Arc Welding Capabilities At EWI

Arc Welding Capabilities at EWINovember 29, 2012Nick Kapustka

Overview Arc welding teamCapabilities listArc welding basic overviewArc welding processes Core processes Process variations / other processes Capability demonstrations

Arc Welding TeamHarvey CastnerProgram ManagerShipbuilding, Heavy Manf., AerospaceFormer VP of Government ProgramsFormer Director of NJC35 Technical PapersState of Ohio PEIIW International Welding EngineerAmerican Welding Society FellowRandy DullPrincipal EngineerAuto & Heavy Manf. TeamsAWS Committee Member (4)AWS Senior CWIAWS Certified Welding EngineerASNT ACCP Level II (VT)State of Ohio PEIIW International Welding EngineerGTAW, PAW, GMAW, FCAW, SAWSS, CS, Ni, Cu, Ti, Al, etc.Distortion ControlCodes & Standards

Arc Welding TeamDr. Ian HarrisTechnology LeaderDirector of AMCAerospace, ProcessesIIW Commission Expert / Chair (3)AWS Handbook Vol. 9 ChairAWS D17.1 CommitteeASTM F42 Group MemberASM Metals Handbook Vol. 6 ContributorNon-FerrousGTAW, PAW, GMAW, HLAWNick KapustkaApplications EngineerAerospace TeamGMAW, GTAW, PAW, CMTThermal CuttingNon-Ferrous Alloys, AHSSAWS CWICodes & StandardsSteve MasseyEngineering ManagerAutomation ExpertAWS D16 Rob. & Auto. CommitteeGMAW, FCAW, GTAW, PAW, SAW, TGMAWCS, SS, Al, Ni, CuAWS CWI

Arc Welding TeamMarc PurslowApplications EngineerArc Welding Invention CoachProcesses, Shipbuilding, Heavy Manf.GMAW, SAW, FCAW, T-GMAW,CS, SS, AlAWS CWIAdam UzielApplications EngineerAerospace TeamGTAW, PAW, GMAWOrbital WeldingSS, Ni, Ti, Al, Coated Steels

Capabilities Project work CSP, GTH, GN5, CSL, GSP, GTO, IRD, etc. Processes GTAW, GMAW, FCAW, PAW, SMAW, SAW, CMT, CSC, T-GMAW, TSAW, OFC, A-CAC, PAC, etc. Expert witness, onsite assistance, codes & standards interpretation,automation expertise, fume generation, etc. Membership Inquiries, membership sales, design reviews Sales Internal sales teams, sales calls, project development Technical leadership AWS, IIW, ASME, AMS, ASME committees Peer reviewed publications, conference presentations

Arc Welding Basic Theory

Arc Welding Overview All arc welding uses an electric arc to produce a weld bymelting the base material and filler metal, if applicableThree main differences between arc welding processes: How the welding arc is initiated and controlled Consumable electrodes Melt and transfer to the weld for filling joint The electrode is the filler metal Non-consumable electrodes Provide electrode for arc and generally do not melt Tungsten or Carbon Filler material, when used, is provided separately How the molten metal weld pool is shielded Whether filler metal is used and how it is supplied to the moltenweld pool

Basic Arc Welding Circuit

Welding Arc

Primary Operating Parameters Arc voltage / arc lengthArc currentElectrode feed rate (consumable)Welding travel speedElectrical polarity

Need for Atmospheric Shielding Molten metal reacts with the atmosphere to formoxides and nitrides Porosity will result if the weld pool is exposed to the atmosphere Metallurgical changes can occur Weld mechanical properties are generally reduced The weld area should be free of dirt, grease, paint,scale, and other foreign objects to ensure weldquality Fluxes and shielding gasses are not designed to scavenge thesecomponents from the solidifying weld metal

Flux Shielding Decomposes and provides a gas to shield the arcand prevent atmospheric contamination of themolten filler metal and weld poolProvides scavengers, deoxidizers, and fluxingagents to cleanse the weld and prevent excessivegrain growth in the weld metalEstablishes the electrical characteristics of theelectrodeProvides a slag blanket to protect the hot weld beadfrom the air and can enhance the mechanicalproperties, weld bead shape and surface cleanlinessProvides a means of adding alloying elements tochange the mechanical properties of the weld metal

