Ferrite Content

8/12/2019 Ferrite Content

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WELDING RESEARCH

SUPPLEMENT TO THE WELDING IOURNAL. FEBRUARY, 1982

Sp o n s o r e d b y t h e A m e r i c a n We l d i n g So c i e t y a n d t h e We l d i n g Re s e a r c h Co u n c i l j ^ j ) []

Effects of Ferrite Content in AusteniticStainless Steel Welds

The elevated-temperature mechanical properties of weldmetal with a wide delta ferrite range are determined

following their deposition using E308-16 covered electrodes

BY D. HAUSER AND ). A. VANECHO

ABSTRACT. The effects of delta ferritelevel on tensile and creep-rupture behavior of E308-16 shielded metal-arc stainlesss teel weld metal were determined. Theall-weld-metal deposits had measureddelta fer rite levels of 2, 6, 10, and 16 FN.Most of the creep-rupture tes ts wereconducted at 1000 and 1200F so thatthe results could be compared with prior

results of tests conducted at 1100F. Thedata obtained included initial and finalelongation, rupture time, reduction ofarea, minimum creep rate, time to attain0.5, 1.0, 2, 5, and 10% creep strain, andthe strain and time to the initiation of thirdstage creep.

The results of the creep-rupture testsinclude the fo l lowing:

The 2 FN and 6 FN as-depositedweld metals have similar stress-ruptureproperties at all three test temperatures.

A t 1000F, there is a convergenceof the creep-rupture curves resulting in

almost a co m mo n strength level at aboutthe 1000 to 3000 hour (h) time period forall four as-deposited weld metals.

At 120 0F, the re is a dive rgen ce o fthe creep-rupture curves producing awidening of strength level among thefour as-deposited weld metals, with the 6

Table 1 Metric Conversions

80F = 27C = 300 K600F = 315C = 588 K1000F = 538C = 811 K

1100F = 593C = 866 K1200F = 649 C = 922 K1950F = 1066C = 1339 KMPa = ksi/6.9N = lbf/4.5

FN material having the highest strengthand the 16 FN material having the loweststrength.

Solution annea ling (1950 F/2 h,water-quenched) produces no change inthe short time (about 100 h) creep-rupture strength of the 6 FN material at1100 CF and reduces the 1000 h strengthlevel from about 34 to 30 ksi. Solution

annealing the 16 FN material results inessentially no change in creep-rupturestrength at either short or long times.

Based on m inimum creep rate data, thefol lowing observat ions were made:

The 2 FN w el d metal has the highestcreep strength at all three test te mp eratures.

At 1100 and 1200F, the creepstrength of the 6 FN weld metal is nearlyequal that of the 2 FN weld metal.

At 1200 F and at lo w cre ep rates at1100F, the 16 FN weld metal has thelowest creep strength. At 1000F and at

high cree p rates at 1100F, the 10 FNweld metal tends to have the lowestcreep s t rength .

Solution annealing lowers the creepstrength of the 2 FN weld metal at1100F. Similar treatment of the 16 FNweld metal produces essentially nochange.

Prior exp osu re for 2500 h at 1100Fproduces little change in the 2 FN and 6FN weld metals and slightly increases thecreep strength of the 10 FN and 16 FNweld metals.

The results of the short-time tensiletests indicate that:

Solution annealing the 6 FN weldmetal reduced the yield strength byabout 50% at 80 and 1100F and 60% at600F, when compared with the as-deposited condition. Solution annealing

the 16 FN weld metal reduced its yieldstreng th by a bou t 30% at 80 F, 45% at60 0CF, and 40% at 1100F.

The ultimate strength was only mildly affected by solution annealing. It wasreduce d by approxim ately 10% at 80 and600F and essentially unch ang ed at1100F.

The ductility of bo th the 6 FN and 16FN we ld m etals was increased significantly by solution annealing. The elongationvalues of th e 6 FN we ld metal increasedby about 35-40% and of the 16 FN weldmetal by about 20-30% at the three testtempe ratures (80, 600, and 1100F).Reduction in area values were increasedto a lesser extent ranging from about 25%at 600F to no change at 80F for the 16FN weld metal. For the 6 FN weld metal,the increase ranged from about 10 to20%.

In general, the yield and ultimatestrengths of all four weld metals at 80 and

1100F are about 5 to 10% lower in thelongitudinal direction than in the transverse direction. The ductility, as evidenced by the elongation and reductionin area values, is 10 to 15% higher, on theaverage, for the longitudinal specimens.Elastic modulus values are lower in thelongitudinal direction by about 10 to20%, with the greatest difference at1100F.

Paper sponsored by the M etal PropertiesCouncil at the 62nd A WS Annual Meeting heldin Cleveland, Ohio, during April 5-10, 1981.

D. HAUSER is Senior Researcher and Croupleader, Fabrication and Quality Assurance Section, and I A. VANECHO is Staff Metallurgist,Physical Metallurgy Section, Battelle-Columbuslaboratories, Columbus, Ohio.

W ELD ING RESEARCH SUPPLEMENT I 37-s


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Metallographic examinations of failedcreep-rupture specimens indicated thatthe formation of sigma phase was promoted by h igher weld metal ferri te level ,test temp erature, and rupture t ime. Solution annealing prior to creep-rupture testing suppressed the formation of sigmaphase, even at high as-deposited ferritelevels.

In troduct ion

Ferrite in austenitic stainless steel weldmetal has been investigated extensively.The characteristics of its formation andmorphology and its influences onmechanical properties, weldability (solidification cracking tendencies), and corrosion resistance have been widelyreported (Ref. 1-8). A need was recognized, however, for the determinat ion ofthe elevated-temperature mechanicalproperties of weld metal deposited bythe shielded metal-arc process usingE308-16 electrodes and having a widerange of delta ferrite content. In performing this investigation, carefully controlledpreparation and metallurgical characterization of the weld metals was planned inorder to maximize understanding of theresults obtained and to permit comparisons with the results of other investigators.

