FABRICATION OF HASTELLOY CORROSION-RESISTANT ALLOYS

SELECTION OF WELDING FILLER MATERIALSelection of welding filler materialsis a critical element in the design ofa corrosion-resistant welded structure. Often, several types of corrosion-resistant alloys are used atvarious locations in the samestructure. The selection of weldingfiller materials for dissimilar metaljoining applications is also critical.Two methods of welding filler material selection are possible. Theyare (1) selection of matching fillermaterials and (2) selection ofoveralloyed filler materials. Whenthe matching filler material technique is used, the filler material isof the same chemical compositionas one or both of the base materials. In dissimilar welding applications, using the matching filler material technique, the filler material ischosen to match the base materialwhich is generally more highly alloyed (more corrosion resistant).With the overalloyed filler materialselection technique, a highly alloyed, highly corrosion-resistantwelding filler material is used. (Figures 1 and 2).WeldingOveralloyed filler metal selectionreduces the chance of preferentialweld metal corrosion attack. In addition, the use of a singleoveralloyed filler material on a jobsite greatly reduces the chance offiller metal mix-up. HASTELLOYC-22 and C-2000 alloys are usedextensively as such overalloyedwelding filler materials.Additional information concerningoveralloyed welding filler metal selection is contained in BrochureH-2062, Universal Weld FillerMetal.Table 2A contains a list of filler materials which are available fromHaynes International, Inc. Table 2Boffers suggestions for selection offiller materials, under both similarand dissimilar welding applications, using both matching andoveralloyed selection techniques.The base material combinations,which apply to a particular application, are selected along a horizontal row and a vertical column ofTable 2B. The numbers listed at4that intersection represent possiblewelding filler materials as listed inTable 2A.The information included hereuses the same filler metal "alloyclass" designation as is used inBrochure H-3167. It is possible,then, to cross-reference the information listed in Brochure H-3167without confusion.When joining the HASTELLOY alloy base materials to carbon steelor low-alloy steel, the arc mayhave a tendency to play onto thesteel side of the weld joint. Propergrounding techniques, a short arclength and torch/electrode manipulation are necessary to compensate for this problem.Additional information on applicable filler metal specificationsand product forms are contained inthe Appendix at the end of this brochure.

Figure 1GAS TUNGSTEN ARC WELDS (GTAW)Alloy 317LFiller MetalAlloy 625Filler MetalC-22 AlloyFiller MetalAlloy 904LFiller MetalAlloy 625Filler MetalC-22 AlloyFiller MetalIN-182 (600-type)ElectrodeIN-112 (625-type)ElectrodeC-22 AlloyElectrodeIN-182 (600-type)ElectrodeIN-112 (625-type)ElectrodeC-22 AlloyElectrode317L Stainless SteelBase Metal9% FeCl3 Solution;950F (350C), 120-hour testAlloy 904LBase Metal9% FeCl3 Solution;950F (350C), 120-hour testFigure 2SHIELD METAL ARC WELDS (SMAW)317L Stainless SteelBase Metal9% FeCl3 Solution;950F (350C), 120-hour testAlloy 904LBase Metal9% FeCl3 Solution;950F (350C), 120-hour test5Welding

Table 2AWELDING FILLER MATERIALSFiller MaterialsHASTELLOY B-2 alloyHASTELLOY B-3 alloyHASTELLOY C-276 alloyHASTELLOY C-22 alloyHASTELLOY C-4 alloyHASTELLOY C-2000 alloyHASTELLOY G-30 alloyHASTELLOY W alloyHAYNES 242TM alloyHAYNES 625 alloyAWS ERNiMo-3ERNiCrMo-3Alloy Class101112131415172098*E - Coated Electrodes**ER - Bare WireTable 2BSUGGESTED FILLER METAL SELECTION GUIDEFor both Matching and Overalloyed Filler MaterialsAlloysHASTELLOY B-2 alloyHASTELLOYB-3 alloyHASTELLOYC-4 alloyHASTELLOYC-276 alloyHASTELLOYC-22 alloyHASTELLOYC-2000 alloyHASTELLOYG-30 alloyHASTELLOYN alloy200/201400600825Stainless 11131011131510111317920101110118108101310138B-3 1108118111311138C-4C-276C-22 C-2000 G-30 171381781713171388989891391386813813138

