This document discusses gas tungsten arc welding (GTAW), also known as tungsten inert gas (TIG) welding. It covers the key components of a GTAW system including the power supply, torches, electrodes, and gas regulators. It provides details on setting the arc, welding techniques, and factors that can influence the stability of the arc. The document is intended to explain the GTAW welding process.

1. Team Work
1.RoyaGinting
2.LukmanulHakim
3.EkoPriyanto
4.TheodorusOxario
5.YodiPrasetyawan

2. 1.GasTungsten-ArcWelding
2.GasMetal-ArcWelding

3. Thisisaweldingprocesswherecoalescenceisachievedbyheatingwithanelectricarcproducedbyavirtuallynon-consumabletungstenelectrode.
Duringtheweldingcycleashieldofinertgasexpelstheairfromtheweldingareaandpreventsoxidationoftheelectrode,weldpuddle,andsurroundingheataffectedzone.
Forjointswhereadditionalweldmetalisneededafillerrodisfedintothepuddleinamannersimlartotheoxyacetyleneprocess

4. Thegastungsten-arcprocessespeciallyadaptableforweldinglightgagematerialswheretheutmostinweldqualityorfinishisrequired.
Latergastungsten-atcprocessfuondtobeverysuitbleforweldingaluminum,stainlesssteel,carbonsteel,copperandnickel.

5. 1. Power Supply
ThechoiceofanACorDCelderdependsorcertaindistinctweldcharacteristicsthatmayberequired.SomemetalsarejoinedmoreeasilywithACcurrentwhilewithothesbetterresultsareobtainedwhenDCcurrentisused.

6. 2. Direct Current Reverse Polarity (DCRP)
WhenthemachineIsetforstraightpolaritytheflowfelectronsfromtheelectrodetotheplateexertconsiderableheatontheplate.Butinreversepolaritytheofelectronsisfromtheplatetotheelectrodethuscausingagreaterconcentrationofheatattheelectrodde.

7. 3. Direct Current Straight Polarity (DCSP)
DCSPisusedforweldingmostmetalsbecausebetterweldsareachieved.Withtheheatconcentratedattheplatetheweldingprocessismorerapid,thereislessdistortionofthebasemetalsandtheweldpuddleisdeeperandnarrowerthanwithDCRP.

10. 4. Alternating Current (AC)
ACweldingisactuallyacombinationofDCSPandDCRP.Duringaweldingoperationthecompletestoppagaofcurrentflow(rectifecation)wouldcausethearctobeunstableandsometimesevengoout.TopreventsuchrectificationACweldingmachenesincorporateahighfrequencycurrentflowunit.Thehighfrequencycurrentisabletojumpthegapbetweentheelectrodeandtheworkpiecepiercingtheoxiefilmandformingapathfortheweldingcurrenttofollow.

13. 5. Thorches
Thesetorchesareeitherairorwatercooled.Aircooledtorchesaredesidnedforweldinglightgagematerialswhrelowcurrentvaluesareused.Watercooledtorchesarerecommendedwhentheweldingrequiresamperagesover200.Sometorchesareequippedwitha“gaslens”toeliminateturbulenceofthegasstreamwhichtendstopullinairandcauseweldcontamination.

17. 6. Types of Electrodes
Basicdiametersofnonconsumableelectrodesare1/16”,3/32”,1/8”.Thediameteroftheelectrodeselectedforawweldingperationisgovernedbytheweldingcurrenttobeused.Largerdiametertungstenelectrodesarerequiredwithreversedpolaritythanwithstraightpolarity.

18. 7. Gas Regulators
Gasflowisregulatedbyasingleordualstagepressureredducingregulatorandflowmeter.Thefloemeterscalibratedincubicfeetperhour(cfh) orliterperminute(lpm).

19. Shieldinggasfortungstenarcweldingcanbeargon,helium,oramixtureofargonandhelium.
Advantagesfromargon:
a)Moreextensivelybecauseitislessexpensivethanhelium
b)Argonis1.4timesashevyasairsoitprovidesabetterblanketovertheweld
c)Argonnormallyproducesabettercleaningactionespeciallyinweldingalumuniumandmagnesiumwithalternatingcurrent.
d)Withargonthereisasmootherandquieterarcaction

20. Higheerweldingspeedsarepossiblewithheliumbecausehigherarcvoltagecanbeobtainedatthesamecurrent.
Amixtureofargonandheliumsoftenusedinweldingmetalsthasrequireahigherheatinput

21. Aweldismadebyapplyingthearcheatontheabuttingeddgesoftheworkpiece.Beforethearcisgeneratedtheelectrodemustbeadjustedsothatitextendsabout1/8”to3/16”beyondtheendofthegascupforbuttweldingandappximately¼”to3/8’forfilletwelding.

24. Thearemaybestruckintwoways:
a)WithaDCmachinetheelectrodeisbriughtdownardtotouchtheplate
b)OnaACmavhinetheelectrodedosen’thavetotouchthemetaltostartthearc
•Oncethearcisinitiatedthetorchispositionedatanangelofabout75degreetothesurfaceoftheweldmetal.
•Thestartingpointoftheweldispreheatedbymovingthetorchinsmallcircles
•Assoonasthepuddlebecomesbrightandfluid,thetorchismovedslowlyandsteadlyalongthejoint.

25. Duringtheweldingprocesstheremaybeoccasionswhenthearchasatendencytowander.Thismaybeduetolowelectrodecurrentdensity,contaminationoftheelectrodes,magneticeffectsandairdrafts.

26. Automaticormachineweldigdoesinvolveagreaterinvestmentofequipmentandrequiresclosercontrolofjointtolerances.Ontheotherlaborcostarereduceddsinceeweroperatorsareneededandweldingspeedsincreased.

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