2005 stainless steels

7/24/2019 2005 Stainless Steels

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Stainless steels

Iron-Chromium, iron-chromium-Nickel

alloys but may contain other alloying

elements that alter microstructure and or

properties

Minimum level of chromium - 11%

Stainless steel discovered by Brarely/

Sheffield in 11!


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"pplications

#o$er %eneration

#etrochemical Industries

Nuclear applications

&omestic applications

#ulp' paper industries

(e)tile industries

&airy' food processing

industries


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Applications

Chemical, po$er ' *ngg - !+

ood Industries - 1.

(ransport - 1.

Consumer goods '

&omestic application - .


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%ood corrosion resistance

%ood o)idation resistance

0igh Stress rupture properties

*rosion resistance

%ood notch toughness properties -

"ustss Cryogenic service

resistance to brittle fracture

#roperties


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Wrought Alloys, Pipes & tubes, Casting

Major Alloying

elements

Prouct forms

Cr, !i, C, Mn, "i, Cb, !,

#i, Mo, Cu, "&P

Physical properties

Properties M"" $"" A""

ensity gcc '() '() '()

Melt pt( *C 1+)-1. 1+)-1. 1+)-1.

#hermal e/apn( 11(0-1(1 11(-1(1 1'(-12(

#her(Con( )(' +(+-0(. 1)('-()


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erritic stainless steel

2artensitic stainless steels

"ustenitic stainless steels

&upel) stainless steels

lassification


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erritic

2artensitic

"ustenitic

&uple)

lassification


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Classification

A3"3 classification

"eries Alloy type

44

.44

+44

Cr,!i

Cr

A3"3 classification

5Castings6

7!" classification

Wrought- " Cast- 8

9:-44

Cr,!i,Mn

94-44C4-44


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2a)imum service temperature in air

for stainless steels

%rade 2a)m(emp 3C4 51,5.16

!51 .+5

!5,!5+ .75

!5. !

!5 .5

!15,!!5 15!5

!18,!17,!1,!+7 .75


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Austenitic stainless steels

%rade C Cr Ni Spladdition

51 516 18-1. !6-66 N 56, 2n 66-76

!5B 516 17-1 .-15 Si -!

!5!Se 516 17-1 .-15 Se 516 - 55

!5+0 55+-515 1.-5 .-156

!5+9 55! 1.-5 .-1

!5+ 9N 55! 1.-5 .-1 N 515 - 518

!5 Cu 55. 17-1 .-15 Cu !-+

!56 51 17-1 156-1!

!5. 55. 1-1 15-1

!5 55 -+ 1-16


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!5S 55. -+ 1-16

!15 56 +-8 1-

!15 S 55. +-8 1-

!1+ 56 !-8 1- Si 16-!5

!18 55. 18-1. 15-1+ 2o -!

!18 55. 18-1. 15-1+ # 5,S 51

!180 55+-515 18-1. 15-1+ 2o -!

!189 55! 18-1. 15-1+ 2o-!

!189N55! 18-1. 15-1+ N 51-518


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!17 55. 1.--5 11-16 2o !-+

!1 55. 17-1 -1 (i - 6:C

!+70 55+-515 17-1 -1! Nb .)C - 15

!!5 55. 517-5 !+-!7

!+. 55+-515 17-1 -1! ;

;Co 5, 15)C, 15 Nb,51 (a


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(ypical mechanical properties of

"ustStsteel

%rade (S32pa4


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ifficulties in ;eling "tainless steel

3ntergranular corrosion

"igma embrittlement

"tress corrosion crac


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- Cracuus temp(

- $ully Austenitic ;el metal are more susceptible

- 9ot crac


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", P, "i, ?, form li>ui films along B

Belo; the solius temperature of the alloy, the metalhas not evelope strength

#he contraction stresses cause tearing along

grain bounaries


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55+

1 1+ 18 1. 515

Crack

No Crack

55.

51

5.Cr e=/ Ni e=

S>#3,4


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?ole of &elta ferrite

- Cracking tendency decreases as the ferrite

increases

- Controlled level of ferrite 3+-15 4 is

beneficial

- errite has higher solubility for impurities

- #rovides additional boundary area to act as

sink for impurities

- errite strengthens grain boundary

- 9o$er thermal e)pansion coefficient


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elta ferrite

$errite level epens on impurity level anservice conitions

$errite reuces corrosion resistance

$or urea service, nil or very lo; ferrite isre>uire

$or e>uipments liuirement, nil ferrite is re>uire

9igh temperature service, sigma embrittlement

+-)% controlle ferrite level

or cryogenic service @


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Austenite

Aust($errite

$errite

AM

MartensiteM$

ACMC$

Cr e>uivalentDCr1("iMo(!b

1 1 . .

