welding dissimilar metals

Objectives

After studying this chapter, you will be able to:• Give examples of possible material combinations

using the GTAW process.• Explain applications of the weld to join various

materials and uses of butt joints, clad materialjoints, and overlay type joints on dissimilar metals.

• Describe the process used for the selection offiller materials for the weld joint.

• Identify and select the proper method of jointpreparation.

• Summarize correct methods of joint cleaning.• Determine characteristics of the metals to be

joined to evaluate which welding practices to use.Welding dissimilar materials is often required to

fabricate weldments of different materials. It is alsorequired to overlay the base material to prevent corro-sion, oxidation from heat, and wear. Finally, weldingdissimilar materials may be required for maintenance orrepair of worn parts.

Material Combinations/Applications

Many material combinations are possible using theGTAW process to make the weld. These may include:

• Steel alloys to steel.• Steel to cast iron.• Steel to stainless steel.• Steel to nickel.• Stainless steel to nickel.• Stainless steel to inconel.• Copper to steel.• Copper nickel to steel.• Copper aluminum to steel.• Silicon bronze to steel.• Surfacing alloys to iron base metals.• Alloy metal to a nonalloy metal.

The application of the weld to join the variousmaterials include the following:

Butted materials, as shown in Figure 19-1.Depending on the alloy mix in the weld desired, one ofthe parent materials is used for filler material.

Figure 19-2 shows a dissimilar metal being used asa filler material. The filler material is compatible withboth parent materials.

Buttered materials, as shown in Figure 19-3, areused to join materials that are very different. However,each material must be “buttered” with a material that iscompatible with the filler material used to make thefinal joint.

Procedure for ManualWelding Dissimilar Metals1919CHAPTER

Stainless steelfiller material

SteelStainless steel

Figure 19-1. Stainless steel filler material is used in manysteel-to-stainless steel combinations where ductility is of primeimportance.

Nickel fillermaterial

SteelCast iron

Figure 19-2. Nickel filler material is compatible with both castiron and steel.

203

Cladded material, as shown in Figure 19-4, isused extensively in the manufacture of processingequipment. The “clad” is bonded to the base materialat the rolling mill. The thickness of the “clad” willvary depending on the final use. The welding materialsused must match the heavier base material and thecladding.

Overlaid materials, as shown in Figure 19-5, aresimilar to a clad or buttered joint; however, overlays aregenerally thicker. As the overlay thickens, the amount ofdilution decreases until the deposit contains the fillermaterial chemistry. Figure 19-6 shows a GTAW borecladding operation. Figure 19-7 shows a cross section ofa bore cladded weld.

Butt Joints of Dissimilar MetalsButt joints with square edges, as shown in Figure 19-8,

are used only where the material thickness can be weldedin a single pass. This type of joint has considerable dilutionbetween the parent materials and the filler materials.

204 Gas Tungsten Arc Welding Handbook

Butteredmaterial

Filler material iscompatible with

buttering material

Alloy copper Steel

Figure 19-3. The “buttering” material is applied to each materialbefore the joint filler material is used.

CladdingBasematerial

Figure 19-4. Welds into the clad require matching fillermaterials. Welds into the heavier base material require fillermaterials for strength, ductility, and other mechanicalproperties.

Layer 4Layer 3Layer 2Layer 1

As the number of layers increases,the amount of dilution decreases.

Base material

Figure 19-5. The number of weld layers required to achieve the desired chemistry is determined by testing the final joint designpreparation by chemical analysis.

Figure 19-6. Several layers of cladding have been applied tothe bore of the tube. The special GTAW torch is oscillatedduring the operation to widen the weld bead.

Figure 19-7. A cross section of the part is used to measure theheight of the cladding and the penetration pattern. Note thedarkened heat-affected zone under the cladding.

CladdingHeat-affected

zone

This sample chapter is for review purposes only. Copyright © The Goodheart-Willcox Co., Inc. All rights reserved.

Butt joints with V-grooves welded from one side, asshown in Figure 19-9, are used to weld thicker materialwith multiple passes. Dilution is high at the edges of thejoint and diminishes near the center of the joint.

