TECHNISCHE HOGESCHOOL DELFT
AFDELING DER SCI4EEPSBOUW- EN SCHEEPVAARTKUNDELABORATORIUM VOOR SCHEEPSCONSTRUCTIES SHIP STRUCTURES LABORATORY
Report No.
SSL 256
REALISTIC TESTING OF WELDS
BY FATIGUE BENDING AT LOW TEMPERATURE
by
J.J.W. Nibbering & H.G. Scholte
11W-doc, X-1014-82
TECH NISCHE HOGE.SCHOOL DELFT
AFDEUNG DER SCHEEPSBOUW. EN SCHEEPVAARTKUNDE
LABORATORIUM VOOR SCHEEPSCONSTRUCTIES SWIP STRUCTURES LABORATORY
Report No.
SSL 256
REALISTIC TESTING OF WELDS
BY FATIGUE BENDING AT LOW TEMPERATURE
by
J.J.W. Nibbering & H.C. Scholte
11W-doc. x-1014-82
11W-doc, X-101482
REALISTIC TESTING OF WELDS BY FATIGUE BENThING AT LOW TEMPERATURE
By J.J.W. N,ibbering* and H.G.
SchoIte*
Summary
This report serves two purposes.
First1y a test method 'Fatigue loading at low temperature' is reintroduced and illustrated with the aid of Electro-slag welded specimens. Secondly the difficulties with this method - which are the difficulties of any realistic method - are illustrated with the aid of submerged arc specimens containing seriöus defects. On account of these it is also argued tha:t standard C.O.D.-testing will often represent reality very poorly, especially in case of multirun welds <containing defects, hard spots and triaxial residual stress-es.) in structures which are subjected to cyclic loading.
1. Introduction
One disadvantage of the COD-test is that only a few cubic millimeters of the material of the whole specimen are tested. The position of the notch-tip is quite haphazard in multirun welds and HAZ's. Therefore a reliable estimate of the fracture toughness can only be obtained by using quite a number of specimens. This problem can partly be met by using hardness-measurements and microscopic analysis for finding the worst places in the weld.. But especially for thick plates this cannot be done satisfactorily, because the welds can only be examined at the outer surfaces of the
specim-ens. A possible way to increase the efficiency of the COD-test is starting with a shallow notch, s,y FO, and loading the specimenup to a COD of
f.i. 0.2 mm. After .that the crack is extended under fatigue loading by about 3 mm and the next COD-test (up to 0.2 mm) can be carried out. When again no fracture occurs the crack is deepened another 3 mm and so on. Although not ideal the method improves the reliability of the COD-test substantially. A logical consequence .of the foregoing is fatigue loading at low tempèrature. This procedure has been in.troduced by Nibbering /1/, /2/, /3/, /4/.
Since 1969 the Delf t Ship Structures Laborato.ry has used the test f o,r fitness for purpose analysis for industry. The main advantage of the method is that during fatigue loading a crack travels through the various zones of welded joints. When for instance 20,000 cycles lead to a crack of 20 'mm length,, the material of the specimen has in fact been analysed at every 0.001 mm along
the crack line.(One might say that the result .is equivalent to that of 20,000 static tests.)'Additional advantages are that from' critical crack length and applied load a K1 -value can be caIculated. COD-measurements' are not neces-sary. Due to this an irregular crack front in case of residual stresses is not objectionable.. When the fatigue crack has grown to its maximum length
(about one third of specimen height) without brittle fracturing, the test may be ended by a static COD-test..
It is obvious that for simulating service conditions, high fatigue load testing is required. This has the additional advan.tages that testing time is limited and that a brittle fracture will not arrest due to an eventual drOp in load. Nevertheless, pop-ins will often occur in case of high heter-ogeneity or as consequence of strain hardening of the crack tip material
Professor Naval Architecture, De'lf..t and Chent University.
-2-due to fatigue loading. Such pop-ins prove that the average quality is satisfactory despite the presence of smal.l bad spots.
The specimen should preferably be higher than normal COD-ones. A minimum of 90 nun or two times plate thickness, whichever is the greatest, is reconnnend-ed. The length of the specimens should be at least four times the height for three point bending. The starting notch should be at least IO nun deep. This is good for any plate thickness. The nominai bending stress may be half yield point. Then the crack length at which the test must be ended is about one third of specimen height. In the beginning a load equivalent to two
thirds of yield point may be applied in order to accelerate the crack initia-tion. When notch plus crack have got a length of 20 mm, the nominal stress should be reduced to one half of yield point.