WELDING JOINT DESIGNSelection of a correct weld jointdesign is critical to the successful fabrication of HASTELLOYcorrosion-resistant alloys. Poorjoint design can negate even themost optimum selection ofwelding filler metal.Various welding documents areavailable to assist in the designof welded joints. Two suchdocuments that provide guidance are American WeldingSociety, Welding Handbook,Volume 1, Eighth Edition,Chapter 5 and ASM International, Metals Handbook, Volume 6, Welding, Brazing andSoldering, Joint Design andPreparation. In addition, fabrication codes such as the ASMEPressure Vessel and PipingCode may impose designrequirements.Typical butt joint designs that areused with the gas tungsten arcwelding (GTAW), gas metalarc welding (GMAW), andshielded metal arc welding(SMAW) processes are (I)Square-Groove, (II) Single-VGroove, and (III) Double-VGroove shown in Figure 3. Gastungsten arc welding is often thepreferred method for depositingthe root pass associated with thesquare-groove (Joint I) or singlegroove (Joint II) where access toonly one side of the joint ispossible. The remainder of thejoint can then be filled usingother welding processes asappropriate. For groove weldson heavy section plates greaterthan 3/4 inch (19 mm) thick, a Jgroove is permissible. Such ajoint reduces the amount of fillermetal and time required tocomplete the weld. Other typicalwelding joint designs are shownin Figure 4. The actual numberof passes required to fill the jointdepends upon a number offactors that include the fillermetal size (electrode or wirediameter), the amperage, andthe travel speed.It should be recognized thatnickel-based alloy weld metal issluggish (not as fluid as carbonsteel) and does not flow out asreadily and "wet" the sidewalls.Therefore, the welding arc andfiller metal must be manipulatedso as to place the molten metalwhere needed. In addition to thesluggishness, the joint penetration is also less than that of atypical carbon or stainless steelweld. With this low penetrationpattern, the possibility of incomplete fusion increases. As aresult of these factors, care mustbe taken to insure that thegroove opening is wide enoughto allow proper torch or electrodemanipulation and placement ofthe weld bead.A general estimate of filler metalrequirements is about four to fivepercent (by weight) of the baseplate requirement. Estimatedweight of weld metal required perunit length of welding is given inTable 3.Figure 3TYPICAL BUTT JOINTS FOR MANUAL WELDINGJoint II C C AJoint III Joint I A B B t t t ATABLE 3MaterialThickness (t),in. (mm)1/16 (1.6)3/32 (2.4)1/8 (3.2)1/4 (6.3)3/8 (9.5)1/2 (12.7)1/2 (12.7)5/8 (15.9)5/8 (15.9)3/4 (19.1)3/4 otOpening (A),in (mm)0-1/16 (0-1.6)0-3/32 (0-2.4)0-1/8 (0-3.2)1/16-1/8 (1.6-3.2)LandThickness (B)in IncludedWeldAngle -7560-7560-75Approx. Weightof Weld MetalRequired,lbs/ft (kg/m)0.02 (0.03)0.04 (0.06)0.06 (0.09)0.30 (0.45)0.60 (0.89)0.95 (1.41)0.60 (0.89)1.40 (2.08)0.82 (1.22)1.90 (2.83)1.20 (1.79)Welding

