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Nippes1988-H2AssistedCracking-HY80Welds.pdf
Investigation of Hydrogen-Assisted
Cracking in FCA Welds on HY-80 Steel
Acidic and basic formulations for flux cored electrodes were
evaluated, as well as two methods of hydrogen analyses
BY E. F. NIPPES A N D D. J. X I O N G
ABSTRACT. Weld metal hydrogen content and hydrogen-assisted cracking in
t w o types of flux cored arc welds on
HY-80 were investigated. The hydrogen
content analyses were carried out by the
RPI silicone-oil extraction method and the
IIW method. The results of measurements by both methods show that the
hydrogen contents of welds produced
with as-received flux cored electrode
wires were approximately 2 ppm. Electrode B, a moisture-resistant, fully basic
flux cored welding wire, produced welds
which had a hydrogen content somewhat less than 2 ppm. Electrode B was
also tested after exposure to air at 32°C
(90°F) with 100% humidity.
Two variants of the augmented-strain
cracking (ASC) tests were used to determine the susceptibility of FCA welds to
hydrogen-assisted
cracking. Acoustic
emission equipment was utilized to
record the crack-initiation and propagation processes. The ASC test results show
that no cracking occurred in FCA welds
subjected to augmented strains of 0.6
and 1.5% when welding with as-received
flux cored wires on HY-80 steel. The
critical hydrogen content of FCA welds
on a single heat of HY-80 was determined to be approximately 4-5 ppm. The
hydrogen content in FCA welds was
increased by immersing the flux cored
electrodes in water for 4, 8 and 12 h, or
by exposing the electrodes to 100%
humidity at 40°C (104°F) for t w o weeks.
When the hydrogen content of FCA
welds on HY-80 reached 9-10 ppm,
hydrogen-assisted cracking occurred extensively. The cracking initiated mainly in
the coarse-grained or partially melted
region of the HAZ and propagated into
the weld metal and the base metal.
introduction
The flux cored arc welding (FCAW)
process is regarded as a low-hydrogen
process (Refs. 1, 2), which combines
versatility and high productivity for industrial use. In particular, it is generally
believed that the use of a basic flux cored
wire with Ar/CC>2 shielding produces a
lower weld metal hydrogen level than
that produced by flux covered electrodes
in shielded metal arc welding (SMAW).
However, some finite amount of hydrogen remains in welds produced with the
FCAW process. Recent investigations
have shown that flux cored filler metals
can produce weld metal hydrogen contents of 0.9 to 6.6 ppm of deposited
metal (Ref. 3). The weld metal hydrogen
level that results from FCAW is influenced
by many factors (Ref. 4), but the most
significant are:
1) Wire lubricant on the external surface of the electrode.
2) Hydrogen content of the flux core
ingredients in the electrode.
The low-hydrogen potential of the
FCAW process makes it a superior choice
for the welding of mild steel. However,
the amount of hydrogen necessary to
cause cold cracking in steels is inversely
related to yield strength. Therefore, highstrength steels, such as the HY-steels,
may be susceptible to hydrogen-assisted
cracking when welded with the FCAW
process.
E. F. NIPPES is Professor of Metallurgical Engineering, Department of Materials Engineering,
Rensselaer Polytechnic Institute, Troy, N.Y.
D. J. XIONG is Department Head, Materials
Science and Engineering, Beijing Polytechnic
University, Beijing, China.
KEY W O R D S
Hydrogen Cracking
FCA Welds on HY-80
Cracking Control
High Yield Strength
Flux Cored Arc Welds
Silicone Oil Extraction
Augmented Strain (AS)
AS Cracking Tests
Acoustic Emission
Crack Susceptibility
Some research has recently been carried out on the properties and diffusible
hydrogen contents of weld metal deposited with flux cored wires (Refs. 3, 4).
These studies show that a weld metal
hydrogen content of 3.0 to 3.6 ppm is
allowable when welding high-strength
steels, such as A517F and HY-80.
Objectives
The objectives of this investigation
were:
1) To determine the hydrogen contents of FCA welds of t w o types of flux
cored wires, using both the RPI siliconeoil extraction method and the IIW mercury-vacuum method.
2) To determine the consistency of the
hydrogen analyses measured by the RPI
and IIW methods.
3) To evaluate the relative susceptibility to hydrogen-assisted cracking of FCA
welds on high-yield-strength steel, HY80.
4) To investigate the microstructures
and the characteristics of hydrogenassisted cracking in t w o types of FCA
welds on HY-80.
Materials and Procedures
Base Metal
A relatively high-carbon heat of 1 Vi -in.
