HSEHealth & Safety
Executive
Integrity of Repaired Welds (Phase 1)- Deliverable 5 Summary Report
Prepared by Serco Assurance for the Health and Safety Executive 2004
RESEARCH REPORT 191
REFERENCES
1. GARDNER L, MELVIN G T AND GOLDTHORPE M R
Integrity of Repaired Welds (Phase 1): Report on Tasks 2, 3, 4 and 5 (Deliverable D2),
Serco Assurance Report, Issued December 2001.
2. DIAZ GARRIDO F A, TOMLINSON R A AND YATES J R
Integrity of Repaired Welds (Phase 1): Report on Task 6 (Deliverable D3)
The University of Sheffield Report, Issued January 2002.
3. GOLDTHORPE M R
Integrity of Repaired Welds (Phase 1): Report on Tasks 7 and 8 (Deliverable D4)
M R Goldthorpe Associates, Issued January 2002.
4. BSI BS 7910:1999
Guide on Methods for Assessing the Acceptability of Flaws in Metallic Structures
British Standards Institution, London, 1999.
5. SHARPLES J K, CLAYTON A M, LACEY D J AND GREEN B L
Assessment of Fracture Mechanics Fatigue Predictions of T-Butt Welded Connections with
Complex Stress Fields
Department of Energy-Offshore Technology Information (OTI 88 536), London,
Her Majesty’s Stationary Office, 1988.
6. ROOKE D J AND CARTWRIGHT D J
Compendium of Stress Intensity Factors, Procurement Executive
Ministry of Defence (ISBN 0 11 771 336 8*), London Her Majesty’s Stationary Office, 1976.
7. R5: Assessment Procedure for the High Temperature Response of Structures
British Energy Generation Limited, Issue 2 Revision 2, 2001.
45
Tab
le 1
Dif
fere
nt
para
mete
rs t
o b
e c
on
sid
ere
d, w
ith
th
e c
od
e f
or
each
vari
an
t in
pare
nth
eses
Par
amet
er
Bas
e ca
se
Alt
ernat
ive
case
s
Pla
te T
hic
knes
s t=
40
mm
(P
T1
) t=
20
mm
(P
T2
)
Surf
ace
Unre
pai
red
def
ect
a=
13
mm
(S
U1
) a=
11
mm
(S
U2
) A
=9
mm
(S
U3
) a=
7m
m (
SU
4)
Em
bed
ded
Unre
pai
red
def
ect
(dep
end
ing o
n p
late
thic
knes
s)
2a=
13
mm
, p
=4
mm
(EU
1)
2a=
11
mm
, p
=6
mm
(EU
2)
2a=
9m
m,
p=
8m
m
(EU
3)
2a=
7m
m,
p=
10
mm
(EU
4)
2a=
11
mm
, p
=2
mm
(EU
5)
2a=
9m
m,
p=
4m
m
(EU
6)
2a=
7m
m,
p=
6m
m
(EU
7)
Evac
uat
ion W
idth
W
ide
exca
vat
ion
(VW
1)
Nar
row
exca
vat
ion
(VW
2)
Surf
ace
Rep
aire
d d
efec
t
a=9
mm
(S
R1
) a=
7m
m (
SR
2)
A=
5m
m (
SR
3)
a=3
mm
(S
R4
)
Em
bed
ded
Rep
aire
d d
efec
t
(dep
end
ing o
n p
late
thic
knes
s)
2a=
9m
m,
p=
4m
m
(ER
1)
2a=
7m
m,
p=
6m
m
(ER
2)
2a=
5m
m,
p=
8m
m
(ER
3)
2a=
3m
m,
p=
10
mm
(ER
4)
2a=
9m
m,
p=
2m
m
(ER
5)
2a=
7m
m,
p=
4m
m
(ER
6)
2
a=5
mm
, p
=6
mm
(ER
7)
2a=
3m
m,
p=
8m
m
(ER
8)
2a=
7m
m,
p=
2m
m
(ER
9)
2a=
5m
m,
p=
4m
m
(ER
10
)
2a=
3m
m,
p=
6m
m
(ER
11
)
2a=
5m
m,
p=
2m
m
(ER
12
)
2
a=3
mm
, p
=4
mm
(ER
13
)
2a=
9m
m,
p=
8m
m
(ER
14
)
2a=
7m
m,
p=
10
mm
(ER
15
)
2a=
5m
m,
p=
12
mm
(ER
16
)
2a=
3m
m,
p=
14
mm
(ER
17
)
Ten
sile
pro
per
ties
of
pla
te a
nd
Unre
pai
red
wel
d
As
mea
sure
d w
ith
over
-mat
ch
(TU
1)
Bo
th h
igher
yie
ld
(TU
2)
Bo
th l
ow
er y
ield
(TU
3)
Pla
te a
s m
easu
red
,
wel
d e
ven
-mat
ch
(TU
4)
Ten
sile
pro
per
ties
of
Rep
air
wel
d
met
al
As
mea
sure
d
(TR
1)
Even
-mat
ch (
TR
2)
Cycl
ic f
atig
ue
pro
per
ties
A
s m
easu
red
(C
Y1
)
Fra
cture
to
ughnes
s (K
)
pro
per
ties
of
Unre
pai
red
wel
d
As
mea
sure
d (
KU
1)
Lo
wer
than
bas
e
case
(K
U2
)
Lo
wer
than
KU
2
(KU
3)
Var
ious
oth
er c
ases
(KU
4 a
nd
so
on)
Fra
cture
to
ughnes
s (K
)
pro
per
ties
of
Rep
aire
d w
eld
As
mea
sure
d (
KR
1)
Sam
e as
KU
1 (
KR
2)
Lo
wer
than
bas
e
case
(K
R3
)
Var
ious
oth
er c
ases
(KR
4 a
nd
so
on)
46
Tab
le 1
(c
on
t’d
)
Dif
fere
nt
para
mete
rs t
o b
e c
on
sid
ere
d, w
ith
th
e c
od
e f
or
each
vari
an
t in
pare
nth
eses
Par
amet
er
Bas
e ca
se
Alt
ernat
ive
case
s
Res
idual
str
esse
s in
Unre
pai
red
wel
d
Full
y s
tres
s-re
liev
ed
wel
d (
RU
1)
Mea
sure
d
as-
wel
ded
(R
U2
)
Inte
rmed
iate
resi
dual
str
ess
case
(RU
3)
Res
idual
str
esse
s in
Rep
aire
d
wel
d
As
mea
sure
d (
RR
1)
Rep
air
wel
ded
und
er h
igh s
truct
ura
l
rest
rain
t (R
R2
)
Rep
air
wel
ded
und
er i
nte
rmed
iate
stru
ctura
l re
stra
int
(RR
3)
Par
tial
ly s
tres
s-
reli
eved
wel
d
rep
air
(RR
4)
Ser
vic
e S
tres
ses
Acc
ord
ing t
o B
S
55
00
w
ith 2
5%
over
load
(S
S1
)
Lo
wer
than
SS
1
(SS
2)
Hig
her
than
SS
1
(SS
3)
Var
ious
oth
er c
ases
(SS
4 a
nd
so
on)
47
Tab
le 2
Resu
lts o
f te
nsile t
ests
Sp
ec N
o
Tem
p
0.2
% P
S
Up
per
YS
L
ow
er
YS
UT
S
%
Elo
ng
ati
on
% R
edu
ctio
n
Ma
teri
al
°C
MP
a
MP
a
MP
a
MP
a
in a
rea
VE
8
19
5
13
6
28
3
1.5
7
9
Cen
tre
Wel
d,
As-
Wel
ded
VE
9
19
5
11
6
17
3
1
76
C
entr
e W
eld
, A
s-W
eld
ed
VE
11
1
9
35
5
41
1
35
1
53
0
43
7
3
Par
ent
VE
12
1
9
34
5
39
4
34
9
52
4
40
7
5
Par
ent
WI7
1
9
53
3
62
7
30
.7
78
R
epai
r w
eld
, n
ear
surf
ace
WI8
1
9
54
6
62
9
28
.9
76
R
epai
r w
eld
, n
ear
surf
ace
WI1
0
19
5
74
6
72
2
8.7
7
4
Rep
air
wel
d,
nea
r ro
ot
WI1
1
19
5
87
6
70
2
7.8
7
7
Rep
air
wel
d,
nea
r ro
ot
WI1
2
19
4
57
6
08
2
3.2
6
8.6
R
epai
r w
eld
, n
ear
roo
t
48
Tab
le 3
Ra
tio
of
cyc
les
to
lim
itin
g c
on
dit
ion
s (
Nre
pair
ed/N
un
rep
air
ed)
for
ed
ge
de
fec
ts i
n a
s-r
ep
air
ed
an
d u
nre
pa
ired
PW
HT
pla
te f
or
vari
ou
s d
ep
ths
an
d f
rac
ture
tou
gh
ne
ss
Nrep
air
ed/N
un
rep
air
ed
Fin
ite
Ele
men
t B
S 7
91
0
Init
ial
Cra
ck
Base
d o
n K
J
Ba
sed
on
K
Ori
gin
al
Ref
ined
K
JC (
MP
aÖ
m)
Dep
th (
mm
)
60
3
.33
0
.49
(0
.66
) 0
.64
(0
.66
) -
-
10
--
--
16.6
7
--
--
80
3
.33
0
.56
(0
.80
) 0
.80
(0
.80
) -
-
10
--
--
16.6
7
--
--
10
0
3.3
3
0.6
4
(0.8
9)
0.8
9
(0.8
9)
0.2
7
(0.2
7)
0.3
5
(0.3
4)
10
--
--
16.6
7
--
--
12
0
3.3
3
0.7
4
(0.9
7)
0.9
6
(0.9
7)
0.5
2
(0.5
1)
0.5
8
(0.5
7)
10
0
.84
(0
.62
) 0
.69
(0
.62
) -
-
16.6
7
--
--
14
0
3.3
3
0.7
7
(0.9
9)
0.9
9
(0.9
9)
0.6
6
(0.6
5)
0.7
1
(0.7
0)
10
1
.05
(0
.85
) 0
.90
(0
.85
) -
-
16.6
7
--
--
16
0
3.3
3
0.7
7
(1.0
0)
0.9
9
(1.0
0)
0.7
5
(0.7
4)
0.7
9
(0.7
9)
10
1
.13
(0
.84
) 0
.96
(0
.94
) -
-
16
.67
0
.26
(0
.21