Figure 4OTHER JOINT DESIGNS FOR SPECIFIC SITUATIONSFlanged Corner WeldtT1 1/2 T1/16” to 3/32”45 60 - 75 t1/16” & 3/32”Flanged corner weld notrecommended for shielded metal arcwelding. No filler rod required for gastungsten arc welding.For joints requiring maximumpenetration. t greater than1/4-inch (6.4 mm). Difficult weld.Butt joint (chisel weld) for roundt up to 1 1/2 inches (38 mm) inbarsdiameter.Shell Plate Openings3/32” to 1/8”Shell Plate45 15 1/16” min.For side openings such as manways,viewports, pipe flanges, etc. Not tobe confused with tube shells.Cleaning, Edge Preparationand Fit-UpProper preparation of the weld jointregion is considered a veryimportant part of welding thecorrosion-resistant nickel-basedalloys. A variety of mechanical andthermal cutting methods areavailable for the preparation ofweld angles. Plasma cutting/gouging, machining, grinding, andair carbon arc gouging are allpotential processes. It is necessaryto condition all thermal cut edgesto bright, shiny metal prior towelding. (This is particularlyimportant if air arc gouging is beingused due to the extreme possibilityof carbon pick-up from the carbonelectrode).In addition to the weld angle, aone-inch (25 mm) wide band onthe top and bottom (face and root)surface of the weld zone should beconditioned to bright metal withabout an 80 grit flapper wheel ordisk. This is essential whenshielded metal arc weldingHASTELLOY B-2/B-3 alloys. If themill scale is not removed, the B-2/B-3 alloys welding flux can interactwith the mill scale and causecracking at the toe of the weld inthe base material.The welding surface and adjacentregions should be thoroughlycleaned with an appropriatesolvent prior to any weldingWeldingConventional fillet weld. Fillet sizeshould equal thickness of thinnestmember.Butt joint (chisel weld) for roundbars over 1 1/2 inches (38 mm) indiameter.operation. All greases, cutting oils,crayon marks, machiningsolutions, corrosion products,paints, scale, dye penetrantsolutions, and other foreign mattershould be completely removed.exercised, no particular correctivemeasures should be necessaryprior to service.Stainless steel wire brushing isnormally sufficient for interpasscleaning of GTAW and GMAWweldments. The grinding of startsand stops is recommended for allfusion welding processes. Ifoxygen or carbon dioxide bearingshielding gases are used duringgas metal arc welding, lightgrinding is necessary betweenpasses prior to wire brushing. Slagremoval during shielded metal arcwelding will require chipping andgrinding followed by wire brushing.Preheat of the HASTELLOY alloysis not required. Preheat isgenerally specified as roomtemperature (typical shopconditions). Interpass temperatureshould be maintained below 200ºF(93ºC).Surface iron contamination (ruststaining) resulting from contact ofcarbon steel with the nickel-basedalloys is not considered a seriousproblem and, therefore, it isgenerally not necessary to removesuch rust stains prior to service. Inaddition, melting of small amountsof such surface iron contamination,into the weld puddle, is notexpected to affect weld metalcorrosion resistance.While such contamination is notconsidered a serious problem, it isassumed that reasonable care isexercised to avoid the problem tobegin with. If such care is8Preheat, InterpassTemperature, and CoolingTechniquesThe base plate may requirewarming to raise the temperatureof the alloy above freezing or toprevent condensation of moisture.Condensation may occur if thealloy is brought into a warm shopfrom cold outdoor storage.Warming should be accomplishedby indirect heating if possible(infrared heaters or natural heatingto room temperature).If oxyacetylene warming is used,the heat should be applied evenlyover the base metal rather than inthe weld zone. The torch should beadjusted so that the flame is notcarburizing. A "rosebud" tip, whichdistributes the flame evenly, isrecommended. Care should betaken to avoid local or incipientmelting as a result of the warmingprocess.