(38-mm) thick HY-80 steel plate was used
in this investigation. The chemical composition of this steel is listed in Table 1, along
with the nominal compositions of HY-80
material. The mechanical properties of
the steel used in this investigation are
listed in Table 2. Figures 1 and 2 show the
microstructure of the HY-80 base metal,
which had been austenitized, water
quenched, and tempered in air at 650°C
(1200°F) by the producer. The microstructure is tempered martensite and the
prior austenite ASTM grain size number is
about 7. Figure 1 shows the banding
typical of the base metal. The picric acid
etch darkens the solute-rich areas, where
elongated sulfide inclusions are usually
found.
WELDING RESEARCH SUPPLEMENT 1131-s
Table 1—Chemical Composition of the HY-80 Base Metal Used in This Investigation
c
Mn
P
0.18
0.32
0.018
Chemical Analysis (wt-%)
S
Si
Ni
0.013
0.20
Table 2—Mechanical Properties of the
HY-80 Base Metal Used in This Investigation
YS,
TS.
% Elong.
ksi
ksi
(1-in. gauge
2
2
(kg/mm ) (kg/mm )
length)
25
108
(76)
(62)
Hardness
(HV 1000 )
239
Filler Metals
Two types of flux cored wire were
used for the tests. Each electrode was
0.063 in. (1.6 mm) in diameter and was
designed for welding HY-80 and similar
high-yield-strength steels:
1) AWS E91T1-K2-This electrode is
an all-position flux cored wire that contains a somewhat elevated percentage of
basic flux components, yet remains within the range of the AWS T-1 classification
for acid slag systems. This electrode was
developed primarily for the welding of
HY-80, and produces high-strength welds
with good low-temperature toughness.
This electrode will be referred to hereafter as Electrode A, i.e., all-position.
2) AWS E90T5-K2-This electrode is a
fully basic flux cored wire. The basic slag
system acts to reduce weld metal inclusion content, resulting in excellent weld
metal properties. However, the basic flux
produces a fluid slag, making the operability of this electrode poor in out-ofposition welding. This electrode will be
referred to hereafter as Electrode B, i.e.,
basic flux.
2.99
Cr
Mo
1.68
0.41
The chemical composition and AWS
classification of Electrodes A and B are
listed in Table 3. Typical impact and
mechanical properties, taken from the
manufacturer's literature (Ref. 5), are
listed in Tables 4 and 5.
Specimen Preparation
Hydrogen content analysis specimens
were cut from the l!/2-in. (38-mm) thick
plate and were machined to dimensions
of 0.5 X 1 X 0.3 in. (12.7 X 25.4 X 7.6
mm) in compliance with the specifications
for IIW specimens. All surfaces were
ground flat and polished with 320-grit SiC
paper. Run-on and run-off tabs were
machined and ground flat to dimensions
of 2.25 X 1 X 0.3 in. (57.2 X 25.4 X 7.6
mm). Polished specimens and run-on and
run-off tabs were individually degreased
with acetone immediately before welding. Following degreasing, they were
positioned and loaded into the welding
fixture, as illustrated in Fig. 3, and the
entire assembly was demagnetized.
The augmented-strain cracking (ASC)
test samples were cut from V/i -in.-thick
plate, as illustrated in Fig. 4. The specimen
was oriented so that the welding direction was perpendicular to the rolling
direction and parallel to the plate surface.
Samples were machined to dimensions of
0.5 X 2 X 0.3 in. (12.7 X 50.8 X 7.6 mm).
The grinding, polishing, degreasing, loading and demagnetizing procedures were
identical to those used for hydrogen
content analysis specimens.
The welding parameters used for both
wires are listed in Table 6. Immediately
after welding, the weldment was first
quenched in an ice water bath (0°C,
32°F) and then in a bath of dry ice and
alcohol at - 7 1 ° C (-96°F) to minimize
the loss of diffusible hydrogen. After
cleaning and separating the specimens,
they were stored in liquid nitrogen at
- 1 9 6 ° C (-320°F).
Diffusible Hydrogen Analysis
The diffusible hydrogen contents of
FCA welds were determined using both
the RPI silicone-oil extraction method and
the IIW mercury-vacuum method. The
silicone-oil extraction method, developed
previously at RPI (Ref. 6), is similar to the
)IS glycerin method (Ref. 7). However,
the RPI method utilizes silicone oil instead
of glycerin in order to facilitate the maintenance of a higher bath temperature —
100°C (212°F) for the RPI method versus
45°C (113°F) for the glycerin test. The
elevated bath temperature ensures that
65% of the diffusible hydrogen can be
collected from a sample within the first
fifteen minutes of the test (Ref. 6).
