9% nickel steel welding

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WELDING RESEARCH

SUPPLEMENT TO THE WELDING JOURNAL, APRIL, 1984

Sponsored by the American Welding Society and the Welding Research Council

Matching Ferritic Consumable Welding

of 9% Nickel Steel to Enhance

Safety and Economy

The brittle fracture initiation characteristicsand fatigue properties o f joints we lded with ma tching ferritic

filler metal are equal to those obtained

with high nickel alloy filler metals

BY F. KOSHIG A, J. TAN AKA , I. WATANABE, AND T. TAKAMURA

SYNOPSIS. The objective of this investigation was to verify the practicabil i ty of anewly deve loped weld ing techn ique forapplication to 9% nickel steel. The technique involved the use of the GTAWprocess and a matching ferri t ic wire f i l lermetal .

Mechanical tests and fracture toughness tests, such as tension, Charpy V-notch impact , COD, deep-notch tens ion,and wide p la te tests , were p erfor me d o nthe weldments at ambient and cryogenictemperatures most ly be low 111 K (i.e.,

-162°C or -260°F). The match ing ferr i t

ic weld metal and welded joints made bythis technique were revealed to possessthe same high yield and tensile strength as9% nickel steel at ambient and cryogenictemperatures .

Fracture toughness test results indicated that the weldments were qu i tetough at the liquefied natural gas (LNG)temperatures of 111 K (-16 2°C,

-260°F) and even a t 77 K (-19 6°C,

—321 °F). In the final stage of the investigat ion, the pressure testing of a spherical9% nickel steel model tank 2 m (6 ft 6 %in.) in diameter and 16 mm (0.63 in.) inthickness, which was fabricated by this

weld ing techn ique, was performed in

l iquefied nitrogen. The pressure testresults provided evidence to indicate thatthe weldments would give satisfactoryperformance in LNG containment plantsand that a design stress as high as 294N / m m 2 (42.6 ksi) is quit e ac cepta ble inthe construction of those plants.

I n t r oduc t i on

A joint investigation was undertakenby a Japan Welding Engineering SocietyCommittee to verify the practicabil i ty ofusing a newly developed matching ferri t ic

f i l ler metal welding technique for 9%nickel steel. The committee consisted ofinvestigators from universities and publicand private research institutes and soci

eties as well as from electric power andgas companies and Nippon Kokan Kabu-shiki Kaisha, one of the leading steel andheavy equ ipme nt m anufacturers in Japan.

Based on a paper originally presented at theA WS 61st Annual Meeting held in Los Angeles,

California, during April 13-18, 1980.

The authors are with the Technical ResearchCenter of Nippon Kokan K.K., Kawasaki-shiKanagawaken, japan.

The objectives of this investigationw e r e :

1. To establish the feasibility of a newly developed gas tungsten arc weldingtechnique and the use of matching ferri t icconsumable wire f i l ler metal.

2. To determine the f rac ture toughness of the weldments at cryogenic t e m peratures by an approach based on thefracture mechanics.

3. To dem onstrate that 9% nickel steelconstructions for LNG containment plantswhich are welded by the new techn iqueare safe from britt le fracture.

This paper mainly deals with a summary of the results of this investigation.

Allowable Design Stresses

Commercial matching ferri t ic f i l ler metal welding for 9% nickel steel, i f establ ished, would furnish solutions to wel l -kno wn techn ica l and economic prob lemsencountered in the high-nickel type austenit ic consumable electrode welding of9% nickel steel. This would eventuallymake it possible to use higher allowabledesign stresses in the construction of LNGcontainment plants for storage and trans

porta t ion .

WELDING RESEARCH SUPPLEMENT 1105-s



Industria l standards of various countries, such as JIS B 8243, ASME Sec. VIIIDiv. 1 and 2, API620, BS5500 and BS5387,contain criteria for calculating the al lowable design stresses in structures builtwith welded construction using 9% nickelsteel. According to BS5387, the al lowabledesign stress must be 1/2.35 of thetensile strength or 1/1.5 of the 0.2%proof s t rength — whichever is lower —prov ided, however, tha t i t must be noth igher than 260 N/mm 2 (37.7 ksi).

For instance, the assumption can bemade that the matching ferri t ic weldmetal and welded joint are equal instrength to the base metal and that theirtensile strength and 0.2% proof strength,respectively, are 690 and 585 N/mm 2

(100 and 84.8 ksi), i.e., the lower limits setby ASTM A553-1 . When this assumptionis made, a simple calculation to meet thecriteria c ited above gives 294 N/mm 2

(42.6 ksi) as an allowable design stressvalue. This value is higher b y ab out 50N / m m 2 (7.25 ksi) than the value of 241

N / m m2

(35.4 ksi) that is used for highnickel type austenitic filler metals.

The criteria for allowable design stressdo not differ from BS5500 to BS5387, butthe latter does not contain the provis ionthat the allowable design stress must benot h igher than 260 N/mm 2 (37.7 ksi).Accordingly, there seems to be a verystrong possibi l i ty that the al lowabledesign stress could be set higher whensafety against brittle fracture of structureswelded wi th the match ing ferr i t ic t ech nique is established.

With this possibility in mind, a spherical

mo del tank of 2 m (6 ft 6% in.) diameterwas fabricated and pressure-tested inliquefied nitrogen in the last stage of thisinvestigation. This was done in order todemonstrate that structures made using

th is newly deve loped weld ing techn ique

are safe against brittle fracture.