Figure 5CONTROL OF DISTORTIONDrawings arecourtesy ofWELDINGENCYCLOPEDIA,Monticello Books,Inc.Transverse shrinkageof weldNeutral axisAngular distortionof butt weldLongitudinal shrinkageof weldPulling effects of weldNeutral axisAngular distortionof filler weldCenter of gravity of weldPulling effects of weldCenter of gravity of weldLongitudinal neutral axisof memberPulling effect of weld above neutral axisAuxiliary cooling methods may beused to control the interpasstemperature. Water quenching isacceptable. Care must be taken toinsure that the weld zone is notcontaminated with traces of oilfrom shop air lines, grease or dirtfrom soiled water-soaked rags, ormineral deposits from hard waterused to cool the weld joint. Thesafest way to maintain a lowinterpass temperature is to allowthe assembly to cool naturally.When attaching hardware to theoutside of a thin-walled vessel, it isgood practice to provide auxiliarycooling to the inside (process side)to minimize the extent of the heataffected zone.Postweld Heat TreatmentHASTELLOY corrosion-resistantalloys, under the vast majority ofcorrosive environments, are usedin the as-welded condition.Postweld heat treatments, eitherfull solution anneal heat treatment,1900 to 2150ºF (1038 to 1177ºC)depending on alloy, or stress reliefheat treatment, typically 1100 to1200ºF (593 to 649ºC), arenormally not required.Specific discussions concerningsolution annealing requirementsare presented in the HeatTreatment section of this brochure.Pulling effect of weld below neutral axisStress relief heat treatments arenormally considered to beineffective with these alloys andcan in some cases affectmechanical properties.HASTELLOY B-2 and B-3 alloysfor example, should never be heattreated or postweld stressrelieved in the 1000 to 1500ºF(538 to 816ºC) temperature range.If stress relief heat treatment ofattendant carbon steel componentsections is required to meet coderequirement, contact HaynesInternational, Inc. for detailedinformation.Inspection and RepairGood manufacturing practicesuggests that some degree ofnondestructive testing (NDT) beconducted. For code fabrications,certain mandatory NDTinspections may be required. Fornon-code fabrication, NDT may beas simple as visual inspection ordye penetrant inspection. NDTshould be considered for bothintermediate quality controlinspections during fabrication, aswell as for final acceptance tests.plasma arc gouging, and aircarbon arc gouging. Extreme caremust be used during air carbon arcgouging to insure that carboncontamination of the weld zonedoes not occur.Generally the prepared cavity isdye penetrant inspected to insurethat all objectionable defects havebeen removed and then thoroughlycleaned prior to welding repair.Because these alloys have lowpenetration characteristics, theground cavity must be broadenough and have sufficientsidewall clearance in the weldgroove to allow for weld rod/weldbead manipulation. "Healingcracks" or "washing out" defects byautogeneously remelting weldbeads or by depositing additionalfiller metal over the defect is notrecommended.Control of DistortionDistortion characteristics of thenickel-based alloys are similar tothose of the austenitic stainlesssteels. Figure 5 is included to showpossible changes in weld jointshape.Welding defects that are believedto affect quality or mechanicalintegrity should be removed andweld repaired. Removaltechniques include grinding,9Welding

