hastelloy fabrication

7/27/2019 Hastelloy Fabrication

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General Guidelines forWelding, Brazing, Hot and

Cold Working, Heat Treating,Pickling and Finishing

H-2010F

FABRICATION OF HASTELLOY

CORROSION-RESISTANT ALLOYS

CORROSION-RESISTANT ALLOYS

Contents

Introduction 2

Welding 3

Safety and Health

Considerations 15

Brazing 16Lining 18

Hot Working 25

Cold Working 27

Heat Treatment 30

Descaling and Pickling 32

Grinding and Machining 34

Appendix - SelectedData and Information 37

Chemical Compositions 37

Available Forms 38

Wire and Electrode Sizes 38ASME and AWS

Specifications 38

Comparative Properties 38

Thermal Expansion 39

Thermal Conductivity 39

Sales Offices Addresses 40

2003, Haynes International, Inc


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INTRODUCTION

Introduction

This brochure is a general guide to thefabrication of the corrosion-resistantalloys produced by Haynes Interna-tional, Inc. It is not meant to be aninstruction manual.

The following corrosion-resistant alloysare covered in this brochure:

HASTELLOY B-3 alloy

HASTELLOY C-4 alloy

HASTELLOY C-22 alloy



HASTELLOY G-30 alloy

HASTELLOY N alloy

HASTELLOY B-3 alloy is an additionalmember of the nickel-molybdenumfamily of alloys with excellent resis-tance to hydrochloric acid at all

concentrations and temperatures. Italso withstands sulfuric, acetic, formicand phosphoric acids, and othernonoxidizing media. B-3 alloy has aspecial chemistry designed to achievea level of thermal stability greatlysuperior to that of its predecessors,e.g. HASTELLOY B-2 alloy. B-3 alloyhas excellent resistance to pittingcorrosion, to stress-corrosion crackingand to knife-line and heat-affectedzone attack.

Ask for Bulletin H-2104

HASTELLOY C-4 alloy is a nickel-

chromium-molybdenum alloy withoutstanding high-temperature stability,as evidenced by high ductility andcorrosion resistance even afterlongtime aging at 1200 to 1900 deg. F(649 to 1038 deg. C). The alloy alsohas excellent resistance to stresscorrosion cracking and to oxidizingatmospheres up to 1900 deg. F (1038deg. C).


HASTELLOY C-22 alloy a versatilenickel-chromium-molybdenum-tungstenalloy with better overall corrosion

resistance than other Ni-Cr-Mo-Walloys available today, includingHASTELLOY C-276 and C-4 alloys andHAYNES 625 alloy. C-22 alloy hasoutstanding resistance to pitting,crevice corrosion and stress corrosioncracking. By virtue of its higherchromium content, C-22 alloy is moreresistant than C-4 and C-276 alloys tooxidizing acids and to acid streamscontaining oxidizing residuals such asdissolved oxygen, ferric ions and wetchlorine. In fact, it is second only to

C-2000 alloy in its versatility. Becauseof such versatility it can be used inmulti-purpose processes and where"upset" conditions are likely to occur.


HASTELLOY

C-22HS

alloy iscorrosion-resistant, nickel-chromium-molybdenum alloy which can be heattreated to obtain a strength approxi-mately double that of other C-typealloys. Importantly, the corrosionresistance and ductility of the alloyremain excellent when in the highstrength condition. In addition to itshigh uniform corrosion resistance inoxidizing as well as reducing environ-ments, the as-heat treated C-22HS alloypossesses high resistance to chloride-induced pitting and crevice corrosionattack.


HASTELLOY C-2000 alloy wasdesigned to resist an extensive range ofcorrosive chemicals, including sulfuric,hydrochloric, and hydrofluoric acids.Unlike previous Ni-Cr-Mo alloys, whichwere optimized for use in eitheroxidizing or reducing acids, C-2000alloy extends corrosion resistance inboth types of environments. Thecombination of molybdenum and copperprovide the outstanding resistance toreducing media, while oxidizing acidresistance is provided by a highchromium content. C-2000 alloy also

exhibits pitting resistance and crevicecorrosion resistance superior to theindustry standard, C-276 alloy. Itsforming, welding and machiningcharacteristics are similar to C-276alloy.


HASTELLOY C-276 alloy has excellentresistance to pitting, stress corrosioncracking, and acid environments. It hasexceptional resistance to a wide varietyof chemical process environments,including strong oxidizers such as ferricand cupric chlorides, hot contaminated

media (organic and inorganic), chlorine,formic and acetic acids, acetic anhy-dride, and seawater and brine solutions.


HASTELLOY G-30 alloy is a highchromium nickel-base alloy whichshows superior corrosion resistanceover most other nickel- and iron-basealloys in commercial phosphoric acidsas well as many complex environmentscontaining highly oxidizing acids such

The nominal chemical compositionsof these alloys and the availableproduct forms can be found inTables A-1 and A-2, respectively, inthe Appendix.

2003 by Haynes International, Inc.

as nitric/hydrochloric, nitric/hydrofluoricand sulfuric acids. The resistance of G-30 alloy to the formation of grainboundary precipitates in the heat-affected zone makes it suitable for usein the as-welded condition.


HASTELLOY G-35 alloy wasdesigned to resist "wet process"phosphoric acid, which is widely usedin the production of fertilizers. Testsindicate that it is far superior toHASTELLOY G-30 alloy and stainlesssteels, in this chemical. It was alsodesigned to resist localized attack inthe presence of chlorides, since under-deposit attack is potential problem inevaporators used to concentrate "wetprocess" phosphoric acid. As a resultof its high-chromium content, G-35alloy is extremely resistant to other

oxidizing acids, such as nitric, andmixtures containing nitric acid. Itpossesses moderate resistance toreducing acids, as a result of itsappreciable molybdenum content, and,unlike other nickel-chromium-molybde-num alloys, it is very resistant to"caustic dealloying" in hot sodiumhydroxide. Finally, G-35 alloy is muchless susceptible to chloride-inducedstress corrosion cracking than thehigh-chromium stainless steels andnickel-chromium-iron alloys traditionallyused in "wet process" phosphoric acid.


HASTELLOY N alloy is a nickel-basealloy that was developed as acontainer material for molten fluoridesalts. It has good oxidation resistanceto hot fluoride salts in the temperaturerange of 1300 to 1600 deg. F (704 to871 deg. C). Alloy N is most useful inenvironments involving fluorides athigh temperatures; however, the alloycompares favorably with otherHASTELLOY alloys in various othercorrosive media. It is especiallysuggested that the alloy be tested inmolten halides of zirconium, beryllium,lithium, sodium, potassium, thorium or

uranium.Ask for Bulletin H-2052


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General WeldingThe welding characteristics of theHASTELLOY corrosion-resistantalloys are similar in many ways tothose of the austenitic stainless

steels and present no specialwelding problems, if proper

techniques and procedures arefollowed.

As a way of achieving qualityproduction welds, development

and qualification of weldingprocedure specifications is

suggested. Such procedures areusually required for code

fabrication, and should take intoaccount parameters such as, but

not limited to, base and fillermaterials, welding process, jointdesign, electrical characteristics,

preheat/interpass control, andpostweld heat treatment

requirements.

Any modern welding power supply

with adequate output and controlsmay be used with the common

fusion welding processes.Generally, welding heat input is

controlled in the low to moderate

range. Wide weave beads are notrecommended. Stringer bead

welding techniques, with someelectrode/torch manipulation, are

preferred.

WELDING

Welding

In general, nickel-based alloys willexhibit both sluggish welding and

shallow penetration characteristics.Therefore, care must be used with

respect to joint design and weldbead placement to insure thatsound welds with proper weld

bead tie-in are achieved. Thenickel-based alloys have a

tendency to crater crack, sogrinding of starts and stops is

recommended.

Cleanliness is considered animportant aspect of welding of thecorrosion-resistant nickel-based

alloys. Contamination by greases,oils, corrosion products, lead,

sulfur, and other low melting pointelements can lead to severe

cracking problems.

It is recommend that welding be

performed on base materialsthat are in the solution annealed

condition. Materials with > 7%outer Fiber Elongations of cold

work should be solutionannealed before welding. Thewelding of mateials have large

amounts of residual cold work

can lead to cracking in the weldmetal and/or the weld heataffected zone. Welding processes

that are commonly used with thecorrosion-resistant alloys are shownin Table 1.

In addition to these common arcwelding processes, other welding

processes such as plasma arcwelding, resistance spot welding

laser beam welding, electron beamwelding, and submerged arcwelding can be used. Because of

the possibility of hot cracking,parameter selection is extremely

important when using thesubmerged arc welding process to

weld nickel-based alloys. ContactHaynes International for welding

parameter and wire/fluxrecommendations.

The plasma arc cutting process iscommonly used to cut alloy plate

into desired shapes and prepareweld angles.

The use of oxyacetylene weldingand cutting is not recommended,

because of carbon pick-up fromthe flame.

