stress rupture behavior of post weld heat treated 2%281 4 cr%2d1mo steel weld metal 12495

8/13/2019 Stress Rupture Behavior of Post Weld Heat Treated 2%281 4 Cr%2d1mo Steel Weld Metal 12495

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Stress Rupture Behavior of PostWeld Heat Treated,2-1 /4Cr-1 Mo Steel Weld Metal IM1rehl,1 -- ( I,,.1 iJ/--

tl!ks Z C, U7l

Ln/din kB -:,S4 - B JFKrl Jw-LG -By C. D. LJndii. C. Kelley, R. Menon, and B. J. KruseU --1 T: - r-- U1--e./ l 2 B ,-- U _tw&dquo;&dquo;.1-r .-CONTEN -. be a third WRC Bulletin on this subject. That Bulletin will

report the results of several long-time stress rupture testsForeword ............................... 1 now underway. It is anticipated that the Bulletin will also

Abstract ................................ 1 report the results of work on some other important aspectsintroduction ............................ 2 of the high temperature performance of Cr-Mo steel weld-History andApplications ................. 2 menta.Properties ...................... 2 The authors are to be commended for this monumentalCreep Strengthening Mechanisms in Low

contribution to our knowledge of the high temperature prop-Alloy Ferritic Steele .................... 3 erties of 2Y4-Cr 1-Mo steel weld metaL

Availability ............................ 4

Literature Review ....................... 4 W. L. Wilcox, ChairmanMicrostructure-Base Metal and Weld Metal 4

Subcommittee on Weld Metals andMicrostructural Effectson Creep Strength .. 7 Subcommittee on Weld Metals andAlloying Element Effects on Creep Strength . 9 Welding Procedures for Pressure

Stress Itnpture DataAnalysis.............. 17 Vessel Steels, of the PressureSummary .............................. 18 Vessel Research Committee

Materials and Experimental Procedure .... 19

Materials .............................. 19Stress Rupture Testing ................... 19Transformation Studies .................. 22

Results and Discussion ............... 23Abstract

Stress Rupture DataAnalysis ............. 23 The goal of this program was to determine the effect of> Comparison of DataAnalysis Techniques .... 45 carbon content and postweld heat treatment (PWHT) on

Tensile Testing ........................ 46 the stress rupture strength of 2-1/4Cr-IMo weld metal InMicrostructuralAnalysis ................. 47 order to establish the correlation between carbon level and

Conclusions 62rupture strength, weld metals with carbon contents in the

Conclusions ............................. 62 range of 0.02-0.13 weight percent were tested. For this, the IAppendixA ............................. 64 first phase of the study, the PWHT selected was 13000 F forReferences .............................. 65 25 hr. For the second phase, the effect ofPWHT on rupture

strength was evaluated by testing 0.08-0.09 carbon weldmetal PWHT at 1175* F for 25.5 hr, comparing the results

Foreword with those for the same material PWHT at 1300 F for 25 hr.To gain further insight into the relationship between the

This WRC Bulletin 315 complements WRC Bulletin 277, rupture strength of 2-1/4Cr-1Mo weld metal and both car-issued in May of 1982. Together, these Bulletins address the bon content and PWHT, additional rupture data were col-creep properties of 21/4-Cr 1-Mo steel weld metal deposited lected from the literature with the restriction that only datawith several different welding processes. They contain data from tests of 100 percent weld metal specimens in theobtained from the literature as well as from the many tests PWHT condition be considered. The resulting data base,conducted on this program. The experimental data, in both consisting of data from this program as well as from thereports, are for weld metal of several different carbon con- literature, was partitioned by both temper parameter andtents postweld heat treated at either of two commonly used carbon content and analyzed using three separate tech-

postweld heat treating temperatures. The welding processes niques. The complete data obtained for this study are avail-for the experimental work reported in Bulletin 277 were able upon request from The Metal Properties Council-

electroslag and submerged arc, whereas the process for the The results of the analysis indicated that the 100,000 hourexperimental work in this Bulletin is shielded metal arc rupture strength of 2-1/4Cr-IMo weld metal increases as the(covered electrodes). The extensive literature review provid- temper parameter [P = (T + 460)(20 + logt) X 10-3], which ed data foach of these three processes, as well as for other charactertzes the PWHT, decreases. This effect is particu-welding processes, larly pronounced for weld metal PWHT withP < 32.0 which, ,.The work continues, and sometime in the future there will at 750 F, has a 100,000-hr rupture strength 40 to 45 KSI f

higher than that of weld metal PWHT with 32 0 < P < 36 2C. D. Lundinis Professor and Director of 1% elding Research and R Menonis

This strength advantage diminishes rapidly with increasingResearchAssooate m the Department of materials Science and Engneenng, temperature and becomes insignificant at approximatelyyThe University of Tennessee, Knoxvtlle,TN S.C. HelleyeaV1-eldmg Metal- 9000 F.ur ist at The Homer Research Laboratories. Bethlehem Steel Corporation .. ff.f...t t ..d dand B J. The Homer Staff Engineer with The Duke Power Company Char. The effect of carbon content on rupture strength dependand B J. Kruse is a Staff Engoneer ..,th The Duke Power Compan. Char. e e ect Car on conenon rup ure strengt epen slotte surth CaroLna

_on the PWHT given to the material For weld metal PWHT

rubhcanon of this report was sponsored bB the Subcommittee on e)d w,th DT- - . 100,000-hr ru ture strenh mcreases wtthPublication of this report %as of the Pressure Vesse) Research Weld %%ith P < 3 5 the 100,000-hr rupture Strength increases withMetals and Welding Procedures of the Pressure Vessel Research Com- p Creases &dquo;&dquo;

mittee of the Reldmg Research Council carbon level 0B er the entire range of carbon contents typical

2-114Cr-IMo Weld Metal 1

##RP%?YG.W*#*ziow* . . .. __ ..- .. -...*m+ - -..&dquo;&dquo; . - -II...


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strength of weld steel In contrast, the 100,000-hr rupture and handling equipment on a regular basis where tem- 1,strength of weld metal given a more extensive PWHT (P > peratures may reach as high as 1000 F to 1100* F.2-3 t37.5) appears to increase with carbon content only for levels In the petrochemical industry, pressure vessels and

up to about 0 05 weight percent. Weld metals having higher , . , ,.carbon contents have similar rupture strengths It should be reactors used in the refining and processing of petro-

noted. however, that the strengthenmg effect of carbon dl- leum are commonly composed of 2-1/4Cr-1Mo steel.4.-l ,minishes as the temperature increases Such processes as thermal reforming, polymerization, .

In support of the rupture testing effort, extensive micro- alkylation, and hydrocracking are performed in these ttstructural examination of the above weld metals in the as- vessels at high temperatures and pressures.3.6 In the jwelded, PWHT, and rupture tested condition was per- vessels at nign temperatures and pressures, in me jformed using the SEM and STEM This microstructural pastfew

years, 2-1/4Cr-lMo steel has also come to be ,work was aimed at characterizing the microstructure as a used in the fabrication of heavy-section well-head ifunction of carbon content and PWHT with the ultimate equipment because of its resistance to sulfide stress- igoal of correlating the microstructure with the stress rupture cracking.44properties. SEM examination of the weld metals revealed 2-1/4Cr-1Mo steel is being favorably considered forthe dependence of microconatituent morphology on prior

a number of uses in the alternative ener field.

material history. Furthermore, to obtain information on the anumber of uses in the alternative energy field.

type, size, morphology, distribution, and composition of the Spurred on by theArab oil embargo of 1973 and in 1alloy carbides present, STEM examination of carbide ex- anticipation of future petroleum shortages resultingtraction replicas taken form weld metal specimens was also from a dwindling supply of a limited resource, researchconducted. la .... . - - and development in the areas of nuclear energy (fastEfforts to correlate the weld metal microstructure with breeder. coal -r- /. r - andobaerved ruputre behavior were successful. Microstructural er. reactors), coal gascabon/uquifactton. apdanalysis indicated that the superior rupture strength of the synthetic fuels has continued.Although its use was0.08-0.09 carbon weld metal PWHT 1175 F/25.5 hr is pri- never fully realized in the ill-fated Clinch River liquid .marily a consequence of the strengthening effect of the fme metal fast breeder reactor,7,8 2-1/4Cr-lMo steel has

acicular M2C carbides present within the matriz. In con- been used in the construction of several European fasttrast, the rupture behavior ofweld metal PWHT 1300 F/25 breeder reactors as well asfor superheaters in thehr is determined primarily by the major constituents present breeder reactors as ell as for superheaters m the in the microstructure. The 0.02-0.03 carbon weld metal has a Russian BOR-350 project.9 Coal, a resource which this !fully ferritic structure and also has the lowest rupture nation possesses in great supply, is of significant inter-strength. The higher carbon materials (0.04-0.05, 0.08-0.09, est as a raw material from which liquid and gaseousand 0.12-0.13 weight percent) have a tempered bainite products can be made for use as fuels and replace.structure and have similar rupture strengths despite the ments for some of the petrochemicals employed today.variations in carbon content. menta for some of the petrochemicals employed today.Weld metal specimens were thermally cycled on the Glee- 2-1/4Cr-Mo steel is considered the primary material

ble using a variety of thermal cycles designed to simulate the for the fabrication of the pressure vessels required forthermal history occurring in the coarse-grained region of the these processes. These vessels would operate at 750 Fweld metal HAZ during welding. Cooling conditions were to 9M* F at pressures of 1000 to 4000 PSI.10chosen to span the normal range of weld energy inputs char-

acteristic of welds in heavy-section Cr-Mo materials.A dila- Propertiestometric technique was employed to detect the weld metal

2-1/4Cr-lMo steel is a low carbon, low alloy ferritictransformation during cycling and the data obtained used to 2-1/4Cr-1Mo steel ia a low carbon, low alloy ferritictranaformatlon dunng cycling and the data obtained used to I.th a. al....T bI 1 I .isconstruct CCT diagrams. SEM examination of the resulting steel with a nominal composition given in Table 1. It ismicrostructures was then performed to determine the micro- particularly well suited to elevated temperature ser-constituents produced as a consequence of the thermal his- vice because of the following properties. First,tory. _ . 2-1/4Cr-lMo steel has good high temperatureBoth the dilatometric studies and the microstructural an- strength2-14 as characterized by elevated temperaturealyses indicated that the as-transformed microstructure of .

the 0.08-0.09 and 0.12-0.13 carbon weld metals is fully baini- tensile strength, creep strength, and rupturetic except in the material thermally cycled 150 KJ/IN (2400 strength.14 It has been called the strongest low alloyF peak temperature, 400 F preheat, 2-inch plate) which steel for high temperature service7 and is second onlycontain traces of polygonal ferrite. The bainite morphologies to austenitic stainless steels in terms of allowableobserved include lath-like, granular, and massive. The lath stresses at temperatures exceeding 1050 F as speci-bainite predominates at faster cooling rates and is gradually stresses at temperaturesexceeding 1050 r as speci-replaced by granular bainite as the cooling rate decreases. fied by theASME Boiler and Pressure VesselSome massive bainite is present at all cooling rates. Compar-ison of the as-transformed microstructures of the 0.08-0.09and 0.12-0.13 carbon weld metals indicated that increasingthe carbon content lowers the bainite start and finish tem- Tele 1. 1Ioa1nal composition of 2-1/4Cr-1!b steel perASTMA 387 (11)

peratures and thus results in a rmer bainitic structure. Element Composition (weight Percent)

Introduction Carbon 0.15 ..x.

