Form #G-82 - UNT Digital Library/67531/metadc871094/...ftustenitic stainless steels are candidates...

Form #G-82- - 7

AUTHOR'S TECHNICAL PAPER FORM*

SOCIETY OF MANUFACTURING ENGINEERSn r ••

| By acceptance of th is a r t i c l e , the publisher or recipient !j acknowledges the U.S. Government's r ight to retain a n o n - Si exclusive, royalty-free license in and to any| covering the a r t i c l e .

1 ADVANCES IN STAINLESS STEEL WELDINGJ ELEVATED TEMPERATURE SERVICE*

! G. M. Goodwin, N. C. Cole, R, T. King, and G. 1

J '; Mailing Address:

J v . G. M. Slaughter{ Oak Ridge National LaboratoryJ "•->. P.O. Box X« ,\ Oak Ridge, Tennessee 37830• \

copyright |

FOR 1

*1. Slaughter {

1 1Thit icpoti wai prepared as in account of worksponsored by the United Stales Government, Neitherthe United Stiles nor the United States EnergyResearch and Development Administration, nor Any ofiheir employee!, not any of ineir .'onttactois.subcontractors, ot iheii employees, nukes toywanamy, c«press or implied, or assumes any legitliability or icsptniibUity foi the accuracy,compler«ne*iat usefulness of any information, apparatus, product orpmccsi disclosed, OT repiesents that its use would notinfringe privately owned light*.

j SME/ERPA WeMlng and JolnXnq Woik&hop [t Chicago, JWjnoli\ OctobQA 2&-30, 1975

[ *Research sponsored by the U.S. Energy Research[Administration under contract with the Union Carbide

and Development iCorporation.

covering the article.

ADVANCES IN STAINLESS STEEL WELDING FORELEVATED TEMPERATURE SERVICE*

G. M. Goodwin, N. C. Cole, R. T. King, and G. M. Slaughter

ft.

Mailing Address:

G. M. SlaughterOak Ridge National LaboratoryP.O. Box XOak Ridge, Tennessee 37830

TT111 icpuit -.wastponsuied hy (tiethe United SlatRewuth and I»tvtheti employeesmbconiracloii.w^iran'y, e*preis

United Sum Uomnrt% not the United Sciopntcni Admiruitraiio

noi any of thenor their emplofcef,

ai implied, 01 auurrliability 01 teipwuibilily fut I he accuiacy.or uiefulnea of apiuccii ducloud.infnnje privately t

ny information, appaial

wned tifixti.

ni of.w.ukncnt Neitheinet tncrgyik nor any ufraniracioit,mtkri *ny

tet any tegalcumplctcncui i . product orI K would not

SME/EUDA Welding and Joining Woik&hopChicago, IZtinoii

OctobeA 2S-30, 7975

*Research sponsored by the U.S. Energy Research and Development[Administration under contract with the Union Carbide Corporation.

*This copy will not be proofread by SME - Type within the dotted l ines.(Consult SME Author 's Manual for typing instruct ions.)

AUTHOR'S N.AMEG. M. Goodwin, N. C. Cole, R. T. King, and G. M. Slaughter

TITLE OF PA PER ADVANCES IN STAINLESS STEEL WELDING FOR ELEVATED TEMPERATURE

PAGE NUMBER

SERVICE

Form #G-82


SOCIETY OF MANUFACTURING ENGINEERS

ADVANCES IN STAINLESS STEEL WELDING FORELEVATED TEMPERATURE SERVICE

ABSTRACT I12345

JAn extensive program to characterize the microstructures and determine themechanical properties of stainless steel welds is described. The amount,

8 Uii.e, shape, and general distribution of ferrite in the weld metal was stud-{9 Jied in detail. The effects of electrode coatings on creep-rupture proper-10 |ties were determined as were the influence of slight differences in analyzed*11 "contents of carbon, silicon, phosphorus, sulfur, and boron. Using the abovej2 dnformation, a superior commercially-produced electrode was formulated which,3 |took advantage of chemical control over boron, titanium, and phosphorus.

{This electrode produced deposits exhibiting superior mechanical properties{and it was successfully utilized to fabricate a large nuclear reactor vessel'.

1617 ! INTRODUCTION18

19 kustenitic stainless steels are candidates for vessels, piping and other coni-20 jponents for advanced nuclear reactor, chemical processing, petrochemical, and21 coal liquefaction and gasification systems. Many of these components are ofj22 }»elded construction and are, or will be, used in service at elevated temper23 Jatures. Despite this wide usage, very little data have been made available24 Concerning the high-temperature creep properties of stainless steel weld-,. deposits. Also the limited data available show a high degree of scatter,, ^specially in creep ductility; much of the data show less than 10% total

2 6 {elongation (1).27 128 &s a result of the low creep ductility and the intense need for additional29 data for high-temperature design, an extensive stainless steel welding study!30 «Ls under way at the Oak Ridge National Laboratory. It involves several as-31 jpects: ferrite morphology characterization, effects of electrode coatings,32 fcnd effects of slight compositional differences on structure and properties.,, Using information developed in the study, an optimized electrode was pro-

duced commercially and used to successfully fabricate a large nuclear reac-Jtor vessel.