TABLE 1

American Welding Common

Process Society Designation DesignationGas Tungsten Arc Welding,

Manual and Machine GTAW TIGGas Metal Arc Welding,

Manual and Machine GMAW MIGStick or Coated

Shielded Metal Arc Welding SMAW Electrode


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4

Selection of welding filler materials

is a critical element in the design ofa corrosion-resistant welded struc-

ture. Often, several types of corro-sion-resistant alloys are used atvarious locations in the same

structure. The selection of welding

filler materials for dissimilar metaljoining applications is also critical.

Two methods of welding filler ma-terial selection are possible. Theyare (1) selection of matching filler

materials and (2) selection ofoveralloyed filler materials. When

the matching filler material tech-nique is used, the filler material is

of the same chemical compositionas one or both of the base materi-als. In dissimilar welding applica-

tions, using the matching filler ma-terial technique, the filler material is

chosen to match the base materialwhich is generally more highly al-

loyed (more corrosion resistant).

With the overalloyed filler material

selection technique, a highly al-loyed, highly corrosion-resistant

welding filler material is used. (Fig-ures 1 and 2).

Overalloyed filler metal selection

reduces the chance of preferentialweld metal corrosion attack. In ad-

dition, the use of a singleoveralloyed filler material on a jobsite greatly reduces the chance of

filler metal mix-up. HASTELLOY

C-22 and C-2000 alloys are usedextensively as such overalloyedwelding filler materials.

Additional information concerningoveralloyed welding filler metal se-

lection is contained in BrochureH-2062, Universal Weld Filler

Metal.

Table 2A contains a list of filler ma-terials which are available fromHaynes International, Inc. Table 2B

offers suggestions for selection offiller materials, under both similar

and dissimilar welding applica-tions, using both matching and

overalloyed selection techniques.

The base material combinations,

which apply to a particular applica-tion, are selected along a horizon-

tal row and a vertical column ofTable 2B. The numbers listed at

that intersection represent possible

welding filler materials as listed inTable 2A.

The information included hereuses the same filler metal "alloy

class" designation as is used in

Brochure H-3167. It is possible,then, to cross-reference the infor-mation listed in Brochure H-3167

without confusion.

When joining the HASTELLOY al-

loy base materials to carbon steelor low-alloy steel, the arc may

have a tendency to play onto thesteel side of the weld joint. Proper

grounding techniques, a short arclength and torch/electrode manipu-lation are necessary to compen-

sate for this problem.

Additional information on appli-cable filler metal specifications

and product forms are contained inthe Appendix at the end of this bro-chure.

SELECTION OF WELDING FILLER MATERIAL

Welding


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Figure 1

GAS TUNGSTEN ARC WELDS (GTAW)

317L Stainless SteelBase Metal

9% FeCl3

Solution;950F (350C), 120-hour test

Alloy 904LBase Metal

9% FeCl3 Solution;950F (350C), 120-hour test

317L Stainless Steel

Base Metal9% FeCl

3Solution;

950F (350C), 120-hour test

Alloy 904L

Base Metal9% FeCl

3Solution;

950F (350C), 120-hour test

Figure 2

SHIELD METAL ARC WELDS (SMAW)

Alloy 317L Alloy 625 C-22 AlloyFiller Metal Filler Metal Filler Metal

Alloy 904L Alloy 625 C-22AlloyFiller Metal Filler Metal Filler Metal

IN-182 (600-type) IN-112 (625-type) C-22 AlloyElectrode Electrode Electrode

IN-182 (600-type) IN-112 (625-type) C-22 Alloy

Electrode Electrode Electrode

Welding


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Filler Materials AWS A5.11/A5.14 Alloy Class

HASTELLOYB-2 alloy E*/ER**NiMo-7 10HASTELLOY B-3alloy E/ERNiMo-10 11

HASTELLOY C-276 alloy E/ERNiCrMo-4 12HASTELLOY C-22alloy E/ERNiCrMo-10 13HASTELLOY C-4 alloy E/ERNiCrMo-7 14

HASTELLOY C-2000alloy E/ERNiCrMo-17 15HASTELLOY G-30 alloy E/ERNiCrMo-11 17

HASTELLOY W alloy E/ERNiMo-3 20HAYNES 242TM alloy - 9

HAYNES 625 alloy ERNiCrMo-3 8*E - Coated Electrodes**ER - Bare Wire

Table 2A

WELDING FILLER MATERIALS

Table 2B

SUGGESTED FILLER METAL SELECTION GUIDE

For both Matching and Overalloyed Filler Materials

Welding

Alloys B-2 B-3 C-4 C-276 C-22 C-2000 G-30 N

HASTELLOY 10B-2 alloy 11

HASTELLOY 11 11B-3 alloy 10 10

HASTELLOY 10 11 14C-4 alloy 11 10 13

13 1314 14

HASTELLOY 10 11 13 12C-276 alloy 11 10 14 13

13 13 12

12 12HASTELLOY 10 11 13 13 13C-22 alloy 11 10 14 12

13 13

HASTELLOY 10 11 13 13 13 15C-2000 alloy 11 10 14 15 15 13

13 13 15 1215 15

HASTELLOY 10 11 13 13 13 13 17G-30 alloy 11 10 14 12 17 15

13 13 17 17 1717 17

HASTELLOY 9 9 9 9 9 9 9 9N alloy 20 20 20 20 20 20 20 20

10 11 14 12 13 15 1711 10

200/201 10 11 14 12 13 15 17 811 10 13 13 13 13 9

400 8 8 8 8 8 8 8 8600 10 11 14 12 13 15 17 9

8 8 8 8 8 8 8 8825 10 11 14 12 13 15 17 9

13 13 13 13 13 13 13

Stainless and 10 11 14 12 13 15 17 9Carbon 13 13 13 13 13 13 13Steel 8 8 8 8 8 8 8 8


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7 Welding

Selection of a correct weld jointdesign is critical to the success-ful fabrication of HASTELLOYcorrosion-resistant alloys. Poor

joint 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 guid-ance are American WeldingSociety, Welding Handbook,Volume 1, Eighth Edition,Chapter 5 and ASM Interna-tional, Metals Handbook, Vol-ume 6, Welding, Brazing andSoldering, Joint Design andPreparation. In addition, fabrica-tion 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), and

WELDING JOINT DESIGN

shielded metal arc welding(SMAW) processes are (I)Square-Groove, (II) Single-V-Groove, and (III) Double-V-Groove shown in Figure 3. Gastungsten arc welding is often thepreferred method for depositingthe root pass associated with thesquare-groove (Joint I) or single-groove (Joint II) where access toonly one side of the joint ispossible. The remainder of the

joint can then be filled usingother welding processes asappropriate. For groove weldson heavy section plates greaterthan 3/4 inch (19 mm) thick, a J-groove is permissible. Such a

joint reduces the amount of fil lermetal and time required tocomplete the weld. Other typicalwelding joint designs are shownin Figure 4. The actual numberof passes required to fill the joint

depends 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 penetra-tion is also less than that of atypical carbon or stainless steelweld. With this low penetrationpattern, the possibility of incom-plete 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 five

percent (by weight) of the baseplate requirement. Estimatedweight of weld metal required perunit length of welding is given inTable 3.

TABLE 3

Included Approx. WeightMaterial Preferred Root Land Weld of Weld Metal

Thickness (t), Joint Opening (A), Thickness (B) Angle (C), Required,in. (mm) Design in (mm) in (mm) degrees lbs/ft (kg/m)

1/16 (1.6) l 0-1/16 (0-1.6) N/A None 0.02 (0.03)3/32 (2.4) I 0-3/32 (0-2.4) N/A None 0.04 (0.06)

1/8 (3.2) I 0-1/8 (0-3.2) N/A None 0.06 (0.09)1/4 (6.3) II 1/16-1/8 (1.6-3.2) 60-75 0.30 (0.45)

3/8 (9.5) II 60-75 0.60 (0.89)1/2 (12.7) II 60-75 0.95 (1.41)1/2 (12.7) III 1/32-5/32 1/32-3/32 60-75 0.60 (0.89)

5/8 (15.9) II (0.8-4.0) (0.8-2.4) 60-75 1.40 (2.08)5/8 (15.9) III 60-75 0.82 (1.22)

3/4 (19.1) II 60-75 1.90 (2.83)3/4 (19.1) III 60-75 1.20 (1.79)

Figure 3

TYPICAL BUTT JOINTS FOR MANUAL WELDING

Joint I

A

t

C

AB

Joint II

C

A

B

Joint III

t

t


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Figure 4

OTHER JOINT DESIGNS FOR SPECIFIC SITUATIONS

Flanged corner weld notrecommended for shielded metal arcwelding. No filler rod required for gastungsten arc welding.

Flanged Corner Weld

1/16 & 3/32

1 1/2 T

For joints requiring maximumpenetration. t=greater than1/4-inch (6.4 mm). Difficult weld.

t

45

1/16 to 3/32

60 - 75

Butt joint (chisel weld) for roundbars up to 1 1/2 inches (38 mm) indiameter.

Conventional fillet weld. Fillet sizeshould equal thickness of thinnest

member.