Butt joints with double V-grooves welded from bothsides, Figure 19-10, are used to weld thicker materialwith multiple passes on each side. Distortion and dilutionof the parent metal is minimized as less metal is requiredto fill the joint.

Butt joints with single or double buttered edges areshown in Figure 19-11. The buttered material is appliedwith sufficient height to achieve weld metal chemistry tomatch the filler material composition. Prior to weldingthe joint, the preparation desired for the final weld isprepared from the “buttered” material.

Clad Material JointsClad material often requires two joint designs. One

design is for the base metal and one design is for thecladding. The base material joint is made to standardpractices. The cladding joint must be designed to allowcladding integrity.

Figure 19-12 shows joint designs for preparingcladded materials and various weld applications.

Overlay Type JointsOverlay type joints require a full weld metal

chemistry at the edge of the weld. To achieve thiscondition, the number of layers of weld metal must becomputed into the joint design, as shown in Figure 19-13.Figure 19-14 illustrates a grooved overlay improperlyprepared, which may result in improper chemistry in thefinal weld.

Filler Materials

The choice of filler materials for the weld jointrequires analyzing the composition of the base materials,dilution percentages, and the final use of the joint. Inmany cases, a sufficient number of welds have been

Chapter 19 Procedure for Manual Welding Dissimilar Metals 205

Figure 19-8. Square-groove weld joint designs require a fillermaterial compatible with each of the base materials due to theconsiderable amount of dilution.

Figure 19-9. Stringer type beads reduce penetration and dilu-tion when welding V-groove welds. Wash beads should beavoided, if possible, to reduce heat input and the amount ofdilution from the base materials.

Figure 19-10. Double V-groove welds have much less dilutionof the base materials since less welding is involved. Usestringer beads to further reduce dilution.

Butteringmaterial

Finalpreparation

Originalpreparation

Figure 19-11. Buttering or overlaid material must always be ofsufficient height to obtain the correct material chemistry.

Cladding

Cladding weld

Base materialweld

Corner Joint T-Joint

Claddingweld

Base material

weld

Cladding weld

Base material weld

Butt Joint

Lap Joint

Cladding weld

Base material weld

Figure 19-12. Common joint preparations used with claddedbase materials.

made to establish which filler materials can be usedsuccessfully. See Figures 19–15 through 19–20. Theyinclude stainless steel filler metals for welding dissimilarsteels, hardfacing and surfacing, filler metals for weldingclad layers, alloys for joining clad steels, and filler wiresfor surfacing applications. Preheat temperatures for hard-facing are shown in Figure 19-21.

Joint Preparation

Selecting the proper method for making the jointpreparation requires consideration of various methodssuch as:

• Machining the joint details has the advantagethat closer tolerances can be held and the part isready for welding after the machining operation.Large weldments or weldments of special designare often prepared by other means as machiningcost may be prohibitive.

• Shearing of sheet and plate is often done as aprimary operation in preparing the joint prepara-tion. In the thinner materials, the sheared edgemay be the actual joint. The sheared edge alwayscontains a rough surface with possible entrap-ment of dirt or other foreign material. Furtherprocessing such as filing or grinding may berequired as shown in Figure 19-22.

Always shear clad materials with the clad surfaceupward. This protects the clad from scratches and nicksduring the operation. The edge of the clad will have a

radius formed on the corner, as shown in Figure 19-23.Further processing is then required to eliminate theradius and to match the cladded areas, as shown inFigure 19-24.

• Flame cutting of steel and steel alloys requirescareful consideration of the carbon and alloycontent. Higher alloy steels may harden duringthe operation due to the fast cooling of the metal.Improperly adjusted torches may introducecarbon onto the surface or oxidize the cut edge.

Steels that have stainless steel or nickel claddingmay be flame cut providing the clad is not more than20% of the total thickness. In these cases, the heaviersteel is placed on the top, as shown in Figure 19-25. Themolten steel then penetrates the alloy, making the cutpossible. Care must be taken to ensure proper travelspeeds. If the cut is lost during the operation, it is almostimpossible to restart. Since the cladding is on the bottom,the cladding requires very good protection from supportsto prevent scratches, nicks, and other marks.

