stainless steel cladding and weld overlays (2).pdf

8/9/2019 Stainless Steel cladding and Weld Overlays (2).pdf

1/13

ainless Steel

verlays

l dding nd eld

A STAINLESS-STEEL-CLADmetal or alloy

a compositeproduct consisting of a thin layer of

tainless steel in the form of a veneer integrally

nded to one or both surfaces of the substrate.

e principal object of such a product is to com

ne, at low cost, the desirable properties of the

ainless steel and the backing material for appli

tions where full-gage alloy construction is not

quired. While the stainless cladding furnishes

necessary resistance to corrosion, abrasion, or

tion, the backing material contributes struc

ral strength and improves the fabricability and

rmal conductivity of the composite. Stainless

eel-clad metals can be produced in plate, strip,

be, rod, and wire form.

The principal cladding techniques include hot

ll bonding, cold roll bonding, explosive bond

g, centrifugal casting, brazing, and weld over

ing, although adhesive bonding, extrusion, and

t isostatic pressing have also been used to pro

e cladmetals. With casting, brazing, andweld

g, one of the metals to bejoined ismolten when

metal-to-metal bond is achieved. With hot/cold

ll bonding and explosive bonding, the bond is

hieved by forcing clean oxide-free metal sur

ces into intimate contact, which causes a shar

g of electrons between the metals. Gaseous

rities diffuse into themetals, andnondiffusi

e impurities consolidate by spheroidization.

se non-melting techniques involve some form

deformation to break up surface oxides, to cre

e metal-to-metal contact, and to heat in order to

accelerate diffusion. They differ in the amount of

deformation and heat used toform the bond and in

the method of bringing the metals into intimate

contact.

This article will review each of the processes

commonly associated with stainless-steel-clad

metal systems as well as the stainless steels used.

Design considerations and the welding of stain

less-steel-clad carbon and low-alloy steels are

also addressed. Additional information can be

found in Ref 1to 3.

o t Roll Bonding Ref 3

The hot roll bonding process, which is also

called roll welding is the most important com

mercially because it is the major production

method for stainless-clad steel plates. Hot roll

bonding accounts for more than 90 of the clad

plate production worldwide (Ref 1). t is known

also as the he t nd pressure process because the

principle involves preparing the carefully cleaned

cladding components in the form of a pack or

sandwich, heating to the plastic range, and bring

ing the stainless and backing material into inti

mate contact, either by pressing or by rolling. A

product so formed is integrally bonded at the in

terface. The clad surface is in all respects (corro

sion resistance, physical properties, and

mechanical properties) the equal of the parent

stainless steel. It can be polished and worked in

the same manner as solid stainless steel.

Table 1 lists the clad combinations that have

been commercially produced on a large scale. As

this table indicates, stainless steels can be joined

to a variety of ferrous and nonferrous alloys. On a

tonnage basis, however, the most common clad

systems are carbon or low-alloy steels clad with

300-series austenitic grades. The types of austeni

tic stainless steel cladding commonly available in

plate forms are:

.. Type 304 (18-8)

• Type 304L (18-8low carbon)

.. Type 309 (25-12)

.. Type 310 (25-20)

.. Type316 (17-12Mo)

.. Type 316 Cb (17-12 Nb stabilized)

.. Type 316L (17-12 Mo low carbon)

.. Type317 (19-13 Mo)

• Type317 L (19-13 Mo low carbon)

lit Type 321 (18-lOTi)

lit Type347 18-11Nb

The carbon or low-alloy steel/stainless steel

plate rolling sequence is normally followed by

heat treatment, which is usually required to re

store the cladding to the solution-annealed condi

tion and to bring the backing material into the

correct heat-treatment condition. Table 2 lists

typical mill heat treatments.

The cladding thickness is normally specified

as a percentage of the total thickness of the com

posite plate.

t

variesfrom 5 to50 , dependingon

the end use. For most commercial applications in-

ble 1

Selected dissimilar metals and alloys that can be roll bonded (hot or cold) into clad-laminate form

Weldabililyraliog(a)

AI

Carbon

Stainless

Ag

AI

alloys

Au

steel

Co Cn

Mo

Mo·N

Nb Ni

PI

steel Steel So Ta Ti U Zr

A

B

B

l A C

B C B B

B

C

D D

D

D D D D

D D

D D D

D

D D D

D D

D

D

D D

D D

D D

D D D D

D

D D D

D

D D D

steel

B

B B

A B A B B B A B B A A B

B

B

B

B A B

B A A B

B

A

B

B

B B B

B

B

B

A

B B

B

A, easy to weld; B, difficult but possible toweld; C. impractical toweld; D, impossible toweld. Source: Ref2

ASM Specialty Handbook: Stainless Steels, 06398G

J.R. Davis, Davis & Associates

Copyright © 1994 ASM Internationa

All rights reserv

www.asminternational

http://www.asminternational.org/search/-/journal_content/56/10192/06398G/PUBLICATION


2/13

8 / Introduction to Stainless Steels

Table 2 Typical millheattreatments forstainlesscladcarbonandlow-alloysteels

Typeof

claddingmaterial

TypeofASTM-grade

backingmaterial

Heat treatment(a)

metallurgical bond that isdue to a sharing of

oms between the materials. The resulting bo

can exceed the strength of either of the par

materials.

a)Heat treatments listedaregenerallycorrect forthematerial combinations shown.Deviationsmaybe madetomeetspecific requirements Procedure

selected

willbeonefavorable forboth cladding andbacking material b)

Stabilized

orlow carbon typesof

stainless

steelshould beusedwhenthisdouble

heattreatment is involved.Source:Ref3

A204, A 302 (up to50mm or 2 in., gage)

A204, A 302 (over 50mm or2 in., gage).

A301 (all gages)

Cold Roll onding

Upon completion of this three-step process,

resultant clad material can be treated in the sa

way as any other conventional monolithic me

The clad material can be worked by any of

traditional processing methods for strip met

Rolling, annealing, pickling, and slitting are ty

cally performed to produce the finished strip

specific customer requirements, so that the mate

can be roll formed, stamped, or drawn into

required part.

Cladsteels prepared by this method show s

stantially the same microstructures as those t

have been bonded by hot roll bonding process

Because of the high power requirement in the

itial reduction, the cold bonding process is

practical for producing clad plates

of

any app

ciable size.