The objective of this study was todeterm ine the effects of delta ferrite levelin E308-16 shielded metal-arc austeniticstainless steel weld metal on mechanicalproperties. This program was a continuation of a previous program, the results ofwhich were published (Ref. 9).

Referring to Table 1 for m etric c onve rsion data, the specific m echanical p roper

ties of interest were measured by thefollowing tests:

1. Single transverse tensile tests at 80,600, an d 1100F for ferrite levels of 6 a nd16 FN after solution annealing at 1950Ffor 2 hours (h).

2. Transverse tensile tests at 600 CF forferrite levels of 2, 6, 10, and 16 FN in theas-deposited condition.

3. Single transverse cre ep rup turetests at 1000 and 1200F to producefailure in 100 and 25 00 h. Specimens of allfour ferrite levels were tested in theas-deposited condition.

4. Duplicate transverse creep rupturetests at 1100F to produce failure in 100and 2500 h following solution annealingat 1950 CF for 2 h in argon. Only weldmetals having ferrite levels of 6 and 16 FNwere included in these tests.

5. Single transverse cre ep rup turetests at 1100F to p rodu ce failure in 100 hfollowing annealing at 1100F for2500 h.

In addition, representative samplesfrom the tes ted specimens were examined metallographicaliy. Emphasis wasplaced on specimens tested at 1200F todocument microstructural changes thatoccurred as a result of the differentthermal and strain histories.

Materials and Test Requirements

Table 2 gives the test requirements andthe particular specimens assigned toeach. In addition to the tests of as-deposited weld metal, tests were madeon solution-anneal (1950'F/2 h , W.Q. ,i.e., water-quenched), and exposed(1100F/2500 h) weld metals. Require

ments for both creep-rupture and short-time tensile tests are given in Table 2. Atotal of six tests were initially scheduledfor the 2 FN and 10 FN weld metals and11 tests for the 6 FN and 16 FN weldmetals. One additional creep-rupture testwas actually made on each material.These were short-time (10 h) tests at1000F made for the purpose of aiding in

the selection of stresses for the long-termtests.

We l d - M e t a l P r o p e r t yC h a r a c t e r i z a t i o n

Creep-Rupture Tests

Final creep-rupture test results aresummarized in Table 3. Data reportedinclude initial and final strain, rupturetime, reduction in area, minimum creeprate, time to attain 0.5, 1.0, 2, 5, and 10%creep strain, and initiation of third stagecreep (strain in percent and time in hours

or h).The rupture times for all tests are

presented versus the stress on log-logplots in Fig. 1 and the m inimum creeprates are plotted vs. the stress in Fig. 2.Results for all three temperatures (1000,1100, and 1200F) and all fer rite leve lsare given on the same plot in order toshow the strength relationships for allweld metals at all three temperatures.The creep-rupture data also were plottedas Larson-Miller (L-M) curves for all fourferrite levels.

An opt imum but d ifferent constantwas derived for each weld metal . However, it was desirable to have a constantcommon to all four weld metals, in orderto compare their rupture strengths. The

Table 2Test Requirements for E308 Weld Metal Program

Delta ferrite levels, FNMaterialidentity

Creeprupturetests

Creeprupturetests

Creeprupturetests

Short timetensiletests

Short time

tensiletestsTotal tests

required(no. specimens)

2 FND 63)

1000F/10h DT-23)1 0 00F /1 0 0h D T- 21 )1000F/2500 h DT-27)

1200F/100 h DT-22)1200F/2500 h DT-24)

1100F/100 h DT-25 )

600F (DT-26)

6 FNA(78)

As-deposited1000F/10h (AT-23)1000F/100h(AT-7)1000F/2500 h (AT-25)

1200F/100 h(AT-8)1200F/2500 h (AT-24)Solution annealed (19 50E/2h)

1100F/100h (AT-27)1100F/25O0 h(AT-28)

Annealed (1l00F/2500 h)1100F/100h(AT-32)

10 FNB 79)

1000F/10 h BT-27)1000F/10 0 h BT- 2 3 )1000F/2500 h BT-25)

1200F/100 h BT-24)1200F/2500 h BT-32)

1100F/100h BT-33)

As-deposited600F AT-26) 600F (BT-26)

Solution annealed (1950F/2 h)80F (AT-29)

600F (AT-30)1100F(AT-31)12 7

16 FNC 80)

1000F/10 h CT-19)1000F/100h CT-24)1000F/2500 h CT-25)

1200F/100 h CT-1)1200F/2500 h CT-32)

1100F/I00h CT-28)11 0 0 0 F /2 5 0 0 h CT-27)

1100F/100h CT-33)

600F CT-26)

80F CT-29)

600F CT-30)1100F CT-31)12

38-s I FEBRUARY 1982


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most appropriate constant for this purpose, based on visual comparisons of theplotted data, appeared to be 25. Thisconstant was used in Fig. 3 that shows thecomparative strength relationship of theweld metals at four ferrite levels. Basedon the various L-M curves, the creep-rupture strength values given in Table 4were calculated. These values do not

necessarily agree with log stress-log timecurve s pres ente d in Fig. 1. The L-M valuesare a collective representation of all temperatures (1000, 1100, and 1200F) andall rupture times. The log-log curves ofFig. 1 are based on a limited num ber oftes ts conducted at each temperature.

Because only two tests were made oneach as-deposited w eld metal at 1200 F,it is not possible to de velo p a trend otherthan linear. Therefore, the values developed from the L-M curves (Table 4) wereused to reconstruct the log-log curves inFig. 4. In addition to the values given inTable 4, the L-M curves permit the determination of stress values for other tem

peratures and rupture times. These arecalculated by inserting the desired t emperature (T, absolute) and time (t, hours)in the equa tion T (25 + log t) X 10 3 . Theintersection of this calculated value withthe appropriate L-M curve gives thestress.