) 0
.26
(0
.21
) -
-
No
te:
Val
ues
in
bra
cket
s o
bta
ined
fro
m E
qu
atio
n (
11
)
49
current practices
repairs and
literature review
engineering
engineering
Review of industrial
companies to assess
and problems
associated with weld
Scoping calculations
using simplified
methods to establish
likely matrix of cases
to consider
Weld/Specimen
Manufacture
Material
characterisation
(mechanical
properties plus
metallurgical
studies)
Residual stress
measurements
Validation
Development of
finite element models
Testing involving
photoelastic coating
and thermal
emission methods in
order to assess effect
of residual stresses
on crack growth
Validation
Application of
analytical models to
matrix cases
Structural tests to
evaluate influence of
weld repairs on
structural integrity
Assessment of
analytical models
and experiments by
procedure methods
General guidance on
weld repairs
General guidance on
procedure method
Figure 1 Flow diagram showing components of project
loadingloading
surface-breaking
defecta
B
repairside 2
side 1
loadingloading
embedded
defect2a
p
B
repair
side 1
side 2
side 1
a
B
loading loading
surface-breaking
defect
repair side 2
Figure 4 Surface defect at the weld root
2a
p
B
loading loading
embedded
defect
repair
side 1
side 2
Figure 5 Embedded defect near the weld root
2a
p
loading loading
original
surface-breaking
defect
wide
excavation
embedded defect
remaining
Figure 6 Wide excavation of surface defect, leaving embedded defect in repaired condition
2a
p
loading loading
original
surface-breaking
defect
narrow
excavation
embedded defect
remaining
Figure 7 Narrow excavation of surface defect, leaving an embedded defect in repaired condition
surface
loading loading
original
defect
excavation
surface defect
remaining
Figure 8 Excavation of surface defect, leaving a surface defect in repaired condition
loading loading
original
embedded
defect
excavation
embedded defect
remaining
Figure 9 Excavation of embedded defect, leaving an embedded defect in repaired condition
t=40mm SU1 ER1 ER2 ER3 ER4 t=40mm SU2 ER5 ER6 ER7 ER8
a=13
2a=9
p=4
2a=7
p=6
2a=5
p=8
2a=3
p=10
a=11
2a=9
p=2
2a=7
p=4
2a=5
p=6
2a=3
p=8
t=40mm SU3 ER9 ER10 ER11 t=40mm SU4 ER12 ER13
a=9
2a=7
p=2
2a=5
p=4
2a=3
p=6
a=7
2a=5
p=2
2a=3
p=4
Figure 10 Proposed defect configurations to be studied in the 40 mm thick plate – surface defect in unrepaired condition (solid line) and embedded in repaired condition
(dashed line)
t=40mm SU1 SR1 SR2 SR3 SR4 t=40mm SU2 SR1 SR2 SR3 SR4
a=13
a=5 a=7
a=3
a=9
a=11
a=5 a=7
a=3
a=9
t=40mm SU3 SR1 SR2 SR3 SR4 t=40mm SU4 SR2 SR3 SR4
a=9
a=5 a=7
a=3
a=9 a=7
a=5 a=7
a=3
Figure 11 Proposed defect configurations to be studied in the 40 mm thick plate – surface defect in both unrepaired (solid line) and repaired (dashed line) conditions
EU1 ER14 ER15 ER16 ER17 EU2 ER14 ER15 ER16 ER17
t=40mm t=40mm
2a=13 2a=9
p=8
2a=7
p=10
2a=5
p=12
2a=3
p=14
p=4
2a=11 2a=9
p=8
2a=7
p=10
2a=5
p=12
2a=3
p=14
p=6
EU3 ER14 ER15 ER16 ER17 EU4 ER15 ER16 ER17
t=40mm t=40mm
2a=9 2a=9
p=8
2a=7
p=10
2a=5
p=12
2a=3
p=14
p=8
2a=7 2a=7
p=10
2a=5
p=12
2a=3
p=14
p=10
Figure 12 Proposed defect configurations to be studied in the 40 mm thick plate -embedded in both unrepaired (solid line) and repaired (dashed line) conditions
ER3 ER4ER2ER1 SU2 ER8ER6ER5
2a=7
a=13
SU1
2a=5 t=20mm 2a=3
2a=9
p=4
p=6
p=8 p=10
a=11
t=20mm
ER7
2a=9
p=2
2a=7
p=4
2a=5
p=6
2a=3
p=8
SU3 ER9 ER10 ER11 SU4 ER12 ER13
a=9 t=20mm t=20mm a=7
2a=5
p=2
2a=3
p=4
2a=3 2a=5 2a=7
p=6 p=4
p=2
Figure 13 Proposed defect configurations to be studied in the 20 mm thick plate – surface defect in unrepaired condition (solid line) and embedded in repaired condition
(dashed line)
SU2 SR3SR1SU1 SR3 SR4SR2SR1
a=7
a=11
a=5
t=20mm
SR4
a=3
SR2
a=9 a=7
a=13
a=5
t=20mm
a=3
a=9
SU4 SR2 SR3 SR4SU3 SR1 SR2 SR3 SR4
t=20mm a=9 a=9 t=20mm a=7 a=7 a=7
a=5
a=3
a=5
a=3
Figure 14 Proposed defect configurations to be studied in the 20 mm thick plate – surface defect in both unrepaired (solid line) and repaired (dashed line) conditions
2a=7 2a=11
2a=5 t=20mm 2a=3 2a=9
p=2 p=4
p=6 p=8
p=10
EU5 ER1 ER2 ER3 ER4
EU6 ER3 ER4ER2 EU7 ER3 ER4ER2
2a=7 2a=9
2a=5 t=20mm 2a=3 2a=9
ER1
p=4 p=4
p=6 p=8
p=10 2a=7
2a=7
2a=5 t=20mm 2a=3
p=6 p=6 p=8
p=10
Figure 15 Proposed defect configurations to be studied in the 20 mm thick plate -embedded defect in both unrepaired (solid line) and repaired (dashed line) conditions
0
50
100
150
200
250
2
D
J-2
J-2
J, kJm-
VE
1 S
ing
le s
pec
imen
dat
a
End p
oin
t V
E1
VE
2 S
ing
le s
pec
imen
dat
a
End p
oin
t V
E2
Curv
e fi
t
J=234.6
1a^
0.5
0062
0.2
BL=
115.5
kJm
0.2
=104.7
kJm
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
ST
AB
LE
CR
AC
K E
XT
EN
SIO
N,
mm
Fig
ure
17
J
-R c
urv
e o
bta
ine
d f
rom
fra
ctu
re t
es
ts o
n a
s-w
eld
ed
sp
ec
ime
ns
0
50
100
150
200
250
300
J, kJm-2
D
J-2
J-2
WI2
End
poin
t of
WI2
Curv
e fi
t to
WI2
Curv
e fi
t to
VE
1/V
E2, as
-wel
ded
mat
eria
l
J=263.3
5a^
0.5
9206
0.2
BL
=119.0
kJm
0.2
=101.6
kJm
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
1.2
ST
AB
LE
CR
AC
K E
XT
EN
SIO
N, m
m
Fig
ure
18
J
-R c
urv
es
ob
tain
ed
fro
m f
rac
ture
te
st
on
re
pa
ir-w
eld
ed
sp
ec
ime
n
da
/dN
(m
/cy
cle
)
1.00E-05
1.00E-06
1.00E-07
1.00E-08
VE5 da/ dN = 1.360* 10-11 DK2.786
Validity Limit
WI6 da/ dN = 1.153* 1-11 D0 K2.762
VE5 Pre weld repai r
WI6 Post weld repair
10 100
DELTA-K(MPam0.5)
Figure 19 Fatigue crack growth test results
Depth (m m ) 40
35
30
25
20
15
Gauges 1
& 5
Gauges 2
& 6
Hole
-drilli
ng v
alu
e,
Sid
e 1
Hole
-drilli
ng v
alu
e,
Sid
e 2
10 5 0 -4
00
-200
0
200
400
600
800
Str
ess (
MP
a)
Fig
ure
20
A
s-w
eld
ed
re
sid
ua
l s
tre
ss
- Y
dir
ec
tio
n -
pe
rpe
nd
icu
lar
to w
eld
Depth (m m )
40
35
30
25
20
Gauges 3
& 7
Gauges 4
& 8
Hole
-drilli
ng v
alu
e,
Sid
e 1
Hole