Shell Plate Openings

For side openings such as manways,viewports, pipe flanges, etc. Not to

be confused with tube shells.

Butt joint (chisel weld) for roundbars over 1 1/2 inches (38 mm) in

diameter.

Shell Plate

1/16 min.

45 15

3/32 to 1/8

t

T

t

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 all

potential 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 welding

operation. All greases, cutting oils,crayon marks, machiningsolutions, corrosion products,paints, scale, dye penetrantsolutions, and other foreign mattershould be completely removed.

Stainless steel wire brushing isnormally sufficient for interpasscleaning of GTAW and GMAWweldments. The grinding of startsand stops is recommended for all

fusion 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.

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 is

exercised, no particular correctivemeasures should be necessaryprior to service.

Preheat, InterpassTemperature, and CoolingTechniquesPreheat of the HASTELLOY alloysis not required. Preheat isgenerally specified as roomtemperature (typical shopconditions). Interpass temperature

should be maintained below 200F(93C).

The 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.

Welding


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Auxiliary 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 low

interpass 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 heat-affected 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 2150F (1038 to 1177C)depending on alloy, or stress reliefheat treatment, typically 1100 to1200F (593 to 649C), arenormally not required.

Specific discussions concerningsolution annealing requirementsare presented in the HeatTreatment section of this brochure.

Stress 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 1500F(538 to 816C) temperature range.If stress relief heat treatment of

attendant 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.

Welding defects that are believedto affect quality or mechanicalintegrity should be removed andweld repaired. Removaltechniques include grinding,

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 thoroughly

cleaned 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.

Drawings arecourtesy ofWELDINGENCYCLOPEDIA,Monticello Books,Inc.

Transverse shrinkageof weld

Angular distortionof butt weld

Longitudinal shrinkageof weld

Angular distortionof filler weld

Neutral axis Pulling effects of weld

Center of gravity of weld

Pulling effect of weld above neutral axis

Neutral axis

Pulling effects of weld

Center of gravity of weld

Pulling effect of weld below neutral axis

Longitudinal neutral axisof member

Figure 5

CONTROL OF DISTORTION

Welding


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10Welding

SPECIFIC WELDING PROCESS CONSIDERATIONS

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 minimizes

buckling and warping of thinsections.

It is suggested that, wherepossible, extra stock be allowed tothe overall width and length.Excess material can then beremoved to hold final dimensions.

Cracking ConsiderationsDuring normal fabrication of theHASTELLOY alloys, cracking israre and one should expect tofabricate large, complex

components with few problems.Fabrication cracking, when noted,can include hot cracking, stresscracking, and cracking related toheat treatment.

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".

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 hot

cracking. 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.

For the HASTELLOY corrosion-resistant 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.

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.

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 1500F (538 to 816C)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 high

strength 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.

Gas Tungsten Arc Welding(GTAW)The gas tungsten arc weldingprocess is a very versatile, all-position welding process. It can beused in production as well as

repair 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.

Generally, power suppliesequipped with high frequency start,pre-purge/post-purge and up-slope/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).

Two 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.


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11 Welding

Figure 6

TYPICAL MANUAL GAS TUNGSTEN ARC PARAMETERS (FLAT POSITION)*

Table 4

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 wire

brushing 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 (usually

copper) 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. Suchwelding conditions are oftenencountered during pipe or tube

circumferential butt welding. Underthese conditions where access tothe root side of the joint is notpossible, special gas flowconditions have been establishedwhich differ from the industryrecommendations publishedelsewhere. Under these open-buttpipe welding conditions, the torchflow rates are reduced to about 10

cubic feet per hour and the backpurge flow rates are increased toabout 40 cubic feet per hour. Adetailed brochure is availableconcerning back-purging duringpipe welding (ask for BrochureH-2065).

It is recommended that the torchbe held essentially perpendicularto the work piece. Stringer beadtechniques, using only enough

current to melt the base materialand allow proper fusion of the filler,are recommended. Duringwelding, the tip of the welding fillermaterial should always be heldunder the shielding gas to preventoxidation of the hot welding fillerwire. Standing still or puddling theweld adds to the welding heatinput is not recommended.

Since the welder controls fillermetal additions to the weldpuddle, care must be taken toensure that the resultant weldbead dilution of the basematerials is minimized.

G rinding M arksR un This Direction

.040 in.

.060 in.

30to 60

Tungsten

Electrode Filler Wire WeldingJoint Thickness Diameter Diameter Current

in (mm) in (mm) in (mm) Amps Volts

0.030-0.063 (0.8-1.6) 0.063 (1.6) 0.063 (1.6) 15-60 9-12

0.063-0.125 (1.6-3.2) 0.063/0.094 (1.6/2.4) 0.063/0.094 (1.6/2.4) 50-95 9-12

0.125-0.250 (3.2-6.3) 0.094/0.125 (2.4/3.2) 0.094/0.125 (2.4/3.2) 75-150 10-13

0.250 (6.3) and up 0.094/0.125 (2.4/3.2) 0.094/0.125 (2.4/3.2) 95-200 10-13

* DCEN

TUNGSTEN ELECTRODE GEOMETRY


12/40


13/40

13 Welding

Typical welding parameters, for thevarious weld metal transfer modes,are documented in Table 5.Electrical polarity is direct currentelectrode positive (DCEP).

Shielding gas selection is criticalduring GMAW proceduredevelopment. Five welding gradeshielding gases are suggested for

the HASTELLOY alloys. Thosegases are 75 percent argon +25percent helium (Ar+He), 90percent helium +7.5 percent argon+2.5 percent carbon dioxide(He+Ar+CO

2), 66.1 percent argon

+33 percent helium +0.9 percentcarbon dioxide (Ar+He+CO

2), a

proprietary argon-helium-carbondioxide mixture known asNiCoBRITE gas, and 100percent argon (Ar).

Generally, shielding gas flow rates

are in the 35 cubic feet per hourrange. The welding torch gas cupsize is suggested to be as large aspossible. It is suggested that thewelding torch be held nearlyperpendicular to the work piece. Ifthe torch angle is held too far fromperpendicular, oxygen from theatmosphere may be drawn into theweld zone and contaminate themolten metal.

As noted in Table 5, either,Ar+He+CO

2, He+Ar+CO

2, or

NiCoBRITE shielding gasesproduces a very stable arc,excellent out-of-position

characteristics, and excellent alloy-to-carbon steel weldingcharacteristics. However, becausecarbon dioxide is present, the weldmetal surface will be highlyoxidized. This oxidized conditioncan increase the possibility of lack-of-fusion defects. It is thereforestrongly recommended thatmultipass welds, made with CO

2

containing gases, be lightly groundbetween passes to remove theoxidized surface.

The use of Ar+He in the shortcircuit mode is characterized bysome spatter and some degree ofarc instability when compared towelds made with CO

2bearing

gases. Because this shielding gasis inert, the surface is expected tobe bright and shiny with minimaloxidation. During multipasswelding, it is not mandatory to

grind between passes. Thissituation also applies to the othermodes of weld metal transfer whenusing Ar+He shielding gas.

In spray transfer welding, eventhough 100 percent argonshielding gas is used, someoxidation and "soot" may be notedon the weld surface. Heavy wirebrushing and/or light grinding/conditioning (80 grit) betweenpasses is recommended.

During spray transfer welding, awater cooled welding torch isalways recommended. During

synergic welding, a water cooledtorch is recommended whenamperages exceed approximately120 amps.

As with gas tungsten arc welding,back-purging is required to ensurethe root side of the weld joint is notheavily oxidized. As an alternative,many fabricators weld without

back-purge shielding. They thengrind the root side after welding toremove all oxidized weld metaland defects, dye penetrant checkthe weld zone, and then fill theweld joint from both sides asneeded.

It should be recognized that thefiller wire conduit liner assemblyand contact tips (parts of theGMAW welding torch) are highwear items and should beexpected to be replaced

periodically. Wear of the lineroccurs as a result of gallingbetween the carbon steel liner andthe alloy filler wire. A worn liner willcause erratic wire feed which willresult in arc instability. Somewelding torches can be fitted with anylon conduit liner. Such a linerwould be expected to reduce wearand thus increase conduit life.

It is recommended that sharpbends in the GMAW torch cable beminimized. If possible, move the

wire feeder so that the torch cableis nearly straight during welding.


14/40

14Welding

Shielded Metal Arc Welding(SMAW)The shielded metal arc weldingprocess is well known for itsversatility because it can be usedin all welding positions, and in bothproduction and repair situations. Itis generally not useful on thin-

sheet material. It requires nospecial equipment and can beoperated easily in remotelocations. It is strictly a manualwelding process.

Welding electrodes available fromHaynes International use lime-titania based coating formulationsand are generally classified asslightly basic to slightly acidicdepending on the particular alloy.All electrodes are classified as AC-DC, but are recommended to beused with direct current electrodepositive (DCEP) electricalcharacteristics.