Based on the creep-rupture dataobtained for the various material and test

conditions: The very low (2 FN) and low fe rrite

(6 FN) as-deposited weld metals havesimilar stress-rupture properties at allthree test temperatures (1000, 1100, and1200F).

At 1000F, there is a conv ergen ceof the creep-rupture curves resulting inalmost a co mm on strength level at aboutthe 1000 to 3000 h time period for allfour as-deposited weld metals.

At 120 0F, there is a div erge nce o fthe creep-rupture curves producing awidening of strength levels among the

four as-deposited weld metals, with the 6FN material having the highest strength

(19.5 ksi to rupture in 10,000 h) and the16 FN material having the lowes t strength(15 ksi to rupture in 10,000 h).

Solution annealing (1950F/2 hr,W.Q.) produces no change in the shorttime (about 100 h) creep-rupture strengthof the 6 FN weld metal at 1100F andreduces the 1000 h strength level fromabo ut 34 to 3 0 ksi. Solution an nealing the

16 FN weld metal results in essentially nochange in creep-rupture strength at either short or long times.

The solution annealed specimens(AT-27 and CT-28) initially deformed 9.59and 4.06%, respectively, when stressedto 40 ksi at 1100F (Table 3). This isunderstandable in that the yield strengthwas greatly reduced by solution annealing. The yield strength of the 6 FN weldmetal (AT-27) dropped from 39.8 (Ref. 9)to 22.3 ksi (Table 7) and the yield strengthof the 16 FN (CT-28) we ld metal dro pp edfrom 42.6 (Ref. 9) to 25.6 ksi (Table 7).The 40 ksi stress on the AT-27 and CT-28specimens was approximately 60% over

Table 3Summary Data on Creep and Rupture Properties of E308 Weld Metal at 1000,

Hours to indicated Initial RuptureSpecimen Stress, percent creep defo rma tion strain, t ime.

number ksi 0.5 I.O 2.0 5 10 % h

1100, an d 1200F 538, 593,

Elongationin 2 Redu ctionin., of area,

0/ 0 /

and 649 C)

Minimumcreepra te ,

/h

Initiation ofthird stage

creeph

AS-WELDED COND ITION1000 E

Extra-low de lta ferriteDT-23DT-21DT-27

AT-23AT-7AT-25

BT-27BT-23BT-25

CT-19CT-24CT-25

DT-22DT-24

AT-8AT-24

BT-24BT-32

CT-1CT-32

AT-27AT-28CT-28CT-27

DT-25AT-32BT-33CT-33

524742.5

544742.5

50434 1

534743.5

3023.5

31.522

27.520.5

26.517.5

40304027.5

40404040

2135

145

0.71865

2.23165

1.21030

17960

3.52300

151460

121290

1.010

0.412

32

0.71.5

3645

460

1.335

164

474

185

2.72375

291075

6.52600

281840

272080

2.535

1.0125

843

4.5

63162

1500

2.466

490

8200610

7.756

210

4 1

11

4540

109335

5

1601400

15480

1560

20194550

65

19

72

97

3.708 142.61.210 400.80.334 2093.3

Low delta ferrite7.103 9.8

24 0 1.542 283.50.742 1769.2

Medium delta ferrite20 3.370 24.7

700 0.358 813.22230 0.355 2526.1

High delta ferrite2.853 35.8

340 0.530 430.2800 0.308 871.2

1200FExtra low d elta ferrite

88 0.294 119.00.122 1127.4

Low delta ferrite26 0.225 34.0

0.145 2748.3Medium delta ferrite

103 0.187 122.80.161 2032.8

High Delta Ferrite147 0.166 153.8

0.118 2267.6SOLUTION ANNEALED CONDITION (195C

6.01602.7

1070

2011

5.516

227808.8

2250

39 9.589 46.8980 3.330 1004.3

20 4.059 39.10.310 2278.0

EXPOSED CONDITION (2500 h at

47332440

1100F75 1.390 99.852 1.536 87.943 0.909 79.665 0.455 79.5

15.612.4

7.7

24.919.212.8

21.719.616.6

14.919.014.0

26.04.1

27.95.9

20.05.1

14.13.4

F/2 h, W.Q.),22.512.326.4

6.41100 F)

21.729.334.017.0

40.520.722.5

47.433.730.7

49.739.428.9

37.229.325.4

27.413.4

47.610.9

38.612.7

27.96.0

1100F25.619.833.212.7

35.049.245.528.5

0.0200.0120.0009

0.670.0320.0029

0.170.00750.0022

0.200.0210.0077

0.0260.00026

0.110.00009

0.0270.00017

0.0330.00022

0.170.00420.430.00027

0.0810.120.200.096

3.93.32.7

7.75.04.5

3.82.32.8

6.05.02.6

0.60.35

0.60.34

0.40.42

0.70.48

-7.0

-2.6

4.55.27.03.3

10170

1820

1110

1100

2250830

13175250

10575

31000

5725

13850

540

-1400

34252825

WELDING RESEARCH SUPPLEMENT | 39-s


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400

350

300

1 ~IAl I four materials,tested at 1100 F and4 0 ksi after prior exposure at I IOO F for2500 hrs .failed in the range 79.5 to99.8hr.

IQOOF

v E xtra-low ferrite0 Low ferritea Medium ferritea H igh ferrite Low f e r r i t e / S o l . Ann. High f e r r i t e /Sol . Ann,

Note : Symbols represent current tiBroken lines (1100 F) from reference

l K

Keyv Extra~tow ferriteo Low ferriteA Medium ferriteo High ferrite Low ferrite/Sol- Ann High ferrite/

Sol. Ann.