-drilli
ng v
alu
e,
Sid
e 2
15
10 5 0
0
100
200
300
400
500
600
700
800
Str
ess (
MP
a)
Fig
ure
21
A
s-w
eld
ed
re
sid
ua
l s
tre
ss
- X
dir
ec
tio
n -
pa
rall
el
to w
eld
Depth (m m )
40
35
30
25
20
Gauges 1
& 5
Gauges 2
& 6
Hole
-drilli
ng v
alu
e, S
ide 1
Hole
-drilli
ng v
alu
e, S
ide 2
15
10 5 0 -4
00
-200
0
200
400
600
800
Str
ess (
MP
a)
Fig
ure
22
R
ep
air
-we
lde
d r
es
idu
al
str
es
s -
Y d
ire
cti
on
- p
erp
en
dic
ula
r to
we
ld
Depth (mm)
40
35
30
25
20
15
10 5 0 -1
00
0
100
200
300
400
500
600
700
800
Str
ess (
MP
a)
Fig
ure
23
R
ep
air
-we
lde
d r
es
idu
al
str
es
s -
X d
ire
cti
on
- p
ara
lle
l to
we
ld
Gau
ge
s 3
& 7
Gau
ge
s 4
& 8
Hole
-drilli
ng v
alu
e, S
ide 1
Hole
-drilli
ng v
alu
e, S
ide 2
Figure 24 Specimen dimensions, in mm
-5
0
5
10
15
20
25
30
Öm
Str
ess In
ten
sity F
acto
r R
an
ge
, M
Pa
Mode I by RAT
Mode I by FGD
Mode II by RAT
Mode II by FGD
KI Theory
AEA3, R=0.13
4 6 8 10 12 14 16 18
Crack length, mm
Figure 25 DKI against crack length. Included is a comparison of the results of processing by
different operators
da/d
N, m
m/c
0.000001
0.00001
0.0001
0.001
AEA1, R=0.13
AEA2, R=0.1
AEA_F3, R=0.58
AEA1, R=0.13, Deltatherm data
AEA2, R=0.1, Deltatherm data
AEA_F3, R=0.58, Deltatherm data
AEAT growth equation
1 10 100
DK
Figure 26 Original weld crack propagation results, using stress intensity factors calculated from
published calibration equations and measured directly using Deltatherm
35
30
25
20
15
10
5
0
0 5
Original weld, R=0.13 Original weld, R=0.1 Repair weld, R=0.13 Repair weld, R=0.1 Repair weld, R=0.28 Original weld, R=0.58 Repair weld, R=0.58
10 15 20
Clo
sure
K,
MP
aÖ
m
25
-5
Crack length, mm
Figure 27 Estimates of crack closure
1
2
3
4
56
7
8
9
Original Weld Side 1Side 2
1
2
3
4
Repair WeldSide 2 Side 1
1
2
3
4
56
7
8
9
Original Weld Side 1Side 2
1
2
3
4
56
7
8
9
1
2
3
4
Repair WeldSide 2 Side 1
1
2
3
4
Plane of symmetry
1
2
3
4
5 6
7
8
9
Original Weld Side 1Side 2
1
2
3
4
Repair WeldSide 2 Side 1
Plane of symmetry
Figure 28 Front face of finite element model of the plate in the region of the weld
axisymm
mesh of
repair weld
axis of
rotation
original weld
etric
sphere
repair weld
axis of
rotation
original weld
axisymmetric
mesh of sphere
Figure 29 Axisymmetric finite element mesh of equatorially welded sphere
Tru
e st
ress
, M
Pa
700
600
500
400
300
200
Specimen VE8, weld material
100 Specimen VE9, weld material
Specimen VE11, parent plate
Specimen VE12, parent plate 0
0.00 0.01 0.02 0.03 0.04 True strain
oFigure 30 Measured true stress versus true strain results at 20 C
(a)
0
100
200
300
400
500
600
700
0.00 0.01 0.02 0.03 0.04True strain
Tru
e st
ress
, M
Pa
Specimen VE8, weld material
Specimen VE9, weld material
Specimen VE11, parent plate
Specimen VE12, parent plate
Extrapolated parent with Luders strain removed
Smoothed weld data
Modified weld data incorporating 12% plastic strain
(b)
0
200
400
600
800
1000
1200
1400
0.00 0.10 0.20 0.30 0.40True strain
Tru
e st
ress
, M
Pa
Specimen VE8, weld material
Specimen VE9, weld material
Specimen VE11, parent plate
Specimen VE12, parent plate
Extrapolated parent with Luders strain removed
Smoothed weld data
Modified weld data incorporating 12% plastic strain
Figure 31 True stress versus true strain at 20oC as used in the analyses: (a) for small
strain, (b) for larger strains, solid blue and red curves show the properties used in the
analyses
(a)
Plate measurements and analyses: Transverse stress perpendicular to weld (S22)
0
10
20
30
40
-800 -700 -600 -500 -400 -300 -200 -100 0 100 200 300 400 500 600 700 800
Stress, MPa
Dep
th m
easu
red
fro
m S
ide
1,
mm
Original Plate Weld - Gauges 1 & 5
Original Plate Weld - Gauges 2 & 6
FEA - Original Plate Weld, no PWHT
Plate Repair Weld - Gauges 1 & 5
Plate Repair Weld - Gauges 2 & 6
FEA - Original Plate Weld (no PWHT), then Repair
(b)
Plate measurements and analyses: Longitudinal stress parallel to weld (S33)
0
10
20
30
40
-200 -100 0 100 200 300 400 500 600 700 800
Stress, MPa
Dep
th m
easu
red
fro
m S
ide
1,
mm
Original Plate Weld - Gauges 3 & 7
Original Plate Weld - Gauges 4 & 8
FEA - Original Plate Weld, no PWHT
Plate Repair Weld - Gauges 3 & 7
Plate Repair Weld - Gauges 4 & 8
FEA - Original Plate Weld (no PWHT), then Repair
Figure 32 Variation of measured and predicted residual stress through the middle of the
plate weld: (a) transverse, (b) longitudinal
(a)
Plate analyses: Transverse stress perpendicular to weld (S22)
0
10
20
30
40
-800 -700 -600 -500 -400 -300 -200 -100 0 100 200 300 400 500 600 700 800
Stress, MPa
Dep
th m
easu
red
fro
m S
ide
1,
mm
FEA - Original Plate Weld, no PWHT
FEA - Original Plate Weld (no PWHT), then Repair
FEA - Plate Weld with PWHT
FEA - Plate Weld with PWHT, then Repair
(b)
Plate analyses: Longitudinal stress parallel to weld (S33)
0
10
20
30
40
-200 -100 0 100 200 300 400 500 600 700 800Stress, MPa
Dep
th m
easu
red
fro
m S
ide
1,
mm
FEA - Original Plate Weld, no PWHT
FEA - Original Plate Weld (no PWHT), then Repair
FEA - Plate Weld with PWHT
FEA - Plate Weld with PWHT, then Repair
Figure 33 PWHT and repaired weld predictions of residual stress in the plate: (a)
transverse, (b) longitudinal
(a)
Sphere analyses: Transverse stress perpendicular to weld (S22)
0
10
20
30
40
-800 -700 -600 -500 -400 -300 -200 -100 0 100 200 300 400 500 600 700 800
Stress, MPa
Dep
th m
easu
red
fro
m S
ide
1,
mm
FEA - Sphere Weld, no PWHT
FEA - Sphere Weld (no PWHT), then Repair
FEA - Sphere Weld with PWHT
FEA - Sphere Weld with PWHT, then Repair
(b)
Sphere analyses: Longitudinal stress parallel to weld (S33)
0
10
20
30
40
-200 -100 0 100 200 300 400 500 600 700 800
Stress, MPa
Dep
th m
easu
red
fro
m S
ide
1,
mm
FEA - Sphere Weld, no PWHT
FEA - Sphere Weld (no PWHT), then Repair