The mercury-vacuum technique is recognized by the IIW as the standard for
diffusible hydrogen measurement. The
mercury-vacuum and gas chromatography techniques were recently recommended by the AWS filler metal committee task force group on weld metal
diffusible hydrogen as the only acceptable methods for the determination of
diffusible hydrogen (Ref. 8). The details of
the former method, which involve the
evolution of hydrogen in a mercury bath
under vacuum, are presented elsewhere
(Ref. 9). However, it should be noted that
the duration of a single test using the IIW
technique is a minimum of three days,
and in some cases, hydrogen evolution is
not complete for 10 to 15 days (Refs. 10,
11). In the present investigation, the IIW
mercury-vacuum
hydrogen
analyses
w^^gSM^FW^ ocw-yy -^y-sy- ^^w^ay
m
m
"Ac-yf
fc
a^'A-*"^*.'
spy
iW*ri
?w%3&&h
•¥'
y?y.
1
ly-^y'yy^y^P'^
mmmm
\CHrr
•"St*
*
*"i^
:
Fig. 1 — Microstructure
nital, 100X
132-s | JUNE 1988
0 . 2mm I
J
of HY-80 in the as-received condition, 2%
Fig. 2 —Microstructure
nital, 500X
of HY-80 in the as-received
condition,
RUN-OFF TAB
SPECIMEN FOR
HYDROGEN ANALYSIS
RUN-ON TAB
1/2 H Y - 8 0 PLATE
Fig. 3 - Welding fixture for hydrogen analyses and ASC test specimens
were judged to be complete w h e n no
f u r t h e r h y d r o g e n e v o l v e d f r o m a test
sample in 24 h. T h e n o r m a l d u r a t i o n o f
these tests, c o n d u c t e d at r o o m t e m p e r a t u r e , w a s 8 t o 12 days.
T h e three-step p r o c e d u r e f o r w a s h i n g
the specimens used f o r b o t h the siliconeoil a n d t h e IIW m e t h o d s w a s a d o p t e d
f r o m the p r o c e d u r e r e c o m m e n d e d b y
the B W R A (Ref. 9):
1) Immerse and agitate specimen in
p u r e e t h a n o l f o r 3 - 5 s.
2) Immerse and agitate in a n h y d r o u s
ethyl ether f o r 3 - 5 s.
3) D r y w i t h a r g o n gas f o r 2 0 - 3 0 s.
Hydrogen content on a weld-metal-adde d basis is c o m p u t e d f r o m the relationship:
AV
PPMd =
AW
X
Fig. 4 - Orientation
of ASC test specimens removed from base plate
sample, A W f , f o r A W in Equation 1 . T h e
value o f A W f for the f u s e d metal is
calculated f r o m the e q u a t i o n :
273
X
AP
760
(RT-F273)
(1)
X90
AcWf
AWf =
w h e r e PPM^ = diffusible h y d r o g e n c o n t e n t , parts per million o n t h e basis o f
d e p o s i t e d m e t a l ; A V = v o l u m e of h y d r o g e n e x t r a c t e d , cc; A W = sample w e i g h t
after w e l d i n g minus sample
weight
b e f o r e w e l d i n g , g m ; AP = a t m o s p h e r i c
pressure, m m H g ; RT = r o o m t e m p e r a ture, ° C ; and 90 = factor to convert
f r o m c c / g t o PPM.
C
Mn
O t h e r investigations (Ref. 3) h a v e
s h o w n that the increase in h y d r o g e n
c o n t e n t resulting f r o m the e x p o s u r e of
flux c o r e d electrodes t o a w a r m , h u m i d
a t m o s p h e r e ( 3 5 ° C , 9 0 % humidity) is n o t
H y d r o g e n c o n t e n t o n a f u s e d metal or
c o m p o s i t e - z o n e basis, PPM C , is calculated
in exactly the same w a y b y substituting
t h e w e i g h t of t h e f u s e d metal in t h e
A
B
0.050
0.060
1.50
1.53
Chemical Analyses (wt-%)
P
Si
S
0.50
0.53
0.010
0.009
0.018
0.017
(2)
w h e r e A c = cross-sectional area of fusion
z o n e , A t = total cross-sectional area o f
the specimen a n d w e l d ; and W f = w e i g h t
of specimen after w e l d i n g , g m . Area
measurements w e r e m a d e w i t h a polar
planimeter o n p h o t o m a c r o g r a p h s
of
w e l d samples.
Table 4—Typical Charpy V-Notch Impact
Properties, Electrode A (Ref. 5)
Table 3—Typical Undiluted Weld Metal Analyses (Ref. 5)
Electrode
WELD
Mo
Ni
0.22
1.75
1.66
AWS Classification
A5.29, Class E91T1-K2
A5.29, Class E90T5-K2
Temperature
°F(°C)
As-Welded
ft-lb (kg-m)
0(-17.8)
-60 (-51)
63 (8.7)
30(4.1)
Table 5—Mechanical Properties of
Electrode B (Ref. 5)
Table 6—Flux Cored Arc Welding Parameters
As-Welded
Yield strength,
85 (59.8)
ksi (kg/mm 2 )
Tensile
95 (66.8)
strength, ksi
(kg/mm 2 )
% Elongation in
26
2 in.