These values are not very critical. They serve to reduce testing time.
Nobody will apply too high loads, because these will lead to conservative results caused by large cyclic plastic straining and corresponding strain hardening. For years the test method has remained in the shadow, mainly because the step from Charpy-testing to static COD-testing had already been big enough for
inspection boards and industry. They would not heartily receive another test improvement. Yet the need for progress has been obvious for many years, especially for multirun welds in thick plates for offshore structures. We all know the shortcomings and problems in connection to procedure and
interpretation of COD-testing. (By the way the authors are generally less pessimistic in this respect than other people), /1/, /8/.
Recent difficulties with COD-testing of weldments with heterogeneous metallic structures in Ni-alloyed steel have brought Japanese investigators also to the idea of fatigue loading at low temperature. Therefore the time seems to be ripe for re-introducing fatigue loading at low temperature as a most
real-istic way of testing. This will be illustrated with earlier and new test results.
2. Origin of the test method and characteristic results
The idea of fatigue loading at low temperature was born in 1968. Wide plate specimens with transverse E.G.-welds (34 mm thickness) or E.S.-welds (46 mm thickness) had been provided with notches parallel to the fusion line at
1, 2 and 3 mm distance They were extended by fatigtie loading at low temper-ature until a brittle fracture occurred. During the testing several 'brittle. steps' (pop-ins) developed before final fracturing. It was decided to simulate the large scale tests by fatigue bending at low temperature of full-thickness specimens made out of E.G.- and E.S.-welded plates. In Fig. I - which
sum-manses the advantages of the test method - is shown the fracture surface for HAZ-material 2 mm from the fusioi line. Originally the 'steps' were attributed
to heterogeneity of the HAZ. But testing with heat-simulated plate specimens revealed that the magnitude of the brittle steps corresponded rather with the size of the cyclically strain hardened plastic zone during fatigue loading.
(From this it is obvious that fatigue testing is essential for structures which will be cyclically loaded in practice like ships and offshore
struc-tures).
Some of the results are shown in Fig. 2. The material was Nb-containing nor-malised steel F'e 5IiO Nb /5/. Heating at 1300 C and slow cooling resulted0in
extreme grain coarsening and a Charpy 28 J transition temperature of +20 C. Figure 2 - left shows that at +20°C the first, small brittle step developed when the fatigue crack had come to half the specimen height. At that moment
the net-section had become so reduced that cyclic plastic straining accom-panied by strain hardening occurred. Nevertheless the material could stand two other brittle steps before final fracturing.
At -20 C two brittle steps developed beföre fracturing at a much lower net-stress and a much smaller crack length.
-3-The cyclic wide plate testing resulted in a 'safe' temperature of about -10°C, although partial fractures still developed during fatigue loading at -4 C. When all relevant fatigue-bend results are taken together (5 welded and 4 weld-simulated) a good correspondence with the wide plate results is manifest. in contrast the Charpy results proved to be much on the pessimistic sidé
(oversafe): +20 C.
It is of interest tonote in Fig.2 the excellgnt distinguishing quality of the test. One hour heating at 750 C for a 1300 C heated specimen resulted in a marked improvement which might be estimated to be equivalent to 30°C shift in safe temperature (4 specimens). The Charp results suggested 50°C improve-ment, while the wide plate results led to 25 C. Again a good correspondence between large and small scale cyclic loading is manifest.
3. Investigations with submerged arc welds containing defects
A recent investigation was devoted to submerged arc welds containing continu-ous lack of penetration at the root of the X (Fig. 3). Plate thickness was 22 mm. Four static wide plate tests have been carried out. Each plate con-tained two transverse S.A.-welds and a longitudinal E.G.-weld (Fig. 4). The fabrication sequence of the FL-specimens was:
S.A.-welding; notched
E.G.-welding; after (N.A.W.).
notch drilling and sawing welding
The first specimen (1 FL) was tested at 39; after fracturing at K3 it vas repaired. Next the test was continued0at -64 C up to fracture at KO.
The second specimen was tested at -59 C and fractured at K3. The notches were placed at different distanes from the centrai EG-weld. At the tips the
peaktemperatures had been 1000 C (KO) and about 150°C (K3). Apparently at 1000 C the material had somewhat improved as the fractures occurred first at K3. The notches in the plates were 0.2 nmi wide. So they. are less sharp than the fatigue cracks used in COD-specimens. The material at the notch tips will also be more tough, due to the absence of cyclic strain hardening. Therefore it was thought to be wise to include also in Table I and Fig. 5 results of experiments in which the notches had been made before EG-welding.