The single largest application for cold-ro

bonded materials is stainless-steel-clad alu

num

for automotive trim (Table 3 and Fig. 2) R

6). The stainless steel exterior surface provi

corrosionresistance, high luster, and abrasion a

dent resistance, and the aluminum on the ins

provides sacrificialprotectionfor the painted a

body steel and for the stainless steel.

xplosive onding Ref1

Explosive bonding uses the very-short-du

tion, high-energy impulseof an explosionto dr

two surfaces of metal together, simultaneou

cleaning away surface oxide films and creatin

metallic bond. The two surfaces do not collide

stantaneouslybut rather progressively over the

Anneal 1065 to 1175 °C(1950to

2150 oF),

air quench

Anneal 1065 to 1175 °C (1950 to2150

oF),

air quench, normalize 870 to900 °C

(1600 to 1650 F) 1hr per 25mm (1in.)

thickness, air quench(b)

Anneal 1065 to 1175°C (1950 to

2150 oF),

air quench

Anneal 1065 to 1175°C (1950 to

2150

OF),

air quench, normalize870 to900°C

(1600 to 1650OF)1hr

per

25mm (1in.)

thickness, airquench(b)

The

cold roll bonding process,

which

is

shown

schematically in Fig. 1, involves three

basic steps:

The mating surfaces are cleaned by chemical

and/or mechanical means to remove dirt , lu

bricants, sur face oxides , and any other con

taminants.

The materials are joined in a bonding mill by

rolling them together with a thickness reduc

tion that ranges from 50 to 80 in a singlepass.

Immediately afterwards, the materials have an

incipient, or green, bond created by the massive

cold reduction.

The materials then undergo sintering, a heat

treatment during which the bond at the inter

face is completed. Diffusion occurs at the

atomic level along the interface and results in a

A285, A201,A212 (up to50mm, or2 in. ,

gage)

A201, A212 (over 50mm or 2 in., gage)

304, 304L, 309, 310, 316, 316Cb,316L,

317 321 or347

304L, 316L, 316Cb,317L, 321, or 347

304, 304L, 309, 310, 316, 316Cb,316L,

317 321 or347

304L, 316L, 316Cb,317L, 321, or 347

volving carbon or low-alloy steel/stainless steel

combinations, cladding thickness generally falls

in the 10 to 20 range.

Hot roll bonding has also been used to c lad

high-strength low-alloy (HSLA) steel plate with

duplex stainless steels

Re f

4, 5). The microal

loyed basemetals contain small amounts of cop

per (0.15 max), niobium (0.03 max), and

nit rogen (0.010 max) and have mechanica l

properties comparable tothose ofduplexstainless

steels. Typically these HSLA base metals have

yield strengths of 500 MPa (72.5 ksi) and impact

values of 60

J

(44 ft-lbf) at

-60°C

- 75 OF The

shear strength

of

the cladding bond can be as high

as

400

MPa (58 ksi).

Other metals and alloys commonly roll

bonded to stainless steels includealuminum, cop

per, and nickel. Table 3 lists properties and appli

cations of roll-bonded clad laminates.

Table 3 Typical properties of roll-bonded stainlesssteel

Tensile

Yield

Composite

Thickness Width

strength strength Elongation,

Materialssystem

ratio,

mm

in.

mm

in.

MPa ksl MPa

ksi

Applications

Type 434 stainless/5052 40 :60 0.56-0.76 0.0 22-0 .030

:0;610 :0;24

395 57 360 52 12

Widely used for automotive body

aluminum

moldings, drip rails, rockerpanels

and other trim components, often

replacing solid stainless steel or

aluminum. Stainlesssteel provides

bright appearance; thehidden

aluminumbase providescathodic

protection, corroding sacrificially

thebody sleel.

CI008 steel/type 347 45:10:45 0.36

0.014 305 12 393

57

195 28

35

Used in hydraulic tubing in vehicles

stainless steel/CI008

replacingteme-coated carbon stee

steel

tubing. The outerlayer of carbons

cathodically protects the stainless

core of thetube, extending its life

significantly.

Nickel201/type

304 7.5:85:7.5

0.20-2.41

0.008-0.095 25-64

1-2.5 310

45 40

Used in formed cans for transistor an

stainless steel/nickel button cell balleries, replacing soli

201

nickel at a lower cost

C opp er 1mOO/type 430 17:66:17, 0.10-0.15 0.004-0 .006 12.7-150

0.5-6

415(a)·

60(a)

275 40

20(a) Replacesheavie rgapes of copperan

stainless steel/copper 20:60:20, bronze in buried communications

10300 33:34:33

cable. The stainless steel provides

resistance to gnawing by rodents,

which isa seriousproblem in

underground installations.

(a)20/60/20three-layerlaminate

Source:

Ref2


3/13


4/13

110 Introduction to Stainless Steels

ig 5

Commercially availableexplosion-cladmetalcombinations

i

>-

Q)

Qi

E

.2

E

Qi

Q)

E

a:l

E

.2

co

::J

::J

CD

E

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E

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Q)

in

::J

.2

c

c

c

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::J

.9

)

::J

co

] .

Q)

f

0

0

c

C

:.0

Qi

c

c.

c

>-

01

;:;

Q)

C.

::J

(ij

.2

] eo

0

2:

0

c

.s

0

eo

:2:

f

a::

o w

Z l -

I

i=

z

o

f

o

Carbon steels

•

ED

•

•

•

•

CD

CD

• •

• •

•

•

Alloy steels

•

•

•

•

•

III

•

III

ED III ED

Stainless steels

•

•

•

I t

•

4

•

I t

Aluminum

•

III

• • •

•

Copper aIIoys

•

III

ED

D D

•

Nickel alloys

• •

ED

III

I t

•

It

Titanium

I t

• • •

•

•

Hastelloy

4

Tantalum

III

ED

•

Niobium

•

•

Silver

•

Gold

Platinum

•

Stellite 68

Magnesium

D

Zirconium

•

the brazing alloy liquefies and forms an intennet

allic alloying zone at the interface of the stainless

and backing material (normally carbon steels), A

wide range of brazing filler metals can be used to

join stainless steels to carbon or low-alloy steels.

The most commonly used are silver-base alloys.

More detailed information on brazing of stainless

steels can be found in the

article

Brazing, Sol

dering, andAdhesive Bonding in this Volume.

el

Overlays

eld overlaying refers to the deposition of a

filler metal on a base metal (substrate) to impart

some desiredproperty to the surface thatis not in

trinsic to the underlyingbasemetal. There are sev

eral types of weld overlays: weld claddings,

hardfacing materials, buildup alloys, and butter

ing alloys.

A weld clad is a relatively thick layer of filler

metal applied to a carbon or low-alloy steel base

metal forthe purposeofprovidinga corrosion-resis

tant surface.Hardfacing is a form ofweld surfacing

that is applied for the purpose of reducing wear,

abrasion, impact,erosion,galling,or cavitation.The

termbuildup refers to theadditionof weld metal to a

basemetal surface for therestoration of thecompo

nent to the required dimensions. Buildup alloys are

generally not designed to resist wear, but to return

the worn part back to, or near, its original dimen

sions, or toprovideadequatesupportfor subsequent

layersof truehardfacingmaterials.Buttering alsoin

volves the addition of one or more layers of weld

metal totheface ofthejoint orsurface tobe welded.