Note: Symbols represent current testresults. Broken lines (HOOF)are for data from reference 9.

IOOT i m e .hours

7 Stress-rupture curves for E308 weld metal containing differentferrite levels tested at 100 0, 1100, and 1200F (538, 593, and 649C)

0.OOI O.OIMinimum Creep Rote, percent/ hour

Fig

7 0

60

5 0

4 0

3 0

2 0

-Low fer r i te (6FN)-High fe r r i t e ( I6FN)

,Extra-low fe r r i t e (2 Ft

450

400

3 0 0

250

200 '

Mediumferri te

High ferri te

3 6

Fig. 3-

3 8 4 0 4 6 4 8 5 02 44

T ( 2 5 + l o g t ) x l O 3

Larson-Miller com parison of stress-rupture properties of E308 weld metal

Fig. 2 Stress vs. minimum creep rate curves for E308 weld metal testedat 1000, 1100, and 1200 F (538, 593, and 649 c'Q

e a c h w e l d m e t a l ' s y i e l d s t r e n g t h . T h e r e a r e o n l y m i n o r d i f f e r e n c e s

b e t w e e n t h e t w o l o g - l o g p l o t s ( Fi gs . 1a n d 4 ) o f c r e e p - r u p t u r e s t r e n g t h p r o p e rt i es o f t h e f o u r w e l d m e t a l s . T h e r e l a t i o nsh ips es tab l i shed by ind iv idua l t es t s (F ig .1) a re a bo ut th e sam e as tho se (F ig . 4 )r e c o n s t r u c t e d f r o m t h e L - M c u r v e s . T h em a j o r d i f f e r e n c e , a n d a d v a n t a g e , o f t h er e c o n s t r u c t e d p l o t is t h a t t h e c r e e p -r u p t u r e c u r v e s e x t e n d t o 1 0 0 , 0 0 0 h a t1 0 0 0 a n d 11 0 0 F, a n d b e y o n d 10,000 hat 1200F.

T h e s t re s s e s r e q u i r e d t o p r o d u c e v a ri o u s m i n i m u m c r e e p r a t e s ( 0 . 1 t o0.0001 % / h ) w e r e t a k e n f r o m t h e l o g - l o gplo ts in F ig . 2 and a re shown in Table 5 .B a s e d o n t h e s e v a l u e s a n d o n t h e c u r v e si n F ig . 2 , t h e f o l l o w i n g o b s e r v a t i o n s w e r em a d e :

Th e 2 FN w el d meta l has the h ighes tc r e e p s t r e n g t h a t a ll t h r e e te s t t e m p e r at u r e s ( 1 0 0 0 , 11 0 0 , an d 12 00F) .

A t 1100 a n d 1 2 0 0 F, t h e 6 F N w e l dm e t a l h a s a p p r o x i m a t e l y t h e s a m es t r e n g t h a s t h e 2 F N w e l d m e t a l .

At 1 200 F an d a t lo w cre ep ra tes a t110 0F, the 16 FN w el d me ta l has thel o w e s t c r e e p s t r e n g t h . A t 1000F and a th igh c reep ra tes a t 1100F, the 10 FNw e l d m e t a l t e n d s t o h a v e t h e l o w e s tc r e e p s t r e n g t h .

S o l u t i o n a n n e a l i n g l o w e r s t h e c r e e ps t r e n g t h o f t h e 2 F N w e l d m e t a l a t1100F. S imi la r t rea tment of the 16 FN

w e l d m e t a l p r o d u c e s e s s e n t i a l l y n oc h a n g e .

P r i o r e x p o s u r e f o r 2 5 0 0 h a t 1100Fp r o d u c e s l i tt l e c h a n g e i n th e 2 F N a n d 6FN w e ld me ta l s and s l igh t ly increases thec r e e p s t r e n g t h o f t h e 1 0 F N a n d 1 6 FNw e l d m e t a l s .

T h e e f f e c t o f s o l u t i o n a n n e a l i n g a n dp r i o r e x p o s u r e o n t h e d u c t i l i t y o f t h e f o u rw e ld m eta l s i s sh ow n in F igs . 5 and 6 .R u p t u r e e l o n g a t i o n ( F i g . 5 ) i s l o w e r e donly s l igh t ly by e i ther o f the hea t t rea tments . Reduct ion in a rea va lues (F ig . 6 )a r e l o w e r e d b y a n a v e r a g e o f a b o u t 5 %b y t h e t w o h e a t t r e a t m e n t s .

I

I25

IOO

IO IOO I 0 0 0 10,000 100,000

T i m e , hours

Hg. 4 -Stress-rupture curves forE308 weld metal with different ferrite numbers testedat 1000, 1100, and 1200F as based on Larson-Miller data

Comparison of Creep-Rupture Propert ies ofWeld-Depos i ted , Cas t , and WroughtStainless Steels

T h e r es u lt s o f w e l d - m e t a l c r e e p - r u p -

4 0 - s I F E B R U A RY 1 9 8 2


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Table 4Stress-Rupture Values for Four Ferrite Levels of E308 Weld Metal Based on L-MCurves

FerriteStress, ksi, to produce

rupture in times indicated in hourslevel

2 FN6 FN

10 FN16 FN

2 FN6 FN

10 FN16 FN

2 FN6 FN

10 FN16 FN

10

605451.555.5

464542.545.5

35.53632.533

100

524946.550.2

39.539.536.538

30302726

1000 F

11 F

1200F

1000

44.5444 143.3

33.5343131

242421.819.5

10 000

383935.537

28.528.525.524.5

18.519.517.715

100,000

3333.530.530.2

23232118.7

--

Table 5Stress vs. Creep Rate Values for Four Ferrite Levels of E308 Weld Metal Based onLog-Log Plots

Stress, ksi, to produceminimum creep rates indicated in /hourerrite

level

2 FN6FN

10 FN16 FN

2 FN6 FN

10 FN

16 FN

2 FN6 FN

10 FN16 FN

0.1 0.01

5349.548.550.5

414136.5

38.5

323129.529

10004844.543.544.511003736.532.5

33.512

28.5282624

F are re p lo t te d in

0.001

4340.539.539

33.53329.5

28.5

2524.522.519.5

0.0001

302926.5

25

22222016.5

ture tests at 1100Fig. 7.

