duplex welding 2

How to Weld Type 2205 CodePlus Two Duplex Stainless Steel

Outokumpu Stainless

Material Description

2205 is a duplex (austenitic-ferritic) stainless steel thatcombines many of the best properties of austeniticand ferritic stainless steels. High chromium andmolybdenum contents provide excellent resistanceto pitting and crevice corrosion. The duplex structureis highly resistant to chloride stress corrosioncracking. 2205 has outstanding strength andtoughness and possesses good weldability.

The trademark Code Plus Two indicates thecommitment, not only to meet the requirementsfor S31803 as established in ASTM and ASME,but also to meet two additional requirements. The first requirement was that nitrogen should bein the 0.14 to 0.20% range to gain its benefits inhigher strength, higher corrosion resistance, greatermetallurgical stability, and superior propertiesafter welding. The second requirement was thatall mill products should pass a test for the absenceof detrimental intermetallic phases. The tests developed by Outokumpu Stainless for this purposehave been formalized as the ASTM A 923 standardtest method.

These special requirements now define a newquality of 2205, designated S32205. S32205 isdual certifiable as S31803, but represents whatusers have come to expect of 2205 steel. BothS31803 and S32205 are included in all applicableASTM product specifications.

The increased strength of S32205, relative tothat of S31803, resulting from its higher nitrogen isnow being recognized by ASTM and ASME. TheASTM has designated S32205 as 2205.

Forming, Heat Treatment, and Machining

Hot Forming

2205 is hot formed in the range 22501750F(1230955C). In this range, the material has lowmechanical strength and good hot ductility. If slowcooled or held at temperatures between 600 and1750F (315955C), the combination of strainand temperature can lead to rapid room temperatureembrittlement by the formation of sigma phaseand other detrimental intermetallic compounds.Full annealing with rapid cooling, ideally waterquenching, is recommended after hot forming.

Cold Forming

Because of its higher strength, 2205 requires higherforces for cold forming than those typical foraustenitic stainless steels. Additional allowance forspringback is necessary. Outokumpu Stainless 2205may be formed on equipment typically used forforming austenitic stainless steels, once allowancehas been made for its higher strength. Designs with2205 frequently have used its higher strength topermit reductions of gauge, significantly easingmany forming applications. Full annealing andquenching is recommended after severe cold forming.

Heat Treatment

2205 is annealed at 1900F (1040C) minimumwith subsequent rapid cooling, ideally water

UNS S32205, S31803 (wrought products)

UNS S39209 (bare welding wire)

UNS J92205 (cast products)

ASTM ASMEPlate, Sheet, Strip A 240, A 480 SA-240, SA-480Bar, Billet A 276, A 479 SA-479Pipe, Tubing A 789, A 790, A 928 SA-789, SA-790Forgings, Fittings A 182, A 815 SA-182, SA-815Castings A 890Testing A 923

ASME Code Case 2186 (Embossed Assemblies)

ASME/ANSI B16.34 for A 182, A 240, A 479, A 789, A 790

ASME/ANSI B16.5, ASME/ANSI B31.1 Code Case 153

ASME/SFA 5.4, SFA 5.9, and SFA 5.22 P No. 10H, Group 1

AWS/A5.4 E 2209-XX, A5.9 ER 2209, A5.22 E 2209T0-X

NACE MR0175

Specifications

Type 2205 Code Plus Two Duplex Stainless Steel2

quenching. This treatment applies for both fullsolution annealing and stress-relief annealing.

Machining

2205 may be machined with high-speed steel tooling at the same speeds and feeds as Type 316Laustenitic stainless steel. With carbide tooling, positive rake angle, and C-5 and C-6 grades forroughing and finishing, respectively, should beused. Cutting speeds should be reduced by about20% from those typical for Type 316L. The highstrength of 2205 requires powerful machines andexceptionally strong and rigid tool mounting.

WeldingGeneral Guidelines

The goal in welding any duplex stainless steel is toobtain fusion and heat-affected zones having theexcellent corrosion resistance of the base metal and sufficiently high impact toughness for theapplication. 2205 Code Plus Two base metalhas an annealed structure with ferrite content inthe range of 3055%, and is virtually free of intermetallic phases. Welding procedures should bedesigned to produce this same structure in the weldmetal and heat-affected zones. The weld thermalcycle, as well as filler metal and protection atmosphere, will control this structure. Near thefusion temperature, the structure of duplex stainlesssteels is entirely ferrite. The desired 3055% ferritecan be achieved only if the cooling rate is slowenough to allow austenite to re-form as the weldcools. If the cooling rate is too slow, however,embrittling intermetallic phases may form in spiteof the presence of the optimum ferrite content.Extremely low heat input followed by rapid coolingwill produce a predominantly ferritic heat-affectedzone with reduced toughness and corrosionresistance. This might occur with a GTAW washpass or resistance spot welding. On the other hand,excessive time in the 13001800F (705980C)range can lead to formation of intermetallic phaseshaving a similar detrimental effect on properties.