All welding electrodes should bestored in a dry rod oven after thecanister has been opened. It isrecommended that the dry rodoven be maintained at about 250to 400F (121 to 204C). TheHASTELLOY B-2 and B-3 alloys

coating formulation are considereda low moisture formulation andtherefore it is mandatory that thoseelectrodes be carefully controlled.If electrodes are exposed to anuncontrolled atmosphere, they canbe reconditioned by heating in areconditioning oven at 600 to700F (316 to 371C) for 2 to 3hours.

Typical welding parameters arepresented in Table 6 for flatposition welding. For maximum arcstability and control of the moltenpuddle, it is important to maintain ashort arc length. The electrode isgenerally directed back toward themolten puddle (backhand welding)with about a 20 to 40 degree dragangle. As a general statement,stringer bead welding techniquesare recommended. Someelectrode manipulation is required

to place the molten weld metalwhere needed. The maximummanipulation width is about threetimes the electrode core wirediameter.

Out-of-position welding isrecommended only with the 3/32inch and 1/8 inch (2.4 mm and 3.2mm) diameter electrodes. Duringout-of-position welding, the

amperage is reduced to the lowend of the range. In order to keepthe bead profile relatively flatduring vertical welding, a weavebead technique is necessary.Using 3/32 inch (2.4 mm)electrodes will reduce the weavewidth and produce flatter beads. Invertical welding, a range ofelectrode positions is possible from

forehand (up to 20 degree pushangle) to backhand welding (up to20 degree drag angle), dependingon welder preference. In over headwelding, backhand welding (dragangle 0 to 20 degrees) is required.

Starting porosity may occurbecause the electrode requires ashort time to begin generating aprotective atmosphere. This is aparticular problem withHASTELLOY B-2 and B-3 alloys.The problem can be minimized by

using a starting tab of the samealloy as the work piece or bygrinding each start to sound weldmetal. Small crater cracks mayalso occur at the stops. These canbe minimized by using a slightback-stepping motion to fill thecrater just prior to breaking the arc.It is recommended that all startsand stops be ground to soundweld metal.

TYPICAL SHIELDED METAL ARC WELDING PARAMETERS (FLAT POSITION)

Table 6

Welding CurrentElectrode Approximate

Diameter Welding Voltage Aim Rangein. (mm) Volts Amps Amps

3/32 (2.4) 22-24 65 - 70 55 - 751/8 (3.2) 22-24 90 - 100 80 - 1005/32 (4.0) 22-25 130 - 140 125 - 150

3/16 (4.8) 24-26 160 - 170 150 - 180


15/40

15 Safety and Health Considerations

SAFETY AND HEALTH CONSIDERATIONSThose involved with the weldingindustry are obligated to providesafe working conditions and beaware of the potential hazardsassociated with welding fumes,gases, radiation, electrical

shock, heat, eye injuries, burns,etc. Various local, municipal,state, and federal regulations(OSHA, for example) relative tothe welding and cutting pro-cesses must be considered.

Nickel-, cobalt-, and iron-basedalloy products may contain, invarying concentrations, thefollowing elemental constituents:aluminum, cobalt, chromium,copper, iron, manganese,molybdenum, nickel, and tung-

sten. For specific concentrationsof these and other elementspresent, refer to the MaterialSafety Data Sheets (MSDS)H2071 and H1072 for theproduct.

The operation and maintenanceof welding and cutting equipmentshould conform to the provisionsof American National StandardANSI Z49.1, Safety in Weldingand Cutting. Attention is espe-

cially called to Section 4 (Protec-tion of Personnel), Section 5(Ventilation), and Section 7(Confined Spaces) of thatdocument. Adequate ventilationis required during all welding andcutting operations. Specificrequirements are included inSection 5 for natural ventilationversus mechanical ventilationmethods. When welding inconfined spaces, ventilation shallalso be sufficient to assureadequate oxygen for life support.

The following precautionarywarning, which is supplied withall welding products, should beprovided to, and fully understoodby, all employees involved withwelding.

CautionWelding may produce fumes andgases hazardous to health.Avoid breathing these fumes andgases.

Use adequate ventilation. SeeANSI/AWS Z49.1, Safety inWelding and Cutting publishedby the American WeldingSociety.

EXPOSURES: Maintain allexposures below the limitsshown in the Material SafetyData Sheet, and the productlabel. Use industrial hygiene airmonitoring to ensure compliancewith the recommended exposurelimits. ALWAYS USE EXHAUST

VENTILATION .

RESPIRATORY PROTECTION:Be sure to use a fume respiratoror air supplied respirator whenwelding in confined spaces orwhere local exhaust or ventila-tion does not keep exposurebelow the PEL and TLV limits.

WARNING: Protect yourself andothers. Be sure the label is readand understood by the welder.FUMES and GASES can be

dangerous to your health.Overexposure to fumes andgases can result in LUNGDAMAGE. ARC RAYS caninjure eyes and burn skin.ELECTRIC SHOCK can kill.


16/40

16Brazing

BRAZING

Designation Brazing TermperatureAWS AMS Composition, % 0F (0C)

BAg-1 4769 45 Ag, 24 Cd, 16 Zn, 15 Cu 1145-1400 (618-760)BAg-2 4768 35 Ag, 26 Cu, 21 Zn, 18 Cd 1295-1550 (702-843)

BAg-3 4771 50 Ag, 16 Cd, 15.5 Cu, 15.5 Zn, 3 Ni 1270-1500 (688-816)BAg-4 40 Ag, 30 Cu, 28 Zn 1435-1650 (779-899)

BAg-8 72 Ag, 28 Cu 1435-1650 (779-899)BAu-4 82 Au, 18 Ni 1740-1840 (949-1004)

70 Au, 22 Ni, 8 Pd 1925 (1052)

54 Pd, 36 Ni, 10 Cu 2300 (1260) 36 Ni, 34 Pd, 30 Au 2175 (1191)

Table 7

SUITABLE FILLER METALS FOR USE WITH HASTELLOY

CORROSION-RESISTANT

Brazing is defined as the joining ofmetals using a filler metal whosemelting temperature is less thanthat of the base material but over840F (449C). It is usuallycharacterized by the distribution of

filler metal between closely fittedsurfaces. The filler metal thenflows with the application of heatby capillary action.

Note: The HASTELLOY alloys aretypically used in situations wheretheir corrosion resistance is ofprime consideration. Typicalbrazing alloys do not possess thesame degree of corrosionresistance. Brazing shouldtherefore only be used for joiningwhen the braze joint will be

isolated from the environment.Secondly, furnace brazingoperations are typically performedin vacuum and involve a slowcooling step. Care should be takento make sure that the respectivebrazing cycle does not produceprecipitation in the HASTELLOYalloy part.

The keys to successful brazing ofHASTELLOY alloys are:1) Thorough cleaning of base-

metal surfaces.2) Proper filler metal selection for

the intended application.

3) Proper fit-up and freedom ofrestraint during brazing.

4) Proper protective atmosphereduring brazing.

5) Short heating and coolingcycles to minimize aging.

PreparationAll forms of surface contaminationsuch as dirt, paint, ink, chemicalresidues, oxides, and scale mustbe removed from the mating partsprior to brazing. Otherwise, themolten brazing material will not

"wet" and flow along the surface ofthe base material. Surfaces mustbe cleaned by solvent scrubbing ordegreasing and then bymechanical cleaning or pickling.Once cleaned, the parts should beassembled as soon as possiblewith the assembler using cleangloves to prevent subsequentcontamination.

Filler Metal SelectionSelection of filler metal dependsupon the end use of theHASTELLOY alloy being joined.For low-temperature serviceapplications,


17/40

17 Brazing

Proper Fit-UpProper fit-up of the parts, prior tobrazing, is just as important asprecleaning since most brazingalloys flow under the force ofcapillary action. Joint gapclearances on the order of 0.001to 0.005 inches (0.02 to 0.13mm) must be maintained at thebrazing temperature. If possible,

parts should be brazed in thesolution annealed condition (i.e.,not cold worked). Excessiveexternal stresses or strainsimposed on the part duringbrazing may cause crackingproblems, especially whenbrazing fluxes are involved.

Protective AtmospheresManual torch brazing with silver-base brazing alloys invariablyrequires the application of a flux(available from the brazing alloy

manufacturer). Flux protectedbrazing operations can also becarried out by using an inductioncoil heating source, or in afurnace with a reducingatmosphere.

Furnace brazing is the usualmethod of brazing HASTELLOYalloys, especially when high-temperature brazing filler metalsare employed. Nickel-basedbrazing alloys, for instance, arecommonly used in conjunction withvacuum furnaces, in high purityargon atmospheres or in hydrogen(reducing) atmospheres. The purity

of the brazing atmosphere is veryimportant to ensure successfulbrazing alloy flow characteristics. Ahigh "leak rate" through a vacuumfurnace, for instance, will easilycause a thin oxide film to form onthe HASTELLOY base materialthereby impeding the flow of fillermetal.

It should be recognized that mostHASTELLOY alloys are designedto form tough oxide films whichhelp them to resist harsh service

environments. These same oxidefilms will cause problems duringbrazing if atmospheres are notrigorously controlled.