The adjusted average creep-rupturevalues for Types 304 and 304H wroughtstainless steels repo rte d b y S mith (Ref. 10)are similar to the results from this program for the medium-ferri te weld metal

at rupture times beyond 1000 h. Fortimes to rupture less than 1000 h, theresults for the high-ferrite weld metal areclose to the values reported by Smith(Ref. 10). The expec ted minim um c reep-rupture values for Type 304 stainless steelpublished in the 1977 ASME Code Case

N-47-12 (1592-12) also are plotted in Fig.7. The rupture times from this Code Case(Ref. 11) are significantly shorter thanthose measured for the ferrite containingweld metals.

Also plotted in Fig. 7 are resultsreported by Voorhees (Ref. 12) and givenin Table 6 for CF8 castings at two ferritelevels. Compared to the weld metal, the

castings have the following creep-rup-tuce properties: Lowe r strength. Lowe r secondary creep rate. Higher elongation and reduc tion of

area at fracture, especially at the longerrupture times.

The CF8 having a calculated ferritelevel of 3% was significantly stronger thanCF8 having a calculated ferrite level of16%.

Short Time Tensile Tests

Ten short time tensile tests were con

ducted on the four weld metals at theconditions described in Table 2. Resultsof these tests include yield and ultimatestrength, elongation, reduction in area,and elastic modulus and are given inTable 7. These values are presentedgraphically in Figs. 8 and 9 together withthose presented in the literature(Ref. 9).

All tensile tests wer e c ond ucte d in aBaldwin Universal hydraulic tensilemachine having a capacity of 60,000pounds. Temperatures were obtained bymeans of an electric-resistance furnaceand contro l led by means of Chromel-Alumel thermocouples at tached to thegage section of th e specimens. Strain wasrecorded on an autographic stress-strainrecorder. A Class B-1 extensometer wasused for ail tests (ASTM Standard E83-74).The extensometer was calibrated prior tomaking the tests to ensure that the maximum error was within the prescribedlimits. Accuracy of the extensometer iswith in 1 0% . After hold ing the specimens at the test temperature for 30 min,the specimens w ere pulled at a strain rateof 0.002 ipm.

The short-time tensile test results indi-

Priore x p o s e d

So l u t i o na n n e a l e d

KeyFe r r i t elevel

T Ex t ra tow (2 FN) L o w ( 6 F N ) o

M e d i u m ( I0 FN) Hi g h (I6FN) n

No t e : So l i d l i n e s r e p re s e n t a s -w e l d e dm a t e r i a l - f r o m r e f e r en c e 9 .

M e d i u m f e r r i t e

IOO IOOOR u p t u r e T i m e , h o u r s

Fig. 5 Relationship of elongation and rupture time in creep-rupturetests at 1100F (593C) for E308 weld metal

Medi

Extra low x.ferrite \ .

High ferr i te

^yLegend

Prior Ferrite Soexposed level an

_ T Extra low(2FN) Low (6 FN}* Medium ( I 0 F N) H i g h ( l 6 F N)

~~ Note: Solid lines represent as

jm ferrite

/ \

T Vf

u t ionnealecl

we l d e d

material-from reference^.

i i

\ \ Low ferrite

QVtt

1 \

-

-

_

IOO IOOO

R u p t u r e Ti m e , h o u rs

Fig. 6 - Relationship of reduction in area (593Q and rupture time increep-rupture tests at 1100F (593 c'Q for E308 weld metal

WELDING RESEARCH SUPPLEMENT I 41-s


6/8

Re f IO(Type 3 0 4 - 3 0 4 H )

Extra low ferr i teLow ferr i teM e d i u m ferri teHigh ferr i te

2 10 IOO IOOO 10, 000Rupture t ime , hours

Fig. 7-Stress rupture curves for E308 weld metal and CF8 castings at 1100 F (593 C)with different ferrite levels

ca te tha t : T h e d a t a o n th e a s - d e p o s i t e d w e l d

m e t a l o b t a i n e d a t 600F a r e g e n e r a l l yc o n s i s t e n t w i t h t h e e s t a b l i s h e d t r e n de x c e p t f o r s o m e v a l u e s f o r t h e 1 6 F Nw e l d m e t a l . T h e y i e l d s t r e n g t h a n d e l a s ti cm o d u l u s f o r t h e 1 6 F N s p e c i m e n s a p p e a rs l i g h t l y h i g h e r a n d t h e e l o n g a t i o n a n dr e d u c t i o n i n a r e a t e n d t o b e l o w e r t h a nt h e t r e n d w o u l d i n d i c a t e .

S o l u t i o n a n n e a l i n g t h e 6 F N w e l dm e t a l r e d u c e d t h e y i e l d s t r e n g t h b y

a b o u t 5 0 % a t 8 0 a n d 11 0 0 F a n d 6 0 % a t6 0 0 F, w h e n c o m p a r e d w i t h t h e a s -d e p o s i t e d c o n d i t i o n . S o l u t io n a n n e a l i n gt h e 1 6 FN w e l d m e t a l r e d u c e d i ts y i e l ds t r e n g t h b y a b o u t 3 0 % at 8 0 F, 4 5 % a t6 0 0 F, a n d 4 0 % a t 1100F.