363738394041

STUDIES LEADING TO OPTIMIZED ELECTRODE

Ferrite Morphology

(The relative amount of ferrite in the austenite matrix is known to depend42 upon the specific composition of the weld deposit. Also the size and dis-43 );ribution are known to vary with welding process and operating conditions44 Jd.tb.in a given process. It therefore seemed appropriate to characterize45 the microstructure present in several differ^ut types of austenitic stain- .45 less steel weldments, considering in particular detail the method of.charac-J47 ,}:erization, and to determine whether or not at least part of the observedAa broperty variations can be attributed tc microstructural differences (2).

7 mechanical properties of stainless steel welds is described. The amount, i8 Isize, shape, and general distribution of ferrite in the weld metal was stud-j9 |ied in detail. The effects of electrode coatings on creep-rupture proper- J10 |ties were determined as were the influence of slight differences in analyzed}\l ^contents of carbon, silicon, phosphorus, sulfur, and boron. Using the above12 [information, a superior commercially-produced electrode was formulated which,

Itook advantage of chemical control over boron, titanium, and phosphorus. ,{This electrode produced deposits exhibiting superior mechanical properties *

1 4 Sand it was successfully utilized to fabricate a large nuclear reactor vessel15 r

1617

48

INTRODUCTION

ftustenitic stainless steels are candidates for vessels, piping and other comj-ponents for advanced nuclear reactor, chemical processing, petrochemical, and

18

19

21 £oal"liquefaction and gasification systems. Many of these components are of.22 gelded construction and are, or will be, used in service at elevated temper-^23 Jitures. Despite this wide usage, very little data have been made available '2 4 toncerning the high-temperature creep properties of stairless steel weld, deposits. Also the limited data available show a high degree of scatter,

(especially in creep ductility; much of the data show less than 10% total2 6 Jelongation (1).27 i28 &s a result of the low creep ducti l i ty and the intense need for additional29 cJata for high-temperature design, an extensive stainless s teel welding study,30 'is under way at the Oak Ridge National Laboratory. I t involves several as- '

h i i f f t f lectrode coatingsis under way at the Oak Ridge National L a y

31 jpects: ferrite morphology characterization, effer.ts of electrode coatings,fand effects of slight compositional differences on structure and propertiesUsing information developed in the study, an optimized electrode was pro-'duced commercially and used to successfully fabricate a large nuclear reac-t

STUDIES LEADING TO OPTIMIZED ELECTRODE

F e r r i t e Morphology

duced commetor vessel.

3536373839404 1 bie relative amount of ferrite in the austenite matrix is known to depend4 2 upon the specific composition of the weld deposit. Also the size and dis-43 fcribution are known to vary with welding process and operating conditions44 Within a given process. It therefore seemed appropriate to characterize45 the microstructure present in several different types of austenitic stain- ^4h !less steel weldments, considering in particular detail the method of.charac-,

fcerization, and to determine whether or not at least part of tl'e observedproperty variations can be attributed to microstructural differences (2).

*This copy will not be proofread by SME - Type within the dotted l i ne s .(Consult SME Autho r ' s Manual for typing in s t ruc t ions . )

AUTHOR'S NAMEG. M. Goodwin, N. C. Cole, R. T. King, and G. M. Slaughter

TITLE OF PAPER ADVANCES IN STAINLESS STEEI. WRLDINC FOR ELEVATED TEMPERATURESERVICE

PAGE NUMBER 2

Form #G-82



{The quantitative television microscope (QTW) was used extensively and found;to be a precise method for measuring ferrite contents in metallographic!cross sections of the weldments. It was noted, however, that metallographifcetching technique affected the reproducibility of the results, as did sev-Jeral equipment variables including the discrimination threshold setting.

•The difference in chemical composition of the filler metals used for each o:four typical welds caused the overall mean ferrite content to vary frtmi 3.1}to 8.2% as measured by the QTM. These results could not be accurately pre-•dicted from the existing Schaeffler, McKay, or similar diagrams. Further•investigation revealed substantial variations in ferrite content from weld•to weld produced under identical conditions (Fig. 1) from location to loca-tion along the center line of a particular weld, and from point to pointwith-1'., j. particular transverse weld cross section (Fig. 2).

•In addition to ferrite content, the distribution of ferrite present was als»•seen to vary substantially in each of the mentioned locations. In all in-Jstances, the ferrite was located at dendritic or cellular dendritic sub-structure boundaries, forming a more or less continuous network. The

10.1%7.3%-13.3%

12.6%10.3%-15.3% \

14.3%9 .4%- 19.8%

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WELD B WELD A, SAMPLE 64

Figure 1

WELD A , SAMPLE 61

jVariation in ferrite distribution in submerged-arc welds. Percent ferrite•values were measured by quantitative television microscopy. 300*. EtchantJ• KOH,K3Fe(CN)6. For each microstructure shown, the percentages give-the{average, minimum, and maximum ferrite contents.