It

differsfrombuildup in thatthe primary purpose of

buttering is to satisfy some metallurgical cons

eration. t is used primarily for the joining of d

similar metal base metals, as described in

section Welding Austenitic-Stainless-C

Carbon or Low-Alloy Steels in this article.

extensive review of the weld processes and ma

rials associated with weld overlays can be fou

in the article Hardfacing, Weld Cladding, a

Dissimilar Metal Joining, in Volume 6 of

S andbook (Ref 10),

WeldCladding

The term

weld cladding

usually denotes

application of a relatively thick layer ;:: mm,

Ys in.) ofweld metal for the purposeof providi

a corrosion-resistant surface. Hardfacing p

duces a thinner surface coating than a weld cla

ding and is normally applied for dimensio

restoration or wear resistance. Typical base me

components that are weld-cladded include the

ternal surfaces of carbon and low-alloy steel pr

sure vessels, paper digesters, urea reacto

tubesheets, nuclear reactor containment vesse

and hydrocrackers. The cladding material is u

ally an austenitic stainless steel or a nickel-ba

alloy. Weld cladding is usually performed usi

submerged arc welding. However, flux-cored

welding (either self-shielded or gas-shielde

plasma arc welding, and electroslag welding c

also produce weld claddings. Figure 6 compa

deposition rates obtainable with differentweldi

processes. Filler metals are available as cover

electrodes, coiled electrode wire, and strip ele

trodes. For very large areas, strip welding w

either submerged arc or electro slag techniques

the most economical. Table 4 lists some of

filler metals for stainless steel weld claddings.

Application Considerations

Weld claddi

is anexcellent way to impart properties to the s

face of a substrate that are not available from t

of a base metal, or to conserve expensive or dif

cult-to-obtain materials by using only a relative

thin surface layer on a less expensive or abunda

base material. Several inherent limitations or po

sible problemsmust beconsideredwhen planni

for weld cladding. The thickness of the requir

surface must be less than the maximum thickne

of the overlay that can be obtained with the p

ticular'process and fillermetal selected.

Weldingposition alsomust be considered wh

selecting an overlay material and process. Cert

processes arelimitedin theiravailableweldingpo

tions (e.g.,submerged arcweldingcanbe used o

in the flat position).

In

addition, when using a hig

deposition-rate process that exhibits a large liqu

pool,weldingverticallyoroverheadmaybediffic

or impossible. Some alloysexhibit eutectic solid

cation, which leads to largemolten pools that sol

ify instantly, with no mushy (liquid plus sol

transition. Such materials are also difficult to w

except in theflat position.

DilutionControl

The economics of stainle

steel weld cladding are dependent on achievi

the specific chemistry at the highest practi

deposition rate in a minimum number of laye

The fabricator selects the filler wire and weldi

process, whereas the purchaser specifies the s


5/13

Stainless Steel Cladding and Weld Overlays

III mperage Increased amperage (current den

sity) increases dilution. The arc becomes hot

ter, it penetrates more deeply, and more base

metal melting occurs.

III

Polarity Direct current electrode negative

(DCEN) gives less penetration and resulting

lower dilution than direct current electrode

positive (DCEP). Alternating UITentresults in

a dilution that lies between that provided by

DCEN and DCEP.

III Electrodesize The smaller the electrode, the

lower the amperage, which results in less dilu

tion.

III Electrode extension

A long electrode exten

sion for consumable electrode processes de

creases dilution. A short electrodeextensionin

creases dilution.

• Travel speed A decrease in travel speed de

creases the amount ofbasemetal melted and in

creases proportionally theamount of filler met

al melted, thus decreasing dilution.

III Oscillation Greaterwidth of electrode oscilla

tion reduces dilution. The frequency of oscilla

tion also affects dilution: The higher the fre

quency of oscillation, the lower the dilution.

III

Welding position

Depending on the welding

position or work inclination, gravity causes the

weldpool torun ahead of, remain under, or run

behind the arc.

the weld pool stays ahead of

or under the arc, less base metal penetration

and resulting dilution will occur. If the pool is

too far ahead of the arc, there will be insuffi-

mum. Less than 10 raises the question of bond

integrity, and greater than 15 increases the cost

of the filler metal. Unfortunately, most welding

processes have considerably greater dilution.

Because of the importance of dilution in weld

cladding as well as hardfacing applications, each

welding parameter must be carefuIly evaluated

and recorded. Many of the parameters that affect

dilution in weld cladding applications are not so

closely controlled when arc welding is per

formed:

34

20

8

642

carbon at a low level to ensure corrosion resis

tance. The prediction of the microstructures and

properties (such as hot cracking and corrosion re

sistance) for the austenitic stainless steels has

been the topic of many studies. During the last

two decades, four microstructure prediction dia

grams have found the widest application. These

include the Schaeffler diagram, the DeLong dia

gram, and the Welding Research Council (WRC)

diagrams (WRC-1988 and WRC-1992). Each of

these isdescribed inRef 10and the article Weld

ing in this Volume.

Althougheachweld claddingprocess hasan ex

pecteddilutionfactor,experimentingwith theweld

ing parameters can minimize dilution. A value

between 10 and 15 is generally considered opti-

14 16 18 20

eposition

rate, kg/h

Submerged

arc -

double wire

120

Comparison of deposition ratesfor various weld cladding processes To obtain equivalent deposition rates in

pounds per hour, multiply the metric value by

2.2.

Source:Ref

1

Pulsed

GM W

Spray transfer

GM W

~ S U b m e r g e d

arc - 60

mm

strip

Submerged arc - 90

mm

strip

< > > ; , * m ~ ,

Submerged arc - 120 mm

strip

Electroslag - 60

mm strip

Electroslag

- 90

mm

strip

Fig 6

Hot

wire GT W

ce chemistry and thickness, along with the base

tal. The most outstanding difference between

lding a joint and depositing an overlay is the

ntage of dilution:

dilution

=....£

x 100

x y

x is the amount of basemetal melted and y is

amount of fillermetal added.

For stainless steel cladding, a fabricator must

derstand how the dilution of the filler metal

th the base metal affects the composition and

tallurgical balance, such as the proper ferrite

evel to minimize hot cracking, absence of

tensite at the interface for bond integrity, and

e: Colombium (Cb) isalso referred toas niobium

(Nb).

(a)Refer tnAWS specificationA5.4. (b)Refert o AWSspecificationA5.9.

tainless

steel fillermetalsforweld cladding applications

E320 ER320

Fig 7 Weld cladding ofa 1.8 m 6 ft inner diameter

pressurevesselshell with SO mm 2 in. wide,

64mm (0.025 in. thick stainlesssteelstrip. Courtesyof l.],

Barger

ABBCombustion Engineering

ER308

ER308L

ER317

ER347

ER347

ER309

ER310

ER316

ER316L

ER317L

Subsequentlayers

E308

E308L

E347

E347

E309

E310

E316

E316L

E317

E317L

Covered Bare rodor

eleelrode(a)

electrodetb)

Firstlaxer

verlay Covered Barerodor

electrode(a) eleclrode(b)

E309 ER309

04L E309L ER309L

E309Cb

21 E309Cb ER309Cb

47 E309Cb ER309Cb

09 E309 ER309

10 E310 ER310

16 E309Mo ER309Mo

16L E309MoL E309MoL

E317L

ER317L

17 E309Mo ER309Mo

E317 ER317

E309MoL

ER309MoL

E317L ER317L

Cb E320 ER320


6/13

2 Introduction to Stainless Steels

ig 8

Closeup view of the 25 mm (1 in. )

wide

by

0.64

mm 0.025 in.) thick stainless steel strip

used

to clad a

300

mm

(12 in.) inner diameter pressure vessel nozzle. Courtesy of).). Barger, ABBCombustion Engineering

Hardfacing Alloys

Hardfacing materials include a wide variety

alloys, carbides, and combinations of these

loys. Conventionalhardfacing alloys are norma

classified as carbides (We-Co), nickel-base

loys, cobalt -base alloys, and ferrous allo

(high-chromium white irons, low-alloy stee

austeni tic manganese s teels, and stainle

steels) . Stainless steel hardfacing alloys i

clude martensitic and austenitic grades, the l

ter having high manganese (5 to 10 ) and/

silicon (3 to 5 ) contents. As will be describ

below, both cobalt-containing and cobalt-fr

austenitic stainless steel hardfacing alloys ha

been developed.