T h e u l t i m a t e s t r e n g t h w a s o n l y m i l dl y a f f e c t e d b y s o l u t i o n a n n e a l i n g . I t w a sr e d u c e d b y a p p r o x i m a t e l y 1 0 % a t 8 0 a n d600F a n d e s s e n t i a l l y u n c h a n g e d a t1100F.

Th e duc t i l i ty of bo th the 6 FN an d 16

F N w e l d m e t a l s w a s i n c r e a s e d s i g n i f i c a n tl y b y s o l u t i o n a n n e a l i n g . T h e e l o n g a t i o nv a l u e s o f t h e 6 F N w e l d m e t a l i n c r e a s e db y a b o u t 3 5 - 4 0 % a n d o f t h e 1 6 F N w e l dm e t a l b y a b o u t 2 0 - 3 0 % a t t h e t h r e e t e s tt e m p e r a t u r e s ( 8 0 , 6 0 0 , a n d 11 0 0 F ) .R e d u c t i o n i n a r e a v a l u e s w e r e i n c r e a s e dt o a l es s e r e x t e n t r a n g i n g f r o m a b o u t 2 5 %at 600F to no change a t 80F for the 16F N w e l d m e t a l . F o r t h e 6 FN w e l d m e t a l ,t h e i n c r e a s e i n r e d u c t i o n o f a r e a r a n g e df r o m a b o u t 1 0 t o 2 0 % .

Nea r ly a ll sh or t - t im e tens i le t es t sw e r e m a d e t r a n s v e r s e t o t h e w e l d i n gd i r e c t i o n . A t 8 0 a n d 11 0 0 F, t e s t s w e r em a d e a l s o i n t h e w e l d d i r e c t i o n ( l o n g i t ud ina l ) on a l l fou r w e ld me ta l s . Th e resu l t sa re presen ted in F igs . 8 and 9 . In genera l ,the y ie ld and u l t imate s t rengths of a l l fourw e l d m e t a l s a t 8 0 a n d 1100F a r e a b o u t 5t o 1 0 % l o w e r i n t h e l o n g i t u d i n a l d i r e c t i o nt h a n in t h e t r a n s v e r s e d i r e c t i o n . T h e d u ct i li t y, a s e v i d e n c e d b y t h e e l o n g a t i o n a n dr e d u c t i o n i n a r e a v a l u e s , i s 1 0 t o 1 5 %h i g h e r, o n t h e a v e r a g e , f o r t h e l o n g i t u d ina l spec imens . E las t ic modulus va lues a rel o w e r i n t h e l o n g i t u d i n a l d i r e c t i o n b ya b o u t 1 0 t o 2 0 % , w i t h t h e g r e a t e s t d i f f e rence a t 1100F.

F r a c t o g r a p h s o f s e v e r a l f a i l e d s t r e s s -r u p t u r e b a r s a r e s h o w n i n F i g . 1 0 . T h e s eare typ ica l o f the fa i lu res seen in a l l t es tb a r s . N o s p e c i m e n d i s p l a y e d a n y u n u s u a la p p e a r a n c e .

Table 6Creep-Rupture Properties of CF8 Castings (Ref. 12)

Spec. no.Temp. ,

FStress

ksiTotal strain

on loading, ,.Start

Cree p, % Time, h

Secondary creep period

CF8, LotD-4. Ingersoil-Rand Co ., Ht. No. 6876. (205 0 F, V/i h, W.Q .)D4-4 7 1100 25 16.1 3.2 63D4-4 9 1100 22.5 10.45 1.8 160D4-6 2 1100 20 7.25 2.3 1080CF8, LotD-10. Esco Co rp. , Ht. No . 40S-25976.D10 -28 1100 25 6.2 4.0 4.ID10 -65 1100 20 3.0 4.9 50D10-2 3 1100 16 2.2 78D10-5 3 1100 12.5 0.13 1.1 1070D10-6 3 1100 10 0.27

Rate% / h

0.0120.002650.00083

EndCreep , % Time, h

4.22.73.2

146500

2160

(0.40)0.037 7.3 1150.0059 6.0 7200.00055 1.8 2320

[0.00017 to 0.91 /3168 h]

Rupturelife, h

Elong.,/4D

R.A.,E. %

3 calculated ferrite.172.9 24.5 34.4763 .0 16 18.8

4794.1 21 36.016 calculated ferrite.

15.8 21.5 35.6182.1 19 23.0

1108.4 17.5 22.5(2.66% c reep /3360 h)

Table 7Short-Time Tensile Propert ies of E308 W eld M eta l in As -W elde d and Solution -Ann ealed C ondit ions11 '

Spec.

DT-26AT-26BT-26CT-26

AT-29CT-29AT-30CT-30AT-31CT-31

Tempera ture ,

F

600600600600

8080

600

60011001100

degC

315315315315

2727

315315593593

Yield strength0.2% offset,

ksi

53.753.455.061.7

Ultimatestrength,

ksi

As-welded condition71.570.272.479.4

Solution-annealed condition (1950F/2 h,37.653.321.2

34.122.325.6

82.694.566.272.154.055.9

Elongation, %

27.528.029.023.0

W.Q.)62.050.042.0

34.040.033.5

Reductionof area, %

45.945.544.035.1

58.349.655.4

48.152.246.0

Elasticmodulus,

IO6 psi

20.122.621.927.5

25.527.820.8

22.224.823.8

(a) All Specimens were taken Iransverse to weld d i rect ion .(b) 1 ksi = 6 .9 MPa,

4 2 - s I F E B R U A RY 1 9 8 2


7/8

L eg en dF er r i t elevel

Trans ,d i rect ion

Longit Solu t iondi rect ion annealed

Ext ra low(2FN)Low (6 FN)Medium (10 FN)High (16 F N )