Outokumpu Stainless 2205 Code Plus Two hasbeen produced to assist the welder. One importantfeature is that 2205 Code Plus Two has 0.140.20%nitrogen, compared to the 0.080.20% nitrogenpermitted by ASTM and ASME. This higher

nitrogen helps austenite re-form quickly duringcooling so that the weld and heat-affected zoneare more easily converted back to the optimalaustenitic-ferritic balance. In addition, special quality assurance procedures combined with thehigher nitrogen content make 2205 Code Plus Twomore resistant to formation of intermetallic phases.Avesta Welding Products 2205 filler metals, typicallydesignated as 2209, are more highly alloyed withnickel relative to the base metal to assure a fusionzone with austenite-ferrite balance, toughness, andcorrosion resistance similar to those of the basemetal. With Outokumpu Stainless 2205 base metaland filler, the welder has a workable range of operating conditions. By following the guidelinesprovided in properly qualified procedures, the weldercan produce economical constructions with consistent, high-quality welds.

Control of Intermetallic Phases

2205 duplex stainless steel can experienceseveral precipitation reactions. The intermetalliccompound, sigma phase, can precipitate between13001800F (705980C). Carbides can

1800

1600

1400

1200

1000

800

6000.1 1 10 100

Time, Hours

TEMPERATURE F

The curve corresponds to an ambient temperature impacttoughness of 20 ft.-lb. (27J).

Figure 1TimeTemperature Precipitation Diagramfor 2205 Plate with 0.14 N

Type 2205 Code Plus Two Duplex Stainless Steel 3

precipitate between 8001500F (425815C),and 885 (425C) embrittlement can occur inthe temperature range of 650950F (340510C).If 2205 is held for sufficiently long times in any ofthese temperature ranges, precipitation reactions willoccur. The formation of precipitates can embrittle2205, reducing its ambient temperature ductilityand toughness, and can reduce its corrosionresistance. The rate of the precipitation reactions isdependent on the chemical composition of 2205and other metallurgical factors. Figure 1 shows aTime-Temperature-Precipitation curve for a 2.25inch (57 mm) thick 2205 plate with 0.14% nitrogen.The curve corresponds to an ambient temperatureimpact toughness of 20 ft.-lb. (27J). Time-temperaturecombinations to the right of the curve have lessthan 20 ft.-lb. of toughness.

Low Temperature Impact Tests

Low temperature impact testing may be required bythe ASME code (e.g., Section VIII Div. 1 UHA-51),by a customer specification, or a requirement tomeet ASTM A 923 Method B, which calls for asingle impact test at -40F (-40C). Many factorsmay adversely affect the low temperature impactproperties of welds, e.g., elevated ferrite content,presence of deleterious phases, and elevated oxygencontent. The latter is a factor in welding processesthat use a flux, and is affected by the type of flux.Welds may not meet the minimum requirements ofA 923 Method B, because these acceptance criteriawere established for solution annealed plate, but thatdoes not necessarily mean detrimental intermetallicphases are present. As a general guideline, it ispossible to arrange the welding processes in orderof increasing impact toughness as follows: SMAW-rutile coating; FCAW; SMAW-basic coating; SAW,GMAW, GTAW. Outokumpu Stainless is willing toassist in choosing the proper welding consumablefor the procedure qualifications based ontest temperature.

Pitting Test

The standard pitting test used on 2205 is ASTM A923 Method C. Prior to the creation of A 923, thepitting test was often referred to as ASTM G 48Practice B modified. Testing is done in a ferric

chloride solution at a specific temperature, 25C forbase material and 22C for annealed welds for 24hours. Other temperatures may be set by customer specifications, sometimes with minorvariations to the test method. The performance ofwelds in this solution may have no correlation tocorrosion performance in other media and is notintended as a fitness for service test in any specificservice environment. As with impact toughness,the welding process can influence corrosionperformance. The welding processes in order ofincreasing corrosion resistance in this solution are:GTAW; GMAW; FCAW and SAW; SMAW-basiccoating; SMAW-rutile coating. The low ranking ofthe GTAW process is explained by a loss of nitrogenfrom the weld pool. To counteract this effect, it ispossible to either add nitrogen to the torch gas oruse an overalloyed filler metal, e.g., Avesta WeldingProducts P100 (25Cr-9.5Ni-3.6Mo-0.22N).

Joint Design

Some joint designs that can be used for 2205 areshown in Joint Designs 18. The goal of thedesigns is full penetration with minimal risk ofburn-through. Many other designs are possible.For example, when the material thickness exceeds0.5 inch (12 mm) and it is possible to weld fromboth sides, the joint designs in Joint Designs 35can be made symmetrical.