Hardfacing alloy selection is guided primar

by wear and cost considerations. However, oth

manufacturing and environmental factors mu

also be considered, such as base metal; depositi

process; and impact, corrosion, oxidation, a

thermal requirements. Usually, the hardfaci

process dictates the hardfacing or filler me

product form.

Hardfacing alloys usually areavailable asba

rod, flux-coated rod, long-length solid wir

long-length tube wires (with andwithout flux),

powders. The most popular processes, and t

forms most commonly associated with each pro

ess, are:

dent

melting of the surface of the base metal,

and coalescence will not occur.

• Arc shielding: The shielding medium, gas or

flux, also affects dilution. The following list

ranks various shielding mediums in order of

decreasing dilution: granular flux without alloy

addition (highest), helium, carbon dioxide, ar

gon, self-shielded flux-cored arc welding, and

granular flux with alloy addition (lowest).

• Additionalfillermet l Extrametal(notincluding

theelectrode),added to theweldpool aspowder,

wire, strip, or with flux, reduces dilution by in

creasing the total amount of fillermetal and re

ducing the amount of base metal that is melted.

For weld cladding the inside surfaces oflarge

pressure vessels, as shown in Fig.

7

and

8,

wide

beads produced by oscillated multiple-wire sys

temsor strip electrodes havebecome the means to

improve productivity and minimize dilution

while offering a uniformly smooth surface. Weld

ing parameters for stainless steel strip weld over

lays are described inRef 10.

Hardfacingprocess

Oxyfuel/oxyacetylene

(OFW/OAW)

Shielded metal arc (SMAW)

Gas-tungsten arc (GTAW)

Gas-metal arc (GMAW)

Flux-cored open arc

Submergedarc (SAW)

Plasmatransferred arc (PTA)

Laserbeam

Consumable form

Bare cast or tubular rod

Coated solid or tubular ro

(stick electrode)

Bare cast ortubularrod

Tubular or solid wire

Tubular wire (flux cored)

Tubularor solid wire

Powder

Powder

Table 5 Characteristics ofwelding

processes

used in

hardfacing

Minimum

Welding Modeof Weld-metal

Deposition

thickness(a)

Deposit

process application

Formof hardfacingalloy dilution,

kg/h

Ib/h

mm

in.

efficiency,

OAW

Manual

Bare cast rod, tubular rod 1-10 0.5-2

1-4

0.8

Y

100

Manual Powder

1-10 0.5-2 1-4

0.8

\-32

85-95

Automatic Extra-long bare cast rod, tubular wire 1-10 0.5-7 1-15 0.8

Y

100

SMAW

Manual

Flux-covered cast rod, flux-covered tubular rod 10-20 0.5-5 1-12 3.2

65

Open arc

Semiautomatic Alloy-cored t ubular wire

15-40 2-11 5-25

3.2

80-85

Automatic Alloy-cored tubular wire 15-40

2-11 5-25

3.2

s

80-85

GTAW

Manual Bare cast rod, tubular rod

10-20 0.5-3 1-6

2.4

2

98-100

Automatic Various forrns(b) 10-20 0.5-5

1-10

2.4

3 :l2

98-100

SAW

Automat ic, single Bare tubular wire

30-60 5-11 10-25

3.2

95

wire

Automatic, multiwire Baretubular wire

15-25 11-27 25-60

4.8

3/

16

95

Automatic seriesarc Bare tubular wire

10-25 11-16 25-35

4.8

3/

16

95

PAW

Automatic Powder(c)

5-15 0.5-7 1-15

0.8

Y

85-95

Manual Bare cast rod, tubular rod

5-15 0.5-4 1-8

2.4

2

98-100

Automatic Various forrns(b)

5-15 0.5-4 1-8

2.4 3.32 98-100

GMAW Semiautomatic Alloy-cored tubular wire 10-40 0.9-5

2-12

1.6

6

90-95

Automatic Alloy-cored tubular wire 10-40

0.9-5 2-12

1.6

1/16

90-95

Laser

Automatic Powder 1-10

(d) (d)

0.13

0.005 85-95

a)

Recommended minimum thickness

of

deposit.

b)Bare

tubular wire; extra long

2.4m,or8 ft barecastrod;tungstencarbide

powder

withcastrodorbare

tubularwire.

c)With

or without

tungsten carbide

granules.

d)

Varies

wid

depending onpowderfeedrateandlaserinput power


7/13

Stainless Steel Cladding and Weld Overlays

113

Typical dilution percentages, deposition rates,

d minimum deposit thicknesses for different

lding processes, along with various forms,

positions, and modes of application of hard

cing alloys, are given in Table 5.More detailed

ormation on the selection of hardfacing alloys

d processes can be found inRef 10.

The buildup alloys include low-alloy pearli

steels, austenitic manganese (Hadfield) steels,

d high-manganese austenitic stainless steels.

r the most part, these alloys are not designed to

esist wear but to return a worn part back to, or

ar, its original dimensions and to provide ade

ate support for subsequent layers of true hard

ing materials. However, austenitic manganese

eels are used as wear-resistant materials under

ld wear conditions. Typical examples of appli

tions where buildup alloys are used for wearing

rfaces include tractor rails, railroad rail ends,

teel mill table rolls, and large slow-speed gear

eth. The stainless steel included in this cate

ory is AWS EFeMn-Cr, which has a hardness

lue of 24 HRC and the fol lowing chemical

produced. The activated particles are incorpo

rated into the oxide layers ofprimary system com

ponents and contribute considerably to the

occupational radiation exposure of maintenance

personnel during the inspection, repair, or re

placement of components. Additionally, material

loss has been found for cobalt-base hardfacings

used for control or throttle valves that areexposed

to high flow velocities, indicating that this type of

alloy has a limited resistance toerosion-corrosion

and cavitation attack.