•The difference in chemical composition of the filler metals used for each o{four typical welds caused the overall mean ferrite content to vary from 3.1}to 8.2% as measured by the QTM. These results could not be accurately pre-dicted froir. the existing Schaeffler, McKay, or similar diagrams. Furtherinvestigation revealed substantial variations in ferrite content from weldjto weld produced under identical conditions (Fig. 1) from location to loca-tion along the center line of a particular veld, and from point to pointwithin a particular transverse weld cross section (Fig. 2).

•In addition to ferrite content, the distribution of ferrite present was alsi•seen to vary substantially in each of the mentioned locations. In all in-• stances, the ferrite was located at dendritic or cellular dendritic sub-structure boundaries, forming a more or less continuous network. The

10.1%7.3%->3.3%

12.6%10.3%- 15.3%

14.3%9.4%-19.8%

Y-98879

WELD B WELD A, SAMPLE 64

Figure 1

WELD A, SAMPLE 61

•Variation in f e r r i t e dis t r ibut ion in submerged-arc welds. Percent f e r r i t eRvalues were measured by quantitative television microscopy. 300x. Etchant}iKOH,K3Fe(CN)6- For each microstructure shown, the percentages give the 'javerage, minimum, and maximum fe r r i t e contents.

*This copy will not be proofread by SME - Type within the dotted l ines.(Consult SME Author 's Manual for typing instruct ions. )


TITLE OF PA PEK ADVANCES IN STAINLESS STEEL WELDING FOR ELEVATED TEMPERATURE

PAGE NUMBER

SERVICE

Form //Ci-82



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Figure 2Variation in ferritc distribution in one cross section of a gas metal-arcweld sample. 300*. Etchant: KOH,K3F^(CN)6.

taverage dimensions and appearance of this network were highly variable fromweld to weld and from location to location within a particular weld.

•Mechanical properties tests indicated that the ferrite distribution plays a!•major role in the fracture process at elevated temperatures. The fracturepath almost exclusively follows the austenite-ferrite boundaries, producing\a fracture surface reproducing the solidification substructure in detail.

Tyje of Electrode Coating

'Shielded metal-arc electrode coverings are first evaluated on such practi-ical grounds as ease of deposition, bead contour, arc stability, depositionefficiency, and case of slag removal. Satisfactory bend and tensile prop-erties of the weld are also mandatory. The collection of sufficient long-time data in the creep range has not been of major concern in the past'because the applications have not required such data. Furthermore, the•influence of particular flux coverings on the creep-rupture properties has•received minimal attention. For this reason, ORNL obtained creep data at1200°F (649°C) on type 30°. stainless steel weld metal deposited with theJthree most common types Oi. E308 covered electrodes (3).

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i Figure 2(Variation in ferrite distribution in one cross section of a gas metal-arc{weld sample. 300*. Etchant: KOH,K3Fe(CN)6.

•average dimensions and appearance of this network were highly variable from){weld to weld and from location to location within a particular weld.

•Mechanical properties tests indicated that the fcrrite distribution plays a!•major role in the fracture process at elevated temperatures. The fracture '•path almost exclusively follows the austenitc-ferrite boundaries, producingJa fracture surface reproducing the solidification substructure in detail.

Type of Electrode Coating

'Shielded metal-arc electrode coverings are first evaluated on such practi-ical grounds as ease of deposition, bead contour, arc stability, depositiontelficiency, and case of slag removal. Satisfactory bend and tensile prop-Jerties of the weld are also mandatory. The collection of sufficient long-Jtirae data in the creep range has not been of major concern in the past•because the applications have not requ? ad such data. Furthermore, the•influence of particular flux coverings *>:< the creep-rupture properties hasireceived minimal attention. For this reason, ORNL obtained creep data atJ1200°F (6A9°C) on type 308 stainless steel weld metal deposited with theJthree most common types of E308 covered electrodes (3).

*This copy will not be proofread by S M E - Type within the dotted lines.(Consult SMI:" Author's Manual for typing instructions. )

AUTHOR'S NAMEG. M. Goodwin, N. C. Colet R. T. King, and G. M. Slaughter

TIT1,E OF P A P E R ADVANCES IN STAINLESS STEEL WELDING FOR ELEVATED TEMPERATURESERVICE '

PAGE NUMBER I 3 I

Form 0G-82


SOCIETY OF MANUFACTURING ENGINEERS IGeneral classes of stainless steel electrode coating formulas are wellknown and accepted throughout the welding industry. For example, stainless!steel electrodes usually have either a "lime," "lime-titania," or "titania"rtype covering. Table 1 gives approximate ingredients one might expect touse in the formulation of the three basic types of stainless steel electrodf• coverings. Each car.ufacturer has his own proprietary formulations, but •generally the lime-type covering contains more calcium carbonate (limestone}and calcium fluoride (fluorspar) than the titania-type covering, and thetitania-type covering contains more titanium dioxide (titania). The lime-titania covering is somewhat of a compromise between the other two types.