1

1

.

.

1%$

"chaeffler iagram

!i e >

u iv a le nt D

!iM

n&1. , C

$CM


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3ntergranular corrosion 53C6

- &uring $elding, 0"A e)periences a $ide temprange

?egions heated to 865 C n slo$ cooling Chromium carbideprecipitation at grain boundary takes place 3sensitiation 4

- 9ess than 865 C, time is short

- Chromium combines $ith C to form carbide 3 Cr! C84

- Carbides are rich in chromium- appro) -+ times the

nominal level

- Cr depletion in adDacent regions of carbide

- Corrosion attack at boundaries- Called as $eld decay $hen attack occurs in 0"A of

$eldment


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I%C

%rain boundary

Chromium carbide

Chromium depletion one

Nominal chromium


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3ntergranular corrosion 53C6

- "ustStsteel subDected to +.5-.16 C, susceptible to I%C

- Cr depletion $hen carbide forms $idth 1 Em

- strains at the carbide matri) interface

Chromium diffusion is slo$er as compared to FC- preferred sites for carbide formation

&elta ferrite - aust %rain boundary

"ust %rain boundary


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(o avoid I%C

?educe carbon level 3 55+ ma)4

(i ' Nb addition- appro) 8-. : C

(i,Nb has higher affinity to$ards C

(iC, NbC formed instead of Cr carbide

Solution anneal

Carbides dissolved in solution

?apid cool to retain the condition

limitatation- &istortion

&ifficult for large ' fully processed component


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(o avoid I%C

9o$ carbon grades

strength is lo$

Nitrogen strengthened aust ststeel

C- 55!, N-558-515

!5+ N% ' !18 N% 3 Nuclear grade4

BG? application - .5 C

?adiation cause Cr depletion and enrichment Ni level

called Irradiation assisted SCC


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:nife line corrosion

?ccurs in stabilise graes of Aust(st(steel

;hen the 9AE e/periences temp( 1. C

#iC, !bC are reissolve in solution

?n @api cooling no stablise carbies are

forme

uring annealing F - 0 C, Cr carbies

are forme(

Corrosion in narro; regions ;here !bC

issolve(

Stablise "nnaling can be done - .+6-55 C/6h


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Stress corrosion cracking 3SCC4

ailure of metal due to the combined effects of corrosion

and stress

Causes

Corrosive environment

Stress - "pplied, residual or both

2echanism

&estruction of passive film at localised region

2icro anode formation

Stress concentration at these points

ormation of primary cracks

Crack propagation - Corrosion and stress interaction


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actors influencing SCC

Stress - "pplied, residual

- 2inimum stress for propagation

- Compressive stresses do not cause

SCC

Corrosive medium - Chlorides- Caustic solution

- 0ydrogen sulphide

(emperature - Susceptibility increases $ith

increase in temperature

Chemical composition- Nickel alloyed reduces SCC

3 !6-+5 Ni fully prevents SCC4


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actors influencing SCC

- Si ' 2o increases ?esistance to SCC

- %rain boundary carbides- Increases SCC

(o prevent SCC

- "void crevices

- ?educe residual stress - #G0( re=d

- Compressive stresses can be induced by

#eening

- Ghen conditions cannot be changed, material has

to be changed


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- #ure metals generally immune to SCC

"lloying a metal $ith more noble metal to forma homogeneous solid solution susceptible to

SCC

Characteristics of SCC

Brittle fracture

(ranscrystalline or inter crystalline

&iscontinuous process


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Gelding of "ust stainless steels

"ustenitic stainless steels $eldability is good

*)cept o)y acetelyne, all $elding process can be

adopted

%enerally matching $eld consumables are available

iller metal selection ' procedure depends on

Ghether ferrite is acceptable in $eld

If ferrite is acceptable, range of filler and procedure

are $ide

If ferrite is not acceptable to $eld, then the procedure

is restricted


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S2"G electrodes ferrite level - 5 - 5 N

Solid rods - ! - . N

*)))-16 electrodes better resistant to hot cracking

Conve) beads are better than concave

*)))16 provides conve) $hile *)))-18 that of nearly

flat profile

ully austenitic ststeel $elding

Impurities H S,# shall be lo$"void high heat input


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Ese lo$er dia electrode

use lo$er range of current

"void narro$ deep $eld puddle

"void $eld pool $ith sharp tail

9o$ heat input

Short arc to be maintained during $elding to avoid N

pick up

No preheat /#ost heat re=uiredInter-pass temperature ma)imum 165 C

cleaning tools such as $ire brushes and chipping

hammers shall be of stainless steels


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iller metal for "ustenitic stainless steels