M a t e ri a ls a n d M e t h o d

The superior notch toughness of 9%nickel steel at cryogenic temperatures isderived mainly from the steel 's excellentproperties imparted by its c lean ferri tematrix structure; the retained austenite

that serves as a sink for impurities playsan auxiliary role in this respect. Accordingly, i t stands to reason that the matching ferritic weld metal also acquires superior notch toughness at cryogenic t e m peratures if impurit ies in the weld metalare suppressed to low levels and if weldmetal is softene d by mult i-w elding thermal cycles to an appropriate extent.

Wi the re l l et al. (Ref. 1) investigated there la t ionsh ip between the notch toughness of weld metal obtained by GMAwelding with matching ferri t ic f i l ler metaland the oxyge n content o f we ld me tal; i twas found that the notch toughness of

weld metal decreased in a sharp curvewhen its oxygen content rose beyond100 ppm. In this respect, GTA welding inan atmosphere of pure argon seemsmost effective in inhibit ing the contamination of weld metal with oxygen and inpreventing the depression of i ts notchtoughness.

In recent years remarkable progresshas been made in the mechanization ofGTA welding. In point of fact, GTA w e l d ing wi th a machine equ ipped wi th anautomatic voltage control ler and an electrode weaving system that can weld in al l

posit ions has come into commercial use.Further, semi-automatic GTA weldingmachines that automatically feed the wirefiller metal into the arc have also beencommerc ia l ized.

Table 1—Chemical Composition and Mechanical Properties of the 9"o Ni Steels Used

Thickness, mm' 3'

Chemical composition, wt—%C 0.03Mn 0.44Si 0.22P 0.006

S 0.005

Ni 8.85

Cr 0.03

M o 0.12

sol. Al 0.016Tensile propertied0.2"„ PS, N /m m 2 68 8

TS, N / m m 2 73 9El, % 28.2

impact properties at 77 Kfc>

vE , joules 148.4

LE, mm 2.00

12

0.03

0.45

0.220.006

0.0058.88

0.03

0.12

0.017

71 4

75 9

34.0

200.7

1.81

16

0.07

0.45

0.250.006

0.005

9.03

0.05

0.11

0.022

61 7

70 6

43.0

215.6

2.19

23

0.05

0.43

0.220.006

0.005

8.81

0.05

0.14

0.026

72 8791

31.0

191.6

1.77

32

0.05

0.43

0.220.006

0.005

8.94

0.05

0.14

The arc voltage, current and the f i l lermetal feeding rate can be control ledindependently of one another in GTAweld ing. Also, heat input control is easilyaccomplished in any welding posit ion.This fact suggests that the notch toughness of weld metal can be improvedthrough judic ious welding thermal cyclecontrol i f normal GTA welding isemployed. It fo l lows that al l weldingrequired in the construction of LNG c o n ta inment plant components can be madeproper ly th rough jud ic ious combinat ionof the two d i f fe rent GTA weld ing t ech niques ment ioned above.

In the present investigation all 9% nickel steel test plate samples were picked atrandom from the product ion l ine . Tab le 1shows the chemica l compos i t ion andmechanical properties of 9% nickel steelsamples. Table 2 shows the chemicalcomposit ion of the matching ferri t ic wirefiller metal tested in this investigation. Asindicated in Table 2, the f i l ler con tained alow proportion of carbon and si l icon that

act to harden the ferri te matrix structureof w e ld meta l . The presence o f phos phorus and sulfur as impurities is also suppressed to a low level, while the f i l lermetal nickel content is 2% higher thanthat of base metal.

We lds we re made unde r tw o d i f fe ren tsets of conditions in three positions: flat,vert ical-up, and horizontal. Heat inputwas varied according to the plate thickness and welding posit ion, result ing inwelds at three levels of heat input —Tables 3 and 4.

M e c ha n i c a l P r ope r t i e s o f W e l de dJoints a t Am bie nt and Cryo gen ic

T e m p e r a t u r e s

The relationships between the strengthof the match ing ferr i t ic we ld meta l a tambient temperature and heat input isshown in Fig. 1, and Fig. 2 shows theresults of tension tests performed on 40kinds of welded joints of differing platethickness, welding process, welding posit ion and heat input at ambient to cryogenic temperatures. Each point in Fig. 2indicates the arithmetic mean value for atotal of 80 welded joints (2 welded joints

each of 40 kinds).

The 0.2% proof strength values wereobtained, assuming the matching ferri t ic

(a) mm/2 5.4 = in.

{b ) PS —proof s t rength; TS —tensile s t re n g th ; El — el onga t i on ; N / m m2

-S-(c) 77 K = -196°C = - 3 2 1 °F. LE-lateral ex pans i on .

0.026

68 3

76 831.2

177.5

1.96

Table 2—Chemical

(0.047 in.) Diamete

Filler Metal, Wt-%

C - 0.04

M n - 0.39

Si - 0.01

P - 0.006

S - 0.006

Composit ion of 1.2 mm

r Matching Ferritic Wire

Ni - 11.06

Co - 0.34

so l Al - 0.020

Ti - 0 .01

B - 0.0007

106-s|APRIL 1 9 8 4



w e l d e d j o in t s t o b e a c o n t i n u o u s h o m o

g e n e o u s b o d y . A s e v i d e n t f r o m F ig . 2 ,

b o t h t h e m a t c h i n g f e rr i t ic w e l d m e t a l a n d

w e l d e d j o i n t s a r e a s s t r o n g as b a s e m e ta l

a t a m b i e n t - t o - c r y o g e n i c t e m p e r a t u r e s .