(Fabrication sequence: S.A.-weiding:; notched
notching; before > (N.B.W.). E.G..-welding welding
Of course the material at the notch tips will be embrit.t.led in a way differ-ent to that due to cyclic loading. But this 'Wells' way of wide plate testing certainly represents a severe situation, which might occur in practice.
As always in cases of notches made befóre welding partial fractures occurred. The corresponding COD-values are also given in Fig. 5.
The partial fractures were very small in length, which means that the notch tips remained more or less in the S.A.-welds. Their tips are very sharp now and comparable to tips of fatigue crack. Looking at Fig. 5 we should realize that in this figure results are brought together which strictly may not be compared. Only 1 FL, K3 and' 2 FL, K3 are of the same. nature. For gs it is important to find the worst case. This is clearly I CL, KO at -26 C.
Turning now to fatigue bending at low temperature,, Fig. 3 shows the results of three of the four specimens.
Table II summarizes the data. In all specimens partial fractures developed, but only in the specimen tested a't the lowest temperature a complete fracture developed during fatigue loading. The other. tests have ended with a static COD-test. The difference with normal COD-testing was, that the irregular
crack front., developed during prior 'cyclic loading, was kept intact. Yet the results will be indicative for what might have been found in a standard
COD-test. Looking at the fracture surfaces in Fig. 3 one might be disappointed by the' very irregular crack fronts. But these are the crack fronts, which develop in practice! and which are suppressed in standard, COD-testing.
The results of the. COD-tests with the before mentioned specimens are given in Fig. 6. Figure 7' shows the Charpy-results. The curve most to the right is based on specimens taken from those parts of the wide plates which had not fractured. The large difference in trans:ition temperature is certainly
alarming.
4o Discussion
It is immediately admitted that for a fair comparison of all 'résults a greater number of specimens was needed, On the other hand 4 wide plates, each
con-taitìing 2 resp. 3 transverse welds with notches at different distances from the centre longitudinal weld should allow a reasonable estimate of the safe temperature for relevant structures in practice. Also 4 COD-specimens and 4 fatigue bending ones are not excessively small in number as compared to what is used in practice. The number of 'Char,py-specimens was high.
In practice it does not happen often. that such an extensive test progranmie is carried out for the simple case of a submerged arc weld in a straight plate structure.. Yet even experts will find it difficult to draw a conclusion f rom
all the test data. Therefore the most essential data have been combined in Table III. But even then the difficulties are great..
This. is for a large part due to the. fact that the results reflect different properties. of the material (resistance to impact and slow loading either static or cyclic; sensitivity to hot straining emb'ri,ttlement).
The first question which should be considered is, for what type of structure an indication of the safe temperature is desired: a pressure vessel,, a bridge, a crane or a ship?
In the context of the present pape.r we felt the need to underline this as.pect, but it will not be discussed now.
A comparison which most obviously i's allowed in Table III is that between the CTOD's obtained in t.he wide plate tests (NAW) and the COD-tests. But an im-portant difference is still present. The wide' plates contained 0.2 nun saw-cuts
and the 'COD-specimens fatigue cracks. This may partly explain the. large difference between the CTOD's to fracture of both. 'For the embrittled wide plates (NBW)', the resül'ts are clearly some 20°c to 40°C worse than those of
the. COD-tests, (desp.ite .the less sharp notches!).
When 28 J Charpy-ener.gy is thought to be equivalent to aboùt 0.2 nun CTOD, then the same discrepancies are, present. On the other hand the 'preloaded' Charpy-data seem to be much too conservative.. All this will not likely in-crease confidence in 'Charpy-testing.
he fatigue bending at low temperature, although strictly d.ifferent from static wide plate testing at least incorporates more or less two factors of the latter:
(cold) strain hardening and (some) aging;
!looking' for the worst place in 'a weld, '(10 wide plate situations, see Fig. 4).
There are two types of fractures: a. partial fractures: fatigue bending " -15°C o } reasonable correlation; wide plate (NBW) > -25 C b.. complete fractures: f atigue bending : -60 C
wide plate (NBW): -20°C (estimated)
5
-Charpy:
-55C
COD -50C..