2aterial S2"G %("G, %2"G

51,5,56 *+5 *?+5

!51,!5,!5+,!56,!5. *!5. *? !5+9

!5+9,C! *!5.9 *? !5.9!5+0 *!5.0 *?!5.0

!5,!5S,!50,C05 *!5 *?!5

!5Cb, !50 Cb *!5Cb

!15,!15S,!150,C5 *!15 *? !15

!15Cb *!15 Cb

!18,C .2 *!18 *? !18



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2aterial S2"G %("G, %2"G

!189,C!2 *!189 *? !189

!180 *!180 *? !180

!17,C%.2 *!17 *? !17

!1,!10,!+7,!+70,!+. *!+7 *?!+7

!5, C2 72 *!5 *?!5

!!5 *!!5 *?!!5

C.,C5 *!5. *?!5.

C%1,C05 *!5 *? !5

C.C *!+7 *? !1

CN!2 *!.6


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Chemical composition of "ustiller metal%rade C Cr Ni Spl

*5 558 5-+ -1 +-72n, 16-!5 2o*1 558 1-1 6-7 .-152n

*+5 558 17-1 +-8 15-1!2n

*!57 55+-51+ 1.-1 -15 56-162o, !- +72n

*!5. 55. 1.-1 -11

*!5.0 55+-55. 1.-1 -11

*!5.9 55+ 1.-1 -11

*!5.2o 55. 1.-1 -1 -! 2o

*!+7 55. 1.-1 -11 .C-1 Cb

*!5 516 -6 1-1+

*!5Cb 51 -6 1-1+ 57-15Cb

*!15 55.-55 6-. 5-


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Chemical composition of austiller metal%rade C Cr Ni Spl

*!15Cb 51 6-. 5- 57-1*!150 5!6-5+6 6-. 5-

*!1 516 .-! .-15

*!18 55. 17-5 11-1+ -! 2o

*!1. 55. 17-5 11-1+ 8:C- Cb -15

*!17 55. 1.-1 1-1+ !-+ 2o

*!5 557 1-1 !-!8 .:C- 1Cb, !-+ Cu

*!59? 55! 1-1 !-!8

*!!5 51.-56 1+-17 !!-!7

*!+ 51! 1.-1 .-15 5!6-5862o, 576Cb

*!.! 55! 8- !5-!! !-+ 2o, 58-16Cu

*!.6 55! 1-1 +-8 +-6 2o, 1- Cu


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#ost$eld heat treatment

- Selection of Stress relief heattreatment depends on

- &esign and operating condition

- Specific materials used

- abrication procedures involved


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#ost$eld heat treatment

"pplication 9o$ C grade (hermal treatment

Stabilised Enstabilised

Severe SCC ",B B," -

2oderate SCC ",B,C B,",C C -

2ild SCC ",B,C,*, B,",C ,*, C,

No SCC ----------not re=d -----

I%C ",C ",C,B C

Severe orming ",C ",C C

"- "nneal 1585-115C, slo$ cool *- S? +.5-865C,slo$ coolB- S? 55C, slo$ cool - S? @+.5C, slo$ cool

C- "nneal 1586-115, =uenching

&- S? 55C, =uenching


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*ssentially iron chromium alloysNi is usually less than 1

(i, "l,Cb ' Se added for spl properties

Service upto 65 JC

BCC structure

2oderate corrosion resistance

9o$ ductility' toughness

?esistance to SCC good than "ES(SS

Can not be hardened by 0(

Eseful In automotive e)haust system

erritic stainless steels


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Chemical compositions of typical ferritic stainless steels

rae C Mn "i !i Cr ?thers

+ 0.08 1.00 1.00 - 11.5-14.5 0.10-0.30 Al

+2 0.08 1.00 1.00 - 10.5-11.75 Ti; 6XC min

+. 0.12 1.00 1.00 - 16.0-18.0 -

+.#i 0.10 1.00 1.00 0.75 16.0-19.5 Ti; 5XC-0.75

+. 0.10 1.00 1.00 0.75 16.0-19.5 Ti; 5XC-0.75

+.+ 0.121.001.00- 16.0-19.5 0.75-1.25 Mo

+.0 0.121.001.00- 16.0-19.5 0.75-1.25 Mo

Nb 5 X C


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Chemical compositions of typical ferritic stainless steels

rae C Mn "i !i Cr ?thers

++ 0.20 1.00 1.00 - 16.0-23.0 Ti 0.20+4(C+N)