The root bead may be deposited using eitherGTAW (TIG) or SMAW (coated electrodes).If GTAW is used, an inert backing gas should beapplied when tacking. The root side of a rootbead deposited by SMAW should be cleaned after

0.08 in (2mm) t 0.16 in (4mm)A = 0.040.08 in (12mm)

Suitable for single-sided SMAW or double-sided SMAWor GMAW.

Square Butt Joint Joint Design 1

A

t


welding. A suitable electrode diameter is 564332inch (22.4 mm), depending on base metal thickness, welding position, and accessibility forroot-side grinding.

Selection of a joint design should accommodatethe following guidelines:

1. It should be easy to achieve full penetrationwith a good margin of safety.

2. The welder should keep slag formation and theweld pool under observation.

3. Adequate backing gas shielding should beprovided to avoid root defects harmful tocorrosion resistance or mechanical properties.

4. Excessive weaving and wide molten poolsshould be avoided to prevent excessively highheat input and high stresses.

5. Extremely low heat inputs with rapid quenchingshould be avoided to prevent predominantly ferritic heat-affected zones.

Joint Preparation Cleaning

Cleaning of joints and adjacent surfaces beforewelding is good practice for all stainless steels.Dirt, oils, and paint can cause weld defects.Common solvents such as acetone or mineral spiritscan be used as cleaning agents. Moisture in thejoint can cause porosity or weld metal cracking.

It is important that joint preparation follow thedesired joint design accurately. Large variations inpreparation can cause substantial variations in theland thickness or the gap distance, thereby affectingthe consistency of the weld. Edge preparation

t 0.1 in (2.5mm)A = 0.040.08 in (12mm)

Suitable for GTAW from one side. Backing gas required.

Square Butt Joint Joint Design 2

A

t

0.16 in (4mm) t 0.50 in (12mm)A = 0.08 in (2mm)B = 0.08 in (2mm)

Suitable for heavier sections with SMAW, FCAW, and GMAW.Increase A to 0.12 in (3mm) for vertical up SMAW and FCAW.Double groove joints of this design are also suitable.

Single V Joint Joint Design 3

A

t

B

60

0.36 in (9mm) < t < 0.5 in (12mm)B = 0.10.2 in (3-5mm)

Suitable for SAW. Grinding after first pass facilitates fullpenetration. Double groove joints of this design are alsosuitable.


tB

Grinding before pass 2

80

0.5 in (12mm) < t < 2.5 in (60mm)A = 0.06 in (1.5mm)B = 0.08 in (2mm)R = 0.25 in (6mm) radius

Suitable for very thick base metal with SMAW, FCAW, and GMAW. Double groove joints of this design are alsosuitable.

Single U Joint Joint Design 4

A

t

B

R

10


may be done by a metal cutting operation, or bygrinding if carefully done. Any grinding burrmust be removed so it does not interfere with complete fusion.

Preheating and Post-WeldHeat Treatment

Preheating of 2205 is not normally necessary. It maybe helpful in cold ambient conditions to avoid therisk of condensation and possible resultant porosity.In such cases the 2205 may be heated carefully anduniformly to less than 200F (95C), and only afterthe weld joint has been thoroughly cleaned.

If the 2205 is greater than about 0.625 inch(16 mm) thickness, and welding is to be done withvery low heat input (12 kJ/inch, 0.5 kJ/mm),preheating to the range of 200300F (95150C)can be useful. The purpose of this preheating is toavoid excessively rapid cooling and a resultingextremely high ferrite content. A similar uppertemperature limit applies to interpass temperatures.

Postweld heat treatment is not normallynecessary. If it becomes necessary for any reason,it should be done at 1900F (1040C) minimum,followed by rapid cooling. Exposure in the range12001830F (6501000C) is very harmful totoughness and corrosion resistance because offormation of carbides, or sigma or otherintermetallic phases.

Interpass Temperature

The maximum interpass temperature for 2205 is300F (150C).

Distortion

Controlling distortion of 2205 is not significantlydifferent from controlling distortion of austeniticstainless steels. Good practice includes properfixturing, cross supports, braces, staggered beadplacement, and weld sequence, etc. The edges ofthe plate or sheet should be squared, aligned, andtacked prior to welding. The coefficient of thermalexpansion of 2205 is intermediate to those forcarbon steel and for austenitic stainless steels suchas Type 304L.

Workmanship, Inspection, andQuality Assurance

2205 should be welded in accordance withpredetermined fabrication and inspection plans by skilled and trained operators.

0.16 in (4mm) t < 0.5 in (12mm)A = 0.1 in (2.5mm)B = 0.08 in (2mm)

Pipe welding. Suitable with SMAW.