F u r t h e r , t h e s i d e - b e n d t e s ts p e r f o r m e d

o n w e l d e d j o in t s ( in a c c o r d a n c e w i t h JIS Z

3 1 2 2 w h e r e R = 2 t ) r e v e a l e d t h a t a ll

s p e c i m e n s w e r e d e f e c t - f r e e — Fig. 3 .

N o t c h T o u g h n e s s a n d C O DC h a r a c t e r i s t i c s o f M a t c h i n g F e r r i t ic

W e l d e d Jo in ts

F i g u r e 4 s h o w s t h e r e l a t i o n s h i p s

b e t w e e n n o t c h t o u g h n e s s o f w e l d e d

jo in ts o f p la tes 12 m m (0 .47 i n . ) th i ck an d

h e a t i n p u t , a n d T a b l e 5 r e c o r d s t h e n o t c h

t o u g h n e s s o f w e l d e d j o in t s i n 2 3 m m

(0 .91 i n . ) th i ck p la tes . These tes t da ta

c l e a r l y i n d i c a te t h a t b o th t h e w e l d m e ta l

a n d h e a t - a f f e c t e d z o n e ( H A Z ) a r e q u i t e

t o u g h e v e n at 7 7 K ( - 1 9 6 ° C , - 3 2 1 °F )

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

d i t i o n s i n d i c a t e d , a l t h o u g h t h e a p p r o p r i

a t e h e at i n p u t r a n g e s a r e g o v e r n e d b y

th e p l a te t h i c k n e s s e s .

T h r e e - p o i n t b e n d i n g C O D t es t s w e r e

p e r f o r m e d a c c o r d i n g t o A S T M E 3 99 a n d

B SI • D D - 1 9 . F i g u r e 5 s h o w s t h e r e l a t i o n

s h ip b e t w e e n C O D v a lu e s o b t a i n e d b y

th e s e t e s t s a n d h e a t i n p u t . In Fig . 5 , c T 0 l

a n d CT02 i n d i c a te t h e c r i t i c a l t e m p e r a

t u r e s a t w h i c h t h e c r it i c a l c r a c k t i p C O D

v a l u e s o f 0 . 1 a n d 0 .2 m m ( 0 .0 0 4 a n d

0.008 i n . ) , r e s p e c t i v e l y , a r e o b ta i n e d . I t i s

o b v i o u s f r o m F ig . 5 t h a t b o t h w e l d m e t a l

a n d H A Z s h o w C O D v a lu e s o f 0 . 2 m m

( 0 .0 0 8 in .) o r m o r e a t t h e L N G te m p e r a

t u r e o f 1 1 1 K ( - 1 6 2 ° C , - 2 6 0 ° F ) .

F r a c t u re T o u g h n e s s o f M a t c h i n g

F e r r it i c W e l d e d J o i nt s

Re la t i onsh ip be tween Cr i t i ca l COD, oc , and

Jc Values

T h r e e - p o i n t b e n d i n g C O D t e s ts a n d

c o m p a c t t e n s i o n t e s ts w e r e p e r

f o r m e d a c c o r d i n g t o B SI • D D - 1 9 a n d

A S TM • E 3 9 9 , u s i n g m a tc h i n g f e r r i t i c

w e l d e d j o in t s o b t a i n e d b y m e c h a n i z e d

G T A w e l d i n g i n t h e v e r t i c a l - u p p o s i t i o n ;

t h e r e l a t io n s h i p b e t w e e n c r it i ca l C O D ,

8c , a n d Jc v a l u e s w a s d e t e r m i n e d . T h e

h e a t in p u t w a s 4 . 3 k j / m m ( 1 0 9 k j / i n . ) .

Th e s h a p e s o f t h e t e s t s p e c i m e n s a r e

s h o w n i n F i g. 6 . C r a c k o p e n i n g d i s p l a c e

m e n t , 5 c, w a s c a l c u la t e d f r o m t h e m e a

s u r e d c r a c k m o u t h d is p l a c e m e n t b y

W e l l s ' f o r m u l a s i n d i c a te d i n B IS • D D - 1 9 ,

a n d Jc b y e q u a t i o n (1 ) a d v a n c e d b y R i ce

(Ref. 2) :

) c _ 2JPdq

B ( W(I)

w h e r e B = t h i c k n e s s , a = c r a c k l e n g t h ,

W = w i d t h o f s p e c i m e n , P = l o a d , a n d

q = l o a d p o i n t d i s p l a c e m e n t . In t h e c o m

p a c t t e n s i o n t e s t , d i s p l a c e m e n t q i n e q u a -

Table 3—Welding Cond i t i ons

Thickness,

m m Process Position

Vert ica l -up

Cond i t i on

250A

12 V

6 5 m m / m i n .

Heat input Edge

k j /mm p repara t i on

2 .8 I

300A

12 V

5 5 m m / m i n .3.9

23 Au tomat i c

C TA

350A

12 V

4 5 m m / m i n .

5 6

Hor i zon ta l 300A

12 V

1 l Om m /m i n .

2.0 i\

Semi-automatic

CTA Vert ica l -up

250A

10-12V

5 0 - 6 0 m m /m i n .2.6-3.3

(a) Edge preparat ion as fo l lows :

60°

6 0

Tab le 4—Welding Cond i t i ons

Thickness,

m m '1 '

8

12

C TA

process'b>

A u to .

A u to

Position

Vert ica l -up

Hor izonta l

Vert ica l -up

Heat input,

k ) / m m

1.0

1.6

2.2

1.3

1.9

3.04. 0

Flat1.9

2.8

4.0

Horizonta l 2 .3

Semi-A.Vert ica l -up 1.0-1.8

Flat 1.5-1.9

23A u to .