FEA - Sphere Weld with PWHT
FEA - Sphere Weld with PWHT, then Repair
Figure 34 PWHT and repaired weld predictions of residual stress in the sphere: (a)
transverse, (b) longitudinal
(a)
Comparison of Plate and Sphere residual stress analyses: Transverse stress perpendicular to weld (S22)
0
10
20
30
40
-800 -700 -600 -500 -400 -300 -200 -100 0 100 200 300 400 500 600 700 800
Stress, MPa
Dep
th m
easu
red
from
Sid
e 1
, m
m
FEA - Sphere Weld with PWHT
FEA - Sphere Weld with PWHT, then Repair
FEA - Plate Weld with PWHT
FEA - Plate Weld with PWHT, then Repair
(b)
Comparison of Plate and Sphere residual stress analyses: Longitudinal stress parallel to weld (S33)
0
10
20
30
40
-200 -100 0 100 200 300 400 500 600 700 800
Stress, MPa
Dep
th m
easu
red
fro
m S
ide
1,
mm
FEA - Sphere Weld with PWHT
FEA - Sphere Weld with PWHT, then Repair
FEA - Plate Weld with PWHT
FEA - Plate Weld with PWHT, then Repair
Figure 35 Comparison of residual stress predictions for the plate and the sphere: (a)
transverse, (b) longitudinal
(a)
40 Comparison of Analyses of Deep and Shallow Repairs in Sphere: Transverse stress perpendicular to weld (S22)
Dep
th m
easu
red
fro
m S
ide
1,
mm
Dep
th m
easu
red
fro
m S
ide
1,
mm 30
20
10
0
-800 -700 -600 -500 -400 -300 -200 -100 0 100 200 300 400 500 600 700 800Stress, MPa
FEA - Sphere Weld with PWHT
FEA - Sphere Weld with PWHT, then Repair
FEA - Sphere Weld with PWHT, then Shallow Repair
(b)
40 Comparison of Analyses of Deep and Shallow Repairs in Sphere: Longitudinal stress parallel to weld (S33)
30
20
10
0
FEA - Sphere Weld with PWHT
FEA - Sphere Weld with PWHT, then Repair
FEA - Sphere Weld with PWHT, then Shallow Repair
-200 -100 0 100 200 300 400 500 600 700 800Stress, MPa
Figure 36 Residual stress predictions for deep and shallow weld repairs in the sphere:
(a) transverse, (b) longitudinal
(a)
-40
-20
0
20
40
60
80
100
120
140
160
180
200
0 2 4 6 8 10 12 14 16 18 20
crack depth a, mm
K,
MP
a m
1/2
Plate PWHT weld, Edge crack, 220 MPa
Plate PWHT weld, Edge crack, 210 MPa
Plate PWHT weld, Edge crack, 200 MPa
Plate PWHT weld, Edge crack, 190 MPa
Plate PWHT weld, Edge crack, 180 MPa
Plate PWHT weld, Edge crack, 170 MPa
Plate PWHT weld, Edge crack, 160 MPa
Plate PWHT weld, Edge crack, 150 MPa
Plate PWHT weld, Edge crack, 100 MPa
Plate PWHT weld, Edge crack, 50 MPa
Plate PWHT weld, Edge crack, 0 MPa
(b)
-40
-20
0
20
40
60
80
100
120
140
160
180
200
0 2 4 6 8 10 12 14 16 18 20
crack depth a, mm
K,
MP
a m
1/2
Plate Repaired weld, Edge crack, 220 MPa
Plate Repaired weld, Edge crack, 210 MPa
Plate Repaired weld, Edge crack, 200 MPa
Plate Repaired weld, Edge crack, 190 MPa
Plate Repaired weld, Edge crack, 180 MPa
Plate Repaired weld, Edge crack, 170 MPa
Plate Repaired weld, Edge crack, 160 MPa
Plate Repaired weld, Edge crack, 150 MPa
Plate Repaired weld, Edge crack, 100 MPa
Plate Repaired weld, Edge crack, 50 MPa
Plate Repaired weld, Edge crack, 0 MPa
Figure 37 K for various nominal primary stresses versus edge crack depth in plate: (a)
unrepaired PWHT, (b) as-repaired
(a)
-40
-20
0
20
40
60
80
100
120
140
160
180
200
0 2 4 6 8 10 12 14 16 18 20
crack depth a, mm
KJ,
MP
a m
1/2
Plate PWHT weld, Edge crack, 220 MPa
Plate PWHT weld, Edge crack, 210 MPa
Plate PWHT weld, Edge crack, 200 MPa
Plate PWHT weld, Edge crack, 190 MPa
Plate PWHT weld, Edge crack, 180 MPa
Plate PWHT weld, Edge crack, 170 MPa
Plate PWHT weld, Edge crack, 160 MPa
Plate PWHT weld, Edge crack, 150 MPa
Plate PWHT weld, Edge crack, 100 MPa
Plate PWHT weld, Edge crack, 50 MPa
Plate PWHT weld, Edge crack, 0 MPa
(b)
-40
-20
0
20
40
60
80
100
120
140
160
180
200
0 2 4 6 8 10 12 14 16 18 20
crack depth a, mm
KJ,
MP
a m
1/2
Plate Repaired weld, Edge crack, 220 MPa
Plate Repaired weld, Edge crack, 210 MPa
Plate Repaired weld, Edge crack, 200 MPa
Plate Repaired weld, Edge crack, 190 MPa
Plate Repaired weld, Edge crack, 180 MPa
Plate Repaired weld, Edge crack, 170 MPa
Plate Repaired weld, Edge crack, 160 MPa
Plate Repaired weld, Edge crack, 150 MPa
Plate Repaired weld, Edge crack, 100 MPa
Plate Repaired weld, Edge crack, 50 MPa
Plate Repaired weld, Edge crack, 0 MPa
Figure 38 KJ for various levels of primary stress versus edge crack depth in plate: (a)
unrepaired PWHT, (b) as-repaired
(a)
0
2
4
6
8
10
12
14
16
18
20
0 10000 20000 30000 40000 50000 60000 70000 80000
number of cycles, N
cra
ck d
epth
, a
, m
m
Plate PWHT weld, Edge crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=16.67mm
Plate PWHT weld, Edge crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=15.00mm
Plate PWHT weld, Edge crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=13.33mm
Plate PWHT weld, Edge crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=11.67mm
Plate PWHT weld, Edge crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=10.00mm
Plate PWHT weld, Edge crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=8.33mm
Plate PWHT weld, Edge crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=6.67mm
Plate PWHT weld, Edge crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=5.00mm
Plate PWHT weld, Edge crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=3.33mm
(b)
0
2
4
6
8
10
12
14
16
18
20
0 10000 20000 30000 40000 50000 60000 70000 80000
number of cycles, N
cra
ck d
epth
, a
, m
m
Plate Repaired weld, Edge crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=16.67mm
Plate Repaired weld, Edge crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=15.00mm
Plate Repaired weld, Edge crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=13.33mm
Plate Repaired weld, Edge crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=11.67mm
Plate Repaired weld, Edge crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=10.00mm