A

t

B

60

0.16 in (4mm) < t < 0.5 in (12mm)A = 0.1 in (2.5mm)B = 0.08 in (2mm)

Suitable for SMAW and FCAW. Tack weld with SMAW, FCAW or GMAW.

Fillet Joint withFull Penetration Joint Design 6

A

B

t

50

0.12 in (3mm) t < 0.5 in (12mm)A = 0.040.08 in (12mm)B = 0.08 in (2mm)

Pipe welding. Suitable with GTAW.

Single U Joint Joint Design 8

A

t

B

R2

0.16 in (4mm)

10


Fabrication of components in 2205 is notdifficult but it does require some modification ofthe practices commonly used for Type 316L. 2205has high strength, which may require changes oftechnique in cold forming. Welding can be donewith little risk of hot cracking, but the welder shouldbe aware that a high cooling rate, weld spatter,strike scars, damp electrodes, and high interpasstemperatures can lead to embrittlement and reducedcorrosion resistance.

To obtain welded joints with corrosion resistanceand mechanical properties equivalent to those ofthe base metal, the welders and inspectors shouldbe informed in advance of the special aspects offorming and welding 2205. Preparing writtenwelding procedures and having welders performtrial welds are sensible precautions prior tobeginning production.

Because 2205 is often selected for criticalcomponents in highly corrosive environments,welded joints must be inspected carefully.Incomplete fusion, incomplete penetration, apoorly cleaned root side, spatter, and strike scarsmust be remedied. Suitable nondestructive testingmethods are X-ray inspection, liquid penetrantinspection, hydrostatic testing, leak detection, andferrite measurement. Destructive testing methodsinclude bend tests, impact tests, and metallographicexamination. A corrosion test such as that inASTM A 923, Method C, may also be useful.

Ferrite Measurement

2205 Code Plus Two is controlled to have anaustenitic-ferrite balance with 3055% ferrite,typically about 45% ferrite. Substantial deviationsof the austenite-ferrite ratio from this range canadversely affect the mechanical properties andcorrosion resistance of the welded joint. Excessivelylow ferrite content (75%) can lead toreduced corrosion resistance and impact toughness.

Metallographic measurement of ferrite is adestructive test and very time consuming, requiringa well-equipped laboratory. A less precise but non-destructive test method is determination offerrite number by a Magnegage equipped with acounterweight. The Magnegage determines the

magnetic capacity of a metal by measuring theforce exerted in lifting a small permanent magnetfrom the test surface. This force is converted to aFerrite Number (FN). Because the original instrumentwent only to 28FN, a counterweight is used toextend the range to higher ferrite numbersexpressed as Extended Ferrite Number (EFN).Outokumpu Stainless has used this method on alarge number of unannealed weld metals anddetermined the relationship of EFN to the volume

fraction of ferrite measured metallographically.This relationship is shown in Figure 2 and may beexpressed as: Volume Percent Ferrite = 0.55 EFN + 10.6

Magnetic measurements of ferrite in duplexstainless welds are best made using metallographicallymeasured reference samples of similar weld geometry.Electronic instruments based on magnetic response,e.g., the Fischer Feritscope, also may be useful forquality control when adequately calibrated.

Dissimilar Metal Welds

For dissimilar welds such as 2205 to carbon or lowalloy steels, appropriate filler metals may be AvestaWelding Products P5 wire (~AWS ER309 LMo,

80

60

40

20

00 20 40 60

EFN

Volume Percent Ferrite

80

3.5

8

100

Percent Ferrite = 0.55 EFN + 10.6

Figure 2Relationship Between Volume PercentFerrite and EFN in Unannealed DuplexWeld Metals


nominal composition 21.5Cr-15Ni-2.7Mo-0.025Cmax) and Avesta Welding Products P5 electrodesand flux cored wire (AWS E309LMo, nominalcomposition 22.5Cr-13Ni-2.7Mo-0.04C max). Forjoining 2205 to an austenitic stainless steel, AvestaWelding Products P5 or another low carbonaustenitic stainless filler metal with molybdenumcontent greater than that of the lesser of the dissimilarmetals may be used. Consideration should be givento whether the filler metal will provide adequatestrength in these dissimilar welds.

Removal of Dirt, Slag, and Heat Tint

To obtain the best corrosion resistance, it is essentialto remove oxide, tarnish, heat tint, and othersurface contamination by mechanical or chemicalmethods, ideally both. Because there is a very thin,chromium-depleted layer below the heat tint, wirebrushing the heat tint alone is not sufficient torestore maximum corrosion resistance.