Gas Shielding Purges the weld area to shield the molten metal fromthe atmosphereArgon is the most common inert gasCO2 is sometimes used Less expensive Similar to gases produced from fluxes CO2 and O2 are commonly mixed with argon Promotes oxidation to stabilize the arc and metal transfer Improves weld bead wetting H2 can be added to increase arc heat in some casesHelium may also be used to increase arc heatRequires addition of deoxidizers to filler materials

Sources of Shielding

Arc Welding Processes

Arc Welding ProcessesCore Processes SMAW, MMAWProcess Variations T-GMAW “Stick” welding GTAW “TIG” welding GMAW “MIG” welding FCAWSAWPAW NG-T GMAW Strip claddingRWF-GMAWPAC-GCAGHybrid welding Hybrid laser arc welding Hybrid GMAW / PAWwelding

Shielded Metal Arc Welding (SMAW) An arc welding process in which coalescence ofmetals is produced by heat from an electric arc thatis maintained between the tip of a covered electrodeand the surface of the base metal in the joint beingwelded

SMAWMedium arc lengthLong arc length

Electrode Covering The electrode covering has numerous functions butdepends on the type Provides a gas cover to shield the arc and prevent excessiveatmospheric contamination of the molten filler metal Provides scavengers, deoxidizers, and fluxing agents to cleansethe weld and (potentially) prevent excessive grain growth in theweld metal Establishes the electrical characteristics of the arc Provides a slag blanket to protect the hot weld metal from the airand enhance the mechanical properties, bead shape, andsurface cleanliness of the weld metal Provides a means of adding alloying elements to weld metal toalter the microstructure and mechanical properties of the weldmetal

SMAW Advantages Most widely used process worldwide – broad skillbaseEquipment andconsumable costs arelow – “low-tech”Extremely versatileEasily implemented forfield weldingRelatively adaptable topart fit-up variances Operator skill is requiredUnderwater welding with SMAW

SMAW Disadvantages Requires relatively highskilled manual welderDeposition rate is lowDefect rates are relativelyhighFume generation ratesare high

Gas Tungsten Arc Welding (GTAW) An arc is formed between anonconsumable (tungsten)electrode and the workpieceelectrodeThe energy from the arcmelts the workpiece, andthe molten metal solidifiesto form a weld beadShielding gas provides themedium for arc formationand protects the moltenpool and electrode fromoxidationSource: AWS Handbook 9th ed. Vol. 1

GTAW Process Terminology Gas Tungsten Arc Welding: GTAW - AWS DefinitionTungsten Inert Gas Welding: TIG - Europe andworldwide, also often used in the U.S.Wolfram Inert Gas Welding: WIG - Used in GermanyHeliarc: Original name in U.S.Argonarc: Original name in U.K.

GTAW Pros & ConsAdvantages Can be used in allpositionsProvides excellent controlon thin and intricate partsNo slag or spatter; postweld cleaning often notrequiredUse with or without fillerwireWelds almost all metalsPrecise control of weldheatHigh qualityDisadvantages Lower deposition ratesthan consumableelectrode processesHigher skill level thanconsumable electrodeprocessesRequires high gas purity,low tolerance for draftyenvironmentsLow tolerance tocontaminantsGenerally requires arcstarting systemRequires precisepositioning of electrode

Gas Metal Arc WeldingSource: AWS Handbook 9th ed. Vol. 1

Flux Cored Arc WeldingGas-Shielded FCAWCourtesy of the AWS Welding Handbook, Volume 2, 8th EditionSelf-Shielded FCAW

GMAW/FCAW EquipmentSHIELDING GASREGULATORELECTRODE SUPPLY7ELECTRODE FEED UNITSHIELDING GASSUPPLY32458POWERSOURCE69WELDING GUNWATERCIRCULATOR101WORKPIECE12WORK LEAD6WATER TO GUN7834WATER FROM GUN5SHIELDING GAS TO GUNGUN SWITCH CIRCUITCourtesy of the AWS Welding Handbook, Volume 2, 8th Edition910CABLE ASSEMBLYSHIELDING GAS FROM CYLINDERWELDING CONTACTOR CONTROLPOWER CABLEPRIMARY INPUT POWER