Heating and Cooling CyclesThe heating and cooling timesassociated with the brazingoperation should be controlled tominimize exposure to intermediatetemperatures. The HASTELLOYcorrosion-resistant alloys tend toprecipitate secondary phaseswhen exposed in the temperaturerange of 1300 to 1850F (704 to

1010C). Such secondaryprecipitation will strongly influencecorrosion resistance. In addition tothe concern about secondaryprecipitation, HASTELLOY B-2and B-3 alloys should not beexposed in the temperature rangeof 1000 to 1500F (538 to 816C)due to the possibility of loss ofductility as a result of long rangeordering. Cooling rates, in vacuumfrom elevated temperatures, canbe increased by backfilling thefurnace with argon or helium.


18/40

18Lining

CORROSION-RESISTANT LININGFigure 7

Figure 8

Metallic Lining HASTELLOY C-22 alloy

Lower Colorado River Authority Power Project.

Heat exchanger inlet section thin-sheet lined with

HASTELLOY C-276 alloy.

The use of solid HASTELLOYcorrosion-resistant alloy isgenerally the preferred method ofconstruction. For manyapplications, however, it may bemore economical to use a steel (orlower alloy) substrate which is then

lined with a corrosion-resistantalloy. The point where lining asubstrate material becomeseconomical, as compared to solidconstruction, depends on anumber of factors which include:the corrosive environment

involved, the corrosion-resistantalloy to be used, design concerns,stresses, the complexity of thecomponent, and the particularlining method to be used.

Four possible methods ofconstruction are presented whichprovide alternatives to solid alloyconstruction. Those methods are:1) Thin-sheet metallic lining.2) Clad plate construction.3) CORFACINGTM weld overlay.4) Thermal spray processes.

Thin-Sheet Metallic LiningThin-sheet metallic lining (oftenreferred to as the "Wallpaper

Concept") is a method of applyingthin-gage, high-performance,corrosion-resistant alloy sheet to avariety of metal substrates. Thisprocess has found wideacceptance in the ducting ofelectric power flue gasdesulfurization equipment. Atypical installation is shown inFigure 7. Such a process is equallyapplicable to many other corrosiveservice applications. Figure 8demonstrates the capability of thistechnique for protection of

chemical processing industryequipment.


19/40

19 Lining

Figure 9A

Figure 9B

The fabrication techniques areconsidered straight forward andrequire no special tools,equipment, or highly trainedpersonnel. Figure 9A shows thegeneral configuration of thisfabrication technique for flue gasdesulfurization construction. As analternative (Figure 9B), battenstrips can be applied to cover the

joints. This method is generallyused in the chemical processindustry.

Key points to consider duringfabrication include: Lay out the installation pattern in

advance. Develop welding parameters

and train welders in advance. Preform sheet in shop whenever

possible. Prepare substrate surface as

necessary.

Structually attach sheets to thesubstrate.

Seal weld all-around. Inspect and test welds for leak

tight condition. Repair questionable areas as

necessary.

One of the important features ofthis fabrication technique is thelack of concern with substratedilution of the weld metal duringseal welding. As shown in Figure9A, all seal welding is performed in

an alloy to alloy configuration.Additionally, this technique reducesfabrication time due to thesimplicity of overlapping one sheetonto another. Midsheet attachmentcan be used to insure the sheet isheld flush with the substrate and tolessen concern about damage dueto vibration.

There are several areas whereshop formed parts can save timeand effort. Edge and cornermolding can be placed

SealFillet Weld

Intermittent

Structural

Fillet Weld

HASTELLOY

Sheet

Arc Spot or

Plug Weld

(midsheet

attachment)

0.062 in.

(Nominal)

C arbon Steel or

Lower A lloy Substrate

First Sheet

Intermittent Fillet Welds

6 in. C enter to Center Distance

Seal Weld

A ll-Around

Seal Weld

Sheet 1

Sheet 2

Sheet 3

Second Sheet

Sheet 2

Approximately 1 in. O verlap of

Second Sheet O ver First Sheet

Sheet 1

Third Sheet

Sheet 3

Sheet 1

Sheet 2

6" min. 6" min.

2t

2t2t

(1.6 mm)

(152 mm)

(152 mm)

(25.4 mm)

GENERAL WELDING AND LAYOUT CONFIGURATION


20/40

20Lining

Figure 10A Figure 10B

Figure 10C

Alloy Sheet

PerformedEdgeM olding

Substrate

Seal Weld

IntermittentFillet Welds

A lloy Sheet

A lloy Sheet

A lloySheet

PerformedC ornerM olding

Substrate

Seal

Weld

Intermittent

Fillet Welds

AlloySheet

AlloySheet

Seal WeldSeam

90 Break

M idsheet Attachment (I f Specified)

Substrate

Seal Weld

Intermittent Fillet Welds

A lloy Sheet

Seal Weld


21/40

21 Lining

Induced draft fan thin-sheet lined with HASTELLOY C-276 alloy.

Figure 11

Figure 10D

over the intersection of wall sheetsto form a sealed joint as shown inFigures 10A and 10B. Preformedsheets with one or two edges bent90 degrees can be fitted onto the

ceiling or floor as shown in Figure10C. Finally, preformed sheetswith prepunched holes (Figure10D) can be used to form anexpansion joint seal.

While this method of lining doesnot produce a metallurgical bondbetween the alloy lining and thesubstrate, the process doesproduce equipment with excellentmechanical properties. Figure 11shows a large fan which was builtfrom carbon steel and then lined

with HASTELLOY C-276 alloy.This fan rotates at high speed andhas not suffered any mechanicaldifficulties in service. Detailedinformation concerning thin-sheetmetallic lining can be found inHaynes publication H-2037.

Sheet 90 BreakBolt Holes Pre-Punched

No Welding RequiredD own Length of Joint

Expansion Joint

Assembly Vie w

Substrate

A lloy Sheet


22/40

22Lining

Complete the first layer of HASTELLOY alloy weld metal as shownabove.

Figure 12A

Grind back the HASTELLOY alloy adjacent to the weld to avoidmelting the alloy while welding the steel. Prepare the joint asshown above and complete the steel weld.

Figure 12B

Figure 12C

Figure 12D

Complete the second layer of HASTELLOY alloy weld metal asshown above.

Complete the third layer of HASTELLOY alloy weld metal asshown above. Use a fourth layer of alloy weld metal if necessary.

Clad Plate ConstructionTwo types of clad plate areavailable for the HASTELLOYalloys. Hot-roll bonded plate andexplosion bonded plate have bothbeen used to fabricate corrosion-resistant components. The natureof the equipment to be fabricated

will dictate the manufacturing routefor the plate which would beacceptable.

Hot-Roll Bonded PlateIn projects, such as flue gasdesulfurization ductwork, wherelarge plates are required with atotal thickness less than 0.375 inch(9.5 mm) and an alloy thickness ofapproximately 0.062 inch (1.6mm), hot-roll bonded plate canoffer an appropriate alternative tothe thin-sheet metallic lining. Sinceannealing is required to obtain thebest corrosion resistance in thealloy material, the backing steelsare usually limited to very lowcarbon grade materials. Thisallows for annealing and waterquenching of the hot-roll bondedplate without producing a brittlesteel backer. Mechanicalproperties of this product will reflectthe combined properties of thealloy and the low carbon steel.

Fabrication, of components fromthis product, is generallyaccomplished by welding with fillermetal which matches thecomposition of the alloy sheet.Overalloyed filler metal may beused if localized attack isexpected, such as in a flue gasdesulfurization environment.

Explosive Bonded PlateFor the construction of chemicalprocess equipment, explosivebonded plate is the predominant

source of the material. Thisprocess allows the use of thetraditional grades of high strengthsteels for vessel fabrication.

A lloy

1/16 in.3/8 in.

Steel WeldSteel

Second BeadFirst BeadLast Bead

Step 1

A lloy

Steel WeldSteel

Step 2

A lloy

Steel WeldSteel

Step 3

A lloy

Steel WeldSteel

Step 4


23/40

23 Lining

625 AlloyTwo Layers Deposit

75 mils per year

Figure 13

HASTELLOY C-22 AlloyOne Layer Deposit

4 mils per year

0.045 in. Crevice Depth Attack No Crevice Attack

10% Ferric Chloride1040F (400C) - 120 Hours

Conventional techniques can beused to fabricate equipment fromthe clad plate. The tube holes oftube-sheets usually have thegrooves machined so that at leastone is located in the cladding andthe balance are in the basematerials.

Care must be taken during weld

fabrication to avoid dilution of thecladding alloy by the basematerial. Figures 12A thru 12Dillustrate the suggested method for

joining clad plates.

After preparation of the weldangles, the alloy is ground backslightly on either side of the jointand below the base metal surface(Figure 12A). The root weld ismade and the base metal jointcompleted from the back side(Figure 12A). The first layer of alloy

filler is deposited on the joint usinga practice that will minimizedilution. This layer may be groundto a uniform thickness to helpcontrol dilution of the next layer(Figure 12B). Two additional layersof alloy are then deposited tocomplete the joint (Figures 12C &12D). During all welding operationsthe interpass temperature shouldbe maintained below 200F(93C).