(50.8 mm)
% Reduction in
69
area
CVN ft-lb
(kg-m) at
72°F(25°C)
106 (14.7)
- 2 0 ° F ( - 2 9 ° C ) 92 (12.7)
- 6 0 ° F ( - 5 1 ° C ) 68 (9.4)
Stress Relieved
1 h at 1150°F
(621 °C)
77 (54.1)
90 (63.3)
28
69
119(16.5)
101 (14.0)
63 (8.7)
Electrode
Electrode diameter, in. (mm)
Welding position
Polarity
Shielding gas
Shielding gas flow rate, cfh
(L/min)
Electrode feed speed, ipm
(mm/s)
Welding current, amperes (A)(a'
Open circuit voltage V
Arc voltage, V
Travel speed, ipm (mm/s)
Heat input, kj/in. (k)/mm)
Contact tube-to-work distance,
in. (mm)
li
Tie (1.6)
Flat
DCEP
75%Ar-25%C0 2
35-40(16.5-18.9)
M1-6)
Flat
DCEP
75%Ar-25%C0 2
35-40 (16.5-18.9)
210 (88.9)
380 (160.9)
200
36
27
11 (4.7)
29.5 (1.16)
1-1.5 (25-38)
265
36
27
15 (6.4)
28.6 (1.13)
1-1.5 (25-38)
(a) In the middle of the current range recommended by the manufacturer.
W E L D I N G RESEARCH S U P P L E M E N T 1133-s
SPECIMEN TO BE TESTED
SPECIMEN TO BE TESTED
end
1X21
Fig. 5 —Schematic diagram of ASC test with loading parallel to the
welding direction
large compared to the amounts incorporated in manufacture. In this investigation,
it was desired to study the effects of
higher hydrogen contents. Therefore, the
hydrogen content was varied by immersing the flux cored wires in water for 4, 8
and 12 h at 21 °C (70°F) or by exposing
the electrodes to 100% humidity at 40°C
(104°F) for t w o weeks in a humidity
cabinet. When rusting occurred on the
Fig. 7 —Schematic
diagram showing
relative directions of
rolling (RD), welding
and cracking in ASC
Test 1 and 2
specimens
Fig. 6-Schematic diagram of ASC test with loading perpendicular to
the welding direction
wire surface, it was easily removed by
abrasion with fine steel wool.
Augmented-Strain Cracking (ASC) Test and
Acoustic-Emission Instrumentation
The ASC test was designed to produce
a known reproducible strain in the outer
fibers of a weld specimen. The critical
diffusible hydrogen content is defined as
TEST I
<0
RD
INCLUSION
-CRACK
TEST 2
RD
INCLUSION
134-s | JUNE 1988
that amount of diffusible hydrogen
which, if present in a steel, in conjunction
with critical levels of stress and hardness
and at an appropriate temperature, will
produce cold cracking. The critical diffusible hydrogen content required to induce
cracking in a particular microstructure at a
given magnitude of augmented strain can
be used as an index of the susceptibility
of a steel to hydrogen-assisted cracking.
Additional information on the initiation
and propagation of hydrogen-assisted
cracking can be obtained by measuring
acoustic-emission counts versus time. A
detailed description of the test procedure
appears in an earlier report (Ref. 10).
The t w o types of ASC test methods
used in this investigation are shown schematically in Figs. 5 and 6. One method
(Test 1), developed previously at RPI,
utilizes loading on a transverse section,
parallel to the welding direction — Fig. 5.
The second method (Test 2) utilizes loading perpendicular to the welding direction — Fig. 6. In both methods, the HAZ
cracking occurs at almost the same location in the ASC specimen — Fig. 7.
Although cracking is easier to observe
using Test 1, Test 2 is easier to operate
and provides a stress system similar to
that in a welded joint. Using identical
welding parameters, the HAZ cooling
rates of the samples will differ somewhat
because the effective plate thickness is
different, i.e., 0.5 in. (12.7 mm) for the
former versus 0.3 in. (7.6 mm) for the
latter method. As shown in Fig. 7, HAZ
cracking usually occurs perpendicular to
the stress direction and under the bead,
somewhat removed from the toe on
either side of the weld.
Metallographic Examination
For metallographic examination, ASC
test specimens were repolished and
immersion etched at room temperature
for 1'/2 h in a 2% aqueous solution of
picric acid mixed with sodium tridecylbenzene sulfonate, a wetting agent. This
etchant revealed both the prior austenite
grain boundaries and the weld solidification substructure.
Results and Discussion
Diffusible Hydrogen Content Analysis
The hydrogen content analysis results
for welds made with Electrodes A and B
on HY-80 are shown in Tables 7 and 8,
respectively. Table 7 shows that the
mean diffusible hydrogen content of
welds made with Electrode A in the
as-received condition ranges from 1.17
to 1.40 PPMC. These values are based
upon measurements made using the RPI
silicone-oil extraction method. A mean
diffusible hydrogen content of 1.31 PPMC
was obtained using the IIW method.