History andApplicationsManganese 0 30-o so eo.

Chromium-molybdenum steels have been used in Phosphcruso 035 ..x

the fabrication of pressure vessels and boiler steam Sulfur o os ma.

pipes since the 1930s.l 2-1/4Cr-1Mo steel, one mem- silicon o 50 maxber of this family, was originally formulated for use at Chromium 200-.&dquo; 50elevated temperatures where creep resistance is re- ,olyDGe-u- . 0 9o-i 10quirted.2 This alloy is employed in steam generating

2 WRC Bulletin 315

quo;&dquo;-; .- ..= . -&dquo;-.., -.>... - _ ,; , ;t +. > ,


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I

. Table 2. Comparlson of the properties of 2-i/4Cr-iMo Plate, microstructure. Brown, et a1.,43 report for quenched 6-ASTMA 387 vs ASTMA 542 (11.18) 1/4-in thick plate (0 13% carbon) a quarter-thickness

St.n..r0 ci... toa01t1on BITS (1.$1) a1DTS (1.$1) SE1 c: )> microstructure of 100% bainite. The variation in cool-A187 i t.i.d &0-85 30 ie ing rate with distance from the plate surface alters the

2 ..u..a 7HOO 45 18 fineness (or coarseness) of the bainitic structure, butTeu&dquo;red no martensite is present. Furthermore, despite the

A 54: 1 QBoaDcl>ad 10HH as I/. quenching treatment, some proeutectoid ferrite may=d be found at the half-thickness location.

2 - ms-,s 100 13 Related to the wide bainitic shelf characteristic of) - 9HH 75 20 the CCT diagram for 2-1/4Cr-1Mo steel, weld metal is4 - 8HOS M 20 primarily bainitic for most welding processes. Excep-

tions to this rule are those processes which have un-

usually high or unusually low energy inputs. Richeyhas shown that for cooling rates characteristic of elec-

1.4 Inspection of the figure indicates that there is an troslag welding, a high heat input process, some proeu-extensive range of cooling rates over which the result- tectoid ferrite does form (in addition to bainite) in 2-1/ing microstructure will be bainitic. 4Cr-lMo steel with a carbon content of 0.12%.At the2-1/4Cr-lMo steel is used in various conditions in- other end of the spectrum, Sims and Fuchats have

eluding annealed, normalized and tempered, and determined that the microstructure obtained in thequenched and tempered. The microstructure of the fusion zone of electron beam welded 2-1/4Cr-lMoannealed steel is

predominantly ferritewith some steel consists

predominantlyof

lath-type martensite,gross carbide areas (that sometimes appear pearlitic) this result atemming from the low heat input and

Iand possibly bainite. The exactmix ofthese microcon- therefore high cooling rate of the weld metal. ,stituents depends on the carbon content. Klueh8 has Examination of the bainite formed in 2-1/4Cr-IMo

reported observing proeutectoid ferrite with a scatter- steel using the scanning electron microscope (SEM)ing of carbides in annealed 0.009 carbon 2-1/4Cr-lMo sometimes reveals a structure termed &dquo;granular&dquo; bain-steel while higher carbon annealed material (0.12% ite. Klueh8 has defined granular bainite as islands of acarbon) also contains some fine pearlite and small second phase dispersed in a bainitic ferrite matrixamounts of bainite. Normalized 2-1/4Cr-lMo steel with a high dislocation density. Habraken and Econo-contains ferrite and bainite with the amount of bainite mopoulos5 have determined that these islands consistincreasing with carbon to nearly 100% of the structure of a combination of martensite and retained austenite.for material with carbon levels greater than about Wada and Eldis4 have maintained that the bainite in0.12%. Quenched 2-1/4Cr-1Mo steel has the potential 2-1/4Cr-1Mo steel with carbon contents less than or

to contain martensite. However in most applications, equal to about 0.1% is all of the granular variety. Theythis steel is used in rather thick sections which limits indicate that the bainite is essentially free of carbidesthe cooling rate and therefore affects the resulting and contains only islands of martensite/austenite.

This statement has been disputed by others includingKar and Todd who report observing only ferrite and

&dquo;

))) t H !! i t )! ! ))) !conventional bainite in 2-1/4Cr-lMo steel cooled at

-

T ttv&dquo;.. Irates comparable to those used by Wada and Eldis.

-.. &dquo; T&dquo;&horbar;L Cerbidea The properties of 2-1/4Cr-lMo steel de- &dquo;Sp -..B,..- .B!-B(-- &horbar;- pend primarily on the carbide type, size, morphology,

-

distribution in the microstructure. Baker and! __B B!! B IJtJ&horbar;&horbar;BZ Nuttingl7 have described the general sequence of car- _< *TMCtflV7* bides formed in both quenched and in normalized 2-1/gr . B


4/56

I i-

Cr7C3 M6C eo L.t I = roG e o 0 0 ,

. c-carbide -cementite

-cement it ef:3C60> 0 0 q

co

4 (3 6

M o 2 c a 10: e o o GCCK02e1C I

(a) Quenched (martensite) 9pC n o o o..- Ivec !-

Cr7Cj hbCC 40C a eo 0 0c-carbide f t 05 6i0 !0 o0 coo+ cementite--rcementlte1 --?lz3C6 T[


5/56

Legend: - e - &dquo;ti &horbar;A&horbar;1 0 Nt&dquo;,w --0-- Nt1 to- l(mi Inn

: 80&dquo;. -.:..&dquo;---,

...

..: o 10. F-- ---- --;:9.. 1r1 - tl -_ -eBB 20. &horbar;&horbar;9, 0-0 _ ,_0 -, -q1 _. t:t&dquo;&dquo;-O f1 ..&dquo;;,..........,, ,. _ - . - 1 --- r-(r*- - - - - .*****tA&horbar; ** - &dquo; -- o, -.---t----aJ a 6 n 10 It . c t to 1 0I - t .. - 1. 10 It

T8..,.rl.. Il- (lrwl 1....,.,.,,& Tiw (rrl Ttt)t Tim (Nrn)

(a) 0.018 carbon (b) 0.06 carbon (c) 0.09 carbon

Fig.4- The variation in the relative amounts of carbides present in 2


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tduced by more conventional beat treatmenla.Aa a resislance. Tbe strengtb of quencbed 2-1/4Cr-1Mo 1duced by more conventional heat treatments.As a resistance. The strength of the extensive dislocation 1result, the mcreased strength may be transitory and steel is mainly derived from the extensive dislocation may decrease during service.51 Smce the rate of micro- substructure formed as a result of the shear transfor-structural change is temperature dependent, one ex- mation from austenite to martensite.53 On tempering,pects that 2-1/4Cr-1Mo steel with strength enhanced this network can become decorated with fine carbides,by heat treatment is of use at lower temperature but stabilizing it as long as the carbides remain in an effec-that the strength advantage diminishes as the service tive condition. It has already been noted however that

temperature increases. This is, in fact, thecase.

Vari- in the heavy sections usually employed in 2-1/4Cr-ous authors have put the cut-off temperature above 1Mo steel applications, quenching 2-1/4Cr-lMo steelwhich there is no strength advantage in the range of results in a bainitic or bainitic/ferritic microstructure.gppo F to lpppo F.13,14,43.52,54-56 The effect is graphical- Bainite/ferrite microstructures also result from nor-ly depicted by Sangdahl and Vorhees-55 in Fig. 6 which malizing but the morphology differs from that ob-is a plot of creep rupture strength vs. room tempera- served in quenched 2-1/4Cr-1Mo steel. The bainite Iture tensile strength. The figure shows that the corre- morphology varies with the temperature at which it Ilation between the tensile strength and the 100,000-hr forms, becoming finer and more acicular as the trans- Irupture strength decreases with increasing tempera- formation temperature decreases (faster cooling Iture until, at 1000 F, there is no correlation (rupture rates).45 Viewanathanbe has indicated that the istrength constant over the tensile strength range). In strength of the bainite increases as the lath-like struc-fact, given a high enough temperature or long enough ture becomes finer. In comparison, ferrite is a muchtime, the strength of all 2-1/4Cr-IMo steel approaches weaker microconstituent than bainite or martensite.a common value.40.57 This results from the evolution of Its effect on the

rupture strength ofa mixed

bainite/the microstructure to one of overaged equilibrium car- ferrite microstructure has not been agreed upon. Bothbides in a carbon-saturated ferrite matrix.58 In this Klueh60 and Viawanathan maintain that the ferritecondition, the carbides are too large to impart any is detrimental to creep resistance and should be elimi- isignificant creep resistance to the steel and the nated by suitable heat treatment or alloying additions. :strength is entirely due to the strength of the ferrite. In contrast, Baker and Nutting17 have alluded to the

Microconstituents. Comparing the relative superiority of normalized and tempered 2-1/4Cr-1Mostrengths of quenched, normalized, and annealed 2-1/ steel over the quenched and tempered material at 5004Cr-lMo steel is basically a comparison of the merits C based on the presence of ferrite in the normalized

- of martensite, bainite, and ferrite with respect to creep and tempered steel since the M2C which precipitatesout in the ferrite persists much longer than in thebainite. Moreover, Cane and Fidler61 have presented

.

data indicating that the rupture strength of 2-1/4Cr-1Mo steel

containinga 65%bainite-35%

polygonalfer-

rite mix is superior to that for a similar material con-!&dquo;&dquo;*r ,. &dquo;- sisting of 100% bainite (see Fig. 7). Based on the obser-

.. &dquo; vation that the rupture mode changes from intergran-

-

, . ular to transgranular as the bainite content of the, &dquo; *_


7/56


8/56

f t,

steel is kept low, less carbon is available for carbide ro 180-

formation, leaving more chromium in solution to E. Qstrengthen the steel. B

Despite the loss in strength due to carbide precipita- J* ? .. Bjtion, the presence of carbides in the matrix can be 0 150 - B.beneficial to the rupture strength, particularly if they 0 kn U rB&horbar;-*are finely dispersed and are of the acicular variety. : ;

.