Types of Continuous WireElectrodes

Modes of Metal TransferSprayShort-circuitingGlobularPulse-spray

GMAW Transfer ModesShort Circuit ModeSpray ModePulse Transfer

GMAW Pros & Cons Advantages Welds all commercial metals All positions High deposition rates compared to GTAW and SMAW Continuously fed filler wire Long welds without stops and starts Minimal post-weld and inter-pass cleaning Disadvantages Welding equipment is more complex than that for SMAW More difficult to use in hard to reach places Welding torch size Welding torch must be kept in close proximity to the workpiecesin order to achieve adequate shielding Arc must be protected against air drafts

FCAW Pros & Cons Advantages High deposition ratesDeeper penetration than SMAWHigh quality weldsLess pre-cleaning than GMAWSlag covering helps with out-of-position weldsSelf-shielded FCAW is draft tolerantDisadvantages Slag must be removedHigher fume generation than GMAW and SAWSpatterEquipment is more expensive and complex than SMAWFCAW wire is more expensive

Submerged Arc Welding (SAW)Definition At least one consumablebare metal electrodeArc(s) produce heatShielded by granular,fusible material onworkpiecesUses similar weldingvariables as GMAW forprocedure and operatorqualificationSource: AWS Handbook 9th ed. Vol. 1

SAW Pros & Cons Advantages Superior weld qualityOften self cleaningHigh deposition ratesMinimum edge preparationNo radiant energyMinimum fume problemDisadvantages Flux housekeeping Usable only in flat position

Plasma Arc Welding (PAW)Definition Nonconsumable electrodeHeat is produced from a plasma jet Arc can be transferred or nontransferred Shielding is obtained from the ionized gas Usually supplemented by an auxiliary source of shielding gas Filler metal may of may not be used Cold wire feed, hot wire feed, dabber technique Variables Plasma currentOrifice diameter and shapeType of orifice gasFlow rate of orifice gasType of shielding gas

Plasma Arc TorchSource: AWS Handbook 9th ed. Vol. 1

PAW Pros & Cons Advantages Columnar plasma jet Higher energy density enables faster welding speeds, lower heatinput, and less distortion Improved arc stability and tolerance to variations in torch-to-workdistance Permits the use of longer torch-to-work distances Less welder skill is required (compared to GTAW) Disadvantages Higher equipment cost Lower tolerance to variations in fit-up Manual PAW torches are more difficult to manipulate thanmanual GTAW torches

Tandem GMAW A variation of standard GMAW withthe following features: Two welding power sources Two wire feeders Two electrically isolated, independentlycontrolled welding arcs One weld poolLeadTrailLeadTrailTop viewTop viewFlow by surface tension and arc forceDamming up force by trailing arcFlow of turning around trailing arc

Why Use Tandem GMAW? Improve Productivity andQuality Increased deposition ratesFaster travel speedsMaintain or improve overallweld quality, gap fillingcapabilityApplications Long straight weld jointsOrbital applicationsMechanized processesAutomated processesDeposition rate (lbs/hr)Image courtesy of Lincoln Electric

Narrow Groove Tandem GMAW Conventional approaches to joiningthick sections include High deposition-rate processeswith conventional joint designs GMAW, SAW V-groove, double V-groove Low deposition-rate processeswith narrow-groove designs Cold-wire GTAW Hot-wire GTAW Parallel or near-parallel sidewalls Narrow-groove tandem GMAW High deposition-rate processin a narrow groove Reduced joint volume Excellent sidewall fusion Reduced distortion

Benefit: Reduced Joint-Volume For a 5-in.-thick joint 75% reduction in joint volume compared to a single-V groove 55% reduction in joint volume compared to a double-Vgroove Bead placement Single bead per layer Minimal torch positioning requiredTraditional 45-DegreeDouble V-Groove5 in.Root Opening: 0.125 in.Cross-sectional area: 5.8 in.2Narrow Groove5 in.Root Opening: 0.5 in.Cross-sectional area: 2.5 in.2

Strip Cladding ProcessDescription Welding takes place under agranular flux which melts andforms a slag to protect themolten weld poolStrip electrodes are 0.5mm thickrange in width from 30 to120mmDeposits wide, flat weld beadswith minimal dilution of the basematerial.Two process variations basedon conductivity of the slag Submerged arc strip cladding &electroslag strip cladding