Table 7 shows that the mean diffusible
hydrogen content for welds made with
Electrode B in the as-received condition,
as measured by the RPI method, ranged
from 1.09 to 1.36 PPMC. A mean diffusible hydrogen content of 1.02 PPMC was
obtained for Electrode B using the IIW
method. Although it has been shown that
the gas collected over glycerin and silicone oil is not 100% hydrogen (Refs. 13,
14), the data obtained in this investigation
indicate that the RPI silicone-oil extraction
method is in good agreement with the
IIW method. This conclusion supports
previous work at RPI (Ref. 6), and it is
postulated that the equivalency of volume results from the exchange of gaseous hydrogen and air as the bubble rises
through silicone oil in the collection tube.
Inspection of Table 7 indicates that the
relative deviation for hydrogen contents
measured with the RPI method is less
than that of the IIW method, within the
same weld. This is also in good agreement with data obtained previously at RPI
(Ref. 6), shown in Table 9, for welds
made with SMAW electrodes.
Hydrogen content analyses were also
conducted on welds made with Electrode
B which had been exposed to ambient
atmosphere ( ^ 2 1 ° C / 7 0 ° F ) for approximately 6 months and with electrodes that
had been subsequently stored in a
humidity cabinet at 32°C (90°F), 100%
relative humidity (RH) for 1, 3 and 7 days.
The results of these tests, shown in Table
10, indicate that Electrode B had high
moisture resistance. Welds made with
Electrode B stored at ambient atmosphere conditions for about 6 months
had a hydrogen content of only 2.33
PPMfj, while the hydrogen content of
welds made with the same electrode in
Table 7—Hydrogen Content in HY-80
Weldments with FCAW Electrode A
Table 8—Hydrogen Content in HY-80
Weldments with FCAW Electrode B
Hydrogen Content,
(PPMC)
Hydrogen Content,
(PPMJ
Number
Test
of
Procedure Specimens Mean
a
SO< >
IIW<b>
SO
3
2
5
1.17
1.31
1.40
Standard
Deviation
Relative
Deviation
Test
Procedure
Number
of
Specimens
Mean
0.26
0.48
0.23
22.3%
36.6%
16.7%
SO
SO
IIW
3
3
1
1.14
1.09
1.02
Standard
Deviation
Relative
Deviation
0.08
0.11
5.6%
10.2%
(a) Silicone oil.
(b) IIW mercury-vacuum.
the as-received condition was 1.8 PPMd.
Figure 8 is a graphical comparison of
the susceptibility to moisture pickup of
FCAW Electrode B and a commercially
available SMAW moisture-resistant (MR)
electrode. Data for this commercially
available SMAW MR electrode were
obtained from Ref. 13. These data were
converted to appropriate units using a
relation between moisture in electrode
coatings and weld metal hydrogen content from Graville (Ref. 14).
Welds made with Electrode B, which
had been exposed to 32 °C, 100% RH for
three days, had a hydrogen content of
approximately 5.5 PPM^. Data are available in the literature for welds made with
a SMAW E7018 MR electrode humidified
for 4 h at equivalent conditions (38°C/
100°F, 90% RH), i.e., conditions which
produce an equivalent partial pressure of
water in the atmosphere to that which
occurs at 32°C, 100% RH. These data
indicate that welds made with the SMAW
electrode typically have hydrogen contents of approximately 10 ppm (Ref. 13).
Therefore, the rate of increase in weld
hydrogen content with increasing electrode exposure time to moisture is relatively low for Electrode B.
Table 9—Hydrogen Content in SMA
Weldments (Ref. 6)
Hyd rogen Content,
(PPMC)
Test
Procedure
Number
of
Specimens
SO
IIW
SO
IIW
3
2
8
2
Mean
Standard
Deviation
Relative
Deviation
I.O
1.5
6.35
6.40
0.08
0.20
0.69
1.10
8.2%
13.3%
10.8%
17.2%
Augmented Strain Cracking Test and Critical
Hydrogen Content Analyses
The results of hydrogen content analyses and ASC tests of FCA welds for
Electrodes A and B on HY-80 plate are
shown in Tables 11 and 12, respectively.