Steels with copper cladding are very difficult to cutwith flame cutting. Copper conducts the heat away fromthe joint very rapidly. Therefore, remove the coppercladding from the steel where the cut is to be made. Thecopper clad may be removed by grinding or by a chisel,as shown in Figure 19-26.

• Plasma arc cutting may be used to cut all typesof materials, including the clads. Figure 19-27illustrates the plasma arc cut may be made fromeither side of the plate. This is an advantage inprotecting the clad. The clad may face upward,thus protecting the clad from scratches, nicks, andother marks.

• Air carbon arc gouging is used for the preparationof U-type joints. This type of preparation offers fastpreparation time with minimum cost. Repairs, spotcladding preparation, and irregularly shaped welds


Overallbuild-up

dimension

Originalcut

Desired jointBuild-up

dimensionScribeline

Figure 19-13. Reference lines or points are used to assureproper overlay build-up dimensions.

Improper build-up dimensioncauses improper chemistry

at the desired joint

Desired cutFinal cut

Original cut

Figure 19-14. Insufficient build-up of the overlay may result inincorrect weld metal chemistry.


201,

202

, 301

,E

308

E30

8E

308

E30

8 E

308

E30

8E

308

E30

8E

308

E30

9E

309

E30

9E

310

E30

9E

309

302,

302

B, 3

03a ,

304,

305

, 308

304L

E30

8LE

308

E30

8E

308

E30

8E

308

E30

8E

308

E30

9E

309

E30

9E

310

E30

9E

309

309,

309

SE

309

E30

9E

309

E30

9E

309

E30

9E

309

E30

9E

309

E30

9E

310

E30

9E

309

310,

310

S, 3

14a

E31

0E

316

E31

6E

317

E31

7E

308

E31

0E

309

E30

9E

310

E31

0E

310

316

E31

6bE

316

E31

6E

316

E30

8bE

309M

oE

309

E30

9E

310

E30

9E

309

316L

E31

6LE

316

E31

6LE

316L

E30

9Mo

E30

9E

309

E31

0E

309

E30

931

7E

317

E31

7E

308b

E30

9Mo

E30

9E

309

E31

0E

309

E30

931

7LE

317L

E30

8LE

309M

oE

309

E30

9E

310

E30

9E

309

321,

347

, 348

E34

7E

309

E30

9E

309

E31

0E

309

E30

933

0aE

330

E30

9E

309

E31

0E

312

E31

240

3, 4

05, 4

10,

E41

0E

430e

E41

0eE

502e

E50

5e

414,

416

, 420

430,

430

F, 4

31,

E43

0E

430

E50

2eE

505e

440A

, 440

B,

440C

446

E44

6E

502e

E50

2e

501,

502

E50

2E

502e

505

E50

5

E30

9E

309

E30

9E

309

E30

9E

309

E31

0E

309

E30

9E

309

E30

9E

309

E30

9E

309

E30

9E

309

E30

9E

309

E31

2E

312

E41

0eE

410e

E43

0eE

430e

E43

0eE

430e

E50

2eE

502e

E50

5eE

505e

Not

es: G

rade

s sh

own

are

thos

e m

ost c

omm

only

sel

ecte

d fo

r mos

t app

licat

ions

; oth

er c

ombi

natio

ns m

ay b

e us

ed. W

here

ver p

ossi

ble,

reco

mm

enda

tion

is b

ased

upo

n th

e m

ost a

vaila

ble

and

low

est c

ost f

iller

met

al. F

iller

met

al d

esig

natio

ns a

re th

ose

appe

arin

g in

AW

S S

peci

ficat

ion,

A5.

9 fo

r bar

e fil

ler w

ire.

a.Th

ese

allo

ys a

re s

ensi

tive

to w

eld

crac

ks a

nd fi

ssur

es; f

or th

is re

ason

, E31

2 fil

ler m

etal

is a

freq

uent

ly re

com

men

ded

alte

rnat

ive.