However, the carbides formed with chromium (M7C3, 0&dquo;5.. .MCs)3 are not stable at elevated temperatures, S


9/56

, carbide which is most effective in this regard is MozC,

4

particularly when present as a fine dispersion of acicu- 112Hr,>lar precipitates.3 I 65 . 6- Such a morphology has been ! &dquo;r

nw,., spot

e- -90 Ij

observed both in ferrite and bainite in 2-1/4Cr-lMo I - 110steel, with the Mo2C being much more stable at elevat- - * zaed temperatures in the ferrite. 17 * ) &horbar;&horbar; -

..

.

o_1 5000 -s&horbar;&horbar; :.

0.aa 1f.6;

.... I . a ftat P2646 .

o ) 2 3Ij

S 6 &dquo;

1

0 wed PZ647

, 1 1

-

O I Z 3 4 5 6 10 I I I I I

chromium content, percent0 6 C I leI/I 1 6 8

&dquo;&dquo; &dquo; .P &dquo;&dquo;tf.tML.-

F1 -.10- Effect of molybdenum and chromiuo content on the creep _*strength of Cr-No steel at 1000FF :1 12-Effect of molybdenum content on the rupture time (for

a fixed stress) of 3Cr-Ko steel at 538 C

Source Miller, R F . Benz, V C . and lnverzagt, t. E , &dquo;TheCreep Strength of 17 LowAlloy Steels at 1000or,&dquo;&dquo; Source Pres-ott. C. R and Braun. c F &dquo;lpda:e on Modified

AS. Proc . 40, 771-781 (1940) 2- 1(r-IIo and 3Cr-yo Allovs.&dquo;wpC.

HB-7

(1983)

2-114Cr-IMo Weld Metal 111

> .raa.:,:....b;,:.F-.=.,::- . _.. . -r ... , ....- _ _._ .. .. --&horbar;&horbar;._ _ _ _ _ .- . -&dquo; ... -T...._.--_


10/56

I

&dquo; t. -I

? bons strengthening effect can be attributed tc one20o bons strengthening effect can be attributed to one or.

, / more of the following (a) its combination with othery

.

elements In the steel to produce carbide precipitates,:- - (b) its effect on the transformation kinetics of austen-

&dquo;&dquo; ite to lower temperature microconstituents thus deter- * * mining the microconstituents present for a given heat

t_ ,, _- v treatment, and (c) its interaction while in solution

t , ,...1_J - /&dquo; / with other alloying elements. y... Carbon readily combines with many elements to

d ,.,, produce carbides. Carbide-forming alloying elements-- &dquo;_ - S often introduced into creep-resistant ferritic steels in-m cx

, , - -= &dquo;- - clude chromium, molybdenum, vanadium, titanium,sc:,o Wr,_ ;,,f,1 - and niobium. The type, size, distribution, and mor- 130 0 oos oso oss oio ( c , s ,v phology of carbide precipitates that result are con- I!0 n no is 2 0 (Mo) trolled by the amount of carbon and alloying elements IA 1 I o Element (wt&dquo;1.) (mo) addedeteeI.Becaofthesn.I088.,.tAlloying Element w I I.)tt%1i#tflt#t2Zllated with mcreased precipitate spacing, it 18 deairable ,Fi03.1:;- iff*ct of changing levels of various alloying additions to produce a large volume fraction of precipitate lIl theIan the 1000 hour rupture ttrmtth of 3 Crsteel. thf carht


11/56

carbides and still leave sufficient quantities of carbide The limited dependence of stress rupture strengthforming substitutional alloying elements in solution to on carbon content at constant temperature has beencontribute to this strengthening effect. observed by others Copeland and Licina9 (see Fig. 15)The relationship between carbon level and stress have stated that the beneficial effect of increasing the

rupture strength has been a source of disagreement for carbon level on stress rupture strength holds primarilysome time. In 1965, Campbell70 published a paper for carbon contents less than about 0.04%. Zeisloft, etindicating that carbon content is not related to stress al.,7 have indicated a similar behavior except with the

rupture strengthin

2-1/4Cr-lMoweld metal. His test-

cut-offat

0.0896 carbon.ing was done in the temperature range of 10500 F to Vanadium. Vanadium is a strong carbide for-12000 F for rupture times up to 1800 hr and carbon mer3,62 which is added to ferritic steels to improvecontents of 0.04 and 0.10 weight percent. However, 10 strength, particularly stress ruptureyears later, Klueh and Canonico58.71 observed both in strength.3.64.67.68.72 The carbide formed, V4C3, is fme2-1/4Cr-lMo base plate and in weld metal an increase when first precipitated62,67 and is responsible for muchin stress rupture strength with increasing carbon lev- of the strengthening effect.5047. V4C3 is relatively sta-els. It should be noted however, that their work was ble72 at intermediate service temperatures but soondone at lower temperatures (8500 F to 10500 F) for coarsens at 6000 C (11120 F). Vanadium has an evencarbon contents in the range of 0.003 to 0.13596. Thus, greater affinity for carbon than does molybdenum62test temperature appears to affect the strength depen- (or chromium) and, as such, can have an additionaldence on carbon level with carbon being of little bene- strengthening effect on the steel by tying up the car-fit at temperatures exceeding 1000 F.3 Fig. 15 plots bon and leaving the molybdenum in solution to

strength as a function of carbon content for 2-1/4Cr- strengthen the matrix.lMo steel.9 Inspection reveals that as the temperature The strengthening effects of vanadium are illuetrat-increases, the strengthening effect of carbon de- ed in the following examples taken from recent litera-creases. This dependence may be due to the accelera- ture. Fig. 16 is a graph of 0.296 proof stress (yield) andtion of carbide growth and evolution in response to tensile strength as a function of vanadium content forincreasing temperature and the accompanying deple- 3Cr-lMo-V-Ti-B steels.63 The vanadium level rangestion of alloying elements from the matrix to feed that from 0.07 to 0.3196. The plot shows that these roomgrowth. temperature properties improve continuously with in-

PWNT

.soot sh

-6 os

TwW ttre,0---

onq ----. - - e-----0 , pp.- .90.

_ - . e /__ -85. _

, o+o.--. &dquo; eo. * 2e&dquo; a. - 1tL.WrW ( ,_.....So- -60 - ] 02 S Pmf Sv&dquo;s 175

.

- o_.._ _

I 52- e

.- .-- -

.70

.

. ,,. ,./

&dquo; o se-r.l ... _. 20

-70... - - . 4B- 2e.II -7 Se

.. I I JI I I I .. 441 ..- .oO-*---v I I . , - 6005 10 15 20 25 !O

V COM8&dquo;,t &dquo;&dquo;,.tcFi,- Effect of carbon content on the creep and rupture

Va.d- Cot.-t wt

strength of 2r-IHo steel Each curve Is labeledvith the test temperature and conditions for which :13 16- Effect of vanadium content on the room temperature yieldthe strength ws determined (1.e. creep test or and UDI1I1 strength of 3Cr-INo-V-TI-B steel for threerupture test). different tempering traatmnts.

Source Copeland. J F and Licina, C J , &dquo;A Review of 2-1/4Cr- Source Mechanical and Metallurgical Properties of aSteel for LlSFBR Steam Generator Applications.&dquo; Symposium 3Cr-IMo-;L%-TI-B Pressure vessel Steel for Coalon Structural llacerials for Service at Elenaced

Liquefaction Reactor. NEDO/JS,Data

Sheet,Sereies

CLR-C,!et:.eratu&dquo;es 1:; &dquo;uclear Pover ee..,e&dquo;.it1on. AS1.. Houstoo, Neu Ene:-EB Development Organization. The Japan Steel(197i) :orAs Ltc (19l)

2-114Cr-]Mo Weld Metal 13


12/56

fect of titanium on the carbides is evident by the fact metal. Thus, more V/Ti/Nb is left in the matrix tothat during creep exposure at 565 C, the M2C car- precipitate out as carbides.

bides in the titanium-free steel dissolve while the TiC Boron. Boron is added to steels to increase their Iand titanium-rich M2C particles in the titanium-mod- hardenability by retarding the transformation from Iified 2-1/4Cr-1Mo steel coarsen only slightly. austenite to fernte and pearlite.6i.68 When used in thisThe benefit to stress rupture strength of titanium capacity, it must be accompanied by sufficient titani-

additions has been observed to depend on the pres- um to tie up the nitrogen in the microstructure. Bor-ence of other alloying elements as well. Viswanathans9 ons influence on creep and rupture strength is indi-has stated that for 1-1/4Cr-1/2Mo steel tested at 538 rect and depends on the type and quantity of otherC (1000 F), the addition of 300 ppm of titanium can alloying elements in the steel.As indicated in the dis-have either a positive or negative effect on rupture cussion of titaniums effect on the creep strength of 1-strength depending on the impurity elements present 1/4Cr-1/2Mo steel, the addition of 50 to 60 ppm ofin the steel. When phosphorus is a major impurity (300 boron along with 300 ppm of titanium results in im-ppm) with tin and antimony levels low, titanium has a proved strength independent of the levels of trampdetrimental effect on rupture strength. However, if elements (P, Sb, Sn). In the absence of titanium,the phosphorus content is lowered and the antimony adding boron alone to 1-1/4Cr-1/2Mo steel with vary-and tin levels raised, titanium increases the strength. ing levels of phosphorus, antimony, and tin appears toFinally, ifboron is added (50 ppm), titanium is benefi- have an uncertain effect on rupture strength In steelscial independent of the impurity levels. with relatively high phosphorus levels (300 ppm), bo-Niobium. Relative to vanadium and titanium, nio- ron additions increase time to rupture78 but also ele-

bium forms carbides which are the most stable.Aus- vate the minimum creep rate, an apparent inconsis-

tenitizing temperaturesas

highas 2370 F76 are re-

tency. Investigation reveals however that the highquired to dissolve the niobium carbides in Nb-stabi- phosphorus level increases the rupture ductility, al-lized 2-1/4Cr-1Mo steel. The stability of these lowing greater reduction in area before failure.precipitates at elevated temperatures makes niobium Silicon andAluminum. Silicon and aluminum arean attractive alloying addition for the purpose of refm- typically added to steel during its manufacture as de-ing grain size,50 stabilizing the microstructure,75.76 and oxidizers.65 Both elements are considered to have aincreasing elevated temperature strengthsl in negative effect on creep strength. Silicons effect islow alloy ferritic steels. particularly detrimental at service temperatures inTo attain stress rupture strength in 2-1/4Cr-1Mo the range of 950 F to 1200 F.3 Recent work aimed at

steel, niobium is added to create a fme dispersion of improving the creep behavior of 2-1/4Cr-1Mo andNbC precipitates in the microstructure.According to 3Cr-lMo steels has involved the reduction of silicon