700

6CC

5 ; :

4 0 0 6 0 0Temperature ,

IOOO 1200

IOO 500 6 0 00 0 3 0 0 4 0 0Temperature , C

Fig. 8 Yield strength and ultimate strength values for E308 weld metalin as-welded and solution-annealed conditions

LegendFerritelevelExtra low (2 FN)Low (6FN)Medium (10 FN)High (16 FN)

Trans.direction

V0A

a

Longit.direction

T

A

Solutionannealed

X

+

(read right)

IOO 2 0 0 3 0 0 4 0 0 5 0 0 6 0 0 T OO

Temperature , C

Fig. 9 Elastic modulus, elongation, and reduction-in-area values forE308 weld metal in as-welded and solution-annealed conditions

Fig. 10 - Fractograph s of E308 weld metal specimens: A - specime n D T-25 (2 FN), 1100 F/40,000 psi, rupture time - 100 h; B - specimen A T-24 (6 FN),1200F/22,000 psi, rupture time-2748 h; C-specime n BT-25 (10 FN), 1000F/41,000 psi, rupture time-2526 h; D-specime n CT-27 (16 FN),1100F/27,500 psi, rupture time-2278 h

Metallography

S e l e c t e d c r e e p - r u p t u r e s p e c i m e n sw e r e c h o s e n f o r a m e t a l l o g r a p h i c e x a m i

n a t i o n . T h e m a i n p u r p o s e o f t h i s e x a m i

n a t i o n w a s t o d e t e r m i n e w h e t h e r a n d t ow h a t e x t e n t s i g m a p h a s e h a d f o r m e dd u r i n g t h e c r e e p - r u p t u r e t e s t s . A r a t h e r

Fig. 11-Creep-rupture specimen AT-25 (6 FN) after failure in 1769 h at 1000F/42.5 ksi. NaCNtreatment. A-X100; B-X1000 (reduced 35 on reprod uction)

e x t e n s i v e m e t a l l o g r a p h i c s t u d y h as a l

r e a d y b e e n p e r f o r m e d o n t h e f o u r f e r r i t eleve ls o f E308 w e l d m e t a l ( R e f . 8 ) . T h e r ef o r e , t h e c u r r e n t s t u d y w a s a i m e d a tm a t e r i a l a n d / o r te s t c o n d i t i o n s n o ti n c l u d e d in t h e p r e v i o u s w o r k . A ll s p e ci m e n s e x a m i n e d w e r e o r i e n t e d t r a n sv e r s e t o t h e w e l d i n g d i r e c t i o n . T h e s e ct i o n s v i e w e d w e r e a l l p a r a l l e l t o thes p e c i m e n l e n g t h a n d i n t h e v i c i n i t y o f t h ef r a c t u r e . T h e s p e c i m e n s w e r e e t c h e d i nN a C N f o r 5 s e c o n d s ( s ) t o b r i n g o u t t h es igma phase , i f p resen t .

Figures 11 a n d 1 2 s h o w t h e m i c r o s t r u ct u r e o f t w o s p e c i m e n s a f te r t e s t i n g i n th ea s - d e p o s i t e d c o n d i t i o n . S p e c i m e n AT- 2 5(Fig. 11) was tes ted a t 1000F and 42 .5k s i a n d f a i l e d in 1 7 6 9 . 2 h . S p e c i m e nAT-24 (F ig . 12) was tes ted a t 1200F a n d22 ks i and fa i led a t 2748 .3 h . No s igmaw a s f o u n d i n t h e s p e c i m e n ( AT- 2 5 ) t e s t e d

W E L D I N G R E S E A R C H S U P P L E M E N T | 4 3 - s


8/8

A- Af

r ~ A

@

r

Fig. 12 Creep ruture specimen A T-24 (6 FN)after failure in 2748 h at 1200F/22 ksi. NaCNtreatment. A-X100; B-X1000 (reduced37 on reproduction)

Fig. 13 Creep-rupture specimen BT-33 (10FN) after failure in 80 h at 1100F/40 ksi. NaCNtreatment. A-X100; B-X1000 (reduced38 on reproduction)

Fig. 14 Creep-rupture specimen CT-27 (16FN) after failure in 2278 h at 11 00F/27.5 ksi.NaCN treatmentprior solution annealing at1950F for 2 h and water-quench ed. A X100; B-X1000 (reduced 38 on reproduction)

a t 1000F. The phase v i s ib le in F ig . 11 a tb o t h X 1 0 0 a n d X 1 0 0 0 is b e l i e v e d t o b ed e l t a f e r r i t e . S i g m a p h a s e , a p p e a r i n g d a r k

g r a y , w a s p r e s e n t i n t h e s p e c i m e n ( A T-2 4 ) t e s t e d a t 1200F a n d s h o w n i n F ig . 1 2 .T h e v a r y i n g a p p e a r a n c e o f t h e p h a s e s i nt h e m i c r o s t r u c t u r e s e e n i n F ig . 1 2 at X100w a s n o t e d i n n e a r l y a ll o f t h e s p e c i m e n se x a m i n e d . I t is be l iev ed to be du e tod e n d r i t e o r i e n t a t i o n r a t h e r t h a n d i f f e rences in fe r r i t e l eve l .