Cracking events are reported on a yes/
no basis, based on metallographic observation. For both Electrodes A and B, no
cracking occurred in the welds from 0.6%
to 1.5% augmented strain when using
as-received flux cored electrodes (about
2 ppm hydrogen content). In addition, no
cracking occurred when using the flux
cored electrodes soaked in water for 4 h
(about 3.5 ppm hydrogen content for
Table 10—Hydrogen Content in HY-80 Weldments of Humidified FCAW Electrode B
Hydrogen Content (PPMC)
Number of
Specimens
As-received' 3 '
Stored in atmosphere
for 6 months
Exposed to 32 °C
(90°F), 100%
humidity for 1 day
Exposed to 32°C
(90°F), 100%
humidity for 3 days
Exposed to 32°C
(90°F), 100%
humidity for 7 days
Exposed to 40°C
(104°F), 100%
humidity for 14
days
Mean
Standard
Deviation
Relative
Deviation
3
1.82
2.33
0.24
0.25
13.0%
10.7%
3
3.65
0.53
14.6%
3
5.53
1.19
21.6%
3
7.15
1.25
17.4%
3
9.40
0.55
5.9%
3
•
(a) Electrode B was received in a sealed plastic container which acted as a moisture barrier.
WELDING RESEARCH SUPPLEMENT 1135-s
£
Q-
/
/
UJ
TYPICAL DATA FOR E 7018 MR
38°C(I00°F),90%RH
8 s
LU
8
6
ac.
Q
1
^ ^ ^ " "
3 2 ° C O O T ) , 1 0 0 % RH
4
2;
0
(3
2
4
6
STORAGE TIME (DAYS)
Fig. 8 — 777e relationship between weld metal hydrogen content and storage time for welds
made with humidified FCA W Electrode B. Also shown are typical data for an E7018 MR SMA W
electrode
Table 11—Augmented Strain Cracking Test Results for FCA Welds of Electrode A on HY-80
Electrode
Treatment
Relation between
Loading and
Welding Directions
Hydrogen
Content ( p p m j
Augmented
Strain (%)
As-received
2.24
parallel
Soaked in water
for 4 h
Soaked in water
for 4 h
Soaked in water
for 8 h
Soaked in water
for 8 h
Soaked in water
for 12 h
Soaked in water
for 12 h
3.62
0.6
1.5
0.6
1.5
3.57
Oh
perpendicular
4.37
1.5
0.6
1.5
parallel
4.53
Ob
perpendicular
parallel
1.5
7.50
Ob
parallel
9.90
1.5
0.6
1.5
perpendicular
Cracking
Observed
No
No
No
No
No
No
Yes/No
Yes
No
Yes/No
Yes
Yes
Yes
Yes
Table 12—Augmented Strain Cracking Test Results for FCA Welds of Electrode B on HY-80
Electrode
Treatment
Hydrogen
Content
(ppm c )
As-received
1.82
As-received
1.81
Soaked in water for
4h
Soaked in water for
4h
Soaked in water for
8h
Soaked in water for
8h
Exposed to a warm,
humid atmosphere
(40 °C, 100%
humidity) for 14
days
2.99
136-s|JUNE 1988
2.76
Augmented
Strain (%)
0.6
I.5
rib
I.5
0.6
1.5
lib
Relation between
Loading and
Welding Directions
perpendicular
No
No
No
No
No
No
No
parallel
No
No
parallel
perpendicular
parallel
I 5
3.75
Ob
3.94
0.6
1.5
0.63
1.5
I 5
9.40
Cracking
Observed
perpendicular
parallel
No
No
Yes
Yes
Yes
Fig. 9 —Initiation of hydrogen-assisted cracking
in HAZ at prior austenite grain boundaries.
FCAW Electrode A, 0.6% augmented strain,
9.90 ppm hydrogen, picric acid etch, 250X
Electrode A and about 3 ppm for Electrode B).
The critical hydrogen content of welds
made with both Electrodes A and B was
found to be approximately 4-5 ppm. This
hydrogen content resulted from immersion of the electrodes in water for 8 h.
The augmented strain necessary to cause
cracking was 0.6% for Electrode A (about
4.5 ppm hydrogen content) and 1.5% for
Electrode B (about 4 ppm hydrogen content). It should be noted that of the six
specimens welded with Electrode A
that had been soaked in water for 8 h,
three exhibited cracking in the ASC test.
Of the six specimens welded with
Electrode B soaked in water for 8 h, only
one exhibited cracking. When the hydrogen content of FCA welds on HY-80
reached
9-10
ppm
(Electrode
A
immersed in water for 12 h and Electrode
B exposed to 40°C, 100% RH for 14
days), extensive hydrogen-assisted cracking occurred.
Metallographic Examination
No significant metallographic differences were found between FCA welds
made with Electrodes A and B on HY-80.
