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Shield Arc Welding Process

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Shield Arc Welding Process

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Shield Arc Welding Process

  1. 1. Team Work 1.RoyaGinting 2.LukmanulHakim 3.EkoPriyanto 4.TheodorusOxario 5.YodiPrasetyawan
  2. 2. 1.GasTungsten-ArcWelding 2.GasMetal-ArcWelding
  3. 3. Thisisaweldingprocesswherecoalescenceisachievedbyheatingwithanelectricarcproducedbyavirtuallynon-consumabletungstenelectrode. Duringtheweldingcycleashieldofinertgasexpelstheairfromtheweldingareaandpreventsoxidationoftheelectrode,weldpuddle,andsurroundingheataffectedzone. Forjointswhereadditionalweldmetalisneededafillerrodisfedintothepuddleinamannersimlartotheoxyacetyleneprocess
  4. 4. Thegastungsten-arcprocessespeciallyadaptableforweldinglightgagematerialswheretheutmostinweldqualityorfinishisrequired. Latergastungsten-atcprocessfuondtobeverysuitbleforweldingaluminum,stainlesssteel,carbonsteel,copperandnickel.
  5. 5. 1. Power Supply ThechoiceofanACorDCelderdependsorcertaindistinctweldcharacteristicsthatmayberequired.SomemetalsarejoinedmoreeasilywithACcurrentwhilewithothesbetterresultsareobtainedwhenDCcurrentisused.
  6. 6. 2. Direct Current Reverse Polarity (DCRP) WhenthemachineIsetforstraightpolaritytheflowfelectronsfromtheelectrodetotheplateexertconsiderableheatontheplate.Butinreversepolaritytheofelectronsisfromtheplatetotheelectrodethuscausingagreaterconcentrationofheatattheelectrodde.
  7. 7. 3. Direct Current Straight Polarity (DCSP) DCSPisusedforweldingmostmetalsbecausebetterweldsareachieved.Withtheheatconcentratedattheplatetheweldingprocessismorerapid,thereislessdistortionofthebasemetalsandtheweldpuddleisdeeperandnarrowerthanwithDCRP.
  8. 8. 4. Alternating Current (AC) ACweldingisactuallyacombinationofDCSPandDCRP.Duringaweldingoperationthecompletestoppagaofcurrentflow(rectifecation)wouldcausethearctobeunstableandsometimesevengoout.TopreventsuchrectificationACweldingmachenesincorporateahighfrequencycurrentflowunit.Thehighfrequencycurrentisabletojumpthegapbetweentheelectrodeandtheworkpiecepiercingtheoxiefilmandformingapathfortheweldingcurrenttofollow.
  9. 9. 5. Thorches Thesetorchesareeitherairorwatercooled.Aircooledtorchesaredesidnedforweldinglightgagematerialswhrelowcurrentvaluesareused.Watercooledtorchesarerecommendedwhentheweldingrequiresamperagesover200.Sometorchesareequippedwitha“gaslens”toeliminateturbulenceofthegasstreamwhichtendstopullinairandcauseweldcontamination.
  10. 10. 6. Types of Electrodes Basicdiametersofnonconsumableelectrodesare1/16”,3/32”,1/8”.Thediameteroftheelectrodeselectedforawweldingperationisgovernedbytheweldingcurrenttobeused.Largerdiametertungstenelectrodesarerequiredwithreversedpolaritythanwithstraightpolarity.
  11. 11. 7. Gas Regulators Gasflowisregulatedbyasingleordualstagepressureredducingregulatorandflowmeter.Thefloemeterscalibratedincubicfeetperhour(cfh) orliterperminute(lpm).
  12. 12. Shieldinggasfortungstenarcweldingcanbeargon,helium,oramixtureofargonandhelium. Advantagesfromargon: a)Moreextensivelybecauseitislessexpensivethanhelium b)Argonis1.4timesashevyasairsoitprovidesabetterblanketovertheweld c)Argonnormallyproducesabettercleaningactionespeciallyinweldingalumuniumandmagnesiumwithalternatingcurrent. d)Withargonthereisasmootherandquieterarcaction
  13. 13. Higheerweldingspeedsarepossiblewithheliumbecausehigherarcvoltagecanbeobtainedatthesamecurrent. Amixtureofargonandheliumsoftenusedinweldingmetalsthasrequireahigherheatinput
  14. 14. Aweldismadebyapplyingthearcheatontheabuttingeddgesoftheworkpiece.Beforethearcisgeneratedtheelectrodemustbeadjustedsothatitextendsabout1/8”to3/16”beyondtheendofthegascupforbuttweldingandappximately¼”to3/8’forfilletwelding.
  15. 15. Thearemaybestruckintwoways: a)WithaDCmachinetheelectrodeisbriughtdownardtotouchtheplate b)OnaACmavhinetheelectrodedosen’thavetotouchthemetaltostartthearc •Oncethearcisinitiatedthetorchispositionedatanangelofabout75degreetothesurfaceoftheweldmetal. •Thestartingpointoftheweldispreheatedbymovingthetorchinsmallcircles •Assoonasthepuddlebecomesbrightandfluid,thetorchismovedslowlyandsteadlyalongthejoint.
  16. 16. Duringtheweldingprocesstheremaybeoccasionswhenthearchasatendencytowander.Thismaybeduetolowelectrodecurrentdensity,contaminationoftheelectrodes,magneticeffectsandairdrafts.
  17. 17. Automaticormachineweldigdoesinvolveagreaterinvestmentofequipmentandrequiresclosercontrolofjointtolerances.Ontheotherlaborcostarereduceddsinceeweroperatorsareneededandweldingspeedsincreased.
  18. 18. Thanks for Watching our presentation

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