It is

pre

ferr

ed e

spec

ially

whe

n th

ick

sect

ions

or h

ighl

y re

stra

ined

join

ts a

re re

quire

d. B

utte

ring

thes

e m

etal

s w

ith ty

pe 3

12 b

efor

e jo

inin

g is

ofte

n de

sira

ble.

b.E

16-8

-2 is

pre

ferr

ed to

low

er e

mbr

ittle

men

t dan

ger i

n el

evat

ed te

mpe

ratu

re s

ervi

ce.

c.W

hen

join

ing

an a

uste

nitic

ste

el, a

ltern

ate

choi

ce is

to b

utte

r car

bon

or c

hrom

ium

ste

el w

ith E

309

and

join

with

E30

8 or

with

fille

r met

al s

imila

r to

aust

eniti

c ba

se m

etal

. E30

7 is

als

o co

mm

only

use

d fo

r wel

ds b

etw

een

aust

eniti

c st

ainl

ess

stee

l and

eith

er c

arbo

n or

low

allo

y st

eels

.d.

EN

iCrF

e3 is

pre

ferr

ed fo

r ele

vate

d te

mpe

ratu

re s

ervi

ce, e

xcep

t whe

n su

lfur c

ompo

unds

are

pre

sent

.e.

If au

sten

itic

wel

d m

etal

is a

ccep

tabl

e fo

r ser

vice

con

ditio

ns, E

309

or E

310

is o

ften

empl

oyed

.

Bas

e A

lloy,

Type

201,

202

, 301

,30

2, 3

02B

, 303

a ,30

4, 3

05, 3

08

304L

309,

309S

310,

310S

,31

4a

316

316L

317

317L

321,

347,

348

330a

402,

405,

410,

412,

414,

420a

430,

430F

,43

1,44

0A,

440B

,44

0Ca

446d

501,

502c,

d50

5c,d

Car

bon

Stee

lsc,

dC

r-M

oSt

eels

c,d

Figure 19-15. Filler materials used for joining stainless steels and dissimilar metals.

are prepared for welding by this process.

Joint Cleaning

Sound, defect-free welds cannot be made if theweld joint is dirty or contaminated. To ensure the bestpossible welding conditions, rigidly inspect the jointbefore starting to weld. Grind or machine slag and scalefrom the part. Follow grinding with wire brushing toremove any particles left from the grinding wheel.Remove oil, grease, and pencil marks by solvent.Remove burrs and nicks to prevent entrapment offoreign materials in the weld joint.

Welding

Welding dissimilar metals requires careful considera-tion of the metals to be joined and the welding parameters.

• Joint fit-up. Joints that are not fit-up properly forwelding can often lead to possible failure or lossof the protection capabilities. Establish joint andassembly tolerances by test weldments when thewelding parameters are made. Should changes berequired in the welding parameters to correct forincorrect fit-up, they should only be allowedwithin a prescribed set of tolerances. Figure 19-28illustrates ways in which excessive tolerancesaffect the welding operation and joint integrity.


Base Surfacing Current Rod Deposit

Metal Material Type Type RcAmps. Hardness

Mild and Haynes ACHF Stellite #1 54stainless Stellite ACHF Stellite #6 39

steels alloys ACHF Stellite #12 47ACHF Stellite #93 62ACHF Hascrome 23–43

Copper Stellite #6 DCEN Stellite #6 42alloy 180–230

for 3/16″material

Steel, copper, Aluminum DCEN Aluminum-and silicon bronze bronze rods

bronzeMild steel Bronze ACHF or A1-bronze

and cast iron and copper DCEN 150 andfor 1/2″ copper rodsmaterial

Stainless Silver ACHF 160steel for 1/2″

materialMild steel Stainless ACHF or

steel DCENCarbon and Tungsten DCEN Tube of

alloy tool carbide 300–375 8/15 meshsteels tungsten

particles

Figure 19-16. Base material and surfacing material combinations.

Cladding Type Filler Material

405, 410, 410S, 429, 430 309, 310 Inconel A, B, 182, or equivalentInconel 82 or equivalent430

304 309, 310309L

304L 309L308L309Cb309CbL

321, 347 309Cb, 310Cb309CbL

316 347309Mo, 310Mo316L

316L 309MoL316L

317 318309MoL, 310Mo, 309Mo

317L 317L309MoL, 310Mo317L

Incoloy 825 Incoloy 65 or equivalentIncoloy 135 or equivalentInconel 625 or equivalentInconel 112 or equivalent

Inconel 600 Inconel A, B, 182, or equivalentInconel 82 or equivalent

Monel 400 Monel70Cu-30Ni Monel90Cu-10Ni 70Cu-30Ni

Nickel NickelCopper Copper, monel, nickel, inconel

Figure 19-17. The cladding listed in the left hand column maybe welded with any of the other materials listed.