Argent, et al.,53 the strength obtained is proportional levels. Kawasaki Steels study of 2-1/4Cr-1Mo steelto the square root of the volume fraction of NbC pre- has indicated that there is a noticeable improvement

cipitated &dquo;on dislocations.&dquo; Because of the stability of in stress rupture strength when the silicon content isthe carbides at elevated temperature and their pin- reduced from 0.4% to 0.0896.9 Graphically illustratedning of dislocation networks in the microstructure, in Fig. 19, this effect is thought to be due to a slowingmicrostructural degradation during creep occurs slow- of molybdenum-precipitate coarsening resulting fromly and the rupture strength is maintained well into the the silicon reduction. Referring back to Fig. 12 is alife of the specimen. Husselage and Dortland have graph of 1000-hr rupture strength at 550 C as a func-reported no significant microstructural changes occur tion of alloy content for 3Cr-lMo steel. This plotin 2-1/4CrlMoNiNb steel after creep testing for 3100 shows that rupture strength begins to fall once thehr at 650 C. Creep strengthening of 2-1/4Cr-1Mo silicon content is increased beyond about 0.06%.68steel by niobium additions appears to yield superior The reduction of creep strength by aluminum isstrength for service temperatures up to about 930 F.6 thought to stem from two causes. First, the aluminumTests at 1020 F have shown that after about 5000 hr, in its deoxidizing role forms highly stable oxides whichthe strength advantage over conventional 2-1/4Cr- have a grain refining effect on the microstructure dur-

lMo steel is lost due to NbC coarsening.76 ing cooling from temperatures above the3.65J!IJ Tra-Gooch62 has indicated that the action of vanadium, ditionally, creep strength is associated with largertitanium, and niobium in weld metal may be some- grain size. Thus the grain refining action reduceswhat different than in base metal. In addition to car- strength. Second, the aluminum combines with dis-bon, these three elements also have a strong affinity solved nitrogen to form nitrides, thus preventing itfor oxygen. Oxide and silicate inclusions in the weld from combining, along with carbon, with the strength- -metal absorb these carbide forming elements from the ening elements to form carbonitrides.65surroundmg matrix by virtue of their oxygen content. Tin, Phosphorus, andAntimony. Tin, phospho-

As a result, in modified 2-1/4Cr-lMo weld metal, the rus, and antimony are impurity elements in low alloyformation of V4C3, TiC, and NbC is suppressed and ferritic steels. Their influence on creep and rupturethe carbides formed are more in keeping with those strength has been studied when present individuallyseen m the unmodified steel. In contrast, the inclusion or in combination with each other. Hopkm and Jen-content of base metal is often lower than in the weld kinsons have mvestigated the effect of0 1 ro tin on the

2-1/4Cr-lMo Weld Metal 155

s--, : . i-= ._. - - ..r .:_--.- - - . -isEgS &dquo;&dquo; -...... ,- - - . - - -.I


13/56

.

rity and strengthening alloying elements occur for ti- such as recrystallization, produce an abrupt change intanium and titanium plus boron slope, replacmg the expected straight Ime with two

- Manganese and Nickel. Manganese and nickel straight line segments, joined at a point and havingare added to low alloy ferritic steels for a number of differing slopes. Gradual changes such as oxidation,reasons. One function of manganese is to tie up the grain growth, or precipitate growth/evolution producesulfur in steel in the form of MnS inclusions.ss This a gradual slope change, causing the line to becomeprevents the formation of FeS which can lead to hot curved. Instabilities are more prevalent at high stress-

tearing. Both manganese and nickel increase hardena- es or temperatures. Wilsons has indicated that, for 2-bihty by retarding the formation of ferrite and pearlite 1/4Cr-1Mo steel, the straight line log stress/log rup-on cooling from austenitizing temperatures.6, Chung, ture time approach is not dependable for test tempera-et al.,83 have experimented with 2-1/4Cr-lMo steel, tures above about 1000 F.investigating the effect of varying manganese and Time-Temperature ParametemAnother datanickel additions. They report that adding 1.0% manga- analysis technique involves the use of time/tempera-nese results in a 30% reduction in short time rupture ture parameters. These parameters are based on anstrength (maximum rupture time, 1000 hr) at 600 C Arrhenius type equation. Invoking theArrhenius rela-and a 15% decrease at 500 C.An alloy with 0.5% tion implies that creep to rupture is a thermally acti-manganese and 0.5% nickel suffers a strength reduc- vated process governed by a single mechanism. How-tion only half that of the 1.0% manganese formulation. ever, as stated by Goldhoff, studies have shown thatDoubling the nickel level to 1.0% while holding the there can be many deformation mechanisms at workmanganese constant does nothing to decrease the during creep rupture. Thus the basis for the parameterstrength any further. Sachs, et al.,67 have seen similar approach is not theoretically rigorous. Despite thistrends in 2-1/4Cr-lMo steel tested at 621 C. High fact, parameters are widely used in the analysis oflevels of manganese and nickel (manganese up to 1.7%, rupture data and can be quite useful. The techniquenickel up to 2.2%) reduce rupture life considerably has the advantage that all of the data for a given heatrelative to conventional 2-l/4Cr-lMo steeL This nega- of material taken at various temperatures can be de-tive effect decreases as the manganese and nickel con- picted on a single master curve. Four of the moretents are decreased. common parameters in use are Orn-Sherby-Dorn,Stress Rupture DataAnalysis Larson-Miller, Manson-Haferd, and Manson-Suc- IThe objective of stress rupture testing is to gather cop.86data on rupture time as a function of applied stress The latest data analysis techniques make extensiveand test temperature for a particular material with the use of computers and are not as rigid in assigning an agoal of characterizing its behavior sufficiently so as to priori relationship between stress, rupture time, and I

permitestablishment of allowable stress levels for de-

temperature.Among others,Booker87.88 and Man-

sign purposes. Structures or components to be used as son89-91 are currently active in this field. Bookers ap-elevated temperatures are generally expected to oper- proach utilizes a computer program which requires anate for a minimum of 100,000+ hr. Since it is impracti- input consisting of a list of the possible terms to becal to test material for such long periods to determine used to construct a parametric relation and the stressthe design stresses associated with that life, data are rupture data. The program then combines the terms tocollected for shorter rupture times and analyzed to generate a multiplicity of parametric equations, fitsdetermine the relationship between stress and rupture the data to each, then outputs a ranked list of thetime. Then extrapolations to 100,000 hr are made and models which give the best fit. It is then up to thethe stresses thus obtained used to develop design cri- analyst to choose the fit which not only describes theteria. data well but also predicts reasonable behavior for theLog Stress/Log Rupture Time. Many methods material upon extrapolation. I

have been evolved as suitable for data analysis and Minimum Commitment Method.Although origi-

extrapolation. By far, the simplest technique involves nally designed to allow the rupture data to determineplotting log stress vs. log rupture time. This method the exact form of the parametric relation used to de-takes advantage of the fact that data plotted in this scribe a materials stress rupture behavior, Mansonsmanner, in general, fall on a straight line. Linear re- minimum commitment method (MCM)89.90.91 hasgression techniques are applied and the coefficients evolved into a form which uses a fixed analytical ex-which define the equation of the best fit straight line pression. In its most general form, theMCM relation is ..derived. It is then a simple matter to extrapolate to given byrupture times of 100,000 hr and determine the associ-

]og(tr)(1 + A1) + Q = G (2)ated stress. However, implicit in this method is the og(tl + A + -G (2)

assumption that the behavior is linear to 100,000+ hr. -where &dquo;t,&dquo; is the rupture time in hours, &dquo;Q&dquo; is a func-Unfortunately, at elevated temperatures, many metal- tion of temperature, &dquo;G&dquo; is a function of stress, andlurgical systems are not microstructurally stable Sig- &dquo;A&dquo; is a structural stability factor characteristic of themficant microstructural change in the rupture speci- matenal The value of &dquo;A&dquo; is usually small and is often i

men during the test will alter the slope of the log set to zero The temperature function. &dquo;Q&dquo;, has beenstress/log rupture time line. Relatively rapid changes, defined as i

2-1/.ICr-IMo Weld Metal 17I

;&dquo;--=-fJ:oI;S._ -.....-a....-.T.....-.....- .. .....-.-. - -.-..&horbar;&horbar;&horbar;&horbar;,.._ -


14/56

Q = R,(T - Tm) + ({1/71 - (1/Tm)) (3) (a) The primary strengthening alloy carbide in 2-1/where &dquo;T&dquo;isCr-1Mo

steel is MC This precipitate canabsolute is the absolute test temperature the is an form in any of the microconstituents found in 2--

absolute temperature at the mid-range of the data. i/4Cr-lMo steel (martensite. bainite, ferrite)and &dquo;R,&dquo; and &dquo;R2&dquo; are regression constants The mini- but persists during tempering for a much longermum commitment method has been applied to the but persists during tempering for a much longeranalysis of multiple heats of data. For this application,

tme in the ferrite.