Table 1. Typical Covering Compositions for Stainless Steel Electrodes

CoveringType

Ingredient, % AlloyAdditionsand OtherCalcium Calcium T. . Sodium Potassium

Carbonate Fluoride ilcanla Silicate Silicate Ingredients'

Lime

tiroe-titania

fitania

37

30

25

33

15

20

3

25

35

15

5 10

15

12

15

5

aFerromanganese, ferrosilicon, binders, etc.

JTable 2 summarizes the creep-rupture data at 1200°F (649°C) for specimenstested at three stress levels. The lime-covered electrode weld metal gen-erally had the shortest rupture times and the greatest total elongation ateach stress level. The lime-titania- and titania-covered electrode deposit^{behaved nearly identically, rupturing with low ductility in long-tena tests}.•They strained less than 1% in tests lasting about 600 hr. The differences

Table 2. Creep-Rupture Test Results on Experimental CoveredElectrode Deposits at 1200°F (649°C)a

CoveringType

Lime

Lime-titania

Titania

Stresses

Rupture Time

25,000psi

27

44

26

are. 172

20,000psi

135

363

322

!, 138,

, hr

18,000psi

212

575

655

and 124

Total

25,000psi

22.5

10.2

23.0

MPa.

Elongation, %

20,000psi

11.5

2.0

1.1

18,000psi

6.0

0.50

0.85

coverings. Each manufacturer has his own proprietary formulations, butgenerally the lime-type covering contains more calcium carbonate (limestone}and calcium fluoride (fluorspar) than the titania-type covering, and thetitania-type covering contains more titanium dioxide (titania). The lime-titania covering is somewhat of a compromise between the other two types.

Table 1. Typical Covering Compositions for Stainless Steel Electrodes

CoveringType

Ingredient,

CalciumCarbonate Fluoride

AlloyAdditions

Calcium „, . Sodium Potassium and Otherlitania S i l i c a t e silicate Ingredients'

Lime 37

lime-titania 30

fitania 25

33

15

20 35

15

5 10

15

12

15

5

rerromanganese, f e r r o s i l i c o n , b inders , e t c .

JTable 2 summarizes the creep-rupture data a t 1200"F (649°C) for specimens• tes ted a t three s t r e s s l e v e l s . The lime-covered e lec t rode weld metal gen-l e r a l l y had the shor tes t rupture limes and the grea tes t t o t a l elongation a teach s t r e s s l eve l . The l i m e - t i t a n i a - and t i tan ia-covered e lect rode deposit*;

{behaved nearly i d e n t i c a l l y , rupturing with low d u c t i l i t y in long-term t e s t s j'They strr.ined l e s s than 1% in t e s t s l a s t i ng about 600 hr . The di f ferences

Table 2. Creep-Rupture Test Resul ts on Experimental CoveredElectrode Deposits a t l200°F (649°C)a

CoveringType

Lime

Lime-titania

Titania

Rupture Time

25,000psi

27

44

26

20,000psi

135

363

322

, hr

18,000psi

212

575

655

Total

25,000psi

22.5

10.2

23.0

Elongation, %

20,000psi

11.5

2.0

1.1

18,000psi

6.0

0.50

0.85

Stresses are 172, 138, and 124 MPa.

*This copy will not be proofread by SME - Type within the dotted l i ne s .(Consult SME Author ' s Manual for typing i n s t ruc t i ons . )


TITLE OF PAPER ADVANCES IN STAINLESS STEEL WELDING FOR ELEVATED TEMPERATURE

PAGE NUMBER

SERVICE

Form //G-8?.



Jin creep behavior at long times include nearly all of the strain-time char-tacteristics. Figure 3 shows that the minimum creep rate and the tertiary{creep behavior of the lime-covered electrode deposits differ markedly from"the titania- and lime-titania-covered electrode deposits at the lowest•stress. The lime-covered deposit has little "steady-state" or secondary•creep strain, while the lime-titania- and titania-covered electrode deposits•remain in second-stage creep for relatively long periods of time with a"much reduced third-stage creep.

I3I fi

1 ORNL-DWG 70-9133

CD LIME COATEO ELECTRODE

A LIME-TITANIA COATED ELECTRODE

+ TITANIA COATliO ELECTROOE

0 »00 200 300 *0C 500 600 700 800TIME (hr)

Figure 3{Elongation versus time for experimental stainless steel deposits at 1200*F

(649°C) and 18,000 psi (124 MPa).

{When the total elongation data, however, were plotted as a function of time{it became apparent that the ductilities of all three deposits tend to ap-proach zero total elongation for rupture times in the order of 1000 hr.

Slight Compositional Variations

•Previous work on compositional effects on stainless steel welds have usualljjibeen concerned with the influence of such elements as S, C, P, and Si onJhot-cracking tendency, tensile strength, tensile ductility, and impact be-[havior. In our study (4), we determined the effects of various amounts ofjthese same elements on the 1200°F (649°C) creep-rupture properties of type•E308 weld deposits. Boron was also included in the experiments because itti

•remain In second-stage creep for relatively long periods of time with a 'V«ch reduced third-stage creep.