++0 0.20 1.50 1.00 - 23.0-27.0 Ti 0.25

0-1 0.006 0.75 0.75 0.50 25.0-27.0 0.75-1.50 Mo. 0.20

-1.0Ti 0.04 N,0.2 Cu

2-+- (1 ( (. (-( )(-.( .(-+(Mo,(1 Cu

CB . (. 1( 1( ( 1)(-1( Casting

CC ( 1(-1( +( 0(-.( Casting


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Martensite

uctility #oughness

rain coarsening

3mprove

@euce

PW9#

@euce

=o; interstials

!l"#bili$%


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9o$ interstials 3ntermeiate

purity

1-) ppm

7ltra high purity

5C!6G 1 ppm


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+' Hmbrittlement

- - "ging of e-Cr alloys at +55 -665 C for e)tendedperiods

causes formation of Cr rich precipitates -

- 0ard brittle inter metallic compound

- 0ardness and strength increases

- &rastic reduction in ductility and toughness

- Impact transition temperature is increased

- "lloying elements Cr,2o, increases embrittlement

- Co, "l' Ni reduces embrittlment

- Corrosion resistance decreased


48/76

- "ging of e-Cr alloys at +55 -665 C for e)tendedperiods causes formation of Cr rich precipitates

- 0ard brittle inter metallic compound

- 0ardness and strength increases

- &rastic reduction in ductility and toughness

- Impact transition temperature is increased

- "lloying elements Cr,2o, increases embrittlement

- Co, "l' Ni reduces embrittlment

+76 *mbrittlement


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Weling of $""

Matching consumable

uctility & toughness lo;

PW9# re>uire

PW9#- ' - ) C cool

rapily throI -+C

H+2Cb H+.#3 H+. Cb


50/76

Weling of $""

%("G

CE??*N(

(ype-&C

#olarity-*lectrode negative

*lectrode-(ungsten (horia

-(apered tip

%as shielding-

"r ,0e ,"r> 0e

0igh purity gas

(railing gas used for high speed

process


51/76

Weling of $""

%("G

Back gas shielding

0igh =uality gas for full penetration

Nitrogen should not be used

Inert gas used atleast for t$o layers

(railing gas shielding

used for high speed automatic process

"rc stability

reduced by o)idation of electrode tip


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Weling of $""

%("G

#rocedure to enhance $eld =uality

%roup III "lloys

(horough degreasing

use clean gloves

keep torch at right angles

$eaving not permitted

prepurge the torch before $elding

gradual increase and decrease of current $hile

initiating and e)tinguishing the arc


53/76

Weling of $""

%2"G

CE??*N( (ype-dc,#olarity-electrode #ositive

2ethods of metal transfer

Spray transfer-high heat input - e)cessive grain gro$th

%lobular transfer-lo$ heat input - minimied spatter

short circuit transfer-lo$est heat input - lack of fusion

(o control grain gro$th

use austenitic filler metal

0igh travel speed

lo$er interpass temperature

use heat sinks


54/76

Weling of $""

%2"G

Shielding gas

"r > or C

pure "r -results in arc instability

for group III alloys o)idising gases reduces toughness

and ductility

(o solve "rc $andering problem

add o)idiing elements into the inert gas


55/76

Weling of $""

C"G

S0I*9&IN%- either supplementary gas shielding or

self shielding consumable

%roup III alloys-difficulty of maintaining alloy purity

$eld deposits not clean

use $hen

application is less critical

filler used is austenitic

mode of operation -spray arc-high heat input

-problem of grain gro$th

Weling of $""


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Weling of $""

S2"G

Current K type dc, polarity-electrode positive

*lectrodeK

choice of electrode-0igh Cr austenite grade to

high nickel alloy grade

Ese dissimilar $elding electrode $hen post$eld

annealing is not practical

for group III alloys covered electrodes for matchingcomposition is not available

Improper storage -pick up of moisture -$eld porosity,0IC

Weling of $""


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Weling of $""

S2"G

$ith matching filler - lo$er toughness0igh nickel alloy $eld metal - sluggish,shallo$ penetration

0eat input K

$hen "SS filler is used provide sufficient heatto fuse SS $eld metal and to avoid lack of fusion

%eneral techni=ues

Geld Doint surfaces to be cleaned using solvents

"rc should be struck in the bevel rather than on base metal

short arc shall be maintained *)cessive crater cracks

must be ground to sound $eld metal


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Weling of M""


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Chemical compositions of martensitic stainless steels