Cladding (alloy) weld Weldoverlay

Alloycladding

Copper clad steelSteel weld

Figure 19-18. Sequence of welding clad steels.

Cladding Alloy for Overlay Alloy for WeldingAlloy on Steel Cladding

Copper RCu RCuRCuAl-A2RCuSi-A

RNi-3Copper-Zinc RCuAl-A2 RCuAl-A2

Copper-Tin-Zinc RCuSn-A RCuSn-ACopper-Aluminum RCuAl-A2 RCuAl-A2

Copper-Silicon RCuSi-A RCuSi-ACopper-Nickel RCuNi RCuNi

Figure 19-19. Filler materials used in welding clad steels.

• Heat input. This is dependent on amperage,voltage, travel speed, and the application of thefiller material. Insufficient heat input results inlack of fusion, voids, porosity, and cold shutswithin the weld joint. Too much heat can causeexcessive dilution within the joint between theparent metal and the filler material. The use ofpulsers to establish heating and cooling cycles


Cobalt Base Alloys

Carbon steel °F 600 300 200 500 900 900 200 400 900 400 70 900 70 .30C maximum °C 325 150 95 275 480 480 95 205 480 205 20 480 20Carbon steel °F 600 400 300 500 900 900 200 400 900 400 100 900 200 .30–.50C °C 325 205 150 275 480 480 95 205 480 205 40 480 95Low alloy steels up °F 600 400 300 500 900 900 200 400 900 400 100 900 200 to 3% total alloys °C 325 205 150 275 480 480 95 205 480 205 40 480 95Medium alloy steels °F 600 400 400 500 900 900 200 400 900 400 200 900 300 3–10% total alloys °C 325 205 205 275 480 480 95 205 480 205 95 480 150High alloy steels °F 600 400 400 500 900 900 200 400 900 400 200 900 300 Martensitic °C 325 205 205 275 480 480 95 205 480 205 95 480 150 e.g. Type 410High alloy steels °F 600 300 200 500 900 900 200 400 900 400 100 900 100 Ferritic °C 325 150 95 275 480 480 95 205 480 205 40 480 40 e.g. Type 430High alloy steels °F 500 300 200 400 900 900 200 400 900 400 70 900 70 Austenitic °C 275 150 95 205 480 480 95 205 480 205 20 480 20 e.g. Types 304, 316Nickel alloys °F 500 300 200 400 900 900 200 400 900 400 70 900 70 e.g. Inconel* °C 275 150 95 205 480 480 95 205 480 205 20 480 20 e.g. Monel*

*Trade names of the International Nickel Co., Inc.

Nickel Base Alloys Fe-CrAlloys

1 6 7 12 T-400 T-800 44 45 46 10XN A T-700 NiobendBase Metal

� Hard Surfacing �

Figure 19-21. Preheating of the base material reduces the amount of cracking in the surfacing alloy during the cooling period.

RCu 50–60 8 28 Corrosionresistant

RCuSn 70–85 35 Corrosionresistant,bearings

RCuSi-A 80–100 25 50–55 Erosion,corrosion

RCuNi 60–80 10–20 50 BearingsRCuAl-A1 100–150 25–30 55–65 Bearing

overlayRCuAl-A2 130–190 30–35 60–75 Cavitation

resistantRCuAl-B 140–220 40–45 90–110 Bearing

overlayRCuAl-C 180–280 40–45 90–100 Cavitation

resistantRCuAl-D 250–350 50–55 75–85 Wear

resistantRCuAl-E 290–390 55–70 70–80 Bearings,

diesNiAl bronze 180–200 55–60 100 Erosion,

corrosionresistant

WireDesignation

BrinellHardness

YieldStrength

(thousands)psi

TensileStrength

(thousands)psi

Applications

Figure 19-20. Common filler materials used for surfacing.