Plate Repaired weld, Edge crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=8.33mm
Plate Repaired weld, Edge crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=6.67mm
Plate Repaired weld, Edge crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=5.00mm
Plate Repaired weld, Edge crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=3.33mm
Figure 39 Crack depth versus number of cycles for different initial edge crack depths in
plate subjected to 180 MPa cyclic primary stress: (a) unrepaired PWHT, (b) as-repaired
(a)
160
140
1/2
100
120
Jc
, Edg , Op , , ( ),
fra
ctu
re t
ou
gh
nes
s, K
. M
Pa
m
Plate PWHT weld, Edge crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=16.67mm
Plate PWHT weld, Edge crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=15.00mm
Plate PWHT weld, Edge crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=13.33mm
Plate PWHT weld, Edge crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=11.67mm
Plate PWHT weld, Edge crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=10.00mm
Plate PWHT weld, Edge crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=8.33mm
Plate PWHT weld, Edge crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=6.67mm
Plate PWHT weld, Edge crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=5.00mm
Plate PWHT weld e crack =180MPa Max=225MPa deltaKJ ao=3.33mm
80
60
40
20
0
0 10000 20000 30000 40000 50000 60000 70000 80000number of cycles to limiting condition, Nf
160
140
100
120
Jc
p , Edg , Op , , ( ),
fra
ctu
re t
ou
gh
nes
s, K
. M
Pa
m
Plate Repaired weld, Edge crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=16.67mm
Plate Repaired weld, Edge crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=15.00mm
Plate Repaired weld, Edge crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=13.33mm
Plate Repaired weld, Edge crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=11.67mm
Plate Repaired weld, Edge crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=10.00mm
Plate Repaired weld, Edge crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=8.33mm
Plate Repaired weld, Edge crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=6.67mm
Plate Repaired weld, Edge crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=5.00mm
Plate Re aired weld e crack =180MPa Max=225MPa deltaKJ ao=3.33mm
1/2
80
60
40
20
0
0 10000 20000 30000 40000 50000 60000 70000 80000number of cycles to limiting condition, Nf
(b)
Figure 40 Fracture toughness versus cycles to the limiting condition for different initial
edge crack depths in plate subjected to 180 MPa cyclic primary stress and occasional
225 MPa overload: (a) unrepaired PWHT, (b) as-repaired
160
140
1/2
fr
act
ure
to
ug
hn
ess,
KJ
c. M
Pa
m
120
100
80
60
40
Plate Repaired weld, Edge crack, Op=180MPa, Max=225MPa
Plate PWHT weld, Edge crack, Op=180MPa, Max=225MPa
4 6 8 10 12 14 16 18 20 critical crack depth ac, mm
Figure 41 Fracture toughness versus critical crack depth to give limiting condition for
edge defects in unrepaired PWHT and as-repaired plate subjected to 225 MPa overload
stress
0.0
0.5
1.0
1.5
Nf
f
, KJc=50
(rep
air
ed)/
N(u
nre
pa
ired
)
deltaKJ, KJc=160
deltaKJ, KJc=150
deltaKJ, KJc=140
deltaKJ, KJc=130
deltaKJ, KJc=120
deltaKJ, KJc=110
deltaKJ, KJc=100
deltaKJ, KJc=90
deltaKJ, KJc=80
deltaKJ, KJc=70
deltaKJ, KJc=60
deltaKJ
0 2 4 6 8 10 12 14 16 18 20
initial crack depth, mm
Figure 42 Ratio of cycles to limiting condition for edge defects in as-repaired and
unrepaired PWHT plate for various initial depths and fracture toughness
(a)
0.0
0.5
1.0
1.5
2.0
0 10 20 30 40 50 60 70 80 90
% reduction of repaired toughness from original PWHT value
Nf(
rep
air
ed)/
Nf(
un
rep
air
ed)
KJc(orig)=160, ao_unr=5.00, ao_rep=5.00
KJc(orig)=160, ao_unr=5.00, ao_rep=4.17
KJc(orig)=160, ao_unr=5.00, ao_rep=3.33
KJc(orig)=140, ao_unr=5.00, ao_rep=5.00
KJc(orig)=140, ao_unr=5.00, ao_rep=4.17
KJc(orig)=140, ao_unr=5.00, ao_rep=3.33
KJc(orig)=120, ao_unr=5.00, ao_rep=5.00
KJc(orig)=120, ao_unr=5.00, ao_rep=4.17
KJc(orig)=120, ao_unr=5.00, ao_rep=3.33
KJc(orig)=100, ao_unr=5.00, ao_rep=5.00
KJc(orig)=100, ao_unr=5.00, ao_rep=4.17
KJc(orig)=100, ao_unr=5.00, ao_rep=3.33
KJc(orig)=80, ao_unr=5.00, ao_rep=5.00
KJc(orig)=80, ao_unr=5.00, ao_rep=4.17
KJc(orig)=80, ao unr=5.00, ao rep=3.33
(b)
0.0
0.5
1.0
1.5
2.0
0 10 20 30 40 50 60 70 80 90
% reduction of repaired toughness from original PWHT value
Nf(
rep
air
ed)/
Nf(
un
rep
air
ed)
KJc(orig)=160, ao_unr=6.67, ao_rep=6.67
KJc(orig)=160, ao_unr=6.67, ao_rep=5.00
KJc(orig)=160, ao_unr=6.67, ao_rep=3.33
KJc(orig)=140, ao_unr=6.67, ao_rep=6.67
KJc(orig)=140, ao_unr=6.67, ao_rep=5.00
KJc(orig)=140, ao_unr=6.67, ao_rep=3.33
KJc(orig)=120, ao_unr=6.67, ao_rep=6.67
KJc(orig)=120, ao_unr=6.67, ao_rep=5.00
KJc(orig)=120, ao_unr=6.67, ao_rep=3.33
KJc(orig)=100, ao_unr=6.67, ao_rep=6.67
KJc(orig)=100, ao_unr=6.67, ao_rep=5.00
KJc(orig)=100, ao_unr=6.67, ao_rep=3.33
KJc(orig)=80, ao_unr=6.67, ao_rep=6.67
KJc(orig)=80, ao_unr=6.67, ao_rep=5.00
KJc(orig)=80, ao unr=6.67, ao rep=3.33
Figure 43 Ratio of cycles to limiting condition for different size edge defects in as-
repaired and unrepaired PWHT plate as a function PWHT fracture toughness and
percentage toughness reduction in repaired state, for depth before repair
of (a) 5 mm, (b) 6.7 mm
(c)
0.0
0.5
1.0
1.5
2.0
0 10 20 30 40 50 60 70 80 90
% reduction of repaired toughness from original PWHT value
Nf(
rep
air
ed)/
Nf(
un
rep
air
ed)
KJc(orig)=160, ao_unr=9.17, ao_rep=6.67
KJc(orig)=160, ao_unr=9.17, ao_rep=5.00
KJc(orig)=160, ao_unr=9.17, ao_rep=3.33
KJc(orig)=140, ao_unr=9.17, ao_rep=6.67
KJc(orig)=140, ao_unr=9.17, ao_rep=5.00
KJc(orig)=140, ao_unr=9.17, ao_rep=3.33
KJc(orig)=120, ao_unr=9.17, ao_rep=6.67
KJc(orig)=120, ao_unr=9.17, ao_rep=5.00