ORNL-DWG 7O-S133

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1

1

i•t8

im

• 1

•1

O D M

+ TIT«

E COATE

E-TITANI

NIA CO A

3 ELECTF

A COATE

TED ELE

?ODE

D ELECT

CTRODE

RODE —

100 200 300 400 500TIME (hr)

600 700 800

Figure 3

{Elongation versus time for experimental stainless steel deposits at 1200*F

(649°C) and 18,000 psi (124 MPa).

{When the total elongation data, however, were plotted as a function of timeit becan.?. apparent that the ductilities of all three deposits tend to ap-proach zero total elongation for rupture times in the order of 1000 hr.

Slight Compositional Variations

•Previous work on compositional effects on stainless steel welds have usuallyibeen concerned with the influence of such elements as S, C, P, and Si onJhot-cracking tendency, tensile strength, tensile ductility, and impact be-Jhavior. In our study (4), we determined the effects of various amounts of'these same elements on the 1200°F (649°C) creep-rupture properties of type£308 weld deposits. Boron was also included in the experiments because it

*This copy will not be proofread by SME - Type within the dotted l i n e s .(Consult SME Author ' s Manual for typing i n s t ruc t i ons . )


TITLE OF PA PER ADVANCES IN STAINLESS STEEL WELDING FOR ELEVATED TEMPERATURE_. SERVICE

PAGE NUMBER

Form #G-82



has been reported (5) to improve the creep resistance of various ferrousalloys.

•The slight differences in the chemical deposit analyses of the differentelectrode batches were brought about solely as a result of small one-at-a-time changes in electrode covering formulation. That is, several batches5 of experimental electrodes were made by an industrial electrode manufac-turer from the same heat of type 308 stainless steel core wire, upon whichseveral slightly different covering formulations were applied. In all•cases, the coverings were of a typical "lime-titania" formulation (ac anddc reverse polarity, all-position electrode). Moreover, in no case did the!•adjusted deposit composition of an experimental batch of electrodes fail to,meet the specification (AWS A5.4-69).

•Table 3 shows the results of the creep tests run at 1200°F (65O°C) under20,000 psi (138 MPa) static stress. The differences in creep behavior ofthe various altered deposits become more apparent at this stress and theresulting longer rupture times, [as compared to shorter tests at 25,000 psi|(172 MPa)]. The deposit of higher carbon content proved to be much stronger•than the "standard" deposit under these conditions. Lowering the carbon

Table 3. Effect of Compositional Variables on the CreepProperties of Shielded Metal-Arc E308 Stainless SteelWelds at 1200°F (650°C) and 20,000 psi (138 MPa)

CompositionalVariables

Std lime-titaniacoveringa

Carbon, % ALow, 0.035 MHigh, 0.074 m

Silicon, % ij:Low, 0.29High, 0.73

Phosphorus, %Medium, 0.023High, 0.034

Sulfur, %Low, 0.006High, 0.027

Boron, %Medium, 0.004High, 0.006

aO.O44% C, 0.47% Si,

RuptureTime(hr)

363

3461334

127651

1661329

333292

11671159

0.012% P, 0.016% S,

TotalElongation

(%)

2.0

4.01.75

15.71.3

9.64.35

2.64.05

7.57.8

0.001% B.

time changes in electrode covering formulation. That is, several batchesi of experimental electrodes were made by an industrial electrode manufac-turer from the same heat of type 308 stainless steel core wire, upon whichseveral slightly different covering formulations were applied. In allcases, the coverings were of a typical "lirae-titania" formulation (ac andJdc reverse polarity, all-position electrode). Moreover, in no case did thel!adjusted deposit composition of an experimental batch of electrodes fail to"meet the specification (AWS A5.4-69).

Table 3 shows the results of the creep tests run at 1200°F (650°C) under20,000 psi (138 MPa) static stress. The differences in creep behavior ofthe various altered deposits become more apparent at this stress and theresulting longer rupture times, [as compt ed to shorter tests at 25,000 psi{(172 MPa)]. The deposit of higher carbon ontent proved to be much stronge*•than the "standard" deposit under these conditions. Lowering the carbon

Table 3. Effect of Compositional Variables on the CreepProperties of Shielded Metal-Arc E308 Stainless SteelWelds at 1200°F (650°C) and 20,000 psi (138 MPa)

CompositionalVariables

RuptureTime(hr)

TotalElongation

Std lime-titaniacoveringa

Carbon, %Low, 0.035High, 0.074

Silicon, %Low, 0.29High, 0.73

Phosphorus, %Medium, 0.023High, 0.034

Sulfur, %Low, 0.006High, 0.027

Boron, %Medium, 0.004High, 0.006

363

3461334

127651

1661329

333292

11671159

2.0

4.01.75

15.71.3

9.64.35

2.64.05

7.57.8

0.04452 C, 0.47% Si , 0.012% P, 0.016% S, 0.001% B.

*This copy wi 1 not be proofread by SME - Type within the dotted l i ne s .(Consult SME Autho r ' s Manual for typing ins t ruc t ions . )


T I T L E OF PA P E P ADVANCES IN STAINLESS STEEL WELDING FOR ELEVATED TEMPERATURESERVICE

PAGE NUMBER *""