Of ail tests fatigue bending at low temperature is the only one of which (in the case concerned) an indication is obtained about both the capacity of the material to arrest short fractures (brittle steps, pop-ins) nd of the danger of complete fractures in wide plates (NBW). In the latter case large brittle steps in the bending specimens are thought to be comparable to complete f rac-tures in wide plate tests. This is defended with the argument that in a bent specimen a fast fracture may arrest in the low stressed region near the neutral axis, while such a region js not present in a wide plate. The COD-and Charpy- COD-and fatigue bending results (complete fracture) correlate rather veli with wide plate results for the case N.A.W.
This paragraph will not give satisfaction to many people.,. but that is mainly due to the nature of things.. We have purposely investigated the case of S.A.-welds containing artificial defects of different kinds (NBW, NAW,
various distances to central weld) and serious natural defects., with residual stresses.
On the other hand in §2 it was illustrated how clean, homogeneous welds cyclic-ally tested in wide. plates as well as in bending, do give 'beautiful results'. A final observation about the irregular crack fronts.
The only practical way to get a fair estimate of the effective crack length during and at the end of the test is by applying COD-recording A COD-measure-ment can always be. translated in an 'average' crack depth.
-6-Conclusions
I. There is no doubt that for cyclically loaded constructipns containing welds of heterogeneous metallic structure, COD-testing is not very
suitable. (Of course. the larger the number of specimens the greater the reliability of this (and any) test method).
2. Screening of a weld with the aid of Charpy-specimens enlarges the chance that hard spots will be included ii the final test result. But, it will immediately raise the point of the relative importance of for instance a single low Charpy-result in a group of, say, 20 results of which 19 are acceptable.
(In fact this problem has led to test methods on complete weidments.). 3. Fatigue bendingat low temperature is the most realistic way of 'small'
scale testing (small in the sense of comparing with wide plate tests and tests with structural components).
It incorporates actual loading conditions,, presence of defects, residual stresses and hard spots.
4. It has been illustrated in this paper that the method leads to straight-forward results in cases of 'simple' homogeneous welds, like E.G.- and E.S.-welds. But for multirun welds, difficulties of interpretation may
arise when irregular brittle steps (pop-ins) develop 4uring fatigue loading. 5. Of course the irregular crack fronts involved may be prevented by
pre-compresssing the specimens in the same way as for static COD-testing. But it has been argued earlier /6/ that then f.i. the elimination of favourable compressive stresses in the root of X-weids may lead to over-severe results. Apatt from that escaping from interpretation problems by making a test less realistic is playing the ostrich.
6. Although the results of the large and small scale experiments in this paper mainly serve to illustrate a state of problem. affairs, i,t is clear that comparing:
wide plate results N.BW.;
"
Charpy results; C.O.D.- "
fatigue bending results
is like comparing apples, pears,, oranges, bananas and peaches.
Moreover the structures which are being built in practice differ to the same extent (pressure vessels, bridges, ships etc.).
Discussions about acceptance testing will never come to. a practical end when this is not taken into account properly (different tests for
differ-ent situations).
For instance Wells wide plate situations (NBW) are far more likely in large structures like bridges., where thousands of weld crossings are present., than in cranes and pressure vessels. On the other hand it does seem that. the Wells effect is much easier obtained in laboratories than in service the. problem requires a thorough statistical investigation. 7. In /7/ Tanaka, Sato and Ishikawa have published results of fatigue bending
at low temperature on. welded specimens containing coarse-grained heat-affected zones. They p.refer to apply a stress ratio equal to 0.5 instead of 0.. 1. With such a big ratio it is possible to measure/calculate the C.T.O.D. at the moment of brittle fracturing. The present authors favour
the idea that a test like fatigue bending at low temperature does not need any COD-measuring (except for controlling crack length). For, the test gives a critical .crack length at the fracture load. Then fracture mechanics allow the calculation of critical crack lengths
-7-Apart. from that, testing time is greatly increased when the stress ratio becomes high.
8. It is recoended that an i.I.W.-Working Group is established, similar to the former W.G. 2912 (Testing of Welds),, /4/, which will further develop the method in international cooperation.
References
/1/ J..J.W. Nibbering':
Some observations on COD-testing.. 11W-doc. X-957-80.
/2/ J.J.W. Nibbering and A.W. Lalleman:
Low cycle fatigue tests at low temperature with E.G.-welded.plates. 11W-doc. X-593-70.
/3/ ibid:
Low cycle fatigue problems in shipbuilding - crack propagation in coarse grained zones..
Paper 16 Fatigue of Welded Structures Conference, Brighton. F970.
/4/ J.J.W. Nibberiúg et al.:
Final report of 11W Working Croup 2912 '!Brittle f rac:ture tests for weld metal'.
