressuredynamicpressure,includingtheplasmapowerandspotpressure,impactforce,theelectromagneticpressuredifference,metalevaporationreaction,cathodemorestress)explosiveforce(shortcircuittransition,theliquidcolumncontraction,resultinginblastingarcspacegasexpansion,localimpactonwireandmoltenpoolresultissplash)andfinedropletimpact(tinymetaldropletspraytransfer,melting,wewerewaitingfortheionflowforceintomoltenpool,withtheplasmajetforcehasagreatinfluenceontheweldtogether.Penetrationarccenterarea)thefactorsinfluencingarcforce1.Gasmedium
2.Currentandvoltage(arclength)3.Electrode(electrode)diameter4.Electrode(weldingwire)polarity5.Geometryoftheextremepartoftungsten6.Influenceofpulsatingcurrent
Four,shortcircuittransitionfeatures:
-filaments,shortarc,smallcurrent,arcarcalternates,Φ(50hz),1.6smallΦ0.8(130hz)--theaveragecurrent,peakcurrentislarge,suitableforthinplateandallpositionwelding,smalldiameterweldingwire,electriccurrentdensity,heatproduction,weldingspeed,arclength,weldingheatingareaissmall,highquality
--processstability--splash
Bridgetransition:
non-meltingelectrodearcwelding.Undertheactionofsurfacetension,gravityandarcforce,thedropletentersthemoltenpool.?
Formingconditions:
non-fusionelectrodefilaments,gasweldingfilaments.
Dropletexcessive:
electricarcvoltageishigh,currentissmall,coarsedroptransition,finedroptransition,rejecttransition.
Spraytransfercanbedividedinto:
shootdropstransition(dropdiameterclosetothewirediameter,arcforceforcefromtheendofthewire,andquicklythroughthearcspace,intheformoftransitiontoamoltenpool.SteelwirepulsedMIGwelding,weldwireMIGwelding,thecurrentmustreachacertainthreshold,thetransitionformwilltransitionfromshapetransitionintoshotdrops),spraytransfer(droparetinyparticles,theendofthepencilpointsalongthewireinsprayformquicklythrougharcspacetransitiontoamoltenpool,intheformofsteelwireMIGwelding,thepureargonprotection,dcreverseconnection,higharcpressure,currentmustreachacertainthreshold),rotatingspraytransfer(outsuper-largeMIGweldingcurrent,weldingwirelengthislarger,theweldingcurrentisgreaterthanthecriticalcurrent,jetlengthincreases,theliquidmetaljetfinedropsofhigh-speedjettransitionhavelargerreaction,oncetheaxisdeviationwillproducerotatingspraytransfer,arcinstability,molding,splash.Currentlyuseditsefficientcharacteristics,inthenarrowgapweldinghasbeenappliedinproduction.),thespraytransfer(arclengthisshorter,moltendroplets,grewup,fromformationatthetransitionofmoltendropsandmoltenpoolshortcircuit,undertheactionofelectromagneticcontractionforcethinneckfracture,completethetransition,arcignitionagain.Formingconditions:
aluminumalloyweldwire,shortarcwelding)
Thetransitionofslagwallisakindoftransitioninweldingelectrodearcweldingandsubmergedarcwelding
Atransitionalformofthemoltenpool.
5.ZoneA:
thecurrentisverysmall,thearcvoltageishigh,theweldingwiremeltsslowly,andthemoltendropletsarelargelumps(bigdrops),whicharenoteasytoescapefromthewire,andcannotbeobtainedcontinuouslywhenwelding.Ifthearcvoltageisreducedinthisarea,thearclengthwillbeshortenedandasolidshortcircuitwilloccur.ZoneB:
smallcurrent.Lowvoltageshort-circuittransitionspecificationarea,highshortcircuitfrequency,lowelectricarcvoltage(7-21v),meltdroptransitionstability,smallsplash,suitableforweldingthinplate.Carea:
shortcircuittransitionofhigharcpressureandtransitionzoneofparticletransition,theratioofthetwoisdifferentfromthatoftheparameters,andthesplashislarger,butthearcheatingefficiencyishigh.Itisoftenusedbypracticaloperation.Weldingmediumthicknessworkpieceisverydeep.AreaD:
mediumcurrentandhigharcpressurespecificationarea,alargeblocktransitionofmoltendrop,orrejectiontransition,weldingspatter.Earea:
largecurrentwelding.Higharcpressure,thenon-axialtransitionofthedropletoffinedroplets,theweldingdepthislarge,thesplashsmalliscalledfineparticletransition,suitableforweldingthickerworkpieces.
1)theweldingcurrentissmallandtheweldingspeedistoohigh.
Orthesizeofthegrooveisnotsuitable,andthecenterlineofthearcisdeviatedfromtheweld,thearcgeneratedbythedeflection,andthefilamentshort-circuittransitionCO2welding,whichcanbeeasilycausedbythesmallamountofthermalinputoftheworkpiece.Inthinplatewelding,iftheclampistothebackoftheweld
Theheatdegreeisbig,alsocanappearthelackofpenetration,orpartofthebackpartoftheweldpenetration,incompletefusionofformingunevenphenomenon,2)burnthroughweldingcurrent,weldingspeedistoosmallorcollapsearelikelytoappearthiskindofdefect.Whenthethickplateiswelded,themoltenpoolistoolarge,andthesurfacetensionofthesolidmetalisnotenoughtoabsorbthegravityandarcforceofmoltenmetal.Ifinthinplatewelding,arcforceistooconcentrated,ortoolargegapalsocanappearweldingwear3)biteedgeandtheformationofthepitisaffectedbythemoltenpoolform,correspondingtothehighspeedweldingarcandpool,duetothefastweldingspeed,meltoneithersideoftheweldmetalisnotverygood,atthesametime,thesurfacetensionofmoltenmetaliseasytogathertogetherandbuttweldtoebodypartsofwettabilityisbad,easytoformasolidliquid,
Aftersolidification,abiteedgeoccurs.4)themoltenmetaloftheweldingtumorflowstotheunmeltedfemalematerialintheweldareaandgathersintoametaltumor,whichiscausedbytheexcessivefillingofthemetal,ortheresultofthegravitationaleffectofthemoltenpool;Ndirectlyaggregatesintolargemetaltumorsontheweld,mostlyduetounstabledroplettransition
Seven,splash:
intheweldingprocess,mostofthenailwiremoltenmetalcantransitiontothepool,apartofweldingwiremeltingmetal(alsoincludesasmallamountofthemoltenpoolofmetal)flytothemoltenpooloutside.Thisphenomenoniscalled"weldingspatter.Measures:
1)correctlyselectthewirecontainingthedeoxygenationelementandlimittheCcontent;2)adoptmulti-elementgasprotection.1)correctlyselecttheweldingpowersource,matchtheappropriatevoltage,andavoidthetransitionformasmuchaspossible.2)
- 配套讲稿:
如PPT文件的首页显示word图标,表示该PPT已包含配套word讲稿。双击word图标可打开word文档。
- 特殊限制:
部分文档作品中含有的国旗、国徽等图片,仅作为作品整体效果示例展示,禁止商用。设计者仅对作品中独创性部分享有著作权。
- 关 键 词:
- 电弧焊基础Arc welding foundation 电弧焊 基础 Arc