Detailed investigations of candidate replace

ment cobalt-free, iron-base alloys have been per

formed since the late 1960s. In the U.S., the

Electric Power Research Institute has developed

cobalt-free NOREM alloys (U.S. Patent

4,803,045, Feb. 7, 1989).These alloys can be de

posited successfully on stainless and carbon steel

substrates with gas-tungsten arc welding, in any

position and with no preheat, using controlled

heat input techniques. Nominal compositions of

the NOREM alloys are as follows:

Composition, wt

0.5

15.0

15.0

1.3

1.0

2.0

bal

Element

Carbon

Chromium

Manganese

Silicon

Nickel

Molybdenum

Nitrogen

Iron

Composition,wt

0.7-1.0

24-26

4.0-5.2

2.5-3.2

5.0-9.0

1.7-2.3

0.05-0.15

bal

NOREM alloys are characterized by high

wear resistance and antigalling properties, and

they have a microstructure consisting of an

austenitic matrix containing eutectic alloy car

bides. The NOREM alloys meet or surpass the

performance of cobalt alloys with respect to cor

rosion, material loss due to wear, and mainte

nance of the valve s sealing function. Galling

wear data forvariousNOREM andcobalt-base al

loys are given in Table6. Chemical compositions

of the alloys tested are provided in Table7. Addi

tional information on these alloys can be found in

Refll to 14.

Considerable work has also beencarried out in

Europe on cobalt-free, iron-base hardfacing al

loys. Everit 50 (47 to53 HRC), Fox Antinit DUR

300 (28 to 32 HRC), and Cenium Z 20 (42 to 48

HRC) are tradenames used by Thyssen Edel

stahlwerke Bochum (Germany), VereinigteEdel

stahlwerke Kapfenberg (Austria), and

L.A.M.E.E Rueil-Malmaison (France), respec

tively. Compositions of these alloys are given in

Table 8. Studies have demonstrated that these al

loys have tribological, corrosion, andmechanical

properties comparable to those of cobalt-base

Stellite 6 (Ref 15).

Cobalt-containing

austenitic

stainless

steels have been developed byHydro-Quebec for

the repair of the cavitation erosion damage of its

hydraulic turbines. vit tion refers tothe forma

tion ofvapor bubbles, or cavities, in a fluid that is

moving across the surface of a solid component.

Surface damage, um, at

Stress,MPa(ksi)

indicatedtestsin air

testsin water

lloy form

140(20) 275(40) 415 (60) 140(20) 275(40) 415(60)

NOREM Ol/solid

0.4 0.9 1.1 0.3 0.4 0.4

NOREM Ol/solid

0.7 1.6 2.8 nt nt nt

NOREMOI/metal- 0.7 0.4

0.6

0.7

1.1

1.3

core

NOREMOl/metal- 1.9

2.3 4.7

1.2

1.3

1.5

core

NOREMOI/metal- 0.3 0.5

1.4 0.3

0.5 0.7

core

NOREM04/metal-

0.6

0.7

1.0 nt nt nt

core

Stellite 21/solid

1.3

1.9

2.4 0.5 1.0 1.5

Stellite 6/solid

2.2

2.6

2.8

1.1

1.7

1.6

Source:H. Ocken,ElectricPowerResearchInstitute

0.3

12.0

2.0

1.0

bal

Composition,wt

lement

Martens it ic air -hardening steels (including Table 6 Gallingwear of gas-tungsten arc weld overlays made from cobalt-free NOREM alloys

ss steels) aremetal-to-metalwearalloysthat,

care,canbeapplied(withoutcracking)towear

areasof machineryparts.Hence,thesematerials

commonly referred to asmachinery hard acing

Typicalapplicationsof this alloy family in

de undercarriage components

of

tractors and

wer shovels, steel m ll work rolls, and crane

eels. The stainless steelin this category is AWS

420, whichhas a hardnessvalue of45 HRC and

followingchemicalcomposition:

Table 7

Chemical

compositions of the NOREM hardfacing alloys listed in Table 6

Cobalt free austenitic stainless steels have

n developed to replace cobalt-base hardfacing

oys (Stellite grades) in nuclear power plant ap

ications. Cobalt-base alloys have been tradi

onally used for hardfacing nuclear plant valves

heck valves, seat valves, and control valves),

they generally show high corrosion resis

nce and superior tribological behavior under

iding conditions. However, even the (usually

w) corrosion and sliding-wear rates of these

rdfacings lead to a release of particles with a

cobalt content. The particles areentrained in

e coolant flow through the core, and Co

60

,

ich is a strong emitter of gamma radiation, is

Nominalcomposition,\,,( (a)

lIoylVendor

C Mn Si

Cr Ni

Mo P

S

Other

NOREM

Ol/Stoody

1.3

9.7 3.3

25

4.2

2

0.02

0.01

O.IN

NOREM

Ol/Cartech 1.27 6.15

3.17

25.5

4.47 2.03 0.006 0.009

0.12N,

0.02Cu,

O.OICo

NOREM 04/Anval 1.17

12.2

5.13

25.3 8.19 1.81

0.029

0.01 0.22N,

0.05Cu,

0.068Co

NOREMA/Anval

1.22

7.5 4.7

26.5 4.9 2.21

0.018

0.Dl5 0.236N,

0.03Nb,

0.007Ti,

0.07Co

(a)Singlevaluesaremaximumvalues.Source:H. Ocken,ElectricPowerResearchInstitute


8/13

/ Introduction to Stainless Steels

able8 European-developed cobalt-free hardfacing alloys

Studiesby Simoneau(Ref 16and 17) atthe

stitut de Recherche d'Hydro-Quebec have det

mined that the elements most favorable

cavitat ion resistance, in decreasing order,

carbon, nitrogen, cobalt, and silicon. The com

nation of carbon and nitrogen has an equival

effect, whereas chromium and manganese show

neutral effect within the 8 to 12 Co ran

Nickel is detrimental. Figure 9 presents the eff

of carbon plus nitrogen, and Fig. 10 presents

effect of cobalt concentration, on the steady-st

rate of cavitation erosion. These results allow

formulation of alloys with the appropriate amo

of austenitizer (carbon, nitrogen, cobalt, mang

nese) and ferritizer elements (chromium, silico

molybdenum) to stabilize the austenite phase

room temperature. Cobalt alone is not suffici

as an austenitizer, because it only very sligh

lowers the martensitic transformation tempe

ture. Thus, it must be supplementedwith mang

nese, carbon, or nitrogen. Inorder to increase

ductility and the corrosion resistance, carbon c

be replacedby nitrogen.

The composition of cobalt-containingauste

tic stainless steels provides a balance of eleme

in such a way that an essentially austenitic

ypha

with a low stacking fault energy is obtained in

as-welded and solidified weld overlay. This m

tastable face-centered cubic (fcc) y-phase tra

forms under stress to a body-centered cubic (be

rx-martensitic phase exhibiting fine deformati

twins. The phase transformation and twinning a

sorb the energy of the shock waves generated

the collapsing of the vapor bubbles. Such beha

ior is similar to that of cavitation-resistant hig

cobalt alloys, which exhibit a transformati

from a fcc y-phase to a hexagonal close-pack

(hcp) s-phase in addition to twinning.