Metallographic examination indicated
that the hydrogen-assisted cracking in
ASC test specimens initiated mainly in the
HAZ at prior austenite grain boundaries
(Fig. 9) and propagated into the weld
metal and the base metal. It was also
observed that, despite the orientation of
inclusions parallel to the primary stress
directions, inclusions sometimes act as
crack initiators. Crack propagation normally occurred in an intergranular manner, along prior austenite grain boundaries—Figs. 10 and 11. However, in sev-
6) T h e hydrogen-assisted cracking of
FCA w e l d s o n HY-80 initiated mainly in
t h e H A Z at p r i o r austenite grain b o u n d aries. Crack p r o p a g a t i o n w a s o b s e r v e d
t o o c c u r b y b o t h intergranular a n d transgranular mechanisms.
i<rtfcWajT)Jc*?-,i,
7) T h e results o f h y d r o g e n c o n t e n t
analyses m a d e using t h e RPI silicone-oil
extraction m e t h o d correlated well w i t h
t h o s e m a d e using the IIW m e t h o d . T h e
relative d e v i a t i o n f o r data c o l l e c t e d using
t h e RPI m e t h o d is s o m e w h a t less than
that f o r data c o l l e c t e d using the IIW
method.
A ckno wledgments
fig. 10 — Intergranular and transgranular propagation of hydrogen-assisted cracking in HAZ,
FCAW Electrode A, 0.8% augmented strain,
9.90 ppm hydrogen, picric acid etch, 250X. 80
Mm
Fig. 11 — Primarily intergranular crack propagation in the HAZ and along the fusion line,
FCAW Electrode B, 0.8% augmented strain,
3.94 ppm hydrogen, picric acid etch, 100X.
0.2 mm
:
yy. yyy^:< "Ay;*,
M
'
• ' • . • ! '
>
^MM
. . . , , ,
i
y
j
I
i
1
I
''
^
"V7J
1
v
I
'
1
1
V
Fig. 12-Hydrogen-assisted
cracking initiated
in the partially melted zones of the weld.
FCAW Electrode A, 0.8% augmented strain,
9.90 ppm hydrogen picric acid etch, 200X.
100 /an
Fig. 13 — Hydrogen-assisted cracking initiated
in the unmixed zone of the weld. FCAW
Electrode B, 0.8% augmented strain, 3.94 ppm
hydrogen, picric acid etch, 500X. 40 nm
eral specimens, cracks also p r o p a g a t e d
transgranularly, t h r o u g h prior austenite
grains —Figs. 1 0 - 1 2 . Occasionally, cracking initiated in the partially m e l t e d z o n e
(PMZ) o r t h e u n m i x e d z o n e — Fig. 13. T h e
m a x i m u m hardness values in t h e H A Z of
w e l d s m a d e w i t h Electrodes A a n d B
w e r e a p p r o x i m a t e l y equal, i.e., H V 1000
317. This w a s e x p e c t e d as b o t h w e l d s
w e r e m a d e using a p p r o x i m a t e l y equal
e n e r g y inputs of 29 k j / i n . (1.14 k j / m m ) .
g e n c o n t e n t (1.8 p p m ) than t h o s e m a d e
w i t h Electrode A , an all-position flux
c o r e d w i r e (2.1 p p m ) .
2) The fully basic flux c o r e d w i r e ,
Electrode B, w a s slightly less susceptible
t o moisture p i c k u p than Electrode A. T h e
hydrogen content of welds made with
w i r e s o a k e d in w a t e r f o r 8 h w a s a b o u t 4
p p m for Electrode B a n d 4.5 p p m f o r
Electrode A .
Conclusions
1) T h e h y d r o g e n c o n t e n t s of w e l d s o n
a single heat o f H Y - 8 0 steel m a d e w i t h
acidic a n d fully basic F C A W electrodes in
the as-received c o n d i t i o n w e r e a p p r o x i mately 2 p p m . W e l d s m a d e w i t h a fully
basic, moisture-resistant, flux c o r e d w i r e ,
Electrode B, h a d a slightly l o w e r h y d r o -
3) N o cracking o c c u r r e d in FCA w e l d s
w i t h a u g m e n t e d strains o f 0.6% a n d 1.5%
using Electrodes A and B in the asreceived condition.
4) The critical h y d r o g e n c o n t e n t o f
FCA welds o n t h e single heat of H Y - 8 0
was approximately 4 - 5 p p m .
5) W e l d s m a d e w i t h Electrode B w e r e
less susceptible t o
hydrogen-assisted
cracking t h a n t h o s e m a d e w i t h Electrode
A.
T h e authors e x t e n d their a p p r e c i a t i o n
t o the A l l o y Rods C o r p . f o r p r o v i d i n g the
filler metals used in this investigation. T h e
a u t h o r s are i n d e b t e d t o N. J. G e n d r o n ,
Dr. D. ). Ball, S. R. Fiore a n d J. P. Balaguer
f o r their enthusiastic help.
References
1. Evans, C. M., and Baach, H. Hydrogen
content of welds deposited by different welding processes. Doc. IIW-1976-MTC.
2. Evans, C. M., and Baach, H. Hydrogen
content
of
welds. Metal
Construction
7(10):508-511.
3. Lathabai, S., and Stout, R. D. 1983.
Hydrogen-induced cracking in flux-cored electrode welds. Welding Journal 62(3):59-s to
62-s.