KJc(orig)=120, ao_unr=9.17, ao_rep=3.33
KJc(orig)=100, ao_unr=9.17, ao_rep=6.67
KJc(orig)=100, ao_unr=9.17, ao_rep=5.00
KJc(orig)=100, ao_unr=9.17, ao_rep=3.33
KJc(orig)=80, ao_unr=9.17, ao_rep=6.67
KJc(orig)=80, ao_unr=9.17, ao_rep=5.00
KJc(orig)=80, ao unr=9.17, ao rep=3.33
(d)
0.0
0.5
1.0
1.5
2.0
0 10 20 30 40 50 60 70 80 90
% reduction of repaired toughness from original PWHT value
Nf(
rep
air
ed)/
Nf(
un
rep
air
ed)
KJc(orig)=160, ao_unr=10.83, ao_rep=9.17
KJc(orig)=160, ao_unr=10.83, ao_rep=6.67
KJc(orig)=160, ao_unr=10.83, ao_rep=5.00
KJc(orig)=140, ao_unr=10.83, ao_rep=9.17
KJc(orig)=140, ao_unr=10.83, ao_rep=6.67
KJc(orig)=140, ao_unr=10.83, ao_rep=5.00
KJc(orig)=120, ao_unr=10.83, ao_rep=9.17
KJc(orig)=120, ao_unr=10.83, ao_rep=6.67
KJc(orig)=120, ao_unr=10.83, ao_rep=5.00
KJc(orig)=100, ao_unr=10.83, ao_rep=9.17
KJc(orig)=100, ao_unr=10.83, ao_rep=6.67
KJc(orig)=100, ao_unr=10.83, ao_rep=5.00
KJc(orig)=80, ao_unr=10.83, ao_rep=9.17
KJc(orig)=80, ao_unr=10.83, ao_rep=6.67
KJc(orig)=80, ao unr=10.83, ao rep=5.00
Figure 43 (cont’d) Ratio of cycles to limiting condition for different size edge defects in
as-repaired and unrepaired PWHT plate as a function PWHT fracture toughness and
percentage toughness reduction in repaired state, for depth before repair
of (c) 9.2 mm, (d) 10.8 mm
(e)
2.0 N
f(re
pa
ired
)/N
f(u
nre
pa
ired
) 1.5
1.0
0.5
0.0
( g) , ao , ao p
KJc(orig)=160, ao_unr=13.33, ao_rep=9.17
KJc(orig)=160, ao_unr=13.33, ao_rep=6.67
KJc(orig)=160, ao_unr=13.33, ao_rep=5.00
KJc(orig)=140, ao_unr=13.33, ao_rep=9.17
KJc(orig)=140, ao_unr=13.33, ao_rep=6.67
KJc(orig)=140, ao_unr=13.33, ao_rep=5.00
KJc(orig)=120, ao_unr=13.33, ao_rep=9.17
KJc(orig)=120, ao_unr=13.33, ao_rep=6.67
KJc(orig)=120, ao_unr=13.33, ao_rep=5.00
KJc(orig)=100, ao_unr=13.33, ao_rep=9.17
KJc(orig)=100, ao_unr=13.33, ao_rep=6.67
KJc(orig)=100, ao_unr=13.33, ao_rep=5.00
KJc(orig)=80, ao_unr=13.33, ao_rep=9.17
KJc(orig)=80, ao_unr=13.33, ao_rep=6.67
KJc ori =80 unr=13.33 re =5.00
0 10 20 30 40 50 60 70 80 90
% reduction of repaired toughness from original PWHT value
Figure 43 (cont’d) Ratio of cycles to limiting condition for different size edge defects in
as-repaired and unrepaired PWHT plate as a function PWHT fracture toughness and
percentage toughness reduction in repaired state, for depth before repair
of (e) 13.3 mm
(a)
-40
-20
0
20
40
60
80
100
120
140
160
180
200
0 2 4 6 8 10 12 14 16 18 20
crack depth a, mm
KJ,
MP
a m
1/2
Sphere PWHT weld, surface crack, 220 MPa
Sphere PWHT weld, surface crack, 210 MPa
Sphere PWHT weld, surface crack, 200 MPa
Sphere PWHT weld, surface crack, 190 MPa
Sphere PWHT weld, surface crack, 180 MPa
Sphere PWHT weld, surface crack, 170 MPa
Sphere PWHT weld, surface crack, 160 MPa
Sphere PWHT weld, surface crack, 150 MPa
Sphere PWHT weld, surface crack, 100 MPa
Sphere PWHT weld, surface crack, 50 MPa
Sphere PWHT weld, surface crack, 0 MPa
(b)
-40
-20
0
20
40
60
80
100
120
140
160
180
200
0 2 4 6 8 10 12 14 16 18 20
crack depth a, mm
KJ,
MP
a m
1/2
Sphere Repaired weld, surface crack, 220 MPa
Sphere Repaired weld, surface crack, 210 MPa
Sphere Repaired weld, surface crack, 200 MPa
Sphere Repaired weld, surface crack, 190 MPa
Sphere Repaired weld, surface crack, 180 MPa
Sphere Repaired weld, surface crack, 170 MPa
Sphere Repaired weld, surface crack, 160 MPa
Sphere Repaired weld, surface crack, 150 MPa
Sphere Repaired weld, surface crack, 100 MPa
Sphere Repaired weld, surface crack, 50 MPa
Sphere Repaired weld, surface crack, 0 MPa
Figure 44 KJ for various levels of primary stress versus edge crack depth in sphere: (a)
unrepaired PWHT, (b) as-repaired
(a)
0
2
4
6
8
10
12
14
16
18
20
0 10000 20000 30000 40000 50000 60000 70000 80000
number of cycles, N
cra
ck d
epth
, a
, m
m
Sphere PWHT weld, surface crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=16.67mm
Sphere PWHT weld, surface crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=15.00mm
Sphere PWHT weld, surface crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=13.33mm
Sphere PWHT weld, surface crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=11.67mm
Sphere PWHT weld, surface crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=10.00mm
Sphere PWHT weld, surface crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=8.33mm
Sphere PWHT weld, surface crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=6.67mm
Sphere PWHT weld, surface crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=5.00mm
Sphere PWHT weld, surface crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=3.33mm
(b)
0
2
4
6
8
10
12
14
16
18
20
0 10000 20000 30000 40000 50000 60000 70000 80000
number of cycles, N
cra
ck d
epth
, a
, m
m
Sphere Repaired weld, surface crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=16.67mm
Sphere Repaired weld, surface crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=15.00mm
Sphere Repaired weld, surface crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=13.33mm
Sphere Repaired weld, surface crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=11.67mm
Sphere Repaired weld, surface crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=10.00mm
Sphere Repaired weld, surface crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=8.33mm
Sphere Repaired weld, surface crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=6.67mm
Sphere Repaired weld, surface crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=5.00mm
Sphere Repaired weld, surface crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=3.33mm
Figure 45 Crack depth versus number of cycles for different initial edge crack depths in
sphere subjected to 180 MPa cyclic primary stress: (a) unrepaired PWHT, (b) as-repaired
(a)
160
140
1/2
1
/2
fra
ctu
re t
ou
gh
nes
s, K
Jc.