Vert ica l -up2.83.9

5.6

Horizonta l 2 .0

Semi-A. Vertical-up 2.6-3.3

32A u to .

Vert ica l -up3.6

5.2

6. 1

Flat3.6

5.2

6.1

Semi-A.Hor izonta l 2.0

Flat 2.3-3.0

(a) 1 in. = 25.4 m m .(b) Auto .— autom at ic ; Semi -A —sem i -automat ic .




9 0 0

8 5 0

f5 5 «

7 5 0

c4)

I -

•oc<o

2V

> 700

.

— ^S . - -

- Open

Filled

It

•- •

oo

•

- 12mmt

- 23mmt

0*0.2

;ou

8 ^

'

*— ?

^ r -

\

•

o—o

A

" ^

I 1

B M . 2. 0 3.0 4.0 5.0

Heat Input ( k j / m m )

6 . 0

Fig. 1—Weld metal strength vs. heat input. <T02 — 0.2% proofstrength (=yield strength); <ru — ultimate tensile strength. Symbols:open —0.2% proof strength; closed - ultimate tensile strength

Fig. 2 (right) —Strength of welded joints (40 kinds). ou —ultimate tensilestrength; o-02-yield strength (0.2 % proof strength); R.A. -reduction ofarea; El— elongation

2000

1800-

1600

1400

1200

£ 1000in

800-

* 600-

400-

200

100 160 200 250

Temperature (K)

100

t ion (1) was substituted by the measuredcrack mouth displacement.

Figures 7 and 8 indicate the relationships between 5c and temperature, andbet we en Jc values and tempe ratures,respectively. The relationship between 8c

and Jc is thought to be expressed byequation (2).

Jc = mov, • 5 c (2 )w h e r e <ry = yield strength and m = c o n stant.

The relationship between 5c and m isindicated in Fig. 9. Average m was on theorder of 1.8 in the temperature rangenear 111 K (-162°C, -260°F) where 5cwas 0.2 or higher. On the other hand,average m tended to rise to 2.0 or more

in the temperature range near 77 K( - 1 9 6 ° , - 3 2 1 °F) whe re 5c was so lo w asto induce a pop-in in the notch t ip or anunstable crack that readily led to comp le te rupture .

Levy (Ref. 3) placed 1/m at 0.467(m = 2.14) fro m th e results of FEM calculation under conditions of plane strain. His

value of 0.467 is in go od ag reement wi thours at 77 K ( - 1 9 6 °C , - 3 2 1 °F).

Initiation of Brittle Fracture from a SharpFatigue Crack

Deep-notch tens ion tes ts were performed on specimens having fatiguecrack 5 mm (0.20 in.) long at the notch

tip —Fig. 10. The test specimens were 12and 23 mm (0.47 and 0.91 in.) thickmatching ferri t ic welded joints that were

made in the vertical-up posit ion at heatinputs of 3.0 and 3.9 kj/mm (76 and 99.1

- 2 5 0tt)3

.O

^ 2 0 0r > -

r * -•4-1

ro

> 1 5 0k_

tt>c

UJ

-o100tt)LuO< /)

B 5 0<

Weld Meta l

O i

-*d

Fusion Line

ED\

•• • •

. i

_l I I l_

Fig. 3 — Side bend test specimens

1.0 2.0 3 .0 4 .0Fig. 4 — Notch toughness vs. heat input

1.0 2.0 3.0 4.0

108-s I APRIL 1984



kj/ in.), respectively. The notch was located in the center of the weld metal ofeach specimen or in i ts fusion boundaryregion.

The test results are presented in Fig.11, and the relationship between fracturetoughness obtained by equation (3)be low and temp erature s is indicated inFig. 12 :

Kc=

c? \ArC sec —W (3)

w h e r e <rf = gross fracture stress, C = halfcrack length, and W = wi dth of specim e n .

The values of 5c obtained in the three-po in t bend ing COD tes ts were converted to Jc by equation (2) (placing m at1.8) and the values of Jc so obtainedwere converted to Kc by equation (4).These values are shown in Fig. 12.

Kc = Jc (4)

wh ere E = Young 's modulus andv = Poisson's ratio.In the three-po in t bend ing CO D test , a

ducti le thumbnail developed at the notchtip in the temperature range at and near111 K (-162°C, -260°F), and in thedeep notch test the test specimens werefractured after general y ielding. Accordingly, all values of Kc at and near 111 K(-16 2°C, -260°F) should be consideredinval id. Conversely speaking, this factprovides evidence that the matching ferri t ic welded joints are quite tough at 111K (-162°C, -260°F). Further, the valuesof Kc were determined to be as high as

5000 N • m m "3

'2

in the temperaturerange near 77 K (-196°C, -321°F)where the values of 5c were 0.1 mm orlower .

On the basis of these test results, theallowable discontinuity s ize was determined for the match ing ferr i t ic we ldedjoints in 23 mm (0.91 in.) thick plates, lnthis case the assump tion was made that asurface discontinuity as deep as half theplate thickness was in the fusion boundary region and that the test specimen wassubjected t o a design stress of 294 N /

Table 5—Results of Charpy V-Notch Testing at 77 K (- 19 6 C, - 32 1°F)

Process

posi t ion

Heat input,

k | / m m

2.8

N o tc h

posi t ion '3 '

W

vE ,

loule

158

194

18 0

19 4

W 21 1

Auto . GTA

Vert ica l3.9

177

20 6

20 5

W 22 0

5.620 3

173

18 9

W 241

Au to . GTA

Horizonta l2.0

13 0

157

116

W 7 1

Semi-A. GTA

Vert ica l

(a) Notch positions shown in sketch below:

W F H Z

2.6-3.313 7

178

7 203(b) L.E. —lateral expansion.