Th e mic ros t ru c tu re in Fig . 13 is tha t o fs p e c i m e n B T- 3 3 ( 1 0 F N ) t h a t h a d b e e np r i o r e x p o s e d a t 11 0 0 F f o r 2 5 0 0 h Inaddi t ion , i t was in tes t a t 1100F a n d 4 0ks i resu l t ing in fa i lu re in 79 .6 h . S igmap h a s e w a s f o u n d i n t h i s s p e c i m e n , s e e n i nt h e X 1 0 0 0 p h o t o m i c r o g r a p h a s t h e d a r kly s ta ined a reas . Spec imen CT-27 (16 FN) ,w h i c h f a i l e d i n 2 2 7 8 h a ft e r c r e e p - r u p t u r etes t ing a t 1 100 F an d 27 .5 ks i , is seen inFig. 1 4 . T h i s s p e c i m e n w a s s o l u t i o na n n e a l e d a t 1950F f o r 2 h a n d w a t e rq u e n c h e d p r i o r t o te s t i n g . T h e m i c r o -s t r u c t u r e s o f t h e 6 F N a n d 1 6 F N w e l dm e t a l s f o l l o w i n g s o l u t i o n a n n e a l i n gs h o w e d n o s i g m a p h a s e . A f t e r c r e e pe x p o s u r e f o r 2 2 7 8 h , t h e m i c r o s t r u c t u r es h o w n i n F ig . 1 4 h a d d e v e l o p e d . A ss h o w n h e r e a t X 1 0 0 0 , a s i g n i f i c a n ta m o u n t o f s i g m a p h a s e h a d f o r m e d i nt h i s w e l d m e t a l d u r i n g t h e 2 2 7 8 h a t1100F.

A l t h o u g h p h o t o m i c r o g r a p h s a r e n o ts h o w n , a n e x a m i n a t i o n w a s m a d e o fs e v e r a l o t h e r t e s t e d c r e e p - r u p t u r e b a r s .S p e c i m e n s AT- 2 7 ( 6 F N ) a n d C T- 2 8 ( 1 6

F N ) t h a t h a d b e e n s o l u t i o n a n n e a l e d a n dtes ted a t 110 0F fa i led in on ly 47 and 39h , r e s p e c t i v e l y, a n d n o s i g m a p h a s e

f o r m e d . S p e c i m e n AT- 2 8 ( 6 F N ) , a l s os o l u t i o n a n n e a l e d b e f o r e t e s t i n g a t11 0 0 F, w a s a l s o e x a m i n e d m e t a ll o g r a p h i c a l i y. A f t e r c r e e p e x p o s u r e f o r1 0 0 4 . 3 h , h o w e v e r , n o s i g m a w a s e v id e n t . T h e d i f f e r e n c e b e t w e e n t hi s s p e c im e n a n d s p e c i m e n C T- 2 7 , w h i c h s h o w e dt h e s i g m a p h a s e , is t h e l o w e r f e r r i t econten t (6 FN vs . 16 FN) and a l so thes h o r t e r c r e e p e x p o s u r e t i m e ( 1 0 0 4 v s .2278 h) .

Ackno wledgments

T h e a u t h o r s a c k n o w l e d g e t h e f i n a n c i a ls u p p o r t o f t h e M e t a l P r o p e r t i e s C o u n c i la n d t h e t e c h n ic a l g u i d a n c e p r o v i d e d b yt h e Ta s k F o r c e o n t h e P r o p e r t i e s o f W e l dM e t a l , D r. VV. D . D o t y, C h a i r m a n , a n dt h e S u b c o m m i t t e e I, E n g i n e e r i n g P r o p e rt ies of Boi le r and Pressure Vesse l Meta l s ,D r. M . S e m c h y s h e n , C h a i r m a n .

References

1. De Lon g, W . T. 1974. Ferrite in austeniticstainless steel weld metal. Welding lournal 53(7): 273-s to 286-s.

2. Lundin, C. D.; Chou, C.-P. D.; and Sullivan, C. ). 1980. Hot cracking resistance ofaustenitic stainless steel weld metals. Weldinglournal 59 (8): 226-s to 232-s.

3 . Goo ch , T. C , and Honey comb e, ] . 1980.We lding variables and microfissuring in austenitic stainless steel weld metal. Ibid: 233-s to241-s.

4. Ca stro, R., and d eC ade net, J. ). 1974.

Welding m etallurgy of stainless and heat-resisting steels. Translated by R. C. Jain, Babcock &Wilcox Co. , Mt. Vernon, Indiana. CambridgeUniversity Press.

5. Arata , Y.; Mats uda , F.; and Katayam a, S.1977. Solidification crack susceptibility in weldmetals of fully austenitic stainless steels (reportII). Transactions of IWRI 6 (1): 105-116.

6. A s t r o m , H.; Loberg, B.; Bengtsson, B.;and Easterling, K. E. 1976. Hot cracking andmicro-segregation in 18-10 stainless steelwelds . Metal Science 10 (7): 225-234.

7. Thomas, R. D., Jr. 1978. Effect of deltaferrite content of E308-16 stainless steel weldmetal weld metal preparation. Proceedingsof the sympo sium on properties of steel w eldments for elevated temperature pressure containment applications, ed. C. V. Smith, pp .1-16. Metal Properties Council publicationMPC-9.

8. Edmonds, D. P.; Vandergriff, D. M.; andCray, R. J. 1978. Effect of delta ferrite contentof E308-16 stainless steel weld metal su pplemental studies. Ibid. 47-61.

9. Hauser, D., and Van Echo, J. A. 1978.Effect of delta ferrite content of E308-16 weldmetal mechanical property and metallographic studies. Ibid: 17-46

10 . Smith, G. V. 1969 (Feb.). An evaluationof the yield, tensile, creep, and rupturestrengths of wrought 304, 316, 321, and 347stainless steels at elevated temperatures.ASTM data series DS 5S2 prepared for theMetal Propert ies Council . Philadelphia: American Society of Testing and Materials.

11 . ASME. 1977 (July). 1977 code cases,nuclear components, 1977 ed ., case N-47-12(1592-12), appendix 1-14, table 1-14.6A,p. 152. Ne w Y ork.

12 . Voorhees, H. R. 1979 (Jan. 8). Interimdata summary. Metal Propert ies Council cont ract no. 174-1, project D.

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