11W-doc, X-754-74; Welding in the World, Vòl. 13, No. 7/8., 1975.
/5/ J.J.W. Nibbering et al.:
Brittle fracture in the H.A.Z. of E.S.-welded plates subjected to low cycle fatigue.
IIW-dòc.. X-6Th-72. /6/ J..J..W. Nibbering:
Desigi against fatigue and fracture for marine structures.
; In: Procs. mt. Symp. on Advances in Marine Technology,, Trondheim,
June 1979.
/7/ K. Tanaka et al.:
Fatigue COD and short crack arrest tests.
Paper 18, mt. Conf. on Fracture Toughness Testing, London, June 1982,
The Welding Institute. .
/8/ J.D. Harrison: .
The state-of-the-art in crack tip opening displacement (CTOD) testing and analysis.
ADVANTAGES:
REALISTIC LOADING, NOTCH AND EMBRITTLED ZONE.
INCLUDES DYNAMIC POP-INS (brittle steps).
RESULT IS CRITICAL CRACK LENGTH.
acr k
or Gnom.)cr
or E(nom.)c,.LARGE PART OF SPECIMEN IS TESTED.
+ 20 °
D. i 1300 °C
Fig.2 BRITTLE STEPS IN NON-WELDED SPECIMENS.
C .O.D.
NIBLINK
about ten thousend on initiation point
initiation points
crack finds" point of lowest material quality)
5. BRITTLE STEP FORMING AT SMALL CRACK LENGTH OCCURS AT NIL-DUCTILITY-TEMPERATURE.
6 NO C.O.D. MEASUREMENTS NOR PROBLEMS WITH ROTATION POINT.
Fig.1 FATIGUE TESTING AT LOW TEMPERATURES.
Fatigue bending load: 2 12,5 ton
Material : St.52-Nb. Thickness : 66mm -20°C -20 °C 0.3 F.3 1300
1300 t
lhr./750 °CFig.3 SUBMERGED ARC WELDS AFTER FATIGUE BENDING AT LOW TEMPERATURE.
Specimens FL: unernbrittted (notched after welding).
Specimens CL: embrittled (notched before welding).
TABLE. I RESULTS OF WIDE PLATE TESTS.
PARTIAL FRACTURES COMPLETE FRACTURES
Li O__ L L ai w Q. V)
4-Z
'I
-L.Z
o U O ci. E w-.X tT w Q. D (N .0 4-o-!
''
Z
(N E E N E o cc1NEEj
bU
>b
E o -. E-
E .OL?15
E-.
-a E
E .caiE
r (N -.,_ -CN E E NZ
E 2b
>-U N E°
Cb
E E .4..'z
L -0 o 4-L w '1 .0 O 1 FL 1sftest
39°C KO 1000° 20,2 }Nopartial fracture
20,2 >345 >0,83 1,29 K0 K3 150° 19,9 19,9 345 0,83 K Fracture 1 FL 2nd test -64°C K0 1000° 20,2 No partial fracture -20,2 409 1,- 3,05 K0 FractureK3
Reparation after fracture at
1st test2 FL
-59°C
KO 1000° 20,4 }No
partial fracture
20,4 >363 >0,88 1,39 K03 150° 19,5 19,5 363 0,88
1,-
1(3 FracturePARTIAL FRACTURES COMPLETE FRACTURES
i CL 1sttest -25°C K0 1000° 17,8 158 0,38 0,08 0,08 18,4 4,2 22,- 168 0,41 0,14 K0 Fracture K1 600° 19,6 19,6 >168 >0,41 0,06 Kl K3 250° 19,2 19,- >168 >0,41 0,05 K3 1 CL 2 test -25°C
K0
Reparation after fracture at ist test
K1 600° 19,6 19,6 340 0,82 1,66 Kl Fracture K3 250° 19,2 19,2 >340 >0,82 1,4e 1(3 2 CL -32°C K0 ioocP 19,6 327 0,79 0,45 Q45 61,5 618 1,01
4,- Ko Fracture
l
600° 19 327 0,79 0,15 0,16 15,6 1,620,6 >418 >1,01 >4,- Kl
K3 250° 19,8 327 0,79 0,30 0,30 38,3 Q6 20,4 >418 >1,01 >4,- 1(3 0,10 0.4 D.13 _200C-30°C
-40°C
Specimens: FL (unernbrit tied notches in centre of weld)
CL (
embrittied ñotches in centre of weid)
Plate material:
= 314 N/mm2 ; = 650 N/mm2; E 31,5 0/S.A-wetding = 413 N/mm2 ; OEfracture: 501 N/mm2; E 23,2%
(for steel L)
Chemical analysis:
Fig.4U Specimens FL - 2 specimens
(notched after welding
/
S.A.-weldsFig. 4b Specimens CL - 2specimens
(notched before welding)
Fig. 6 WIDE PLATE TEST SPECIMENS.