O p e n ; Weld M e ta l , F i l l e d ; Fus ion L i ne1 3 0

7 0

12mmt 2 3 m m t

o • : cTo.i

A A ; cTo.2

LE,<b>

m m

1.48

1.95

1.58

1.63

1.63

1.55

1.95

1.92

1.85

1.33

1.87

2.15

1.62

1.65

0.88

1.27

1.35

1.95

3 2 m m t

1.0 2.0 3.0 4.0 2.0 3. 0 4.0 5.0 6 .0

Fig. 5 — Critical temperatures vs. heat input

3.0 4.0 5.0 6.0 7 0

3 0 0

6 0

150 1 5 0

V 3 0

0.15

AAp-

2-

3 0

3 0 ,

F a t i g u e " - u * - i -

N o t c h

Fig. 6 — Bend and tension test specimens. Dimensions in mm




1.00

0.50

O20

0.10

0.05

0.02

0.0170 80 90 100 110 120 130 140

Temperature (K )

Fig. 7 - Critical CO D vs. temperature

O

-Open

Fi l led---

•

•*>'

Weld Meta l

Fusion Line

z&

^ Xt-'A ^ -

O

i I

o

•

/' y

<sS v/

/ A

,-'*'/ '1-~-'

'» L-o^r to*

< # ' A

s7

°»: Bend inga A ; Tens ion

i i ,

1 0 0 0

5 0 0

E 2 0 0

z

~ 1 0 0

5 0

2 0

_- O p e n ;

- F i l led ;

•

"

"

Weld Me ta l

Fusion Line

A

•*""' ^^

O

/ • // A J^

7

o •

& A

-0 - -« -A- - *-

3O**O-/ -tr

; Bend ing

' Ten t ion

—*•

I Inva l id -va lue

1070 8 0 90 10 0 110 120

Tempera tu re ( K )

Fig. 8 — jc vs. temperature

130 140

m m 2 (42.6 ksi) as well as to a welding

residual stress of 365 N /m m 2 (52.9 ksi)wh ich was obta ined by measurement.

The re la t ionsh ip between f rac turetoughness Kc and al lowable f low size acan be expressed by equation (5)

below:

Kc = o-m • M m V ^ I T Q (5)

where <xm = design stress + w elding residual stress, M m = mag nif ication fac torin tension, Q = nondimensional functionof el l ipt ic integral, y ield strength and

applied stress; and a = half crack length.

Let the value of Kc be 5000 N •m m " 3 ' 2 that is obta ined at 77 K (-1 96°C,

—321°F), and allow able flaw size a can

be calculated by equation (5) to be 19.2mm (0.76 in.). The extreme length of the

allowable surface discontinuity is therefore 38.4 mm (1.51 in.). A discontinuity of

this size is large enough to be easilydetected by the nondestructive inspec

t ion a f ter we ld ing. In o ther words , thevalue indicates that the matching ferritic

welded joints are safe from britt le frac

ture .

Results of Large-Scale Type Brittle FractureTests

Through-thickness notched- and cross-welded wide plate tension tests and sur

face notched wide plate tension testswere performed on a large scale. They

were carried out using matching ferri t icwelded joints in plates that were 12 and

23 mm thick (0.47 and 0.91 in.).

Fig. 9 —Relationship between Jc and critical COD

lOOOr

500

EE 200

100

50

20

10

." 0 • ; Bending

. A A ; T ens ion

• ° °A °̂ /: / /

~'/y7

/ /

# ' /

A/& 7

AA 7

O p e n ; W e l d Metal

F i l l e d ! F u s i o n L i n e

-o - - * - ^ - * - ; I n v a l i d

- v a l u e

11 '10 20 50 100 200 500 1000

< V 6 C ( N / m m )

3 .0

2 .5

2 .0

u

lOb^i-5

s

o

1.0

0 .5

- * —

° • ; Be n d i n g

A A ; Tens ion

Op e n ; W e l d M e t a l

Fi l led ; Fusion Line

-<>-•"&-*•; Invalid-value

0 .01 0 .02 0 .0 5 0 .10 0 . 20 0 . 5 0 1 .00

C r i t i c a l C O D , 6 c ( m m )

110-sl APRIL 1984



Fat igue

N o t c h

F u s i o n L i n e

N o t c hP o s i t i o n s

ig. 10 — Deep-notch tension test specimen. Dimensions in mm

1200

E 1000E\z- 800

| 600

400

2 200

Open ; Weld Metal

Filled; Fusion Line

°» ;l2mmto* ; 23mmt

0 80 100 120 140

Temperature ( K)

Fig. 11-Deep-notch tension test results

The results obtained in these tests are

sen ted in Figs. 13 and 14. As is clear in13, the weld metal and weld interface

90 K ( -1 72 and -1 83 °C , i.e., - 2 7 8nd —290°F) or more, respectively, after

en at a tem pera ture ofK ( - 1 9 6 °C , - 3 2 1 °F) at whic h fr act ure

base metal, the fracture stress

le design stress of 294 N /m m 2

14 , and the fracture surfaces are shownin Fig. 15. W he n the effect o f notc hacuity is taken into con sideration, thesetests results are in good agreement withthose discussed in the preceding sect ion.