the stress function, heats is given bythis application, (61 Prolonged exposure to elevated temperaturesthe stress function. &dquo;C&dquo;. is given by results in a continuous decrease in stress rup-

G = B + C log(s) + Ds + Es22 (4) ture strength as a result of carbide evolution,In this equation, &dquo;B&dquo;, 16ctv, &dquo;D&dquo;, and &dquo;E&dquo;are constants coarsening, spheroidization,

and agglomera-

determined by regression and &dquo;s&dquo; is stress. In the Tnelossofstrengthdescribedin-b-abovemaymulti-heat case, the terms &dquo;B&dquo; and &dquo;Clog(s)&dquo; are heat (c) The loss of strength described in b above maycentering terms and as such, the values of &dquo;B&dquo; and be significantlyslowed by the addition of strong&dquo;C&dquo; change for each heat of material.

carbide formers such as titanium or niobium

Manson has published a computer program9l suited which precipitate as MC carbides. These pre-Mansonhaspubbshed acomputercomputer smted cipitates are effective creep strengtheners and ;for running on a desk-top personal computer which are more stable than M2C. ll/ fll

performs are input into the program in a single of data. (d) Significant increases in stress rupture strength

All data are input into the program in a single file. The , tempering or PWHTprogram does the analysis and then prints out the treatments toproducetempering with highvalues

of the constants which, when inserted in the

room temperature tensile strength. However,MCM relation describe the rupture behavior of each the strength advantage thus obtained decreasesheat of material as well as the average behavior of all of with increasing service temperature and is in-the data considered as a single population, significant aboveservice temperature and is in-significant above about 900 .Summary (e) The strength of all 2-1/4Cr-lMo steel, howeverThe preceding literature review has discussed, in heat treated, approaches a common value given

detail, the microstructure of 2-1/4Cr-lMo steel (base sufficient time at temperature as the micro-metal and weld metal) and its effect on stress rupture structure evolves to one of overaged equilibriumproperties. In addition, the effects of elevated tem- carbides in a carbon-saturated ferrite matrix.perature exposure (PWHT, tempering, in service ex- (/) The influence on rupture strength of introduc-posure) and chemical composition have also been ad- ing polygonal ferrite into an otherwise bainitic Idressed. Finally, a brief discussion of some of the ana- material is not clear.

lytical techniques currently being used to characterize (g) Solid solution strengthening plays a minor rolethe stress

rupturebehavior of materials based on data in conferring stress rupture strength to 2-1/

collected during rupture testing has been presented. 4Cr-lMo steel. Interactions between substitu-The important points concerning the microstruc- tional (chromium, molybdenum) and intersti-

ture of 2-1/4Cr-lMo steel are summarized as follows: tial (carbon, nitrogen) atoms are described.

(a) Depending on the cooling rate from tempera-(h) Some evidence exists that the stress rupture

tures above the A3 during welding or heat treat- strength of fully bainitic 2-1/4Cr-1Mo steel in-ment, the microstructure obtained is typically

creases with decreasing prior austenite grainment, the microstructure obtained is typically .bainitic or ferritic/bainitic. Cooling rate is con-

size.

trolled by the cooling method employed, the The effects of individual alloying elements may beweld energy input, the preheat/interpass tem- summarized as follows:perature, and the member size and thickness. (a) Decreased rupture strength has been associatedThe amount of ferrite formed can also be influ- with increases in levels of chromium, silicon,enced by the carbon content of the material. aluminum, and manganese.Under extremely rapid cooling conditions, mar- (b) Improved rupture strength is obtained by in-

tensite may also form.. creasing the levels of molybdenum, vanadium, The alloy carbides in the microstructure precip- creasing the levels of molybdenum, vanadium,(6) The alloy carbides in the microstructure precip- titanium, and niobium.

itate and evolve according to a complea scheme 1 d niobium.,itate and evolveaccordingto a complexdetails (c) Stress rupture strength increases as the carbondetermined by Baker and Nutting. 17 The details content is increased. However, the effect isonlyof the scheme are similar for martensitic and significantfor carbonlevels below about is onlybainitic microstructures but differ significantly significant foras thetemperatureincreases, the

forferrite. ., strengthening effect decreases until at 1000 F,(c) The evolution of the carbides in 2-1/4Cr-1Mo the strength advantage becomes insignificant.

weld metal appears to be slowed by increases in influence of boron additions on rupturecarbon content,

strength is not clear and appears to depend onThe influence of microstructure on stress rupture the levels of other elements present including

strength maybe summarized as follows. titanium, phosphorus, tin, and antimony.

18 WRC Bulletin 315


15/56

(e) Tin and phosphorus appear to increase the CCT diagrams. SEM examination of the resulting mi-

creep rate with the latter also increasing the crostructures were then performed to determine therupture ductility,. The mfluence of phosphorus microconstituents produced as a consequence of theis further bolstered by increases m the carbon thermal history. content.

(f)At levels up to 1.0%, increases in the nickel con- Materialstent do not affect rupture strength. Four 2-1/4Cr-lMo weld metals were used in this

The discussion of the analysis of stress rupture data programwith carbon contents of 0.02-0.03, 0.04-0.05,

may be summarized as followa:

0.08-0.09, and 0.12-0.13 weight percent. The carbonmay summarizeas 10 ows:

...d f fi ed al fl.hrange is given instead of a fixed value reflecting thee(a) The objective of stress rupture testing is to variability observed in the carbon level from analysis

gather data on rupture time as a function of to analysis. This variation most probably results fromapplied stress and test temperature for a partic- the inhomogeneity of weld metal deposits as well asular material with the goal of characterizing its from statistical variation in the analysis results. Thebehavior sufficiently so as to permit establish- chemical compositions of the four weld metals studiedment of allowable stress levels for design pur- are shown in Table 3.

,

poses. The weld metal specimens were made from material(b) Some of the analytical techniques currently em- eatracted from shielded metal arc weldments. These

ployed in rupture data analysis include the log weldmenta were fabricated in 2-1/4 to 2-1/2 inch thickstress/log rupture time method, various time/ SA 387 Grade 22 plate using a single-V groove prepa-temperature parameter methods, and the Man- ration employing a backing bar. The chemical compo- ,son minimum commitment method. sition of the base plate is given in Table 3. The elec-trodes used were all of the E9018-B3 type, except for

Materials and ExperimentalProcedurethose utilized to make the 0.02-0.03 carbon weldmentMaterials and Experimental Procedure .. , were E9015-B3L electrodes. Welding was con-

&dquo; an penmen oc ure which were E9015-B3L electrodes. Welding was con-The goal of this program was to investigate the ef- ducted using good low hydrogen practice, a preheat

fect of carbon content and PWHT on the stress rup- temperature of 300 F, and an interpass temperatureture strength of 2-1/4Cr-lMo weld metals. In order to of 500* F. Subsequent to the completion of welding,establish the correlation between carbon level and each weldment was postheated at 400 F for 4 hr andrupture strength, rupture testing of weld metals with cooled in still air. Details of the groove geometry, elec-carbon contents in the range of 0.02-0.13 weight per- trode type and size, as well as welding parameters arecent was conducted. For this phase of the study, the summarized in Table 4.PWHT selected was 1300 F/25 hr. Second, the effectofPWHT on the rupture strength of 0.08-0.09 carbon Stress Rupture Testing

weld metal was evaluated using a PWHT of 1175 F/ To determine the effects of carbon content and25.5 hr. PWHT on stress rupture strength, rupture testing ofIn support of the rupture testing effort, extensive the 2-1/4Cr-1Mo weld metal was conducted in two

microstructural examination of the above weld metals phases. In the first phase, specimens of weld metalin the as-welded, PWHT, and rupture tested condi- PWHT 1300 F/25 hr and having carbon contents oftion was performed using the SEM and STEM. This 0.02-0.03, 0.04--0.05, 0.08-0.09, and 0.12-0.13 weightmicrostructural work was aimed at characterizing the percent were rupture tested at 850, 950, and 10500 F,microstructure as a function of carbon content and temperatures selected as being representative of thePWHT with the ultimate goal of correlating the mi- current and anticipated operating range of 2-1/4Cr-crostructure with the stress rupture properties. SEM 1Mo pressure vessels. ThePWHT employed producedexamination of the weld metals revealed the depen- Class 2 properties (as defined for SA 387 Grade 22dence of microconstituent morphology on prior mate- steel) in the weld metal. The tensile strength range forrial history. Furthermore,to obtain information on the this class of material is 75 to 100 KSI.type, size, morphology, distribution, and composition In phase 2, only the 0.08-0.09 carbon weld metal wasof the alloy carbides present, STEM examination of studied. This material, PWHT 1176 F/25.5 hr, wascarbide extraction replicas taken from weld metal rupture tested at 950 and 1050 F. The phase 2PWHTspecimens was also conducted. produced weld metal properties in agreement withWeld metal specimens were thermally cycled on the those proposed by the Metal Properties CounCil93 for a

Gleeble using a variety of thermal cycles designed to new class of SA 387 Grade 22 steel, i.e., Class 3. This &dquo;simulate the thermal history occurring in the coarse- proposed class of SA 387 has an allowable tensilegrained region of the HAZ during welding. Cooling strength range of 90 to 110 KSI.

,

conditions were chosen to span the normal range of Stress rupture specimens tested in this program Iweld energy inputs characteristic of welds in heavy- consisted of 100% weld metal and were fabricated withsection Cr-Mo materials.A dilatometric technique their longitudinal axis parallel to the welding direc-was employed to detect the weld metal transformation tion.As shown in Fig. 22, the specimen gage length wasduring cycling and the data obtained used to construct 1.125 inches with a gage diameter of 0 125 mches The

2-114Cr-IMo Weld Metal1 19

. --: - ._ _ _ ... f _=,a:_ _,...._ .s...._ _ _ _ _ _ _ . __ _ ,. , :n- ;,:u...-,,,..,:....--...,.


16/56

I,

.

Table 3. Chemical composition of base metals and weld metals employed in the study.