E.G.-weld
Detail of notches
Steel L
C. Mn Si. P. S. Cu. Ni. Cr. Al. Sn. Mo. Nb.0,100 0,56 0,178 0,006 0,028 0,240 0,165 0,075 0,030 0,024 0,012
-rÑotch
Peak femperature Dista nce to E:G. -weldioOo 15mm
[
K3 150°C 85mmNotch Peak temperature
Distance to EG-weid
K0 1000 °C 15mm
Ki 600 °C 30mm
[_K3
j 250 °C
4
K0 (ductiLe tear\
1FL KO 2FLf
((ductae tsar) K0L(L
K3
i FLKi
1iCL Specimens: FL Specimens: CL a.4-I
K.
04 mmOK3 1CL 1$mmOK1 K0 O I .1 1 I2m
_700 _600 _500 _400 _300 _200 _100 Test temperature (°C)Fig.5
Results of wide plate tests.
Partial. fracture No fracture
atendoflest
fracturei4A. (unembrittLed)
ELO
N3.W ( embrittled)(L
. ri ri r r r r c,t iso°C K3 C C C C Currrr«
1000°C K0(rr(((r
600°C SKi f r 250°C K3 CfCLL-20°C
4
/
#07
-30 °C -40 OC r-75ip
2TA'BLE. RESULTS OF SUBMERGED ARC WELDS UN 0ER'FATIGUE BENDING
AND [.0.0.-TEST AT LOW TEMPERATURE.
Load reduction
Brittle step
Thickness: plate: 22mm weld: 26mm PL :pL
325Specimen Fatigue Static C.O.D.
Nr. T nx103 max. amean BrittLe step
crack surface
8tip
(°C)
( kN) (mm) ('mm2 ) (mm) 0.10 , 200 ' 0 575 97 97 10 205 3 59;5 97/76 22,6 70,7 76 25 33 71,5 76/58 29,2 H L 87,8 58 36,277;
36,2 0;51 300 0 97 10 40 97 H 14 5 53 97 16,1 43 563 97/76 22,5 62,6 76 23,5 13 63 76 24 227 63,2 76/58 36,5 65 58 38,6 78 38.6 0,89 0.13 -40° 0 9.7 10 12 97 17,5 7 124 97 17,8 36 12,5 97/76 21,6 20,4 76 25,2 12 21,6 76 27 23V.2'
76/58 ' 28;8 42 58 323 40 44.5 58 38.6 63 38,6 0.46 0.5 54° 0 97 10 35 76 28 complete fracture'0.6
+200 0 10 88,4 41 550 ' 62 41 0,170i0
4 0.131,25 0,75 0s0 E Q. 4-co 35 Nm/cm2 :28J 75 160
"o
120 60Testbars taken from 100 virgin (unloaded) material Testbars taken from fractured specimens. E
J
E Test temperature (.'JC) -120° -100° _800-0°
-40° -20° 00 +20° +40° +60°. +80°Fig.7 Charpy-V notch resuLts of steeL-L i. SA. weLding.
0,25 o Fig.6 Results
.
I I I I I -60° -50°-40°
-30° -20° -10° 0° fatigueTest temperature (°t)
of [0.0-tests on submerged arc welds after
bending at Low temperature.
.
TABLE III. Summary of results for submerged arc welds.
Non-embrittled (NAW)
Wide plate tests
Embrittied Several partial fractures of small length:
(NBW) worst result 4.2 mm crack depth at -25 C;
O = 0.38 o
nom y
Complete fractures:
worst result 0.14 mm C.T.O.D.. at -25°C;
0
=0.410.
nom y
C.O.D.-tests
Worst result 0.17 sim C.T.0.D. at -55°C.
Charpy- tests Unloaded material 28 J at -55°C. (virgin) Pre loaded 't 28 J at +15°C. Fatigue bending . o
Partial fractures below -15 C (estimated). Complete fractur.e at 28 mm crack length: -55 C. No partial fractures.
Characteristic complete fracture:
1 smi C.T.0.D. at -60"C; o