In the large-scale brittle fracture tests,

mm (0.47 in.) th ick plates were not fracured at al l test temperatures despite the

presence of a notch. It was also shown

2 0 0 0 0

1 0 0 0 0

5 0 0 0

that the stress leading to fracture was far

greater than the yield strength of basemetal. The results of large-scale typebritt le fracture tests provided evidence to

indicate that the matching ferri t ic weldedjoints exhibit superior fracture toughnessat cryogenic temperatures.

Fatigue Character ist ics of MatchingFerritic Welded Joints

Crack propagation tests were performed a t room temperature and in l iquefied nitrogen at 77 K (-19 6°C,

—321 °F) in order to d eterm ine thefatigue characterist ics of matching ferri t ic

welded joints. The test results are presented in Fig. 16. The values of C and mshown in Fig. 16C were obtained by acalculation of the relationship betweenthe rate of crack propagation and therange of stress intensity factor accordingto Parris' law expressed by equation (6); itis evident from Fig. 16 that the values soobtained do not differ at al l from match-

o

2 0 0 0 -

1 0 0 0

*a

: ®o •

A A

12mmt

O p e nF i l l ed

O ^ ^ = < cA

Deep-notch Test

Bend ing Test

• • • I '

We Id M e t a lFusion Line

s<4

AA

2 0 0 0 0

£ 1 0 0 0 0EE

Z 5 0 0 0

o

8 9 10 11 12 13

T e m p e r a t u r e ( V K ) x 1 03

2 0 0 0

1 0 0 0

ing ferri t ic welded joints to ordinary c o n

structional steel and joints:

d a

dN= C(AK)

n(6)

wh ere a = crack length, N = cycle,AK = range of stress intensity factor, andC, m = material constants.

Butt joint fatigue strength test resultsare presented in Fig. 17.

Cryogenic Pressure Test of theSpher ical Model Tank

That matching ferri t ic welded struc

tures are safe from britt le fracture wasdemonstra ted f rom a prac t ica l s tandpoint. Accordingly, a spherical modeltank 2 m (6 ft 6 % in.) in diameter wi th a16 mm (0.63 in.) nominal wall thicknesswas fabricated and subjected to pressuretest in liquefied nitrogen at 77 K( - 1 9 6 °C , - 3 2 1 °F ) .

The welding condit ions are indicated in

A

A A

2 3 m m t

«k AOpen;Weld M e t a lFilled:Fusion Line

o • : De ep -n o tch Tes tA * : Bend ing Tes t

9 10 11 12 13

T e m p e r a t u r e ( V K ) X 1 03

12 —Fracture toughness vs. temperature

WELDING RESEARCH SUPPLEMENT! 111-s



EE 1 4 0 0V.

2

$ 1 2 0 00)

trt

j ; 1 0 0 03

utc

"it 8 0 0

O

O 6 0 0 -

- 1 0 0 0 -

3 0 0 ,

I I I I mi uTTT J

^ 3 5

fagma

H 1 0 -

2 3

6 0 0 I 3 5

0.15

-fl-

W . M .

LAI F.L.

F u s i o n L i n e

0o2of B a s eM e t a l

° W e l d M e t a l

6 0 8 0 1 0 0 1 2 0 1 4 0

T e m p e r a t u r e ( K )

1 6 0

Fig. 13 —Brittle fracture test results; dimensions in mm. Symbols: open —experimental values for specimens with notch at the weld metal-closed — experimental values for specimens with notch at the w eldinterface; rr0.2~0.2?i proof strength (yield strength)

1200

u, 1 0 0 0

8 0 0n

a.Im

3

un£ 600V)</)o

T- 1 0 0 0 -

(-300-|

i i 'oo

r fo2 o f BaseM e t a l

6 0 8 0 1 0 0 1 2 0 1 4 0

T e m p e r a t u r e ( K )

Fig. 14 — Additional brittle fracture test results. Open symbols —specimen experimental values, rroj — 0.2'% proof strength (yieldstrength)

Fig. 15 —Brittle fracture test specimens withresulting fracture appearances. A—at 77 K

(-196°C, -321 °F); B and C- at 111 K(-162"C, -260' 'F)

Fig. 18, and the model tank is shown inFig. 19. The wel de d butt jo ints for the

tank shell p lates were made by a mechanized automatic CTA welding machine inthe vert ica l -up pos i t ion , and the weldedbutt jo ints for the crown plates and shellplates, were made with a semi-automaticweld ing machine.

The spherical model tank was fabricated in accordance with the Law Pertaining to Co mpre ssed Cas Regulations ofJapan. To comply with the law, weldingprocedure and product ion tes ts wereperformed, and the ent i re weld l ineswere tested by x-ray radiographic andultrasonic inspection after fabrication.The procedure for x-ray radiographic

inspection is schematically presented inFig. 20, and the nondestructive inspectionresults are shown in Table 6.

The welding discontinuit ies revealedwere al l merely minute porosit ies. Theresults of nondestructive inspection clearly indicated that the occurrence of w e l d ing discontinuit ies was rem arkably inhibited in the spherical model tank. Further,the results of hydrostatic test and nitrogen gas airt ight test (performed at pressures ranging up to 8.1 and 5.9 N/mm 2 ,i.e., 1175 and 856 psi respectively) conf irmed the soundness of weldments in

this tank.The schematic diagram of the pressure

test is sh ow n in Fig. 21 . The pressu re o fthe model tank reached a peak of 15.4

N / m m

2

(2234 psi) at 13 minutes (min)after onset of pressurization and held atthe pressure for about 5 min. During thisperiod of t ime, the tank pressure wasreduced to 14.7 N/mm 2 (2132 psi).