%rade C 2n Si Cr Ni others

+5! 516 155 565 116-1!5

+15 516 155 155 116-1!5

+1+ 516 155 565 116-1!5 16-65

+18 516 16 565 15-1+5 S-516 mi

+5 516 min 155 15-1+5

+ 55-56 576 115-1!5

+!1 55 155 155 165-175 16-65

++5" 585-576 165-175 16-65 5762o

++5B 576-56 C ++5 C K 56-15 C

Ch i l iti f t iti t i l


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Chemical compositions of martensitic stainless

steels

%rade C Cr Ni others

C"8N2 558 116-1+5 !6-+6 5+5 -15 2o

C"16 516 116-1+5 15 565 2o

C"+5 5+5 116-1+5 15 56 25

Cr-317:C4 @ 16 2ss

Cr-317:C4 L 16 SS


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Geldingof Martensitic stainless steels

2SS- highly sensitive to 0ydrogeninduced cracking

Causes

0igh strength and inade=uate

toughness, ductility

0ydrogen

?estraint

Weling of martensitic stainless steels


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Weling of martensitic stainless steels

Ese e)tra lo$ hydrogen $elding

Ese lo$ heat input

2aintain preheat , #ost heat and

interpass temp control

Post ;el 9eat treatment for Martensitic


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+5!,+15,+18 865-785 JC .!5-..6

+1+ 865-7!5 Not recommended

+5 8.5-785 .!5-..6

+!1 85-755 Not recommended

++5",B,C8.5-785 .65-55

C"8N2 855-85 7.5-.16

C"16,C"+5 85-865 .65-55

; urnace cool up to 855 JC and then air cool

Post ;el 9eat treatment for Martensitic

stainless steels

#ype "ubcritical PW9# $ull annealing J

KC

(ypical preheat and post $eld heat treatment re=uirements of


64/76

(ypical preheat and post $eld heat treatment re=uirements of

martensitic stainless steelss

Carbon #reheat 3C4 #G0(@556 15 ptional

556-516 55 ?ecommended

L556 !16 Necessary


65/76

Thank you


66/76

&uple) stainless steels

-($o phase alloys

- "ppro)imately e=ual amounts of ferrite and austenite

- Carbon ma) 55!

- Better $eldability

- 0igher strength compared to "ustss

- Better SCC resistance than "ust SS

- Better ductility and toughness than SS


67/76

Composition of &uple) stainless steels

%rade Cr Ni N 2o(s


68/76

Gelding of &SS

- #erformance significantly affected by $elding

- No preheat re=uired

- No #G0( re=uired

- I #G0( is re=uired, then heating to 1565 C and

cooled rapidly

- Interpass temp 165 C for 56 steel and 75 C for

657 steel


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.55

1555

155

1+55

15 16

"

>

"

9

9>"

9>">9>

(emp C

Ni

Si b ittl t


70/76

Sigma embrittlemnt

- 0eating in 6+5-1555 C results in formation of

sigma

- Sigma is mainly e, Cr compound $ith otherelements like 2o

- sigma formation is sluggish

- orms congruently from ferrite at .16 C

- Cold $ork accelerates Sigma


71/76

Influence of sigma

- "mount of sigma- &istribution

- isolated colonies - little effect

- Continuous net$ork - brittleness

- &elta ferrite promotes sigma

- 2inor effect on tensile and hardness

- Notch sensitivity increased

- Impairs corrosion resistance in highly

o)idising *nvt

# i it ti h d i t i l t l


72/76

#recipitation hardening stainless steels

Properties

9igh strength better than Aust( "t(steel

Corrosion resistance comparable to A3"3 .1, .+'

corrosion resistance -


73/76

0eating above .18C ferrite transforms to "ustenite

martensite forms on cooling

0igh chromium SS - does not transform to 2artensite

Carbide precicptitation

%rain gro$th above 5 C

(ransition temperature - above ?oom temp

Carry out #G0( to improve the toughness ' ductility


74/76

&issimilar Gelding

#roblems of dissimilar $elding

Incompatibility of materials on either side

ptimiation of 0eat treatment

Selection of filler metal

&ifferences in thermal e)pansion coefficient

"ustenitic stainless steels castings


75/76

"ustenitic stainless steels castings

%rade $rought C Cr Ni

C"16 +15 2 516 11-1+ 1 562o

C"+5 +5 2 5+5 11-1+ 1 56 2o

CB!5 +!1,++ >C 5!5 1.- -

Not re=d

Hffect of elta ferrite on tensile properties


76/76

Hffect of elta ferrite on tensile properties

$errite 5%6 #" J5MPa6 JL"5MPa6 %H J %@AJ

. +0..2 101+ 0+ 0+0.

1 +2). .+12 01+. '.02

)++' 201). ..0 )+'

+1 0.++)) ..11)) +.. +'+2

J @oom temp. KC

2005 stainless steels

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