Form //G-82



1234567891011121314151617181920212223242526272829303132333435363 73839404142434445464748

* content below the "standard" did not appear to have any significant effection the rupture life of the deposit, but it did increase rupture ductility.! Adding boron to the type E308 deposit seemed to improve significantly both{the rupture life and t^e rupture ductility. Lowering the amount of siliconjJ in the type E3O8 deposit very markedly increased the final rupture ductilitt•but this effect is probably due to a corresponding loss of rupture life.•There seems to be very little difference as a result of sulfur content.i

|At a lower stress level of 18,000 psi (124 MPa), where longer times to rup-Jture are involved, it became apparent that additions of phosphorus and boroft•significantly strengthen the weld deposit and add resistance to creep em-ibrittlement when compared with other type E308 deposits.

•Figure 4 summarizes the effect of composition on the creep ductility of the|type E308 deposits studied in this investigation. If one would imagine the;• lines missing, it would become apparent how difficult it is to assemble•good creep ductility data on a certain type of weld deposit, such as type{E308. Nevertheless, it can be seen from Fig. 4 that the boron-doped deposi^J(0.004% B) demonstrates the best creep ductility for any given rupture life

ORNLDWG. 70-40«2R

1.0 100 1000 10,000

TIME(hr»)

Figure 4•Effect of composition on the creep ductility of shielded metal-arc welds atiil200°F (650°C).

•The high-phosphorus deposit (0.034% P) was the next best, followed by the•low-silicon deposit (0.29% Si). Somewhat disquieting was the fact that allithe deposits tended toward zero ductility with extended rupture lives.• Again, the boron-doped deposits, as well as the high-phosphorus and -low-Jsilicon deposits, appeared to be most resistant to this phenomenon.

5'6789101112131415161718192021222324252627282930313233343536373839404142434445464748

J *n *«w EJUD deposit "Very warreaiy increased r.ne i max rupture aucriiXTYjbut this effect is probably due to a corresponding loss of rupture life.iThere seems to be very little difference as a result of sulfur content.

{At a lower stress level of 18,000 psi (124 MPa), where longer times to rup-_Jture are involved, it became apparent that additions of phosphorus and boroftjsignificantly strengthen the weld deposit and add resistance to creep era-is brittlement when compared with other type E308 deposits.

•Figure 4 summarizes the effect of composition on the creep ductility of the• type E308 deposits studied in this investigation. If one would imagine the;ilines missing, it would become apparent how difficult it is to assemblei good creep ductility data on a certain type of weld deposit, such as type{E308. Nevertheless, it can be seen from Fig. 4 that the boron-doped deposi^| (0.004% B) demonstrates the best creep ductility for any given rupture life

OBNL OWS. 7O-4O4 2R

1.0 100 1000 10,000

TIME<hr»)

Figure 4

•Effect of composition on the creep ductility of shielded metal-arc welds atiJ1200°F (650°C).iiiJThe high-phosphorus deposit (0.034% P) was the next best, followed by the•low-silicon deposit (0.29% Si). Somewhat disquieting was the fact that allithe deposits tended toward zero ductility with extended rupture lives,iAgain, the boron-doped deposits, as well as the high-phosphorus and -low-Jsilicon deposits, appeared to be most resistant to this phenomenon.ii _

*This copy will not be proofread by S.ME - Typo within the dotted l i n e s .(Consult SME Author ' s Manual for typing in s t ruc t ions . )

AUTHOR'S NAMEG.'M. Goodwin, N. C. Cole, R. T. King, and G. M. Slaughter

TITLE OF PAPER ADVANCES IN STAINLESS STEEL WELDING FOR ELEVATED TEMPERATURESERVICE

PAGE NUMBER

Form #G-82



'Interestingly, the standard composition curve falls at the lower boundaryiof the family of curves.

BEHAVIOR OF OPTIMIZED ELECTRODE

An optimized E308 stainless steel electrode that contained 0.007% B, 0.06%jTi, and 0.04% P was produced by an industrial manufacturer. It has been{designated type 308 CRE stainless steel for the controlled residual elements•it contains. We conducted an extensive mechanical properties and metallo-graphic investigation of welds deposited on 2 3/8-in.-thick (60 mm) type304 stainless steel plate (6).

•The test specimens were categorized according to distance from the nearestjplate surface regardless of the side of the midplane from which they came"(Fig. 5).

L1

L2

L3

L3

L2

LI

6

71

8

10

ILONGITUDINAL BLOCKING

Figure 5

•Location and orientation of standard specimens in the test weld. Hour-glas^{shaped region represents weld metal.

•The superiority of the type 308 CRE stainless steel composition is evidentJin Fig. 6. All the total strain data are contained in a scatter band whenplotted against rupture time and are compared with standard commercial weld j'.metal and earlier developmental welds in the ORNL program. The lowest ob-served total creep strain for a CRE all-weld-metal specimen is 13%. In-Sternal cracks did not develop at interphase boundaries, as they tended toJdo in standard stainless steel weld metal.