During explosion-bonding, the

explosive force produces a zoneadjacent to the bond line thatcontains considerable colddeformation. Presence of this coldwork can accelerate aging of someof the alloys during certainsubsequent stress-relieving heattreatments for the carbon steel.

HASTELLOY B-2 and B-3 alloysshould not be explosive bonded.Results have been inconsistentwith a high risk of crackingduring the bonding process.

CORFACINGTM Weld OverlayWeld overlay cladding, using high-performance, corrosion-resistantalloys is an accepted alternative tosolid alloy construction for manyapplications. Weld overlaycladding of tube sheets and oflarge diameter shafts are commonapplications. In both cases, theheavy section carbon steelsubstrate components aresurfaced with a relatively thin layerof corrosion-resistant alloy. A

second area where weld overlaycladding is used is in the localrepair and refurbishment ofchemical process components. Inthis case, the substrate is probablynot carbon steel.

It is important to recognize,however, that the corrosionresistance of a weld overlaydeposit is not equivalent to thewrought base material, of similarcomposition. Several factorsstrongly influence the corrosion-

resistance of a weld overlaydeposit. By far the most importantcontrollable factor is substrate(base metal) dilution. A secondfactor, which affects all weld metaldeposits, is alloying elementsegregation.

Base metal dilution is the meltingand mixing of the substrate with

the corrosion-resistant weldoverlay filler material. As substratebase material is mixed with thealloy filler metal, the iron content ofweld overlay deposit increases.This increase in iron contentlowers (dilutes) the total content ofthe critical elements (chromium,molybdenum, tungsten) of a high-performance alloy system. Thisincrease in iron, coupled with thelowering of other alloyingelements, leads to lower weldoverlay corrosion resistance.

Welding techniques must,therefore, be employed whichminimize base metal dilution.

The most common method toovercome base metal dilution is touse multiple weld layers. As ageneral rule, a three layer deposit,even with relatively high basemetal dilution, will approach thefiller wire composition. With carefulcontrol of welding parameters, atwo layer deposit may approachfiller wire composition.


24/40

24Lining

Approx. Approx.Wire Welding TravelDiameter Shielding Flow Rate Current Approx. Speed

in. (mm) Gas ft.3/hr. Amps Volts in./min.

Globular Transfer

0.045 (1.1) 100% Argon 50 170-180 26-28 6.8

*Technique: Mechanical weave 5/8 in. wide, minimum dwell, 100 cycles/minutes, 200F (max.) interpass temperature.

GAS METAL ARC WELD OVERLAY PROCESS (FLAT POSITION)*

Table 8

Dilution can be controlled by usingwelding processes that have lowpenetration patterns. For example,gas metal arc welding in theglobular and short-arc transfermodes have lower penetrationpatterns when compared to thespray transfer mode. In addition,oscillation of the welding torch willlower penetration (dilution). Finally,

bead placement affects totalsubstrate dilution. In some cases,gas metal arc welding (short-arcmode) beads are overlapped insuch a way that part of the weldpenetration is in the previous alloyweld bead, rather than in thesubstrate base material.

Welding parameters which havebeen shown to give low basemetal dilution are provided in Table8. In this case, a low penetration

welding process is coupled withwelding torch oscillation. Such aprocess would be expected toproduce dilution under ten percentin a two layer deposit.

Figure 13 illustrates gas metal arcwelding in the short-arc modewhere bead overlap was used tocontrol dilution. Because

HASTELLOY C-22 alloy hasinherently higher crevice corrosionresistance, when compared to 625alloy, a one layer C-22 welddeposit has significantly lowercorrosion attack when comparedto a two layer 625 deposit.

Additional information concerningweld overlaying with HASTELLOYC-22 filler material can be found inTechnical Brochure H-2054,CORFACING Weld Overlays withHASTELLOY C-22 alloy.

Thermal Spray ProcessesCorrosion protection by nonfusionwelding processes (i.e., thermalspray techniques) has been donesuccessfully. Use of theseprocesses has received increasedattention by the pulp and paperand power utility industries as a

method of refurbishing digesterinteriors and boiler tubes.However, it should be recognizedthat most thermal spray methodsdo not achieve a 100 percentdense deposit and are usually onlymechanically bonded to thesubstrate.

Thin coatings, offering someprotection, can be made byplasma spray (powders), wireflame spray and by electric-arcspraying (wire), however it is not arecommended practice for longterm aqueous corrosion service.


25/40

25 Hot Working

HOT WORKINGHASTELLOY corrosion-resistantalloys are readily hot worked into avariety of shapes and productforms. However, these alloys aresomewhat more sensitive to strainand strain rates than are typical

austenitic stainless steels. The hotworking temperature ranges forthese alloys tend to be narrow.Care must be exercised during hotworking to achieve satisfactoryresults.

The characteristics ofHASTELLOY alloys that must beconsidered during hot workinginclude relatively low meltingtemperatures, high hot strength,high strain rate sensitivity, lowthermal conductivity, and relatively

high strain hardening coefficients.Furthermore, the strength of thesealloys increases rapidly as thetemperature decreases in the hotworking range.

Because of these factors, relativelymoderate reductions per pass andfrequent reheating operations givethe best results. Also, relativelyslow hot deformation processing

tends to achieve better results,because lower forces are requiredand the heat buildup due toworking is kept within reasonablelimits.

ForgingThe following are generalguidelines to follow in forgingHASTELLOY corrosion-resistantalloys:

Soak billets or ingots at least 1/2hour at forging temperature foreach inch of thickness. The useof a calibrated optical pyrometeris essential.

The stock should be turnedfrequently to present the cooler

side to the furnace atmosphere.Direct flame impingement on thealloy must be avoided.

Forging should beginimmediately after withdrawalfrom the furnace. A short timelapse may allow surfacetemperature to drop as much as100 to 200F (38 to 93C). Donot raise the forging temperature

to compensate for heat loss, asthis may cause incipient melting.

Moderately heavy reductions (25to 40 percent) are beneficial tomaintain as much internal heat

as possible, thus minimizinggrain coarsening and thenumber of reheatings.Reductions greater than 40percent per pass should beavoided.

Do not make radical changes inthe cross sectional shape, suchas going from a square directlyto a round, during initial formingstages. Instead go from squareto round cornered square tooctagon to round.

Condition (remove) any cracksor tears developed duringforging. Very often this can bedone at intermediate stagesbetween forging sessions.

The temperature rangesrecommended for forgingHASTELLOY alloys are shownin Table 9.


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26Hot Working

FORGING TEMPERATURES

Table 9

Forging Temperature

Start* Finish**

Alloy 0F (0C) 0F (0C)

HASTELLOYB-2 alloy 2250 (1232) 1800 (982)HASTELLOY B-3 alloy 2250 (1232) 1800 (982)

HASTELLOY C-4 alloy 2150 (1177) 1750 (954)HASTELLOY C-22 alloy 2250 (1232) 1750 (954)HASTELLOY C-276 alloy 2250 (1232) 1750 (954)

HASTELLOY C-2000 alloy 2250 (1232) 1750 (954)HASTELLOY G-30 alloy 2100 (1149) 1700 (927)

HASTELLOY N alloy 2200 (1204) 1600 (871)*Maximum**Depends on nature and degree of working.

Hot RollingHot rolling of HASTELLOY alloyscan be performed to produce any

conventional rolled forms. Theconsiderations listed above forforging generally apply to hotrolling also. Moderate reductionsper pass (15 to 20 percentreduction in area) and rollingspeeds of 200 to 300 surface feetper minute tend to give goodresults without overloading the mill.

Frequent reheatings are usuallyrequired to keep the temperatureof the work piece in the hotworking range. Because of the low

thermal conductivity and thesomewhat sluggish minor phasedissolution kinetics associated withthese alloys, it is good practice tosoak the work piece thoroughly atthe hot working temperaturebefore rolling.

Hot UpsettingHASTELLOY alloys can be hotupset when the length of the part

to be upset is no greater thanabout three times the diameter.Care should be taken to ensurethat the temperature of the pieceto be upset is in the upper end ofthe forging temperature range.

Impact ExtrusionParts such as engine valves,pump rotors, jet engine bolting,and gears can be produced fromHASTELLOY alloys by impactextrusion. Impact extrusion iscarried out at the solution heat-

treating temperature so that thealloy is forged in its most plasticstate. Accurate temperaturecontrol and maintenance of auniform temperature throughoutthe work piece are essential.Restrikes should be avoided.

Hot FormingThe forming of plate intocomponents such as dished heads

is normally done by cold pressingor spinning with intermediateanneals. However sometimes the

size and thickness of materialrequires that hot forming beutilized. When this is required, thefurnace temperature is usually setat an intermediate temperaturebetween that suggested forannealing (Heat Treatmentsection, Table 10) and lowerforging temperature (Table 9).Temperature during hot workshould not be less than the finishforging temperature. Reheat asnecessary to maintain the propertemperature. Dies should be

warmed so that excessive chillingof the surface does not occur.