Mechanical methods include fine grinding andpolishing, and abrasive blasting with 75100micron soda-lime glass beads. Subsequent chemicalcleaning is not required if it is certain that themechanical cleaning methods will not transfer ironto the surface. However, a chemical cleaning withnitric acid or similar media, as described in ASTMA 380 or A 967, subsequent to mechanical cleaningis good practice because it guards against contami-nation from the cleaning medium. Mechanicalcleaning with steel brushes or an abrasive blastingmedium capable of transferring iron (for example, asteel blasting medium or any blasting medium pre-viously used on steel) must be avoided unless thereis to be a subsequent complete chemical cleaning.

If mechanical cleaning is not to be used, thenthe removal of oxide or heat tint will require theuse of pickling, a more aggressive form of chemicaltreatment than the removal of free iron, commonlycalled passivation. 2205 is more difficult to picklethan the 300-series austenitic stainless steels andrequires an aggressive pickling solution. Pickling isreadily accomplished using Avesta WeldingProducts RedOne 140 paste or 240 spray gel or asolution of 20% nitric acid and 5% hydrofluoricacid in water. Avesta Welding Products regularpickling paste may be used also but requires longerpickling times (e.g., two 2-hour applications vs. a

single 3-hour application with RedOne 140 pasteor 240 spray gel). All of these chemicals are aggressive and appropriate precautions for personalsafety, and the safety of others that you work with, as defined in ASTM A 380 must be followed.Proper environmental procedures are required forthe disposal of wash liquors from pickling operations.

When SMAW or FCAW is used as a root pass,it is especially important to remove all weld splatter,slag, and heat tint from the root side. This is bestaccomplished by mechanical means followedby pickling.

Gas Tungsten Arc Welding (GTAW, TIG)

Equipment

Gas tungsten arc welding, also called TIG, maybe performed manually or by machine. A constant-current power supply should be used, preferablywith a high-frequency circuit for starting the arc anda stepless control current delay unit incorporated inthe power supply unit. GTAW should be done usingdirect current straight polarity (DCSP), electrodenegative. Use of direct current reverse polarity(DCRP) will result in rapid electrode deterioration.

Choice of Filler Metal and Electrode

The nonconsumable electrode shall meet therequirements of AWS specification 5.12 ClassificationEWTh-2 (2% thoriated tungsten electrode).Good arc control is achieved by grinding theelectrode to a point. Vertex angles of 3060 degreeswith a small flat at the point are generally used.For automatic GTAW, the vertex angle will affectpenetration. A few simple tests prior to actualfabrication should be made to determine the bestelectrode configuration.

For optimal corrosion performance, GTAWwelds should be made with filler metal. For GTAWwelding with filler, Avesta Welding Productsprovides a 2209 wire that is more highly alloyedwith nickel relative to the 2205 base composition.It has 7.0 to 9.0% nickel as compared to the 5.5%nickel typically in the base metal. Extensive studiesdemonstrated that higher nickel was the mostreliable and effective method of maintaining thedesired austenite-ferrite balance in the weld metal


with mechanical properties and corrosion resistanceequivalent to those of the base metal.

Weld Pool Protection

The weld pool in GTAW should be protected fromatmospheric oxidation by inert gas flowing throughthe weld torch. Turbulence of the inert gas, withthe resulting entrainment of air, can be minimizedby a gas diffuser screen (gas lens) on the torch.

Operating procedures should be adjusted toassure adequate inert gas shielding. Gas flow shouldprecede arc initiation by several seconds and shouldbe held over the pool for at least five seconds afterthe arc is extinguished. If the flow is too low, theweld pool will not be adequately protected. If theflow is too high, gas turbulence may aspirate airinto the weld region. Argon backing gas is requiredon the back side of the joint for all root passes,regardless of joint design. The argon should bewelding grade 100% argon with a purity of at least99.95% argon.

Approximate flow rates are 0.40.6 cfm (1218liters/minute) {0.20.3 cfm (68 liters/minute) ifusing a normal gas nozzle} for the electrode, and0.10.7 cfm (320 liters/minute) for the backingpurge, depending on the root volume. The enclosedvolume should be purged a minimum of seventimes before welding. Argon should be fed at thebottom and out at the top because of its weightrelative to air.

Addition of up to 3% dry nitrogen may beconsidered in the torch gas for enhanced corrosionperformance; however, increased electrode wearmay result. Addition of helium may be useful insome circumstances. Additions of oxygen andcarbon dioxide to the argon welding gas aredetrimental to the corrosion resistance of the weld.

There should be regular inspections of O-ringsfor water-cooled torches and of gas hoses to assurethat only pure, dry shielding gas is delivered to theweld area.

Welding Techniques

The joint should be prepared in one of the suggestedgeometries with attention to surface preparation,edge preparation, alignment, and root spacing.A non-copper backing bar may be installed to

ensure full argon backing gas coverage while makingtack welds and the root pass.

Ignition of the arc should always take placewithin the joint itself. Any strike scars outside ofthe joint should be removed by fine grinding.

