Stainless Steel cladding and Weld Overlays (2).pdf
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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
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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
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110 Introduction to Stainless Steels
ig 5
Commercially availableexplosion-cladmetalcombinations
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Carbon steels
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Alloy steels
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Stainless steels
•
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Titanium
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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
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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
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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
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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
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/ 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-
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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
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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
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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
-
8/9/2019 Stainless Steel cladding and Weld Overlays (2).pdf
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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