•The microstructure varied systematically through the thickness of the weld.<In the initial passes at the center of the weld, dislocation densities are

BEHAVIOR OF OPTIMIZED ELECTRODE

An optimized E308 stainless steel electrode that contained 0.007% B, 0.06%|Ti, and 0.04% P was produced by an industrial manufacturer. It has been'designated type 308 CRE stainless steel for the controlled residual elements•it contains. We conducted an extensive mechanical properties and metallo-graphic investigation of welds deposited on 2 3/8-in.-thick (60 mm) type304 stainless steel plate (6).

JThe test specimens were categorized according to distance from the nearestplate surface regardless of the side of the midplane from which they came(Fig. 5).

LONGITUDINAL BLOCKING

Figure 5

{Location and orientation of standard specimens in the test weld. Hour-glas^shaped region represents weld metal.

iThe superiority ot the type 308 CRE stainless steel composition is evident|in Fig. 6. All the total strain data are contained in a scatter band wheniplotted against rupture '.ime and are compared with standard commercial weld'metal and earlier developmental welds in the ORNL program. The lowest ob-•served total creep strain for a CRE all-weld-metal specimen is 13%. In-Sternal cracks did not develop at interphase boundaries, as they tended to!do in standard stainless steel weld metal.

•The microstructure varied systematically through the thickness of the weld.•In the initial passes at the center of the weld, dislocation densities are

*This copy will not be proofread by SME - Type within the dotted l ines .(Consult SMF. Au thor ' s Manual for typing in s t ruc t ions . )

AUTHOR'S NAMEG. M. Coodwin, N. C. Cole, R. T. King, and C. M. Slaughter

TITLE OF PA PICK ADVANCES IN STAINLESS STEEL WELDING FOR ELEVATED TEMPERATURE

PAOK NUMP.KR 8

SERVICE

2

Form 0CJ-82



0RNL-0WG73-6355R3110

100

90

eo

I — I ! I ! I I I I 1 1 I I M I I I777 CRE 308 STAINLESS STEEL WELOS

SPECIMEN TYPE TEST TEMPERATURELI L2 L3 °C 'fo o • 482 900o • • 565 1050a n * 593 1100v • » 649 1200

' STANDARD 308 STAINLESS STEEL WELD METAL" AT 1050 AND 1200°F, ASTM STP 226308 STAINLESS STEEL DEVELOPMENT SERIESWELDS AT 1200°F (ORNL)

2 5 102 2 5 103 2 5 104 2RUPTURE TIME <hr)

Figure 6

{Ductility in creep-rupture testc of type 308 stainless steel welds.

highest, dislocation loops form, cell structures form, and MzaCg carbidesprecipitate on austenite-ferrite interfaces as a result of numerous thermal;•and mechanical cycles experienced during welding. The carbide precipitate•density, loop density, and dislocation density decrease gradually coward t•surface of the weld, where less thermal and mechanical cycling occur. Near!the surface lew dislocation loops and no precipitate arc present, and thedislocation density is about a factor of 2.8 lower than near the center of•the weld. The dislocations near the surface are generally straight, with•only a hint of crude cell structure. These characteristics are shown in'Fig. 7.

jThe systematic variations in creep properties at small and large strains•and in tensile properties arc at least partly attributable to these

90

80

g 70

2Op 60

z

2 50

40

30"

20

10

oo

482 900565 (050593 1100649 1200 t

STANDARD 308 STAINLESS STEEL WELD METALAT 1050 AND 1200'F, ASTM STP 226308 STAINLESS STEEL DEVELOPMENT SERIESWELDS AT 1200'F (ORNL)

101 102 2 5 103 2RUPTURE TIME (hr)

Figure 6

'Ductility in creep-rupture tests of type 308 stainless steel welds.

highest, dislocation loops form, cell structures form, and M23C6 carbidesprecipitate on austenite-ferrite interfaces as a result of numerous thermal"{and mechanical cycles experienced during welding. The carbide precipitate'density, loop density, and dislocation density decrease gradually toward th{surface of the weld, where less thermal and mechanical cycling occur. Nearthe surface few dislocation loops and no precipitate are present, and thedislocation density is about a factor of 2.8 lower than near the center ofthe weld. The dislocations near the surface are generally straight, withonly a hint cf crude cell structure. These characteristics are shown inFig. 7.

The systematic variations in creep properties at small and large strains•and in tensile properties arc at least partly attributable to these

*This copy will not be proofread by SNiF! - Typo within the dotted lines.(Consult S M K Author's Manual for typing instructions. )

AUTHOR'^ N A M EG. M. Goodwin, W. C. Cole, R. T. Kinft, and G. M. Slaughter

TITl.F: OK 1JAPEH_AHVANCKS IN STARLESS STEEL HELPING FOR ELEVATED TEMPERATURE-SERVICE

PAGF. N

Form HG-SZ



Figure 7

As-welded microstructure of type 308 CRE stainless steel weldment. (a)jMacrostructure; (b) weld metal contained in LI specimen; (c) weld metal•contained in L3 specimen.

microstructural variations. Weld metal from initial passes is stronger•than weld metal in the final passes.