Tacking welds of appropriate length andspacing should be made with full argon shielding.The root pass should be made using OutokumpuStainless 2209 filler metal and the appropriateshielding gas flow. There should be no tack weld atthe starting point of the actual root pass weld.To avoid cracking of the root pass weld related totack welds, the welder should interrupt the rootpass before a tack weld. Either grind away thetack completely with a slitting wheel grinder, ormake the tack shorter by grinding the start andfinish of the tack prior to restarting the root pass.The width of the root gap should be maintainedagainst shrinkage.

The start and finish of the root pass weldshould be ground off prior to the start of any fillerpasses. The filler passes should be allowed to cool toless than 300F (150C) between passes. The jointmay be filled using 116-, 332-, or 18-inch diameter(1.6-, 2.4-, or 3.2-mm) Outokumpu Stainless 2209filler metal with 100% argon filler gas. GTAwelding gives the best results when done in the flatposition but vertical welds can be made successfully.The torch should be as near to perpendicular to theworkpiece as possible. Excessive deviation from theperpendicular may cause air to be drawn into theshielding gas. Filler wire should be kept clean at alltimes and stored in a covered container.

Gas tungsten arc welding parameters depend onthe material thickness, joint design, welding process,and other variables. Typical heat inputs for GTAWrange from 15 to 65kJ/inch (0.52.5kJ/mm).Heat input is calculated by the expression:

Heat input = V x A x 60S x 1000

where V = voltage (volts)A = current (amps)S = travel speed (in/min)


All welds should be cleaned in accordance with theprocedures outlined on page 7.


Gas Metal Arc Welding (GMAW, MIG)

Equipment

Gas metal arc welding, also called MIG, is performedusing a constant voltage power supply with variableslope and variable inductance control or withpulsed arc current capability. Three arc transfermodes are available.

Short-Circuiting Transfer

This mode requires separate slope and secondaryinductance controls. It is useful for material upto 0.125 inch (3 mm) thick. Short-circuitingtransfer occurs with low heat input and is particularlyuseful for joining thin sections that could bedistorted by excessive heat. It is also useful forout-of-position welding.

Pulsed Arc Transfer

This mode requires two power sources, one for eachof the two ranges. Switching sources produces thepulsed output. The current has its peak in the spraytransfer range and its minimum in the globularrange. This method provides the benefits of sprayarc but limits heat input, making the method usefulin all positions.

Spray Transfer

This mode provides a stable arc and high depositionrates but occurs with high heat input. It is generallylimited to flat position welding. The best results aregenerally achieved with synergic pulsed arc. GMAWshould be done with direct current reverse polarity(DCRP), electrode positive.

Choice of Filler Metal and WeldingParameters

GMAW uses a consumable electrode in the form ofa continuous solid wire fed through the GMA torchby an automatic wire feed system. Avesta WeldingProducts 2209 filler metal is more highly alloyedwith nickel relative to the base metal to helpachieve the desired ferrite-austenite balance in theweld metal.

Shielding gas is typically 80% welding-grade argon with additions of helium, nitrogen,

and oxygen to enhance weldability andcorrosion performance.

Typical welding parameters for spray arctransfer at a shielding gas flow rate of 0.50.6 cfm(1416 liters/minute) are:

Typical welding parameters for short-circuitingarc transfer at a shielding gas flow rate of 0.40.5cfm (1214 liters/minute) are:


The weld pool in GMA welding should be protectedfrom atmospheric oxidation by inert gas flowingthrough the torch. The shielding gas is typically100% welding grade argon. Other gas mixturesmay be suitable also. Appropriate flow rates are0.40.6 cfm (1216 liters/minute) for 0.0350.063inch (1.01.6 mm) diameter wire. There should beregular inspections of O-rings in water-cooledtorches and of gas hoses. Welding in the presenceof air drafts, regardless of welding positions, shouldbe avoided.

Welding Techniques

Joints should be prepared in one of the suggestedgeometries with attention to surface preparation,edge preparation, alignment, and root spacing.A backing bar may be installed to assure gascoverage while making tack welds and the root pass.Copper backing bars should be avoided toeliminate the possibility of copper contaminationand to avoid excessive cooling rates.

Ignition of the arc should always take placewithin the joint itself. Strike scars and spatter have

Weld Wire Diameter Current Voltage(in) (mm) (amps) (volts)0.035 1.0 170-200 260.045 1.2 210-280 290.063 1.6 270-330 30

Table 1

Weld Wire Diameter Current Voltage(in) (mm) (amps) (volts)0.035 1.0 90-120 19-210.045 1.2 110-140 20-22

Table 2


a microstructure with a very high ferrite content, astructure susceptible to cracking and possibly lowerin corrosion resistance. Such defects should beremoved by fine grinding.