Smooth

Rough

Stock to beremoved

Figure 19-22. Sufficient stock should be removed from theedge of sheared material to eliminate all rough edges.


Upper shearknife

Radius formed bypulling material

Clad facingupward

Shearbed

Lower shearknife

Figure 19-23. Due to the ductility of the clad material, the metalwill stretch during the shear operation. This reduces the cladthickness at the sheared edge.

Remove cutend to thispoint forfull clad

thickness

Figure 19-24. Remove sufficient stock from the sheared edgeto assure full clad thickness.

Oxyacetylenecutting torch

Protectthis

surface

Steel

Not more than20% of total

thickness

Figure 19-25. Make a test cut on scrap clad material beforemaking the full cut to establish the cutting parameters. (Gaspressures, tip size, travel speed.)

Cut line

Removecopper area

Figure 19-26. The cladding should be removed far enoughfrom the edge or cut line so the copper is not melted into theburn area.

Protect thissurface

Plasma arccutting torch

Figure 19-27. The plasma arc cutting process will cut ferrous ornonferrous metals.Therefore, the cut may be made from either side.

will regulate amperage and reduce the overallheat input required to weld the joint.

• Welding technique. Maintain position of thetungsten and the angle of the torch to melt as littlebase material as possible. The filler materialshould be added to the weld pool as rapidly as

possible to provide a “cold pool.” Large moltenareas stir the pool and cause more dilution.

Welding done “out of position” usually generatesmore heat in the base material, causing more penetrationand dilution. Welds made in these positions should be“stringer beads” with no oscillation allowed.

Sizes of welds and sequencing of beads should bemade to control dilution of one bead to another. Eachweld should overlap the previous bead by one-half of theprevious bead width, as shown in Figure 19-29.

Each layer of weld should be flat without valleys orhigh spots, as shown in Figure 19-30. These conditionscan lead to defects within the weld if not corrected priorto starting the next layer. To correct this condition, grindall high spots even and fill or grind valleys even.

Clean each weld and visually inspect for porosity,voids, slag, silicon, etc., before applying the next bead.Always deposit the required number of layers specified.Adding or reducing the number of layers may radicallyaffect the dilution and composition of the final layer ofthe weld.

Review Questions

Write your answers on a separate sheet of paper. Donot write in this book.

1. List three areas where welding of dissimilar metalsare often used.

2. When another type of material is added to a joint ora build-up is made, this is called _____ or _____.

3. Where is cladded material made? Is all cladding thesame thickness?

4. Which is usually thicker, an overlay or a claddedsurface?

5. Does a single V-groove butt weld have more or lessdilution than a double V-groove butt weld?


Incorrect rootface dimensions

Incorrect gap dimensions

Incorrect rootface dimensions

Incorrectbevel

angles

Figure 19-28. Incorrect joint dimensions affect the alloy mix withinthe joint. This may affect the mechanical properties of the weld.

Step-overdistance

Figure 19-29. The amount of overlap of one weld to another iscalled the “step-over” distance. This dimension must beestablished during testing and maintained in production tocontrol the alloy mix.

Grind highareas, fill

and smoothlow areas

Figure 19-30. Welds with valleys or high spots do not have theproper alloy mix. These areas may cause defects such as lackof penetration, lack of fusion or bond, and improper dilution.

6. Which type of weld, the single V-groove butt or thedouble V-groove butt, has the greatest distortion?

7. Why are clad materials usually sheared with the cladsurface facing upward?

8. What happens to the clad at the sheared edge? Canthis be prevented?

9. Steels with stainless or nickel cladding may be flamecut if the cladding is not more than _____% of thetotal thickness.

10. Which type of cladding metal must be thoroughlyremoved from steel before thermally cutting? Why?

11. Which thermal cutting process may be used to

prepare dissimilar metal joints on all types of metals?12. Which process is used to prepare U-groove type

weld joints?13. Scale and slag may be removed from the weld joint

area by_____ or _____. This is followed by _____to remove particles of metal.

14. What type of equipment may be used to regulateheat input into a weld?

15. What is the major problem caused by weldingdissimilar metals with a “hot pool?”

16. Why should each layer of an overlay weld be flat?


welding dissimilar metals

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