In the incubation periodof the alloy surfa

under a cavitat ion condition, the hardness

creases as deformation twins form on the surfac

The metal loss during this per iod is genera

minimal, and the surface is smooth and hardene

Unlike the case for other alloys, such as 300-s

ries stainless steels, this incubation period is lo

and high hardness levels (450 HV) are reached

the steady state.

After the surface is fully hardened, furth

cavitation causes damage by initiating fatig

cracks and subsequent detachment of particula

at the intersections of the deformation twins. B

cause the twins are relatively small and the me

particles also small, the resul t is a uniform a

slow degradation of the metal surface.

The main effect of these chemical compo

tion modifications on the mechanical propert

of austenitic stainless steels is illustrated by t

tensile curves shown in Fig. 11. The work-

strain-hardening coefficient increases marked

when going from 304 to 301, and in particular f

the cobalt-containing stainless steel. Decreasi

the nickel and replacing it with cobaltresults i

decrease in yield strength and in an important i

crease in ultimate tensile strength. Although t

initial strain-hardening coefficient for these stee

is quite similar, itincreases to a very highvalue

larger strains (up to 1.26) for cobalt-containi

stainless steels. This larger strain hardening is a

0.6

0.2

17

9.5

2.5

9

0.2

bal

0.5

Olher

0.5V

301

304

Fe-18Cr-l0CD

2.0W, unspecified

other elements ,,5

Composition,wt

o

o

Mo

3.2

0.2 0.3 0.4

True strain

0.1

Tensilestress-straincurves of 308,301, and co

balt-contain ing stainless steels.Source: Ref

18

O --_.L-_- -_--- -_--- -_--IL. . .- - ---I

o

1600

2000

a.

1200

Element

moval of small metal lic particles from the ex

posed surface. This eventually results in serious

erosion damage to the metallic surfaces and is a

major problem in the efficient operation of hy

draulic equipment, such as hydroturbines, run

ners, valves, pumps, ship propellers, and so on.

The damage caused by cavitat ion erosion fre

quently contributes to higher maintenance and re

pair costs, excessive downtime and lost revenue,

use of replacement power (which is very expen

sive), reduced operating efficiencies, and short

ened equipment service life.

The outstanding cavitation erosion resistance

of cobalt-containing austenitic stainless steels

comes from a patented chemistry formulated to

yield the highestwork-hardening rate, with a high

interstitial carbon and nitrogen content. For the

same reason, and in order to stabilize a fully

austenitic structure, nickel has been replaced by

manganese and cobalt, which are balanced with

silicon and chromium to give good corrosion re

sistance. The nominal composition for these al

loys is:

Carbon

Chromium

Manganese

Silicon

Cobalt

Nitrogen

Iron

ig

11

1.1

o

8 10 12 14 16 18 20

CDbait concentration,

0.3 0.5 0.7 0.9

C + N concentration,

Effectofcobalt additions on cavitation erosion

of austenitic stainless steels. Source: Ref

17

6

o

0 0

0 10

0 tp 0

o

o

Cb 0

o

d ;:.°.:: .° : 0; 1

0

a

°

0

0.6L...-_--- -

- -

. L - _ - - I

0.1

0 .6 - - - - - -_ - -_ .L- - - _ - - - -_ - -_L- - - l

4

_ 1.8

c

o

w 1.4

Chemicalcomposition,wt a)

Alloy

C

Mn

Si

Cr

Ni

Everit50

2.5

,,1.0

,,0.5

25.0

Fox Antinit Dur 300 0.12

6.5 5.0 21.0 8.0

CeniumZ20

0.3 NR(b)

NR(b)

27

18

a)Single valuesare

maximum

values. b)NR,notreported Source:Ref 15

2.6

3

These vapor bubbles are caused by localized re

ductions in the dynamic pressures of the fluid.

The collapse of these vapor cavities produces ex

tremely high compressive shocks, which leads to

local elastic and/or plastic deformation of the me

tallic surfaces. These repeated collapses (com

pressive shocks) in a localized area cause surface

tearing or fatigue cracking, which leads to the re-


9/13

Stainless Steel Cladding and Weld Overlays /

35

30

304N

304

301N

Fe-1BCr-l0Co

5

O u : ; ~ ~ ; : : : [ g - : : : : I : : : = - - - - - - , - - - - - - , - - - - - , - , - -

o 5 10 15 20 25 30 35 40 45

Elongation,

35 00

34

30 00

25 00

s

§;

E

20 00

ell

'§

c

15 00

(;;

e

UJ

10 00

5 00

0 00

1020

308SS 301SS

CA 6NM fe 15Mn 14Cr Stellile 21 Stellile 6

fe IOCr lOCo

fe 18Cr 8Co

12

Deformation-induced martensitic transforma

tion measuredin tensile tests.Source:Ref 18

Alloy

Fig 14

Comparison of cavitation erosion rateof various materials. Source:Ref18

1OO ........ L ~ . o 1 ~ ~ l o . _ _ ~ . L . . . . . . . . . . . . L . . . . . . . . . . . . J

o

50 100 150 200 250 300 350 400 450

Depth.jim

SELFBRAZINGMATERIAL

CopperClad StainlessSteel

Heatexchanger fabricated using clad brazing

( self-brazing ) materials

Fig

15

The choice of a material for a particular applica

tiondepends on suchfactorsas cost, availability,ap

pearance, strength, fabricability, electrical or

thermalproperties, mechanical properties, and cor-

Designing with lad etals Ref6

thematerialsareadequateformostapplicationsin

flowingriveror tap waters.

The original experimental cobalt-containing

stainless steels were named IRECA to denote Im-

proved REsistance to CAvitation

The currently

commercially available welding consumables

that can be depositedon stainless and carbon steel

substrates are 1.2 mm (0.045 in.) and 1.6 mm

(1/16 in.) gas-metal arc welding wires and 3.2 mm

(1/8 in.) and 4.0 mm (5/32 in.) shielded metal arc

welding electrodes. The name for these consu

mables isHydroloyHQ9 13,which is a tradename

of Thermodyne Stoody. Additional information

on cobalt-containing stainless steel hardfacing al

loys can befound inRef 16to 23 and in the article

Tribological Properties in this Volume.

SELF R ZING MATERIAL

CopperClad StaInlessSteel

sociated with a faster initial martensitic transfor

mation, Y ~ a , of the less stable austenite phase,

as shown in Fig. 12. The higher the cavitation re

sistance, the less the plastic deformation required

to transform the fcc {-austenitic phase to the bee

a'-martensitic phase. For the cobalt-containing

steel, only 5 elongation is required to produce

some 25 transformation,

Figure I3 presents the actual hardness values

reached by the material surface exposed to cavita

tion. Almost no cavitation-deformation harden

ing could be detected for 1020 carbon steel,

whereas substantial strain hardening was meas

ured for austenitic stainless steels and the cobalt

base alloy, in good correlation with their ultimate

tensile strength and cavitation resistance. The

hardness values measured on the surfaces ex

posed to cavitation also correspond quite well to

values equivalent to their ultimate strength.