The root pass should be made using AvestaWelding Products 2209 filler metal with theappropriate shielding gas. There should be notack welds at the starting point of the actual rootpass weld. To avoid cracking of the root pass weldrelated to tack welds, the welder should interruptthe root pass before a tack weld. Either grind awaythe tack completely with a slitting wheel grinder,or make the tack shorter by grinding the start andfinish of the tack prior to restarting the root pass.The width of the root gap should be maintainedagainst shrinkage.

The start and finish of the root pass weld shouldbe ground prior to the start of any fill passes.The fill passes should be made with straight stringerbeads. The metal should be allowed to cool to lessthan 300F (150C) between passes. The jointmay be filled using 0.035-, 0.045-, or 0.063-inch(1.0-, 1.2-, or 1.6-mm) diameter Avesta WeldingProducts 2209 filler metal. GMA welding givesthe best results when done in the flat position butvertical welds can be made successfully. The torchshould be as near to perpendicular to the workpieceas possible. Excessive deviation from the perpendicularmay cause air to be drawn into the shielding gas.The filler metal and guide tube should be keptclean at all times. Filler wire should be stored in acovered container.



Flux Cored Wire Welding (FCW)

Equipment

Flux cored wire welding is closely related to GMAW.The flux-filled wire is automatically fed throughthe center of the gun using the same equipment aswhen GMA welding. The shielding gas is suppliedthrough the gun. The flux inside the wire will pro-tect the weld from the atmosphere because it formsa slag which covers the weld. The FCW process can

be made automatic or semiautomatic. The methodis economical because of the high weld depositionrate, suitability for out-of-position work, and suit-ability for a wide range of thicknesses.

Choice of Filler Metal andWelding Parameters

Avesta Welding Products 2209 flux cored wirecarries the AWS destination A5.22 E 2209T0-1.The filler metal is more highly alloyed with nickelrelative to the base metal to help achieve the desiredferrite-austenite balance in the weld metal.

The shielding gas typically used is either 75%argon plus 25% carbon dioxide or 100% carbondioxide. The argoncarbon dioxide mixture offersthe best weldability in the horizontal position andcarbon dioxide the best in vertical welding.

Typical welding parameters for horizontal FCWusing 75% argon plus 25% carbon dioxide shieldinggas at 0.70.9 cfm (2025 liters/minute) are:

Typical welding parameters for vertical FCWusing 100% carbon dioxide shielding gas at0.70.9 cfm (2025 liters/minute) are:

Welding Techniques

Joints should be prepared in one of the suggestedgeometries with attention to surface preparation,edge preparation, alignment, and root spacing.Copper backing bars should be avoided to eliminatethe possibility of copper contamination and toavoid excessive cooling rates.

Ignition of the arc should always take placewithin the joint itself. Strike scars and spatter havea microstructure with a very high ferrite content, astructure susceptible to cracking and possibly lowerin corrosion resistance. Such defects should be

Weld Wire Diameter Current Voltage(in) (mm) (amps) (volts)0.045 1.2 150-250 22-38

Table 3

Weld Wire Diameter Current Voltage(in) (mm) (amps) (volts)0.045 1.2 60-110 20-24

Table 4


removed by fine grinding.Tack welds of appropriate length and spacing

should be made with full argon shielding. The rootpass should be made using Avesta Welding Products2209 filler metal with appropriate shielding gasflow. There should be no tack weld at the startingpoint of the actual root pass weld. To avoid crackingof the root pass weld related to tack welds, thewelder should interrupt the root pass before a tackweld. Either grind away the tack completely with aslitting wheel grinder, or make the tack shorter bygrinding the start and finish of the tack prior torestarting the root pass. The width of the root gapshould be maintained against shrinkage. The startand finish of the root pass weld should be groundprior to the start of any fill passes. The fill passesshould be made with straight stringer beads. Themetal should be allowed to cool to less than 300F(150C) between passes. The filler metal and guidetube should be kept clean at all times. Flux coredwire should be stored in a covered container.



Shielded Metal Arc Welding (SMAW)

Equipment

Shielded metal arc welding, also called stick orcovered electrode welding, is performed using aconstant current power supply. SMA welding isdone using direct current reverse polarity (DCRP),electrode positive.

Electrode Selection and Use

SMA welding uses a consumable electrode having astainless steel core wire with a flux coating. Thiscoating provides arc stability, shields the moltenmetal during arc transfer, and protects the weldduring solidification.

Avesta Welding Products offers four electrodesfor welding 2205 duplex stainless steel. 2205 Basicprovides the highest impact toughness. 2205-PW-17is an all-position electrode. 2205-17 AC/DC is anall purpose electrode for long, flat welds. 2205-VDXis for vertical down welding. All Avesta Welding

Products covered electrodes conform toAWS E 2209 requirements.