AnnealingFollowing any hot workingoperations, HASTELLOY alloysshould be reannealed for optimumcorrosion resistance. Annealingtechniques are detailed in the HeatTreatment section (Table 10) ofthis brochure.


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27 Cold Working

COLD WORKINGFigure 14Cold working is the preferable

method of forming theHASTELLOY corrosion-resistantalloys. Since they are generallystiffer than the austenitic stainlesssteels, more energy is required

during cold forming. In addition,these alloys tend to work hardenmore readily than do the austeniticstainless steels. Depending on theseverity of deformation, they mayrequire a number of intermediateforming stages to produce the finalpart. Figure 14 shows the effect ofcold work on the hardness of theHASTELLOY alloys. A curve fortype 304 stainless steel has beenincluded for comparison.

Generally, mill annealed sheet has

sufficient ductility for mild formingwithout the need for subsequentheat treatment. Generally, thepresence of cold work does noteffect either the uniform or pittingcorrosion resistance of theHASTELLOY corrosion-resistantalloys. The presence of heavy colddeformation can increase thestress corrosion crackingsusceptibility in certainenvironments. Annealingcomponents with deformationgreater than about 7 to 10 percent

outer fiber elongation will reducethat susceptibility.

For more severe cold deformation,where cracking is possible due toreduction in ductility, a series ofsuccessive forming operations arerecommended, each followed byan intermediate anneal. Undermost conditions, intermediateannealing should be performed atthe recommended solutionannealing temperature. It is highlydesirable to remove scale from the

part prior to the next formingoperation either by pickling ormechanical means. A final solutionanneal is recommended after suchsuccessive intermediate cold work/annealing operations.

Care should be taken to avoid a"critical cold reduction" of about 2to 10 percent, if solution annealingis specified. Under theseconditions, abnormal grain growthis possible which can lead to a

surface condition often referred toas "orange peel" or "alligator hidesurface."

Cold formed components withresidual tensile stresses, inconjunction with the possibility ofintermediate temperatureembrittlement, caused byexposure at intermediatetemperatures for critical periods oftime, have been observed to

produce intergranular crackingduring the heat treatment ofHASTELLOY B-2 alloy. It has beenobserved that shot peening theknuckle radius and straight flangeregions of a cold-formed head,prior to heat treatment, can helpreduce intermediate temperatureintergranular cracking of B-2 alloyby lowering the tensile residualstress patterns at the surface ofthe cold formed component.

In the case of cold formed heads

of HASTELLOY B-2 or B-3alloys, a solution annealedshould be done whendeformation is greater than 7%outer fiber elongation of coldwork. Without the anneal thesealloys are very susceptable tocracking at welds and heataffected zones duringsubsequent fabrication. Thecracking may not becomeobvious until the unit has been

put into service.HASTELLOY B-3 alloy is moreresistant to heat treat crackingthan B-2 alloy. In any event,annealing of cold formedcomponents (>7% outer fiberelongation) is required and careshould be taken to use wellcontrolled furnaces (fast heat-uprate, good temperature control,and rapid cool down rate).

Lubrication is a significantconsideration for successfully coldworking these alloys. Althoughlubrication is seldom required for asimple "U" bend on a brake press,heavy duty lubricants are requiredfor cold drawing. Mild formingoperations can be successfullycompleted by using a lard oil orcastor oil, which are easilyremoved. More severe formingoperations require metallic soaps,or chlorinated or sulfochlorinatedoils. NOTE: When the sulfo-

chlorinated oils are used, the workpiece must be carefully cleaned ina degreaser or alkaline cleaner.

Lubricants that contain white lead,zinc compounds, or molybdenumdisulfide are not recommendedbecause they are difficult toremove prior to the final anneal.Also, lead, zinc, and sulfur tend toembrittle these alloys. Care shouldbe taken to remove die material,lubricants, or other foreign

450

400

350

300

250

200

150

100

0 10 20 30 40 50 60

C -276

C -22

C -4

G -30

304SS

B-2/B-3

Percent Cold Work

VickersHardnessNumber

EFFECT OF COLD WORK ON HARDNESS


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28Cold Working

materials from the part beforeannealing as many of theseproducts can affect the mechanicaland corrosion properties of thealloys.

Tube FormingHASTELLOY corrosion-resistantalloys can readily be formed coldin standard pipe and tube bending

equipment. The minimumrecommended bending radiusfrom the radius point to thecenterline of the tube is three timesthe tube diameter for most bendingoperations. When measured fromcenterline to centerline of the"hairpin" straight legs, it is six timesthe tube diameter (see Figure 15).Under special circumstances (tubediameter and wall thickness), theminimum bending radius can bereduced to twice the tube diameter.

Figure 15Minimum Bending Radius

As the ratio of tube diameter towall thickness increases, the needfor internal and external supportbecomes increasingly important inorder to prevent distortion. If toosmall a bending radius is used,wrinkles, poor ovality, and bucklingcan occur in addition to thinning.When forming tubing for heatexchangers, a minimum of threeinches should be added to the total

developed length of each tube

before bending. This additionallength is necessary to allow formismatch of the ends after formingand for trimming the ends of thetubes for stuffing the tube bundle.Heating during forming is notrecommended, nor is stressrelieving of the tubes after coldforming because of the possibleformation of precipitates that

decrease the corrosion resistance.If the corrosion application issevere or if stress relieving isrequired, annealing the entire tubeshould be done as described in theHeat Treatment section of thisbrochure.

SpinningSpinning is a deformation processof forming sheet metal or tubinginto seamless hollow cylinders,cone hemispheres, or othersymmetrical circular shapes by a

combination of rotation and force.There are two basic forms knownas manual spinning and power orshear spinning. In the formermethod no appreciable thinning ofmetal occurs, whereas in the latter,metal is thinned as a result ofshear forces.

Nearly all HASTELLOY corrosion-resistant alloys can be spinformed, generally at roomtemperature. The control of qualityincluding freedom from wrinkles

and scratches as well asdimensional accuracy is largelydependent on operator skill. Theprimary parameters that should beconsidered when spinning thesealloys are: Speed Feed Rate Lubrication Material Strain Hardening Characteristics Tool Material, Design and

Surface Finish Power of the Machine

The minimum speeds normallyemployed are about 200 surfacefeet per minute but generally lowspeeds are seldom used exceptfor spinning small diameter workpieces. Speeds of 400 to 1500surface feet per minute are mostwidely used. The feed ratesnormally used are 0.010 to 0.080inches per revolution. Feed rate is

important since it controls the workpiece finish. To find the optimumcombination of speed, feed, andpressure, a few pieces should bespun experimentally when a "new

job" is set up. During continuousoperation, the temperature of themandrel and spinning tool changesmay necessitate the adjustment ofpressure, speed, and feed toobtain uniform results.

Lubrication should be used in allspinning operations. The usual

practice is to apply lubricant to theblank prior to loading in themachine. It may be necessary toadd lubricants during operation.During spinning, the work pieceand tools should be flooded with acoolant such as an emulsion ofsoluble oil in water. Sulfurized orchlorinated lubricants should notbe used since the operation ofspinning may burnish the lubricantinto the surface.

In cone spinning, metal

deformation is such that forming isin accordance with the sine law.This law states that the wallthickness of the starting blank andthat of the finished work piece arerelated as:

t2

= t1Sin

where t1

= thickness ofstarting blank

where t2

= thickness ofspun piece

where a = one half theapex angle ofcone

6Dr=3DD

r=M inimum Bending Radius

D= Tube Diameter


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29 Cold Working

When spinning cones with smallangles (less than 35 degreesincluding angle), the best practiceis to use more than one spinningpass with a different cone angle foreach pass. HASTELLOY alloyscan be reduced 30 to 50 percentbetween process annealsdepending on the material and itsstrain hardening characteristics.

The tool material and work piecedesign and surface finish are veryimportant in achieving a trouble-free operation. Mandrels used inspinning must be hard, wearresistant, and resistant to fatigueresulting from normal eccentricloading. Finish of mandrels shouldbe no rougher than 50microinches, preferably 15 to 32microinches. The variousdiameters should be trueconcentric with each other.

Power spinning is a severe, coldworking operation which markedlyincreases the ultimate and yieldstrengths of the alloy. In manyapplications, this increase is highlydesirable, but for someapplications the spun piece shouldsubsequently be annealeddepending on the alloy and theservice environment.

Drop HammeringHASTELLOY corrosion-resistantalloys can be formed by using thesame techniques that are used instainless steel drop-hammeroperations. Annealing is essential ifthe depth of the draw is severe.Particular care should be taken toremove all foreign material fromthe part before annealing.