It

ap

pears to be not somuch the initial hardness or the

strain energy (area under the stress-strain curve)

that controls cavitation resistance, but rather the

strain-hardening capability under cavitation ex

posure (Ref 18). Figure I3(b) shows that strain

hardening is restricted to a very thin surface layer

«

50 um), which is even thinner for the cobalt

containing alloys.

Cobalt-containing austenitic stainless steels

are about ten times more resistant to cavitation

erosion than the standard 300-series stainless

steels (Fig. 14). Although cobalt-containing

sta inless s tee ls may become less ducti le be

cause of their high work-hardening coefficient,

the ir duc ti li ty is good enough to be welded or

cast without cracking. The as-welded hardness

is around 25 HRC, with work-hardened materi

als reaching 50 HRC. With a tensile elongation

between 10 and 55 , the annealed yield

s trength is around 350 MPa, and the ul timate

strength can exceed 1000

MP a

(145 ksi). The

corrosion resistance is fair, comparable to that

of type 301 stainless steel, being somewhat lim

ited by the higher carboncontent. Nevertheless,

301

30B

1020

Fe-1BCr-l0Co

A_

Stellite-21

Fe-18Cr-l0Co

A

Stellite-21

d d

50 100 150 200 250

Cavitation time, min

Cavitat ion-induced surface (a) and cross

section (b) hardening in various materials.

{ 3 B

o

ID - - -

1020 (ferrite)

o

100 _ _ _ _ _

-50

400

500

0

400

~

>

I

c

E

«l

s

§

200

: 300

0

~ - - :

200

l : l

__

== _o

- - - - - - - X J o - - - _ : > - - - - ~ ~ t

rce: Ref18


10/13


11/13

Stainless Steel Cladding and Weld Overlays /

Low-carbon steel

a

Low-carbon steel

Stainless steel

b

. 19

Illustrations of the corrosion barrier princi-

ple. a Solid carbon steel. b Carbon-steel

d stainless steel

be elements for boilers, scrubbers, and other

stems involved in the production of chemicals.

Another group of commonlyused noble metal

ad metals uses aluminum as a substrate. For ex

ple, in stainless-steel-clad aluminum truck

umpers Fig. 18 , the type 302 stainless steel

adding provides a bright corrosion-resistant

rface that also resists the mechanical damage

stone impingement encountered in service. The

luminum provides a substrate with a high

ratio.

Corrosion

Barrier Systems. The combina

n of twoormoremetals toform a corrosionbar

er system ismost widely used where perforation

used by corrosion must be avoided Fig. 19 .

carbon steel and stainless steel are suscepti

e to localized corrosion in chloride-containing

vironments and may perforate rapidly. When

eel is clad over the stainless steel layer, the cor

sion barrier mechanism prevents perforation.

calized corrosion of the stainless steel is pre

nted: The stainless steel is protected galvani

lly by the sacrificial corrosion of the steel inthe

tal laminate. Therefore, only a thin pore-free

er is required.

The example shown in Fig. 20 of carbon steel

ad to type 304 stainless steel demonstrates how

is combination prevents perforation in seawa

r, while solid type 304 stainless steel does not.

is material can be used for tubing and for wire

applications requiring strength and corrosion

a

Carbon steel cannot be used when increased

general corrosion resistance of the outer cladding

is required. A low-grade stainless steel with good

resistance to uniform corrosion but poor resis

tance to localized corrosion can be selected.

seawater service, type 304 stainless steel that is

clad to a thin layer ofHastelloy C-276 provides a

substitute for solid Hastelloy C-276. this corro

sion barrier system, localized corrosion of the

type 304 stainless steel is arrested at the C-276 al

loy interface.

The most widely used clad metal corrosion

barrier material is copper-clad stainless steel

Cu 430 SS/Cu for telephone and fiber optic ca

ble shielding. In environments in which the corro

sion rate of copper is high, such as acidic or

sulfide-containing soils, the stainless steel acts as

a corrosion barrier and thus prevents perforation,

while the inner copper layer maintains high elec

trical conductivity of the shield.

Sacrificial metals, such as magnesium, zinc,

and aluminum, are in the active region of the gal

vanic series and areextensively used for corrosion

protection. The location of the sacrificial metal in

the galvanic couple is an important consideration

in the design of a system. By cladding, the sacrifi

cial metal may be located precisely for efficient

cathode protection, as described for the stainless

steel-clad aluminum automotive trim shown in

Fig. 2.

Transitional Metal Systems. A clad transi

tionalmetal system provides an interface between

two incompatible metals. It not only reduces gal

vanic corrosion where diss imilar metals are

joined, but also allows welding techniques to be

used when direct joining is not possible.

Complex

Multilayer Systems.

many

cases, materials are exposed to dual environ

ments; that is, one side is exposed to one corrosive

medium, and the other side is exposed to a differ

ent one. A single material may not be able tomeet

this requirement, or a critical material may be re

quired in large quantity.

In small battery cans and caps, copper-clad,

stainless-steel-clad nickel Cu/SS/Ni is used

where the external nickel layer provides atmos

pheric-corrosion resistance and lowcontact resis

tance. The copper layer on the inside provides the

electrode contact surface as well as compatible

b

cell chemistry. The stainless steel layer provides

strength and resistance to perforation corrosion.

Welding Austenitic-Stainless-Clad

Carbon

or

Low-Alloy Steels Ref 26

Topreserve its desirable properties, stainless

clad plate can be welded by either of the two fol

lowing methods, depending on plate thickness

and service conditions:

• The unclad sides of the plate sections are bev

eled and welded with carbon or low-alloy steel

fillermetal. A portion of the stainless steel clad

ding is removed from the back of the joint, and

stainless steel filler metal is deposited.

The entire thickness of the stainless-clad plate

is welded with stainless steel filler metal.

When the nonstainless portion of the plate is com

paratively thick,as in most pressure vessel applica

tions, it is more economical to use the first method.

When the nonstainless portion of the plate is thin,

the second method is often preferred.When weld

ing components for applications involvingelevated

or cyclic temperatures, thedifferencesin thecoeffi

cientsof thermalexpansionof thebaseplateand the

weld shouldbe taken into consideration.

All stainless steel deposits on carbon steel

should be made with filler metal of sufficiently

high alloy content to ensure that normal amounts

of dilution by carbon steel will not result in a brit

tle weld. Ingeneral, filler metals of type 308, 316,

or 347 should not be deposited directly on carbon

or low-alloy steel. Deposits of type 309, 309L,

309Cb, 309Mo, 310, or 312 are usually accept

able, although type 310 is fully austenitic and is

susceptible to hot cracking when there is high re

straint in a welded joint. Thus, welds made with

type 310 filler metal should be carefully in

spected. Weldsmade with types 309 and 312 filler

metals are partially ferritic and therefore are

highly resistant to hot cracking.