Electrodes are furnished in factory-sealedcontainers suitable for storage until ready for use.Once the container is opened, electrodes should bestored in an electrode oven heated to at least 200F(95C) to keep the coating dry because any moistureabsorbed into the flux coating can cause weld poros-ity or weld metal cracking. The operating currentrequired for good welding characteristics increaseswith increasing electrode diameter. Typical SMAwelding parameters are:


In SMAW, the weld pool is protected by gases andslag from the electrode coating. To maximize thisprotection, the welder should maintain as short anarc as possible. Long arc, an increased gap betweenelectrode and workpiece, can produce weld porosity,excessive oxidation, excessive heat input, and reduced mechanical properties.

Welding Techniques

The root pass should be made with 564-inch or 332-inch (2.0- or 2.5-mm) diameter electrodes.Larger electrodes may be used for subsequent fillerpasses. Ignition of the arc should always occur with-in the joint itself. Any strike scars or spatter shouldbe removed by fine grinding.

SMAW should not be used to weld 2205 of lessthan 0.08 inch (2 mm) thickness. For optimalspeed and economy, the workpiece should be inthe flat position. The electrode should be held at20 degrees (drag angle) from the perpendicularwith the electrode grip inclined toward thedirection of travel. The metal should be depositedin a straight stringer bead with the width of weavenot exceeding two times the electrode diameter.The current should be set only high enough to

Electrode Diameter Current Voltage(in) (mm) (amps) (volts)

564 2.0 35-60 22-28332 2.5 60-80 22-2818 3.25 80-120 22-28532 4.0 100-160 22-28

Table 5


obtain a smooth arc and good fusion of the weldto the parent metal.


All welds should be cleaned in accordance withthe procedures outlined on page 7.

When SMA welding is used for the root pass, the root side should subsequently be groundsmooth. All weld spatter, slag, and heat tintshould be removed.

Submerged Arc Welding (SAW)

2205 Code Plus Two can be welded by submergedarc welding with minimal risk of hot cracking.Joint preparation differs somewhat from that foraustenitic stainless steels. Because the 2205 weld metaldoes not penetrate as deeply as do the austeniticfiller metals, the land or the welding parametersmust be adjusted to obtain full penetration.

Choice of Filler Metal andWelding Parameters

Highly basic fluxes seem to give the best impacttoughness for the duplex stainless steels. AvestaWelding Products Flux 805 provides excellenttoughness with 2205 Code Plus Two.

Avesta Welding Products Flux 801 can givegood impact toughness for material less thanabout 0.75-inch (20-mm) thick.

For SAW, Avesta Welding Products 2209 wireshould be used. However, if 2205 is to be weldedto austenitic stainless steels, carbon steel,or low-alloy steels, Avesta Welding Products P5 (nominalcomposition, 21.5Cr-15Ni-2.7 Mo-0.025C max)filler can be used.

Typical submerged arc welding parameters are:



Outokumpu StainlessWelding Consumables

Avesta Welding Products, Inc. provides coated elec-trodes; wires for GTAW, GMAW, FCW, and SAW,welding fluxes, and pickling pastes, all of whichhave been formulated to produce excellent resultswhen welding Outokumpu Stainless 2205 CodePlus Two. For these products, call Avesta WeldingProducts at 1-800-441-7343.

Technical Support

Outokumpu Stainless, assists users and fabricatorsin the selection, qualification, installation, operation,and maintenance of 2205 Code Plus Two duplexstainless steel. Technical personnel, supported bythe research laboratory of Outokumpu Stainless, candraw on years of field experience with OutokumpuStainless 2205 Code Plus Two to help you makethe technically and economically correctmaterials decision.

Outokumpu Stainless is prepared to discussindividual applications and to provide data andexperience as a basis for your selection andfabrication of 2205 Code Plus Two.

Outokumpu Stainless works closely with itsdistributors to ensure timely availability of2205 Code Plus Two in the forms, sizes, andquantities required by the user. For assistancewith technical questions and to obtain top quality2205 Code Plus Two, call Outokumpu Stainlessat 1-800-833-8703.

Weld Wire Diameter Current Voltage(in) (mm) (amps) (volts)

332 2.6 250-450 28-3218 3.25 300-500 29-34532 4.0 400-600 30-351364 5.0 500-700 30-35

Table 6

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Outokumpu Stainless, Inc.425 North Martingale Road, Suite 1600,

Schaumburg, IL 60173-2218 USATel. 1-800-833-8703 Fax 1-800-545-8617

[email protected]

Outokumpu Stainless

Outokumpu Stainless is a core businesswithin Outokumpu, a dynamic metalsand technology group operating worldwideand marketing its metals, metal products,technology and services to customers in awide range of industries.

www.outokumpu.com/stainless/NAD

2205 Code Plus Two is a registered trademarkof Outokumpu Stainless, Inc.

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