Base Metal Weld Metal

Elementt BP-1I BP-22 0.02-0.03C 0.04-0.05CC O.OH-0.09C 0.12-O.l3C

C 0.111 0.111 0.024G 0.0455 0.0911 0.133

Mn 0.399 0.388 0.96 0.66 0.599 0.522P 0.010 0.0111 0.0199 0.0133 0.010 0.010

S 0.0188 0.0222 0.024G 0.018 0.014G 0.0133

SiI 0.18 0.299 0.755 0.311 0.39 0.37

Cu 0.17 0.155 0.111 0.08 0.024G 0.027

Nii 0.233 0.155 0.09 0.08 0.0333 0.036

Cr 2.29 2.077 2.39 2.311 2.488 2.522

Mo 1.155 0.88 1.20 1.1lI 1.17? 1.18

V 0.0033 0.004 0.006 0.014 0.0155 0.008

As 0.016 0.0077 0.026 0.0177 0.0033 0.0033

Sb 0.0033 0.009 0.0022 0.0022 0.004 0.004

Sn 0.0122 0.0122 0.008 0.0033 0.0022 0.0022 j*

All ND 0.008 ND ND 0.0144 0.0133B ND 0.00033 ND ND 0.0004 0.0004

*i

ND - Not Determined

small size of the rupture specimen not only increased being independently adjustable. Each furnace is con-I

- the number of specimens which could be fabricated trolled by a Leeds and Northrup Electromax II con- I

from a given length of weldment, but also kept the load troller which utilizesa

chromel-alumel thermocouplerequirements necessary to obtain rupture times in the to monitor the temperature at the center of the middlerange of ten to several thousand hours within the capa- zone.All furnaces were profiled and the zone controlsbilities of the testing apparatus. used to obtain a constant temperature profile over theRupture testing was conducted on eight constant specimen gage length (:i: 10 F).

load, dead-weight creep frames. Each frame contains a Each specimen was mounted in a testing frame andthree-zone furnace with the power level for each zone suspended within the creep frame furnace. See Fig. 23

I

Table 4. Welding procedure and parameters employed in fabrication of the 2-1/4Cr-IMo SMA weldments.

Weldment Base Plate Electrode Arc

I.D. I.D. Thickness Type AnRle Root Type Dia. VoltaRe Current

0.02-0.03C BP-1 2 1/4&dquo; Single V 25&dquo; 3/4&dquo; E9015-B3L 1/8&dquo; 24-28 V 145A

5/32&dquo; 24-28 1I 195A

0.04-0.05C BP-1 2 1/4&dquo; Single V 180

1/2&dquo; E9018-B3 1/8&dquo; 24-28 V 135A

5/32&dquo; 24-28 V 180A

0.08-0.09C BP-22 2 1/2&dquo; Single Vv 300

3/4&dquo;&dquo; E9018-B33 5/32&dquo; 24-28 V 160-210AA

I3/16&dquo; 24-28 V 220-290A j

0.12-0.13C BP-2 2 1/2&dquo; Single V 300

3/4&dquo; EI,018-B3 5/32&dquo; 24-28 V 160-210A

3/16&dquo; 24-28 V 220-290 A

20 WRC Bulletm 315 ,I

I

_ , -_ .-- , ., ..., _ , , _, , . , , , .. _.

-l I...&horbar;&horbar;&horbar; - .......... . _:. _ ,_..&dquo;..,aB


17/56

k

0 3125 DIA The obtained SMA weld metal rupture data were(12 3 mm)> ro 1258 CIA analyzed using three techniques; (a) the log stress/log______

(32 mm )> rupture time method, (b) the Larson-Miller parameterI I I I t I II I method, and (c) the Manson minimum commitment t method The results were examined to determme theT ! effect of carbon content and PWHT on stress rupturet GAGE LENGTH strength. Comparisons of the 100,000-hr stress predic-I1258- tions derived using each method were also made.

( 28 6 mm) In an attempt to gain further insight into the depen-. 2 620 - dence of the rupture strength of weld metal on carbon( 66 5 mm) content and PWHT, additional rupture data were col-

lected from the literature with the restriction that onlydata from tests of 100% weld metal specimens in the

Fig. 22- Stress-rupture test specimen. PWHT condition be considered. During the compila-tion, data from all welding processes were considered.However, because the thesis research dealt primarily

for a schematic view of the test geometry.A chromel- withSMA weld metal, a second abbreviated set of dataalumel thermocouple wired to the center of the epeci- consisting of only SMA material was created.men gage length was connected to a digital tempera- In order to facilitate determination of the correla-ture meter which, in turn, was used to monitor the tion between stress rupture strength and both carbontemperature of the specimen during testing. To mini- content and PWHT, the augmented data were parti-mize the convection of air through the furnace, both tioned using two criteria. First the data were separatedthe top and bottom orifices of the furnace were packed by temper parameter,with ceramic wool.At the beginning of each test, thespecimens were heated to the desired temperature and P = [(T + 460)(20 + logt) X 103],stabilized there before any load was supplied. Loadingwas in uniaxial tension with the load a constant the value of which is directly related to the degree ofthroughout the test. In addition to temperature, speci- PWHT. Based on the work done by Baker and Nut-men extension, measured by a dial gauge attached to ting&dquo; to describe the carbides in 2-1/4Cr-lMo steel asthe testing frame, was also recorded as a function of a function of tempering time and temperature (seetime. Fig. 3), average temper parameter values characteris-

tic of the regime boundaries in the figure were calcu-lated and used to defme the dividing points for the

CERAMICc data base. The resulting temper parameter ranges em-

WOOLPLUG

ployed wereP < 32.0, 32.0 < P < 36.2, 36.2 < P < 37.5,B and P > 37.5. The second partitioning criterion wasB . based on weld metal carbon content. Keeping in mindBJ the dependence of rupture strength on carbon level

.,.. reported by Copeland and Licina,9 the carbon rangesFURNACE --. established were C < 0.02, 0.02 < C < 0.04, 0.04 < C 0.12. Partitioning by

, , :. , , SPECIMEN carbon level was performed within each temper pa-.- - ... rameter range so that observed variations in strength

-

-

were minimally affected by PWHT variation.fl -&horbar; EXTENSOMETER For analysis of rupture data using the log stress/log

T*&dquo; rupture time approach, a model for stress as a function&horbar; of rupture given by

Y log(s) =A + Blog(t) (5)IIE t GNTS - IWEIGHTS

fi-r**] TIMER was assumed where &dquo;s&dquo; is stress in KSI, &dquo;t,&dquo; is rupture T&horbar;&horbar; INTERRUPT time in hours and &dquo;A&dquo; and &dquo;B&dquo; are regression con-&horbar;J< SWITCH stants. Using linear regression analysis, a best fit&horbar; straight line was calculated. Stress for 100,000-hr rup- ..f1 ture was also obtained by extrapolation. Because this) model does not include a temperature term, the above ,

r &horbar;) analysis had to be performed for each test temperatureat which data were available.

Analysis of rupture data using the Larson-Miller. - schematic of creep frame with specimen in parameter was also conductedA parameter value for-

place each data pointwas

calculated using the equation,2-l/4Cr-lMo Weld Metal 211

. _ ..__ ,. - _ - &dquo; , .., w . y. : &dquo;,.-.,-.,.....-._ _ &horbar;-- -.-.


18/56

! ILMP = (T + 460)(C + logk P X 10-3 (6) senses variation in the specimen diameter due to ther-

mal expansion/contraction as well as volumetric .where &dquo;7- is the test temperature m degrees Fahren- changes which result from phase transformations The ihe it, &dquo;C&dquo; is a constant, and &dquo;t,&dquo; is the rupture time in dilatometer signal is fed to a multi-channel light beam Ihours.A value of 20 was used for &dquo;C&dquo; for all analyses oscillograph where a resulting trace of specimen dila- iand is generally accepted as an average value application and temperature as a function of time is recorded.ble in most cases.After plotting the data on a log stress Determination of transformation start and finish tem-vs. Larson-Miller parameter graph, curves were fitted

peraturesis

accomplished by plottingrelative dilation

to the data using regression analysis techniques. In a asa function of temperature Start and finish tem-majority of cases, a quadratic equation of the form peratures are indicated by the points at which the plot ,

log(s) = A + B(LMP) + D(LMP)2 (7) deviates from linear expansion/contraction behavior.. , ,, ,, ,

,Weld metal transformation specimens 0.250 inches

was used in the analysis where &dquo;s&dquo; is stress in KSI, Weld metal transformationwere thermally cycled in .&dquo;LMP&dquo; is the Larson-Miller parameter, and &dquo;A&dquo;, &dquo;B&dquo;, indiameterand 4inches longwere thermally cycled in ;and &dquo;D&dquo; are regression constants. The resulting curves

the Gleeble. Seven thermal cycles were used to deter- )

providedareasonable constants. Thewhere only few mine transformation behavior, each with a peaktem-

provided a reasonable data fit except where only few perature of 2400 F. Six of the cycles corresponded to.

data points were available. In such cases, application the thermalhistoriesofmaterial immediately adja-of a quadratic fit sometimes resulted in a curve which the thermal fusion line in two inch thick steel plate ,la llcalflpladlalernatillln 8ucl , cent to the fusion linein two inch thick steel plate .was concave upward.As an alternative, in such cases, preheated to 400 F and welded with energy inputs ofregression was performed using a linear fit of the form, gg gQ g0 KJ/IN, respectively. These

log(8) = A + B(LMP) (8) inputs are in the range characteristic of SMAW andSAW, two welding processes commonly used in theThe curve fits were used to calculate stress for 100,000- fabricationwelding processes commonly used in sev-hr rupture.

fabrication of 2-1/4Cr-lMo pressure vessels. The sev-hrp enth thermal cycle was obtained by heating the speci- (

Stress rupture data analysis using the Manson mini- men to 2400F atthe same rate as employed in the Imum commitment method was performed on an IBM other cycles. However, on reaching the peak tempera- mum nllD1tment method was designed by Manson91 other cycles. However, on reaching the peak tempera- IPCusing a computer program designedbyManson ture, the Gleeble was shut off, allowing the specimenand modified by Pepe. The details of the Manson to cool at the maximum rate determined by the geome-method have already been discussed in the literature try of the sample/cooling jaw assembly.Analysis of the ireview. From files stored on magnetic disc, data listed cooling profile indicated that it was roughly equivalent ,by heat were read and processed using regression anal- that resulting from an 18 KJ/IN weld in 2-inch plate &dquo;

ysis. The constants determined were used to construct at room temperature. Fig. 24 is a graphical representa-isotherms which defined the average behavior of the tion of the thermal cycles employed in the transforma-

material having data in the input file. Heat constants tion study.were also calculated which made it possible to drawisotherms for each individual heat of material. Deter- Results and Discussion