MP
a m
120
100
Sphere PWHT weld, surface crack, Op=180MPa, Max=225MPa, (deltaKJ),
ao=16.67mm Sphere PWHT weld, surface crack, Op=180MPa, Max=225MPa, (deltaKJ),
ao=15.00mm Sphere PWHT weld, surface crack, Op=180MPa, Max=225MPa, (deltaKJ),
ao=13.33mm Sphere PWHT weld, surface crack, Op=180MPa, Max=225MPa, (deltaKJ),
ao=11.67mm Sphere PWHT weld, surface crack, Op=180MPa, Max=225MPa, (deltaKJ),
ao=10.00mm Sphere PWHT weld, surface crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=8.33mm
80
60
40
20
0
0 10000 20000 30000 40000 50000 60000 70000 80000number of cycles to limiting condition, Nf
(b)
160
140
100
120
Jc
Sp p , , Op , , ( ),
fra
ctu
re t
ou
gh
nes
s, K
. M
Pa
m
Sphere Repaired weld, surface crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=16.67mm
Sphere Repaired weld, surface crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=15.00mm
Sphere Repaired weld, surface crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=13.33mm
Sphere Repaired weld, surface crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=11.67mm
Sphere Repaired weld, surface crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=10.00mm
Sphere Repaired weld, surface crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=8.33mm
Sphere Repaired weld, surface crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=6.67mm
Sphere Repaired weld, surface crack, Op=180MPa, Max=225MPa, (deltaKJ), ao=5.00mm
here Re aired weld surface crack =180MPa Max=225MPa deltaKJ ao=3.33mm
80
60
40
20
0
0 10000 20000 30000 40000 50000 60000 70000 80000number of cycles to limiting condition, Nf
Figure 46 Fracture toughness versus cycles to limiting condition for different initial edge crack depths in sphere subjected to 180 MPa cyclic primary stress and occasional 225
MPa overload: (a) unrepaired PWHT, (b) as-repaired
160
140
1/2
fr
act
ure
to
ug
hn
ess,
KJ
c. M
Pa
m
120
100
80
60
40
Sphere Repaired weld, surface crack, Op=180MPa, Max=225MPa
Sphere PWHT weld, surface crack, Op=180MPa, Max=225MPa
4 6 8 10 12 14 16 18 20 critical crack depth ac, mm
Figure 47 Fracture toughness versus critical crack depth to give limiting condition for
edge defects in unrepaired PWHT and as-repaired sphere subjected to 225 MPa overload
stress
0.0
0.5
1.0
1.5
Nf
f
, KJc=55
(rep
air
ed)/
N(u
nre
pa
ired
)
deltaKJ, KJc=110
deltaKJ, KJc=105
deltaKJ, KJc=100
deltaKJ, KJc=95
deltaKJ, KJc=90
deltaKJ, KJc=85
deltaKJ, KJc=80
deltaKJ, KJc=75
deltaKJ, KJc=70
deltaKJ, KJc=65
deltaKJ, KJc=60
deltaKJ
0 2 4 6 8 10 12 14 16 18 20
initial crack depth, mm
Figure 48 Ratio of cycles to limiting condition for edge defects in as-repaired and
unrepaired PWHT sphere for various initial depths and fracture toughness
(a)
0.0
0.5
1.0
1.5
2.0
0 10 20 30 40 50 60 70 80 90
% reduction of repaired toughness from original PWHT value
Nf(
rep
air
ed)/
Nf(
un
rep
air
ed)
KJc(orig)=110, ao_unr=5.00, ao_rep=5.00
KJc(orig)=110, ao_unr=5.00, ao_rep=4.17
KJc(orig)=110, ao_unr=5.00, ao_rep=3.33
KJc(orig)=100, ao_unr=5.00, ao_rep=5.00
KJc(orig)=100, ao_unr=5.00, ao_rep=4.17
KJc(orig)=100, ao_unr=5.00, ao_rep=3.33
KJc(orig)=90, ao_unr=5.00, ao_rep=5.00
KJc(orig)=90, ao_unr=5.00, ao_rep=4.17
KJc(orig)=90, ao_unr=5.00, ao_rep=3.33
KJc(orig)=80, ao_unr=5.00, ao_rep=5.00
KJc(orig)=80, ao_unr=5.00, ao_rep=4.17
KJc(orig)=80, ao_unr=5.00, ao_rep=3.33
KJc(orig)=70, ao_unr=5.00, ao_rep=5.00
KJc(orig)=70, ao_unr=5.00, ao_rep=4.17
KJc(orig)=70, ao unr=5.00, ao rep=3.33
(b)
0.0
0.5
1.0
1.5
2.0
0 10 20 30 40 50 60 70 80 90
% reduction of repaired toughness from original PWHT value
Nf(
rep
air
ed)/
Nf(
un
rep
air
ed)
KJc(orig)=110, ao_unr=6.67, ao_rep=6.67
KJc(orig)=110, ao_unr=6.67, ao_rep=5.00
KJc(orig)=110, ao_unr=6.67, ao_rep=3.33
KJc(orig)=100, ao_unr=6.67, ao_rep=6.67
KJc(orig)=100, ao_unr=6.67, ao_rep=5.00
KJc(orig)=100, ao_unr=6.67, ao_rep=3.33
KJc(orig)=90, ao_unr=6.67, ao_rep=6.67
KJc(orig)=90, ao_unr=6.67, ao_rep=5.00
KJc(orig)=90, ao_unr=6.67, ao_rep=3.33
KJc(orig)=80, ao_unr=6.67, ao_rep=6.67
KJc(orig)=80, ao_unr=6.67, ao_rep=5.00
KJc(orig)=80, ao_unr=6.67, ao_rep=3.33
KJc(orig)=70, ao_unr=6.67, ao_rep=6.67
KJc(orig)=70, ao_unr=6.67, ao_rep=5.00
KJc(orig)=70, ao unr=6.67, ao rep=3.33
Figure 49 Ratio of cycles to limiting condition for different size edge defects in as-
repaired and unrepaired PWHT sphere as a function PWHT fracture toughness and
percentage toughness reduction in repaired state, for depth before repairof (a) 5 mm, (b) 6.7 mm
(c)
0.0
0.5
1.0
1.5
2.0
0 10 20 30 40 50 60 70 80 90
% reduction of repaired toughness from original PWHT value
Nf(
rep
air
ed)/
Nf(
un
rep
air
ed)
KJc(orig)=110, ao_unr=9.17, ao_rep=6.67
KJc(orig)=110, ao_unr=9.17, ao_rep=5.00
KJc(orig)=110, ao_unr=9.17, ao_rep=3.33
KJc(orig)=100, ao_unr=9.17, ao_rep=6.67
KJc(orig)=100, ao_unr=9.17, ao_rep=5.00
KJc(orig)=100, ao_unr=9.17, ao_rep=3.33
KJc(orig)=90, ao_unr=9.17, ao_rep=6.67
KJc(orig)=90, ao_unr=9.17, ao_rep=5.00
KJc(orig)=90, ao_unr=9.17, ao_rep=3.33
KJc(orig)=80, ao_unr=9.17, ao_rep=6.67
KJc(orig)=80, ao_unr=9.17, ao_rep=5.00
KJc(orig)=80, ao_unr=9.17, ao_rep=3.33
KJc(orig)=70, ao_unr=9.17, ao_rep=6.67
KJc(orig)=70, ao_unr=9.17, ao_rep=5.00
KJc(orig)=70, ao unr=9.17, ao rep=3.33
(d)
0.0
0.5
1.0
1.5
2.0
0 10 20 30 40 50 60 70 80 90
% reduction of repaired toughness from original PWHT value
Nf(