The procedure most commonly used for mak

ing welded joints in stainless-clad carbon or low

alloy steel plate is shown inFig. 21. Stainless steel

filler metal is deposited only in that portion ofthe

weld where the stainless steel cladding has been

removed, and carbon or low-alloy steel filler met

al is used for the remainder. The backgouged por-

e

g. 20

Photomicrographs of cross sections of materials after 18 months of immersion in seawater at Duxbury, MA. a Low-carbon steel. b Type304 stainless steel. c Carbon

steel-clad type 304 stainless steel


12/13

8

Introduction to

Stainless Steels

b

Fit ted up

b Fit ted up

d Surfaced fromsid

d Inlaid and welded

c

Weldedfromside A

d

Welded fromside B

Butt

j o i n t

a Faces beveled

c

Welded fromside A

d

Welded fromside B

Cornerjoint -

a

Faces beveled

ig

23

Procedures for welding V-groove butt a

corner joints instainless-clad carbon or lo

alloy steel plate, using stainless steel fillermetal exclusive

The clad plates are beveled and fitted up a and b, butt a

cornerjoints , The rootof the weld iscleaned and gouged,

necessary, before depositing stainless weld metal from t

stainless steel side d, butt and cornerjoints ,

b

Fitted up

b Filled up

q

--e- ..

3

< ..

a min

a Faces beveled

and claddingstripped

c

Weldedfromside A,

weldground flushan side B

~ e t h a d

c

el e fromside A,

weldgroundflushon side B

~ e t h o d

~

ig22

Alternative procedures for joining stainless-clad carbon and low-alloy steel plate involving different tec

niques for replacing portions ofthe stainless steelcladdingremoved before welding the carbon or low-all

steel side. The joint isprepared by beveling side A and removing a portion of the stainless steel cladding from side B t

minimum width of9.5 mm

in. from each side ofthe joint, and the joint isfitted up inposition for welding. Use ofa ro

gap not shown ispermissible a and b, methods Aand B .Carbon steel fillermetal isdeposited, and the root ofthe weld

ground flush with the underside ofthe carbon steel plate c, methods Aand B .The area fromwhich cladding was remov

issurfaced with at least two layersof stainless steel weld metal d, method A ,or an inlay ofwrought stainless steel can

welded inplace d,method B .

filler metal is limited to replacement of the clad

ding thatwas removed prior tomaking the carbon

or low-alloy steel weld. This method is more ex

pensive than the method described in Fig. 21 be

cause of the cost of removing a larger portion of

the cladding and depositing more stainless steel

filler metal. Because there is no danger of alloy

contamination from the cladding layer, method A

in Fig. 22 permits the use of faster welding proc

esses, such as submerged arc welding, in deposit

ing the carbon steel weld.

In depositing thestainless steel weld metal, the

first layer must be sufficiently high in alloy con

tent to avoid cracking as a result of normal dilu

tion by the carbon steel base metal. A stringer

bead technique should be employed; penetration

must be held to a minimum.

the proper weld

metal composition is not achieved after the sec

ond layer has been deposited, a portion of the sec

ond layer should be ground off and additional

filler metal should be deposited to obtain the de

sired composition. Figure 22 d of method B

shows an alternative procedure in which the ex

posed carbon steel weld on side B is covered by

welding an inlay of wrought stainless steel to the

edges of the cladding.

The most common method of joining stain

less-steel-clad carbon or low-alloy steel plate

with a weld that consists entirely of stainless steel

is shown in Fig. 23. This method is most

fre

quently used forjoining thin sections of stainless

clad plate. The same basic welding procedure is

followed for both the butt and comerjoints shown

in Fig. 23. After the plate has been beveled and fit

ted up for welding, a stainless steel weld is depos

ited from the carbon steel side, using a fillermetal

sufficiently high in alloy content to minimize dif

ficulties such as cracking resulting from weld

dilution and joint restraint. Types 309 and 312

filler metals are suitable for this application.

SIDE A

d

Gougedfrom side B

f Protective plate weldedan

el metal carbon steel

~

? i ; ~ 3 1 1 f j ~ ~ C l a d d i n g SluE B

b

Fitted up

e Welded fromside B

ig

21

Procedure for welding stainless-clad carbon

and low-alloy steel, using stainless steel filler

metal only in portion of joint from which cladding was re

moved. a and b The clad plates are machined for a tight

f itup, with the bot tom ofthe weld groove not less than 1.6

mm 1/16 in. above the stainless steel cladding. c Carbon

steel filler metal isdeposited from side A a low-hydrogen

fillermetal isused for the first pass , taking care not to pene

trate closer than 1.6 mm 1/16 in. to the cladding. d Stain

lesssteel cladding on side Bis backgouged untilsound carb

on steel weld metal isreached. e The backgouged groove

isfilled with stainless steel weld metal ina minimum oftwo

layers.

f

When required for severely corrosive service, a

protective strip ofstainless steel plate may be filletwelded to

the cladding to cover the weld zone.

tion of the stainless steel cladding should be filled

with a minimum of two layers of stainless steel

filler metal Fig. 2Ie ; an additional layer is rec

ommended if a high weld reinforcement at the

cladding surface can be tolerated.

the cladding isof type 304 stainless steel, the

first layer of stainless steel weld metal should be

of type 309 or 312. Subsequent layers of weld

metal can be oftype 308. If the cladding isof type

316, the first layer is deposited with type 309 Mo

filler metal and the subsequent layers with type

316.When the cladding isof type 304L or 347, the

welding proceduremust be carefully controlled to

obtain the desired weld metal composition in the

outer layers of the weld. Chemical analysis of

sample welds should be made before joining clad

plates intended for use under severely corrosive

conditions.

In some applications, anarrow protectiveplate

of wrought stainless steel of the same composi

tion as the cladding is welded over the completed

weld Fig. 21f to ensure uniformity of corrosive

resistance. The fillet welds joining the protective

plate to the cladding should becarefully inspected

after deposition. These welds, of course, are made

with stainless steel filler metal.

Figure 22 illustrates an alternative method

method A ofwelding cladplate, inwhich a carb

on or low-alloy steel weld joins the carbon steel

portion of the plate, and the use of stainless steel


13/13

After the stainless steel weld has been depos

d from the carbon steel side Fig. 23c), the root

the weld is cleaned by brushing, chipping, or

inding, as required, and one or more layers of

inless steel filler metal are deposited Fig. 23d).

e filler metalcompositionshouldcorrespond to

at normally employed to weld the type of stain

steel used for cladding. Ifthe cladding is type

4, the final layer

of

weld metal should be type

the cladding is type 316, it may be neces

y to backgouge before deposition of the final

ld metal layers to ensure that the proper weld

tion is obtainedat the surfaceof the

The edi tor thanks Howard Ocken, Project

nager, Electric Power Research Institute

PRI) and Raynald Simoneau, Vice-Presidence

chnologie, Institut de Recherche d Hydro

IREQ), for their significant contr ibu

ns to this article. Mr. Ocken supplied material

n cobalt-free

NOREM

alloys developed at

I. Mr. Simoneau contributed material on co

IRECA alloys that he developed

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