&dquo;

mination of the 100,000-hr stresses associated with Stress Rupture DataAnalysiseach isotherm as well as the statistical parameters Despite the volume of stress rupture data that hasdescribing the scatter of the data about the fitted been collected for 2-1/4Cr-lMo weld metal, only lim-curves was accomplished using additional computer ited analysis has been done to determine the effects ofprograms developed by Pepe.98 PWHT and carbon content on stress rupture strengthTransformation Studies of these materials. Wagner and Seth84 have analyzedThe transformation behavior of 0.08-0.09 and 0.12- rupture data to ascertain the correlation between

0.13 carbon weld metal was determined with the aid of room temperature tensile strength (related to PWHT)

a 510 Gleeble. Developed at Rensselaer Polytechnic and rupture properties. Their data base consisted of

Institute (RPI), the Gleeble is a &dquo;high speed time/ data from tests of weldmetal in the

as-welded,temperature control device&dquo;99 which can impose a pre- quenched and tempered, and PWHT condition. By

programmed thermal cycle on a metallic sample. The partitioning their data by room temperaturetensile

specimen is clamped at each end in water-cooled cop- strength alone, they ignored the microstructuraldif-

per jaws which also serve as points of electrical con- ferences which result fromthese varying treatments,

tact. The sample is resistance heated.A small wire differences which, although not affecting room tem- .thermocouple percussion welded to the sample is used perature strength, can influence rupture behavior.

to monitor the specimen temperature both for record- Klueh and Canonico,1 Campbell,7o and Pendley

ing and control purposes. The pre-programmed ther- have all investigated the correlationbetween carbon

mal cycle is achieved by continuously altering the bal- content and stress rupture strength.The experimental

ance between the resistance heating and the cooling work of Klueh and Canonico7l and Campbell7 yielded

resulting from heat flow down the length of the sample conflicting results and thereforedid not clarify the

to the water-cooled jaws. relationship between carbonand rupture strength

For conducting transformation studies, the Gleeble Pendley---5 reviewed the literature for stress ruptureis also fitted with a high speed dilatometer which data of PWHT weld metal hch he analyzed after

22 WRC Bulletin 315

- - -..- ...-.... _ -.. , , ;,=- &dquo;


19/56

.

log(t) = B +C In(,) + D, + E, (ll) &dquo;...ULLII &dquo;..nil ...,,&dquo; , Ilog(t,) = B, + C, ln(s) + Ds + Es22 (11) LARSO*-MILLER PAAarcretAALrsis iEquation (11) can be differentiated with respect to &dquo;s&dquo; 1888 :

LITERATURE DATA (ALL WELDING PROCESSES) B:

and set equal to zero to determine the maxima and : !minima of the curve described by the equation. Upon S : isimplification, the result is T [

i t2Es2 + Ds + C, = 0 (12)

s

9 118

f__

!

Using the quadratic formula, one obtains s &dquo;

---- . B /Using the quadratic formula, one obtains S . , Is = [-D + (D 2 - 8ECI)I/2][1/4E]. (13)

I 11

Assuming that both solutions to Eq. (13) are real, this S. f - - - < 33 :IS 37 39 ITherefore, the data for a particular data set must be

LAISOIHnWI PdMITIIi

best represented by the portion of the Manson curveFl 25- Streoa Tu>ture

behavior of 2-1/4Cr-111 ...Id _tal..a function

, . fl f

.... Fi-.25- Stress vupture behavior of 2-1/4Cr-INo weld metal &a a functimhi h is welly from a maximum orff.

of temper parameter determined by analysis of literature data jthe maximum or minimum does not occur in the rup- for ...ld cal depoited by a variety of welding processes.I

ture time interval ofinterest,

in order for anaccept- /able curve fit to be obtained. Unfortunately, this re- Iquirement is not always met and problems therefore ture data base and for the SMA data only. Table 6 Ido arise. Elimination of this difficulty would require containsbase and for the SMA data only. Table 6 .1modification of the Manson model to remove either contains of test temperature and carbon obtained forthe &dquo;log(s)&dquo; or the &dquo;s2&dquo; term. Such an action, however, a function of test temperature and carbon content for ,

would sacrifice some of the ability of the obtained data. Table 7 presents the stresses derived from thecurves to conform to the data.

data. Table 7 presents the stresses derived from the

The results of the various rupture data analyses areSMA data only. i

presented in the discussions which follow. Because Figs. 25 and 26 depict the bestfit curves for log many of the curves in the figures fall close to one

stress vs. Larson-Miller parameter for each temper

another,they are shownwithout data points to avoid parameter range. Fig. 25 represents the entire data ianother, they are shown WIthout data pomts to aVOid base while Fig. 26 is derived from the SMA data only.confusion which would arise due to data overlap. The Examinationof thefiguresfromthecorresponding iindividual curves with all of the datapoints

shown are

stresses in Table 5 reveals thefollowingtrends. First,j

available upon request from The Welding Research the stress for 100,000-hr rupture generally decreasesj

and Engineering group at The University of Tennes-as the temper parameter increases. This holds true at

see. Requests should be addressed to: least for service temperatures in the range of 750- iDr. Carl D. Lundin 1050 F. However, the strength advantage gained byMaterials Science and Engineering lightly tempering 2-1/4Cr-1Mo weld metal (P < 32.0)307 Dougherty Engineering BuildingUniversity of Tennessee

Knoxville, TN 37996LAleS011-ftILLei PfiRMETERANALYSISS II

The complete data base for both the literature data IiTJ


20/56

jII

Table 5. Stress for 100,000 hour rupture as a function of test temperature and temper parameter

determined by Larson-Miller analysis of 2-1/4Cr-IMo weld metal literature data.

Temper Parameter Stress for 100,000 Hour Rupture (KSI)Data Range 750F 800F 850F 900F 950F 1000FF 1050F

All P


21/56

i

I I.

Table 7. Stress for 100,000 hour rupture as d function of test temperature, carbon content., I

and temper parameter determined by Larson-Hiller analysis of 2-)/


22/56

LAISOIHULLD PATOMB MMLYStS LMMtWOLLn MMMTMANALYSISLITILMAT MM (ALL MtmXt fOMKStS) LITI&Mlt MM (IIIU 1I1L81111i fMCMtS)

.

imi tmEw pwnirw x ?.p.3> s

less1 imw mnmEw p. 3> s: TMR PAKWIEN 36 2-P-37 5 : TERKR Ptft


23/56

f

.

LAISON-ftILLII TAAAfICtAA AlIALYSISS LAASON-IIILLAA MA11I1LTAAANALYSIS11EA SMAW DATA

lm1111 9fA11 DATA

1881 : 1- : PIIIf1 laaPFrrs

TS

_

.TS

.

&dquo;

II

111 :1

111 .

SS.

.j--

-- I

A

.[ - - , _

o

8 .

BB11 11

.

t

BB,

s

I III II S :s I : f I 1_. - O.a:z-o.CDt

I. - Cll811D O.IJII-o.CI5C.)&horbar;&horbar;&horbar;cmss!

X a M 32 34 MWS8HtILLD PdMIITII

MSOtHttUn MMttTM Fit.3;- 6tnu ruptun bobevur gf 0.0Z-0.07 aed 9.0&dquo;.13 earbon 2-1/6(0-1110

Pig.]]-Stnu rvptore beluviot ot 7-1/t:r-t!b 9N vwlWeul w a tvmctioo- wId nul !11ft lJOO&dquo;/Z5 bn. u fUDCtl. or earbaat

Pig.33- S.r... r. behavior of :-.-. -1< -........ TJ. .* &dquo; &dquo; &dquo; &horbar;&horbar;&horbar;&horbar;

of temper parameterr denrvlMd by analysis of If date.determined by analysis et Vft dau.

previous figures for SMA literature data. Tables 10tion. Fig. 35 shows the curves obtained and more clear- and 11 contain the calculated 100,000-hr rupturely illustrates the difference in strength between the stresses for each temper parameter range and carbon0.02-0.03 carbon weld metal and that of the higher content range, respectively.carbon materials. Table 9 lists the stresses calculated Fig. 36 is a plot of log stress vs. Larson-Miller pa-for the combined data population. rameter as a function of temper parameter for com-Analyses to determine the effect of carbon content binedSMA literature data andUTK data. Extrapolat-on the rupture strength of the Class 3 weld metal were ed 100,000-hr stresses for the curves in the figure arenot performed. Testing of the Class 3 material was given in Table 10. Comparing Tables 5 and 10 showslimited to only one lot of filler metal with a carbon that the addition of UTK data to the SMA literaturelevel of 0.08-0.09%. data base has a negligible effect on the predictedCombinedAnalysis of Literature and UTK Data 100,OOO-hr stress values. Comparison of Figs. 36 and

(Larson-Miller Parameter). The effect of expanding 26 bears this out as the curves are essentially un-the SMA data base with the addition of the UTK data changed, the only exception being that the curve foris shown in Figs. 36-38 and Tables 10 and 11. These weld metal PWHT with P > 37.5 is extended to lowerfigures are summary plots constructed to compare the Larson-Miller parameter values.curves for various temper parameter ranges and car- Fig. 37 shows the effect of carbon content on rupturebon contents. Only those curves which were altered by behavior of PWHT weld metal (32.0 < P < 36.2) asthe addition/combination of the data are shown. For indicated by combined SMA literature and UTK data.the curves not affected, the reader is referred to the The only curve to be altered by the addition of the new

data is that for 0.08 < C < 0.12. Comparison with Fig.28 indicates that that curve has been extended to low-er values of the Larson-Miller parameter, crossing the

LAISOIHIILUI ..MlI1I1ANALYSISLql sw DATA

1811 :i NIT J30dIf IZ5 ..s: Tablo B. Stress for 100.000 hour rupture as a function of test

S , temperature. and PWHT determined by Larson-Miller1

. T , analysisof UTK 2-1/4Cr-lfb SMA veld metal daca.

1. I I.: Stress for 100,000 Hour Rupture (RS1)!

SI^-s : 1 ,

- - ,Temperature (oF) Class 3 (P.35.0) Class 2 (P-37 7)

.

,

,

*- 7507:0 51 11 36 99i

AI II

j

.