It is suggested that, wherepossible, extra stock be allowed tothe overall width and length.Excess material can then beremoved to hold final dimensions.The creation of stress is inevitableduring welding because of thecomplex thermal stresses that arecreated when metal solidifies."Strain intolerant microstructures"temporarily occur at elevatedtemperatures near the melting andsolidification point of all alloys.Surface contaminates such assulfur can contribute to hotcracking. Certain geometricfeatures such as concave welddeposits and tear-drop shapedweld pools can also lead to hotcracking. For each alloy system, acritical combination of theseconditions can produce hotcracking.Cracking ConsiderationsDuring normal fabrication of theHASTELLOY alloys, cracking israre and one should expect tofabricate large, complexcomponents with few problems.Fabrication cracking, when noted,can include hot cracking, stresscracking, and cracking related toheat treatment.For the HASTELLOY corrosionresistant alloys, the onset of hotcracking has been observed whenwelding current reaches about 350amps in restrained,uncontaminated GMAW (spraytransfer mode) welds. Hot crackinghas also been found in C-276 alloysubmerged arc welds when theamperage was above 400 amps.Hot cracking is a conditiongenerally confined to the fusionzone but occasionally can occur inthe heat-affected zone. Twoconditions are necessary toproduce hot cracking: stress and a"strain intolerant microstructure".Cold cracking will occur insolidified weld metal and in basematerial only when externallyapplied stresses exceed the tensilestrength of the alloy. Classicalhydrogen embrittlement is not afabrication cracking problem innickel-based alloys.Jigs, fixturing, cross supports,bracing, and bead placement/ weldsequence will help to holddistortion to a minimum. Wherepossible, balanced welding aboutthe neutral axis will assist inkeeping distortion to a minimum.Proper fixturing and clamping ofthe assembly makes the weldingoperation easier and minimizesbuckling and warping of thinsections.Bead shape can play a role in weldmetal cracking. Root pass weldbeads that have a concave shapecan crack during root passwelding. This results from theapplied stresses exceeding thestrength limit of the very small weldbead cross-section. Convex weldbeads and clamps/fixtures cancontrol this cracking problem.Weldments of HASTELLOY B-2alloy can suffer cracking duringheat treatment. Such crackingoccurs in the temperature range1000 to 1500ºF (538 to 816ºC)upon heat-up during solution heattreatment. In this temperaturerange the alloy becomes verystrong, with an attendant decreasein ductility due to the metallurgicalcondition known as long rangeordering. Residual tensile stressesin conjunction with the highstrength causes the alloy to crack.This condition is controlled by rapidheating during annealing and shotpeening high residual stress areas.More information concerning thisproblem is included in the HeatTreatment section of this brochure.B-3 alloy is a significantimprovement; however, crackingwill occur with longer exposure timein the deleterious temperaturerange.SPECIFIC WELDING PROCESS CONSIDERATIONSGas Tungsten Arc Welding(GTAW)The gas tungsten arc weldingprocess is a very versatile, allposition welding process. It can beused in production as well asrepair situations. It can be usedmanually or adapted to automaticequipment to weld thin sheet orplate material. It is a process thatoffers great control and is thereforeroutinely used during tack weldingand root pass welding. The majordrawback of the process isproductivity. For manual weldingsituations, GTAW weld metaldeposition rates are low.WeldingGenerally, power suppliesequipped with high frequency start,pre-purge/post-purge and upslope/down-slope (or foot pedal)controls are recommended. It isrecommended that the GTAWwelding torch be equipped with agas diffuser screen ("gas lens") toprovide optimum shielding gascoverage. Generally, the gas cupshould be as large as practical.Typical welding parameters, whichare suggested for theHASTELLOY corrosion-resistantalloys, are presented in Table 4.Electrical polarity should be directcurrent electrode negative(DCEN).10Two percent thoriated tungstenelectrodes are recommended. Theclassification for these electrodesis EWTh-2 (American WeldingSociety Specification A5.12). Thediameter of the tungsten electrodewill vary with amperage. Generalrecommendations for electrodediameter selection are given inTable 4. It is recommended thatthe electrode be ground to a coneshape (included angle of 30 to 60degrees) with a small 1/16 inch(1.6 mm) flat ground at the point.See Figure 6 for details.

Welding grade argon (99.996percent minimum purity) shieldinggas is recommended for all normalfabrication situations. The flowrates are normally in the 25-30cubic feet per hour range. Whenproper shielding is achieved, theas-deposited weld metal shouldhave a bright-shiny appearanceand require only minor wirebrushing between passes. Onspecial occasions, argon-helium orargon-hydrogen shielding gasesare used in high travel speed,highly specialized mechanizedwelding systems.In addition to welding torchshielding gas, a back-purge at theroot side of the weld joint isrecommended (welding gradeargon). The flow rates are normallyin the 5 to 10 cubic feet per hourrange. Often backing bars (usuallycopper) are used to assist in beadshape on the root side of GTAWwelds. Backing gas is oftenintroduced through small holesalong the length of the backing bar.There are situations wherebacking bars cannot be used.Under these conditions, open-buttwelding is often performed.

affected zone. Welding processes that are commonly used with the corrosion-resistant alloys are shown in Table 1. In addition to these common arc welding processes, other welding processes such as plasma arc welding, resistance spot welding, laser beam welding, electron beam welding, and submerged arc welding can be used. Because of