4. Franke, C. L. 1980. HY-80 Flux-Cored Arc
Welding Electrodes for Flat Position Welding Summary Report. David W . Taylor Naval Ship
R & D Center, DTNSRDC/SME-80/02.
5. Manufacturer's literature for Dual Shield
II, Alloy Rods, Corp., Hanover, Pa.
6. Ball, D. J., Gestal, W . )., and Nippes, E. F.
1981. Determination of diffusible hydrogen in
weldments by the RPI silicone-oil extraction
method. Welding Journal 60(3):50-s to 56-s.
7. Tsunetomi, E., and Murakami, S. 1971.
Comparison Between IIW and )IS Procedures
for Determination of Diffusible Hydrogen.
Doc. ll-A-288-71, International Institute for
Welding.
8. Kotecki, D. )., and LaFave, R. A. 1985.
AWS A5 committee studies of weld metal
diffusible hydrogen. Welding journal 64(3):
31-37.
9. Coe, F. R. 1973. Welding Steels Without
Hydrogen Cracking. The Welding Institute,
Abington, Cambridge, England, pp. 64-66.
10. Savage, W. F., Nippes, E. F., and Homma, H. 1976. Hydrogen induced cracking in
HY-80 steel weldments. Welding Journal
55(11):368-s to 376-s.
11. Quintana, M. A. 1984. A critical evaluation of the glycerin test. Welding Journal
63(5):141-s to 150-s.
12. Madeka, |. P. 1985. Unpublished
research, Rensselaer Polytechnic Institute,
Troy, N.Y.
13. Effective Use of Weld Metal Yield
Strength for HY-80 Steels. 1983. National
Materials Advisory Board Report #NMAB-30.
14. Graville, B. A. 1975. The Principles of
Cold Cracking Control in Welds. Dominion
Bridge Co., Quebec, Canada.
WELDING RESEARCH SUPPLEMENT 1137-s
WRC Bulletin 328
November 1987
This bulletin contains two reports covering related studies conducted at The University of Kansas
Center for Research, Inc., on the CTOD testing of A36 steel.
Specimen Thickness Effects for Elastic-Plastic CTOD Toughness of an A36 Steel
By G. W. Wellman, W. A. Sorem, R. H. Dodds, Jr., and S. T. Rolfe
This paper describes the results of an experimental and analytical study of the effect of specimen size
on the fracture-toughness behavior of A36 steel.
An Analytical and Experimental Comparison of Rectangular and Square CTOD Fracture Specimens of an
A36 Steel
By W. A. Sorem, R. H. Dodds, Jr., and S. T. Rolfe
The objective of this study was to compare the CTOD fracture toughness results of square specimens
with those of rectangular specimens, using equivalent crack depth ratios.
Publication of these reports was sponsored by the Subcommittee on Failure Modes in Pressure Vessel
Materials of the Pressure Vessel Research Committee of the Welding Research Council. The price of
WRC Bulletin 328 is $20.00 per copy, plus $5.00 for postage and handling. Orders should be sent with
payment to the Welding Research Council, Suite 1301, 345 E. 47th St., New York, NY 10017.
WRC Bulletin 330
January 1988
This Bulletin contains two reports covering the properties of several constructional-steel weldments
prepared with different welding procedures.
The Fracture Behavior of A588 Grade A and A572 Grade 50 Weldments
By C. V. Robino, R. Varughese, A. W. Pense and R. C. Dias
An experimental study was conducted on ASTM A588 Grade A and ASTM A572 Grade 50 microalloyed
steels submerged arc welded with Linde 40B weld metal to determine the fracture properties of base
plates, weld metal and heat-affected zones. The effects of plate orientation, heat treatment, heat input,
and postweld heat treatments on heat-affected zone toughness were included in the investigation.
Effects of Long-Time Postweld Heat Treatment on the Properties of Constructional-Steel Weldments
By P. J. Konkol
To aid steel users in the selection of steel grades and fabrication procedures for structures subject to
PWHT, seven representative carbon and high-strength low-alloy plate steels were welded by shielded
metal arc welding and by submerged arc welding. The weldments were PWHT for various times up to 100
h at 1100°F (593°C) and 1200°F (649°C). The mechanical properties of the weldments were
determined by means of base-metal tension tests, transverse-weld tension tests, HAZ hardness tests,
and Charpy V-notch (CVN) impact tests of the base metal, HAZ and weld metal.
Publication of these reports was sponsored by the Subcommittee on Thermal and Mechanical Effects
on Materials of the Welding Research Council. The price of WRC Bulletin 330 is $20.00 per copy, plus
$5.00 for postage and handling. Orders should be sent with payment to the Welding Research Council,
345 E. 47th St., Suite 1301, New York, NY 10017.
138-s | JUNE 1988
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