*-,

800 1..0 305S :

&dquo;

I : --IIH) ox B50 355 238. -0 04-0 osc

--- o ae-0 o9c 900 :777 183. OU-01K1 , , , 950 :9 1 132Zb 28 3 3Z i4 ], 38 950 21 1 132Zb 2B 39 32 34 36 382b 18

3 kARSO*-Ql kkii 32 ?AiMiTER 343b 38

loeo-

-

MSO)W1)LL[)) MfiMirTH D50. -S[r


24/56


25/56

.

LAtS-IIILLL1 MtNflBT AMALYSISS Figs. 39-44 are plots of log stress vs. log rupture time

IBMCCHttXH tilterrtutc Mtt trrk 2M MA derived from the SMA literature data partitioned by :

I TEJPEN PAIGlETEP r11S temper parameter. Figs. 39, 40, 41, and 42 have been

s ; determined for the data in the parameter ranges P 37.5), the beneficial effects of increasing ible.the carbon content is limited to carbon levels below UTK DataAnalysis (Log StressILog Rupture Ti-0.04 weight percent.At higher carbon levels, little ad- me). Figs. 45-54 are log stress vs. log rupture timeditional strengthening is realized. plots obtained for the UTK data. Values of 100,000-hrLog Stress/log Rupture TimeAnalysis. Litera- rupture stress determined by extrapolation of the

ture DataAnalysis (Log StressILog Rupture 7Yme). curves in the figures may be found in Tables 14 and 15.

Table 10. Stress for 100,000 hour rupture of 2-l/4Cr-lMo SMA weld metal as a

function of test temperature and temper parameter determined byLarson-Miller analysis of combined literature and UTK data.

Temper Parameter Stress for 100,000Hour Rupture (KSI)

Range 750F 800FF 850FF 900F 950F 1000F 1050FF ,>

P


26/56

Table I1. Stress for 100.000 hour rupture of 2-1/4Cr-IMo SMA weld metal as a function oftest temperature and temper parameter determined by Larson-Miller analysis ofcombined literature and UTK data.

Temper CarbonStress for 100,000 Hour Rupture (KSI)

Parameter Content 750P 800FF 850F 900F 950FF 1000 0F 1050FF

32.0


27/56

L0C STItSS/LOC NUMIS T)HtANALYSIS L0C STAtSSI0C AUfTUAt TtHtANALYSIS t.

LITLAATUAE SlfAl1 IATA LITLAATUAE STlAl1 IATA tinTEPIPER PAPAWTER 36 2-P-37 5 ... t,.t PARAFWTER 32 0,P-36 2 TEPWERATURE lOrAOF

3 tE) 37.5, the addition ofUTK data. Figs. 57 and 58 show the effect of carbon the UTK data only increases the number of test tem-level on the rupture behavior of weld metal PWHT peratures studied as the two data bases in this range

!

,

L0C sTAtssit0i AUPTUAt Tlnt RlIALYSIS L0C srAtssiLOC NUMIT TMANALYSTSj CiTEAATUAI NMH DATA11e ,

UTtMYUM NMH IATA&dquo; :1 lUpER PARMETEA f.!755 &dquo; TUKN PARAFWM St oD)6.7 TEIPERATORF 1)OOdF

TS 1 s&dquo;.

t, T 8 . Te ..

sS

i

io g

.

- , _ ,

. , _ _ &dquo;

...._ _8,

i, ;

,

-

- - , -

&dquo;

&dquo;,._&dquo;.,,.__

E

__

sIs_

_, &dquo;

&dquo;

..

&dquo;

s,..

. - - - - - 1022OF1 - - ........ 00 02:E:O011100F -o OBtU 17

1............., ........ , t ............., ........

to too 1M8 toooo ieeeea le too leee 18808 1808MAUPTUAE T111E - HRS AUPTUIlL T)Ht - HIS

_ _ _ $.ie55 . s,.,-,,&dquo;.H!--.--s,,,(,;, 5 _ $(re55 rUDtUle be1v10! ol ISHT :-i/.Of-IYO $YA vlld w.(1 () U


28/56

Table 12. Stream for 100.000 hour rupture as a fuacU of test Lpl mDllLOC IUPTUII TIlIIAIMI.YSISu.pentun and ctear parter determined by

&dquo;

&dquo;-.B.tuLti&dquo;&dquo;*&dquo;

log stress/log rupcure u- analysis of 2-1/loCr-11Io SMA ,aun SPW ..

_

weld rcal literature data . wn iico/K xs TII{UTUR 8%GF

o

Stress for 100,000 Hour Itupture (KSI) sS

-*


29/56

.

LOC tTtt

ILOGun SIWI MIA temperature and carbon content determined by I

IIINIT Uts gm WATUR WfF log strase/log rupture time analysis of Cl. 2 UTK data111 ,. PU/Kms TENEPATURE 95&F log atrasa/log ruptura ctaa malyaia of C1. 2 UTK data

S

CarbonStress for 100.000 Hour Rupture (KSI)

T Content asoor 950oF 1050OF

1 .9g

,002-003 24.4 13.2 6 2

s 0.04-0 OS 32.66 15.5S 92

0.08-0 09 284 16.77 7 7

St

, 0 12-0.1J 29.9 15 2 8.1s . 0 12-0.13 29.9 15 2 8.11I - - - 0.02-11 03C

0.0-0 OS. 0 08-0 09.1 -0.03cl 0.04-0 OS. 0 oa-o 09.

0 0&dquo; OKosc 0 12-0 13 Combined 30 3 15 7 8 4- - 0 12-G.1X

II ......................................I@ in leee low 1-

I1IPIUII TIfIL - HIS

Fig 46- !n... nt.T. b.h.i of2-L/4Cr-lho SMA -t< *.t.t crrrt moofa hre.)> have been obtained using the iterative program previ-data. at SOO?I u a fUDCt1oa. of &dquo;rbm cooteat d8tara11Wd by -..1,.18 of Ufr ously described and are for test temperatures at whichthere is no data available.Although the isotherms for850 and 900 F (for which some data exist) are not well

limited to weld metal PWHT P > 37.5 due to the behaved, the point at which the individual curves be-limited data availability. In this temper parameter come unreasonable moves to longer rupture times as

range, rupture strength increases with carbon content the test temperature decreases. Based on this trend,up to 0.04-0.05 weight percent. The rupture strength the stress for 100,000-hr rupture at 750 and 800 Fof higher carbon weld metals appears insensitive to have been determined and have been used to givecarbon leveL some idea of the magnitude of those stresesea. TheManson Minimum Commitment Method. Liter- values are enclosed in parentheses to indicate that

ature DataAnalysis (Manson MCM). Figs. 625 are they are extrapolations.stress rupture curves for the SMA literature data as Some correlation between temper parameter anddetermined using the Manson MCM technique. These the 100,000-hr rupture strength ofPWHT SMA weldfour figures present isothermal rupture curves for each metal can be discerned by eumining Table 18. Intemper parameter range includingP < 32.0, 32.0 < P < general, the rupture strength decreases with increas-36.2, 36.2 < P < 37.5, and P > 37.5, respectively. The ing temper parameter. This is especially evident atisotherms are projected to 100,000 hr except in those temperatures below about 950 F where the magni-instances where the fit calculated by the Manson tude of the stresses is large compared to the uncertain-

method predicts long term behavior which is in gross ty introduced by data scatter effects. In the case ofcontradiction with reality. In those cases, the curves weld metal PWHT with P < 32.0, the 750 and 800 Fhave been truncated at the approximate point where stress values indicate that, in this low temperaturethe prediction becomes unreasonable. regime, the rupture strength of mildly PWHT weld

Table 18 lists the extrapolated 100,000-hr rupture metal is significantly higher than that of material giv-stresses associated with Figs. 62-65. The rupture en a more extensive PWHT. This same trend has beenstrengths listed for weld metal PWHT with P < 32.0 observed in the results ofboth the Larson-Miller para-

metric analysis and the log stress-log rupture time ianalysis.

La STRCSSAX gunvu tint MMYSIS- Comparison of the stresses for weld metal PWHT

Lx Uri swu mu MlALVSIS with 32.0 < P < 36.2 and 36.2 < P < 37.5 indicates thatin

ton 13111&dquo;fm I8S TDKMNK 1lBPF the former has a higher strength but that the strength

8 difference decreases with increasing temperature until

I

T. I

t .t i

II.

- Table I5. Stress for 100.000 hour ruptura of 2-1/Kr-1!(o BHA vald

,B aatal u a function of temperature and PIIBT


30/56


31/56


32/56


33/56

Table 16 Strttt for tOO.000 hour rupture of 2-1/iCr-1YO wId -..1 Table 18 Stress for 100.000 hour rupture of 2-1/4Cr-IMoas a function of test temperature and temper parameter S1A weld metal as a function of test tempera-determ1nad by log stress/log rupture time analysis of ture and temper parameter determined by Mansoncombined literature and un data

MCM analysis of literature data

0

Stress for 100,000 Hour Rupture (KSI)Strtss for 100,000 HOur Rupture (KSI)Temperature (or) F02 0 32 0


34/56


35/56

Table 19 Stress for 100.000 hour rupture of 2-1/4Cr-lMo 1N111S0111tQ1 MMLYSIS1

S4A weld metal as a function of test tempera- 1/11 SMII tATA I1 ture, carbon content, and temper parameter 188 p,, IyOpo,?5 RRS (CLASS 2) CAM04 COm7tWT 0 02-C 0 13

determined by Manson MCM analysis of liter- :NO 1 ns IfRS (LASS 11 CARWo (001[111 002.( 0 1B i

ature data IS :----T - --

Stress for 100.000 Hour Rupture (II51) 1 ---- - -- &dquo;&dquo;&dquo;&dquo;-- i

T_sru...7x Odh..101 of 21/4Ct-ltIo Ch.. 2 SMA _ld wtal astantttm10)8 .Q - - 50 0 of tut tR8p8uture d8t....t.ned by anal,.18 of UTK due1067 7 6 - - t9

1100 6 1 - - 422

1112 S S - - 4 0 material (0.0.03C) is of significantly lower magni-1200 - - - x 5 tude than that of the three higher carbon content weld

metals.As a result, an additionalanalysis

of the Class2 weld metals has been performed excluding the 0.02-0.03C data

stress rupture behavior of post weld heat treated 2%281 4 cr%2d1mo steel weld metal 12495

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