The stress that acted on the tank shelland crown plates when its pressure wasat the peak level was 481 N/mm 2 (69.8ksi) theoretically, whereas the valuesobtained by the strain gauges attached tothe beads and shell p lates ranged from408 to 456 N/mm 2 (59.2 to 66.1 ksi).These values are 1.39 to 1.55 times aslarge as the a llowa ble design stress of 29 4N / m m 2 (42.6 ksi). The relationship

between measured pressure and strain ispresented in Fig. 22.

In the experiment with the tank, thepressure tests revealed no abnormalit ies.Also, no discontinuit ies were revealed bynondestructive inspection after the pressure test. The experiment also c o n f irmed that matching ferri t ic weldedstructures are safe from britt le fracture.

Weld Discontinui t ies

For these tests, welds that were 7.4,

65.5, 55.7, and 18.7 m (24.3, 214.9, 182.7

and 61.4 ft) long were made using 9%nickel steels that were 8, 12, 23 and 32

112-s | APRIL 1984



1 0

2>

u

•aNro

TJ

1 0

W e l d M e t a l

®

•o

A

A

Temp.

( K )

R.T.

R.T.7 77 7

a d

( N / m m2

)

1 4 7

9 8

1 4 7

9 8

_L

10

o>

os

E£io

4

z\n•o

10

1 0 ' 1 0J

A K ( N / m m ^ )

Fig. 16-Results of fatigue-crack propagation test: A —

weld metal; B — fusion line (i.e., weld in ter face); C —relation between C and m. Symbols: Aa —stress ampli

tude; AK = Aa\7rrC le., amplitude of stress intensity

factor; c— half crack length

1 0 '

F u s i o n L i n e

o

•

T e m p .

( K )

R.T.R.T.

7 77 7

Ad

(N/mm2)

1 4 79 8

1 4 79 8

1 0 * 1 0J

A K ( N / m m3 /

2 )

1 0 '

5 0 0

rtT

| 2 0 0

z" 100

15

<5 0

Thick

i

n e s s . 2 3 m m

- t f —

6: No Te s t

i , i

o -

o-

• 1 0

- 1 1

-1 2

o

10° 10

N ( c y c l e )

Fig. 17 — Welded butt joint fatigue strength test results. Open

circles are data plottings

- 1 3 -

- 1 4 -

- 1 5

- 1 6

- 1 7

.

"

- ©

o •

A •

O p e n

- Fil led :

k v.

\

\

=c(aKrAK ;N

k•

\ log C=-2.7 3

W e l d M e t a l

F u s i o n L i n e

a t 7 7 Ka t R.T.

>imm'TI

• n - 4 . 3

m m ( 0 . 3 1 , 0.47, 0 . 9 1 , and 1.26 in.) t h i c k ,

r e s p e c t i v e l y . F u r t h e r , in the f a b r i c a t i o n of

t h e s p h e r ic a l m o d e l t a n k , w e l d s t h a t

w e r e 24 m ( 7 8 .7 ft) l o n g w e r e m a d e u s i ng

t h e n e w t e c h n i q u e .

I n e v e r y c a s e , s o u n d w e l d s w i t h o u t

d i s c o n t i n u i t i e s w e r e o b t a i n e d . In f a c t , th e

w e l d d i s c o n t i n u i t i e s d e t e c t e d by n o n d e

s t r u c t i v e t e s t i n g s w e r e all m i n u t e p o r o s i

t ies as s h o w n in T a b l e 6. The w e l d i n g

t e c h n i q u e u s e d was, t h e r e f o r e , d e t e r

m i n e d to p r o v i d e a r e l a t i v e l y e a s y m e a n st o m a k e w e l d m e n t s of h igh re l i ab i l i t y .

C o n c l u s i o n

To e s ta b l i s h th e feas ib i l i t y of the

m a t c h i n g f e r r i t i c c o n s u m a b l e w e l d i n g of

9 % n i c k e l s t e e l , th e s a fe t y of w e l d m e n t s

f r o m b r i t t l e f r a c t u r e wa s i n v e s t i g a t e d

u s i n g an a p p r o a c h b a s e d o n f r a c t u r e

m e c h a n i c s .

A s a r e s u l t , it b e c a m e c l e a r t h a t b r i t t l e

f r a c tu r e i n i t i a t i o n c h a r a c te r i s t i c s and

f a t i g u e p r o p e r t i e s of the j o i n t w e l d e d

w i t h m a tc h i n g f e r r i t i c f i l l e r m e ta l w e r e asg o o d as t h o s e w i t h h i g h - n i c k e l a l l o y f i l l e r

m e ta l s . In p a r t i c u l a r , 0.2% p r o o f s t r e s s of

w e l d m e ta l w i t h m a tc h i n g f e r r i t i c fi l le r

m e t a l wa s m u c h h i g h e r t h a n t h a t of the

w e l d m e t a l w i t h h i g h - n i c k e l- a l lo y

m a te r i a l s , and e q u a l to t h a t of 9% n i c k e l

s t e e l p l a t e . T h e r e f o r e , the a p p l i c a b l e

h ighe r des ign s t ress resu l ts in a d e c r e a s e

i n w a l l t h i c k n e s s of LNG s t o r a g e t a n k s .

Th e p r e s s u r e t e s t r e s u l t s of the s p h e r i c a l

m o d e l t a n k in l i q u e f i e d n i t r o g e n r e v e a l e d

t h a t th e s a f e t y of 9% n i c k e l s t e e l and its

w e l d w i t h m a t c h i n g f e r r i t i c w i r e f i l l e r

m e t a l wa s s a t i s f a c t o r y .