•This optimized electrode was successfully used in the construction of alarge nuclear reactor vessel.

ACKNOWLEDGEMENT

The breadth and duration of the efforts described in this paper preclude• individual recognition of each of those who have contributed to its progress;Some who are highly involved in the early stages of the work are not nowinvolved in the continuing study or are with other companies. Additionallythe cooperation and counsel of staff members of Combustion Engineering,JNuclear Division, have been invaluable through many phases of the program.{Within the Oak Ridge National Laboratory, members of many groups, including!•Welding and Brazing, Mechanical Properties, Metallography, ElectronMicroscopy, and the Reports Office have contributed.

REFERENCES

!l. H. R. Voorhees and J. W. Freeman, The Elevated-Temperature Pvopertiesof Weld-Deposited Metal and Weldments, ASTM Speo. Tech, Publ. 226,American Society for Testing and Materials, Philadelphia, 1958.

i ySKtt^i^Atot^ * i

Figure 7

As-welded microstructure of type 308 CRE stainless steel weldment. (a)JMacrostructure; (b) weld metal contained in LI specimen; (c) weld metal•contained in L3 specimen.

microstructural variations. Weld metal from initial passes is strongerJthan weld metal in the final passes.

iThis optimized electrode was successfully used in the construction of alarge nuclear reactor vessel.

ACKNOWLEDGEMENT

The breadth and duration of the efforts described in this paper precludeindividual recognition of each of those who have contributed to its progress•Some who are highly involved in the early stages of the work are not nowinvolved in the continuing study or are with other companies. Additionallythe cooperation and counsel of staff members of Combustion Engineering,JNuclear Division, have been invaluable through many phases of the program.JWithin the Oak Ridge National Laboratory, members of many groups, includingWelding and Brazing, Mechanical Properties, Metallography, Electron•Microscopy, and the Reports Office have contributed.

REFERENCES

1. H. R. Voorhees and J. W. Freeman, The Elevated-Temperature Propertiesof Weld-Deposited Metal and Weldments, ASTM Spec. Tech. Publ. 226,American Society for Testing and Materials, Philadelphia, 1958.

*This copy will not be proofread by S M F - Type within the dotted lines.(Consult S M E Author's Manual for typing instructions. )

A U TM OR' S N A M EG. M. Goodwin, N. C. Cole, R. T. King, and G. M. Slaughter

TITLE O F P A P E R ADVANCES IN STAINLESS STEEL WELDING FOR ELEVATED TEMPERATURESERV̂ .'l*

PAGE NUMnnU I I10

Form 0G-82



27 " "G" M" "Goodwin",~ 57"c." "bole""and" G"~M7 "slaughter,""'A* Study""of"Ferrite"Morphology in Austenitic Stainless Steel Weldments," Weld. J. (Miami)51(9): 425-s-429-s (September 1972).

3. N. C. Binkley, G. M. Goodwin, and D. G. Harman, "Effects of ElectrodeCoverings on Elevated Temperature Properties of Austenitic StainlessSteel Weld Metal," Weld. J. (Miami) 52(7): 306-s-311-s (July 1973).

4. N. C. Binkley, R. G. Berggren, and G. M. Goodwin, "Effects of SlightCompositional Variation on Type E308 Electrode Deposits," Weld. J.(Miami) 53(2): 91-s-95-s (February 1974).

5. J. J. Heger, "Residual Elements in Stainless Steel — General Character-istics," p. 13A in Effects of Residual Elements on Properties ofAustenitic Stainless Steel, ASTM Spec. Tech. Publ. 418, American Societ;for Testing and Materials, Philadelphia, July 1967.

6. R. T. King, J. 0. Stiegler, and G. M. Goodwin, "Relation BetweenMechanical Properties and Microstructure in CRE Type 308 Weldments,"Weld. J. (Miami) 53(7): 307-s-313-s (July 1974).

\

•-J»ut»"» Jl 'A"

4. \ N. C. Binkley, R. G. Berggren, and G. M. Goodwin, "Effects of SlightCompositional Variation on Type E3O8 Electrode Deposits," Weld. J.(Miami) 53(2): 91-s-35-s (February 1974).

5. J . J . Heger, "Residual Elements in Stainless Steel — General Character-i s t i c s , " p. 134 in Effects of Residual Elements on Properties ofAustenitio Stainless Steel, ASTM Spec. Tech. Publ. 418, American Societyfor Testing and Mate r i a l s , Phi ladelphia , July 1967.

6. R. T. King, J . 0. S t i e g l e r , and G. M. Goodwin, "Relation BetweenMechanical P rope r t i e s and Microstructure in CRE Type 308 Weldments,"Weld. J. (Miami) 53(7): 307-s-313-s (July 1974).

# T h i s copy will not be proofread by SMVJ - Type within the dotted l i n e s .(Consul t SME A u t h o r ' s Manual for typing i n s t r u c t i o n s . )


T I T L E OF P A P E R ADVANCES IN STAINLESS STEEL WELDING FOR ELEVATED TEMPERATURE

PAGE NUMBERSERVICE

11

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