PunchingPunching is usually performedcold. Perforation should be limitedto a minimum diameter of twice thegage thickness. The center-to-center dimension should beapproximately three to four timesthe hole diameters. The punch todie clearances per side are:

ShearingBecause of the toughness of thesealloys, compared to carbon steelsand austenitic stainless steels,shearing equipment with greaterpower is required. For example, ascissor type shear capable ofshearing 3/8 inch (9.5 mm) thickmild carbon steel could be used toshear HASTELLOY alloys up to 1/

4 (6.4 mm) inch thick. Generally,HASTELLOY alloys 3/8 inch (9.5mm) or less in thickness aresheared and thicknesses above 3/8 inch (6.4 mm) are abrasive sawcut or plasma arc cut.

Cold rolled and annealed sheet

Up to 1/8 in. (3.2 mm) incl. 3-5% of sheet thicknessHot rolled and annealed sheet

Over 1/8 in. (3.2 mm) 5-10% of sheet thickness


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30Heat Treatment

Temperature* Type of

Alloy 0F (0C) Quench

HASTELLOY B-2 alloy 1950 (1066) WQ or RACHASTELLOY B-3 alloy 1950 (1066) WQ or RAC

HASTELLOY C-4 alloy 1950 (1066) WQ or RAC

HASTELLOY C-22 alloy 2050 (1121) WQ or RACHASTELLOY C-2000 alloy 2075 (1135) WQ or RACHASTELLOY C-276 alloy 2050 (1121) WQ or RACHASTELLOY G-30 alloy 2150 (1177) WQ or RAC

HASTELLOY N alloy 2150 (1177) WQ or RACWQ=water quench.RAC=rapid air cool.* 25 deg. F.

HEAT TREATMENT

HEAT-TREATING TEMPERATURES

Table 10

Wrought products of HASTELLOYalloys are supplied in the mill-annealed condition unlessotherwise specified. This annealingprocedure has been designed toplace the material in the optimum

condition with respect tomechanical properties andcorrosion resistance. Following allhot-forming operations, a reannealof the material should always bedone to restore those properties.

Annealing is often performed aftercold working operations to restoreductility and lower the yield andultimate tensile properties.Generally, annealing is notrequired if the cold work is belowseven percent outer fiber

elongation.

In general, the only heat treatmentthat is acceptable for these alloysis a full solution anneal. Stressrelief temperatures commonlyused for steels, stainless steels,and some other nickel-based

alloys are not effective for thesealloys. If the heat treatment is doneat an intermediate temperature,high enough to actually relieve thestresses, it may also promotesome precipitation that could bedetrimental to corrosion resistance.

Annealing may be performed toreduce residual stresses whichcan play a role in stress corrosioncracking resistance. It is generallyheld that stresses above 7 to 10percent outer fiber elongation can

cause increased stress corrosioncracking in some environments.

Because of the very low carboncontents or stabilizing elements,welded wrought HASTELLOYcorrosion-resistant alloys do notrequire heat treatment afterwelding. Annealing can be used to

increase the corrosion resistanceof the weld fusion zone.

Before heat treatment, makeabsolutely sure that grease,graphite, and other foreignmaterials are removed from allsurfaces. Carburization of thesematerials at the heat-treatingtemperatures can reduce corrosionresistance. Proper control oftemperature and time cycle arealso important. Table 10 lists theproper heat-treating temperatures

and type of quench.


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31 Heat Treatment

Holding TimeAn inflexible set of rules governingsoaking-annealing time is notfeasible because of the manyvariations in types of furnaces,furnace operation, facilities forloading and unloading the furnace,etc. Temperature should bemeasured with a thermocoupleattached to the piece being

annealed. The actual holding timeshould be measured starting whenthe "entire section" is at thespecified annealing temperature. Itis important to remember that thecenter of a section does not reachthe solutioning temperature assoon as the surface.

Normally, hold time is specified inthe range of 10 to 30 minutesdepending on section thickness.Thin-sheet components are held atthe shorter time, while heavier

sections are held at the longertimes. The effect of cold workingthat result from stamping, deepdrawing, bending, etc. can beeliminated by holding a minimumof 5 to 10 minutes, depending ongage size, at the solutionannealing temperature.

QuenchingRapid cooling is essential aftersolution heat treatment to preventthe precipitation of secondaryphases and the resultant lowering

of the corrosion resistance of thesealloys. Water quenching isrecommended on material thickerthan 3/8 inch (9.5 mm). Rapid aircooling can be used on sections

thinner than 3/8 inch (9.5 mm),however, water quenching ispreferred. The time from thefurnace to the quench tank or tothe start of rapid air cooling, mustbe as short as possible (less thanthree minutes).

HASTELLOY B-2 alloyThe method of annealing

HASTELLOY B-2 alloy isdemanding and the following itemsshould be considered verycarefully. Extended exposure in anintermediate temperature range of1100 to 1500F (593 to 816C),especially for cold work conditionmaterial, can cause intergranularcracking.

The following steps are designedto minimize intermediatetemperature cracking ofHASTELLOY B-2 alloy.

Furnace must be at theannealing temperature. Thethermal capacity of the furnaceshould be large to insure a quickrecovery of furnace temperature.

It has been observed that shotpeening the knuckle radius andstraight flange regions of a cold-formed head, prior to heattreatment, can help reduceintermediate temperatureintergranular cracking, ofHASTELLOY B-2 alloy bylowering the tensile residual

stress patterns at the surface ofthe cold formed component.

The improved thermal stability ofHASTELLOY B-3 alloy

minimized the problemsassociated with fabrication ofB-2 alloy components. This isdue to the reduced tendency toprecipitate deleteriousintermetallic phases in B-3 alloy,thereby, affording it greaterductility than B-2 alloy duringand following various thermalcycling conditions. Nevertheless

for heavy section weldments orfor those weldmentscharacterized by high residualwelding stresses, fabricatorsmay wish to follow the heat treatrequirements recommended forB-2 alloy.

Shot PeeningCold formed components withresidual tensile stresses, exposedat intermediate temperatures forcritical periods of time, have beenobserved to produce intergranular

cracking during the heat treatmentof HASTELLOY B-2 alloy. It hasbeen observed that shot peeningthe knuckle radius and straightflange regions of a cold-formedhead, prior to heat treatment, canhelp reduce intermediatetemperature, intergranular crackingof B-2 alloy by lowering the tensileresidual stress patterns at thesurface of the cold formedcomponent.

HASTELLOY B-3 alloy is less

sensitive to the above issues,however, the same methods forB-2 alloy should be used toeliminate the risk of cracking ofB-3 alloy.


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32Descaling and Pickling

Sulfuric- Nitric-Hydrochloric Hydrofluoric

VIRGO Descaling Water Acid Bath Acid Bath WaterSalt Bath Rinse 1650F 125-1600F Rinse

Time Time, (740C) (52-710C) Time,Alloy Temp. min. min. Time, min. Time, min. min.

B-2, B-3 8000F 1-3 1-2 25-45 3(4270C) (Steam spray)

C-276, C-4, C-2000, 9700F 1-3 1-2 3 25 3C-22, G-30, N (5210C) (Steam spray)

DESCALING AND PICKLING

VIRGO DESCALING SALT BATH

Table 11

Sulfuric- Permanganate- Nitric- Nitric-Hydrochloric Sodium Hydrochloric Hydrofluoric

Sodium Acid Bath Hydroxide Bath Acid Bath Acid BathHydride Bath* 1650F 135-1550F 1650F 125-1600F

Time (740C) (57-680C) (740C) (52-710C) WaterAlloy Temp. min. Time, min.* Time, min.* Time, min.* Time, min.* Rinse

B-2, B-3 750-8000F 15-20 20-30 20-30 20-30 1 max. Steam

(399-4270C) sprayC-276, C-4, 750-8000F 15 15 15 DipC-2000, C-22, (399-4270C)

G-30,N*Followed by a water rinse.

SODIUM HYDRIDE (REDUCING SALT BATH) PROCESS

Table 12

Because of their inherent corrosionresistance, HASTELLOY alloysare relatively inert to cold acidpickling solutions. After heattreatment, the oxide film is moreadherent than that of stainless

steels. Molten caustic bathsfollowed by acid pickling are themost effective descaling methods.Baths of VIRGO descaling salt,sodium hydride (DuPont), or DGSoxidizing salt have been usedeffectively.

Tables 11, 12 and 13 providepickling media, temperatures andtimes for each method. Thecompositions of the picklingsolutions are listed in Table 14.Sand, shot, or vapor blasting are

acceptable for removing scaleunder certain conditions. Theblasting material should be suchthat it provides for a rapid cuttingaction rather than smearing thesurface. Sand should not bereused especially if contaminated

with iron. After blasting, it isdesirable to give the part an acidpickle to remove any imbeddediron or other impurities. Extremecare should be taken when sandblasting thin-gage parts because of

the danger of distortion and ofembedding sand or scale in themetal surface. Sand blasting alsotends to work harden the metal'ssurface.


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33 Descaling and Pickling

Nitric-HydrofluoricDGS Oxidizing Salt Bath Acid Bath

Time Water 130-1500F (54-660C)Alloy Temp. min. Rinse Time, min. Water Rinse

B-2, B-3 850-9500

hastelloy fabrication

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