WELDING RESEARCH SUPPLEMENT! 113-s



Fig. 18—Schematic configuration of tank and welding condit ions

B - 1

Crown P la te

Shel l Plate

Antarc t i c Manho le P la te

Number ; X - ray F i lms

5^-—i 4

Fig. 20-Schematic representation of x-ray procedure as applied to tank welds

B a n k

Fig. 19 - Fabricated tank

It c a n , t h e r e f o r e , b e c o n c l u d e d t h a tt h e n e w w e l d i n g t e c h n i q u e a n d w e l d i n g

m a te r i a l h o l d a g o o d p r o m i s e o f s u c c e s s

i n t h e e c o n o m i c a l c o n s t r u c t i o n o f L N G

s t o r a g e t a n k s m a d e f r o m 9 % n i c k e l

s t e e l .

T h e n e w t e c h n i q u e h as b e e n r e c o g

n i ze d as su i tab le fo r 9% n i ck e l s tee l by

th e ) a p a n W e l d i n g E n g i n e e r i n g S o c i e t y

and the )apan H igh Pressu re Ins t i tu te .

A l s o , t h e v a l u e o f 2 9 4 N / m m 2 (42 .6 ks i )

h a s a l s o b e e n a c c e p te d a s a n a l l o w a b l e

des ign s t ress fo r s t ruc tu res bu i l t us ing the

n e w w e l d i n g t e c h n i q u e .

Acknowledgment

T h e a u t h o r s e x p r e s s t h e i r d e e p a p p r e

c i a t i o n t o C h a i r m a n H. K i h a ra a n d M F N

m e m b e r s f o r ha v i n g a f f o r d e d t h e m a n

o p p o r t u n i t y o f p r e s e n t i n g t h is p a p e r

b e f o r e t h e a n n u a l m e e t i n g o f t h e A W S .

A p p r e c i a t i o n i s a l s o d u e t o M r . T .

G o d a i a n d M r . T . S u g i y a m a at t h e W e l d

i n g D i v i s i o n o f K o b e S te e l , L t d . f o r t h e i r

15.4

wmmmmmwwm,Fig. 21 — Schem atic showing pressure test procedure as applied to fabricated tank

2 4 6 8 10 12 14 16 18

P r e s s u r e ( N / m m 2 )

Fig. 22 —Strain vs. pressure

1 1 4 - s | A P R I L 1 9 8 4



Table 6—Result

GTA process

posi t ion (b )

Auto., ver t ica l

Semi-A, ver t ica l

Semi-A, Flat

s of X-Ray Inspection'8'

loints

A-1 to A-6

B-1 to B-2

C

(a) Per |IS Z3106

( b ) Au t o — aut om at i c ; Sem i

(c) " m " d i v i ded by 0 . 3048

A— s em i au t omat i c .

= f t .

Tota l length,

m<c>

10.5

8. 1

1.4

Films

42

32

6

Class

Grade 1

40

30

6

|(a)

Grade 2

2

2

0

cooperation in the development of thematching ferritic wire filler metal over theyears, and we think the matching ferritic

wire filler me tal used in the present investigation merits identification as TGS-9N ofKobe Steel, Ltd.

References

1 . Witherel l , C. E., and Peck, | . V. 1964.

Progress in welding 9% nickel steel. We/ding

Journal 11(4): 473-s to 480-s.

2 . Rice, |. R., Paris, P. C. and Merkle, |. G.

1 9 7 3 . Some further results of Hntegral analysis

and est imates. ASTM STP 536, pp. 231-245.

Philadelphia, Pa.; American Society Testing

Mater ia l .

3 . Levy, N„ Marcal , P. V., Ostergren, W. ) . ,

and Rice, ). R. 19 71. Small scale yielding near a

crack in plane strain: a fini te element analysis.

International journal of Fracture Mechanics 7:

143-156.

WRC Bulletin 286August, 1983

F a t i g u e B e h a v i o r of A l u m i n u m A ll o y W e l d m e n t s

b y W. W. Sanders, Jr. and R. H. Day

This report provides a summary and overview of the fatigue behavior of aluminum alloy weldments. In1 9 7 2 , a first state -of-the-art repo rt, WRC Bulletin 1 71 , was prepared and a com puterize d data bank wasinitiated. This report has emphasized the knowledge gained since the publication of that first summaryand indicates the extent of the data added to the bank.

Publication of this report was sponsored by the Aluminum Alloys Committee of the Welding ResearchCouncil. The price of WRC Bulletin 286 is $12.75 per copy, plus $5.00 for postage and handling. Orders

should be sent with paym ent to th e Welding Research Council, Room 1 30 1, 345 E. 47 th S treet, NewYork, NY 10017.

WRC Bullet in 288October , 1983

F r a c t u r e of P i p e l i n e s a n d C y l i n d e r s C o n t a in i n g C i r c u m f e r e n t i a l C r a c k

b y F . E r d o g a n a n d H . E z z a t

This study is concerned with the problem of a pipe containing a part-through or a throughcircum feren tial crack. The main objective is to give the necessary theore tical inform ation for th etreatment of the subcritical crack growth process. The problem of a through crack in the presence oflarge scale plastic de form ations is also cons idered. The crack opening displacem ent (COD) is used as themain parameter to analyze the fracture instabil i ty problem and to correlate the experimental results.

Publication of this report was sponsored by the Weldabil i ty Committee of the Welding ResearchCouncil. The price of WRC Bulletin 288 is $12.75 per copy, plus $5.00 for postage and handling. Ordersshould be sent with p aym ent to th e Welding Research Council, Room 13 01 , 345 E. 47t h S t., New York,NY 10017.

9% nickel steel welding

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