rep
air
ed)/
Nf(
un
rep
air
ed)
KJc(orig)=110, ao_unr=10.83, ao_rep=9.17
KJc(orig)=110, ao_unr=10.83, ao_rep=6.67
KJc(orig)=110, ao_unr=10.83, ao_rep=5.00
KJc(orig)=100, ao_unr=10.83, ao_rep=9.17
KJc(orig)=100, ao_unr=10.83, ao_rep=6.67
KJc(orig)=100, ao_unr=10.83, ao_rep=5.00
KJc(orig)=90, ao_unr=10.83, ao_rep=9.17
KJc(orig)=90, ao_unr=10.83, ao_rep=6.67
KJc(orig)=90, ao_unr=10.83, ao_rep=5.00
KJc(orig)=80, ao_unr=10.83, ao_rep=9.17
KJc(orig)=80, ao_unr=10.83, ao_rep=6.67
KJc(orig)=80, ao_unr=10.83, ao_rep=5.00
KJc(orig)=70, ao_unr=10.83, ao_rep=9.17
KJc(orig)=70, ao_unr=10.83, ao_rep=6.67
KJc(orig)=70, ao unr=10.83, ao rep=5.00
Figure 49 (cont’d) Ratio of cycles to limiting condition for different size edge defects in
as-repaired and unrepaired PWHT sphere as a function PWHT fracture toughness and
percentage toughness reduction in repaired state, for depth before repair
of (c) 9.2 mm, (d) 10.8 mm
(e)
2.0 N
f(re
pa
ired
)/N
f(u
nre
pa
ired
) 1.5
1.0
0.5
0.0
( g) , ao , ao p
KJc(orig)=110, ao_unr=13.33, ao_rep=9.17
KJc(orig)=110, ao_unr=13.33, ao_rep=6.67
KJc(orig)=110, ao_unr=13.33, ao_rep=5.00
KJc(orig)=100, ao_unr=13.33, ao_rep=9.17
KJc(orig)=100, ao_unr=13.33, ao_rep=6.67
KJc(orig)=100, ao_unr=13.33, ao_rep=5.00
KJc(orig)=90, ao_unr=13.33, ao_rep=9.17
KJc(orig)=90, ao_unr=13.33, ao_rep=6.67
KJc(orig)=90, ao_unr=13.33, ao_rep=5.00
KJc(orig)=80, ao_unr=13.33, ao_rep=9.17
KJc(orig)=80, ao_unr=13.33, ao_rep=6.67
KJc(orig)=80, ao_unr=13.33, ao_rep=5.00
KJc(orig)=70, ao_unr=13.33, ao_rep=9.17
KJc(orig)=70, ao_unr=13.33, ao_rep=6.67
KJc ori =70 unr=13.33 re =5.00
0 10 20 30 40 50 60 70 80 90
% reduction of repaired toughness from original PWHT value
Figure 49 (cont’d) Ratio of cycles to limiting condition for different size edge defects in
as-repaired and unrepaired PWHT sphere as a function PWHT fracture toughness and
percentage toughness reduction in repaired state, for depth before repair of (e) 13.3 mm
(a)
-40
-20
0
20
40
60
80
100
120
140
160
180
200
0 2 4 6 8 10 12 14 16 18 20
crack height 2a, mm
KJ,
MP
a m
1/2
Plate PWHT weld, Embedded crack, 220 MPa
Plate PWHT weld, Embedded crack, 210 MPa
Plate PWHT weld, Embedded crack, 200 MPa
Plate PWHT weld, Embedded crack, 190 MPa
Plate PWHT weld, Embedded crack, 180 MPa
Plate PWHT weld, Embedded crack, 170 MPa
Plate PWHT weld, Embedded crack, 160 MPa
Plate PWHT weld, Embedded crack, 150 MPa
Plate PWHT weld, Embedded crack, 100 MPa
Plate PWHT weld, Embedded crack, 50 MPa
Plate PWHT weld, Embedded crack, 0 MPa
(b)
-40
-20
0
20
40
60
80
100
120
140
160
180
200
0 2 4 6 8 10 12 14 16 18 20
crack height 2a, mm
KJ,
MP
a m
1/2
Plate Repaired weld, Embedded crack, 220 MPa
Plate Repaired weld, Embedded crack, 210 MPa
Plate Repaired weld, Embedded crack, 200 MPa
Plate Repaired weld, Embedded crack, 190 MPa
Plate Repaired weld, Embedded crack, 180 MPa
Plate Repaired weld, Embedded crack, 170 MPa
Plate Repaired weld, Embedded crack, 160 MPa
Plate Repaired weld, Embedded crack, 150 MPa
Plate Repaired weld, Embedded crack, 100 MPa
Plate Repaired weld, Embedded crack, 50 MPa
Plate Repaired weld, Embedded crack, 0 MPa
Figure 50 KJ for various levels of primary stress versus height of plate embedded
defects (p+2a=16.7 mm): (a) unrepaired PWHT, (b) as-repaired
(a)
160
140
1/2
1
/2
fra
ctu
re t
ou
gh
nes
s, K
Jc.
MP
a m
80
60
40
20
0
0 20000 40000 60000 80000 100000 120000 140000 160000 180000 200000number of cycles to limiting condition, Nf
100
120 , , Op , , ( ),
Plate PWHT weld, Embedded crack, Op=180MPa, Max=225MPa, (deltaKJ), 2ao=13.33mm
Plate PWHT weld, Embedded crack, Op=180MPa, Max=225MPa, (deltaKJ), 2ao=11.67mm
Plate PWHT weld, Embedded crack, Op=180MPa, Max=225MPa, (deltaKJ), 2ao=10.00mm
Plate PWHT weld, Embedded crack, Op=180MPa, Max=225MPa, (deltaKJ), 2ao=8.33mm
Plate PWHT weld, Embedded crack, Op=180MPa, Max=225MPa, (deltaKJ), 2ao=6.67mm
Plate PWHT weld, Embedded crack, Op=180MPa, Max=225MPa, (deltaKJ), 2ao=5.00mm
Plate PWHT weld Embedded crack =180MPa Max=225MPa deltaKJ 2ao=3.33mm
(b)
160
140
100
120
Jc
p , , Op , , ( ),
fra
ctu
re t
ou
gh
nes
s, K
. M
Pa
m
Plate Repaired weld, Embedded crack, Op=180MPa, Max=225MPa, (deltaKJ), 2ao=13.33mm
Plate Repaired weld, Embedded crack, Op=180MPa, Max=225MPa, (deltaKJ), 2ao=11.67mm
Plate Repaired weld, Embedded crack, Op=180MPa, Max=225MPa, (deltaKJ), 2ao=10.00mm
Plate Repaired weld, Embedded crack, Op=180MPa, Max=225MPa, (deltaKJ), 2ao=8.33mm
Plate Repaired weld, Embedded crack, Op=180MPa, Max=225MPa, (deltaKJ), 2ao=6.67mm
Plate Repaired weld, Embedded crack, Op=180MPa, Max=225MPa, (deltaKJ), 2ao=5.00mm
Plate Re aired weld Embedded crack =180MPa Max=225MPa deltaKJ 2ao=3.33mm
80
60
40
20
0
0 20000 40000 60000 80000 100000 120000 140000 160000 180000 200000number of cycles to limiting condition, Nf
Figure 51 Fracture toughness versus cycles to limiting condition for different initial plate
embedded crack heights (with p+2a=16.7 mm) subjected to 180 MPa cyclic primary
stress and occasional 225 MPa overload: (a) unrepaired PWHT, (b) as-repaired
160
140
1/2
fr
act
ure
to
ug
hn
ess,
KJ
c. M
Pa
m
120
100
80
60
40
20
Plate Repaired weld, Embedded crack, Op=180MPa,
Max=225MPa Plate PWHT weld, Embedded crack, Op=180MPa, Max=225MPa
4 6 8 10 12 14 16 critical crack height 2ac, mm
Figure 52 Fracture toughness versus critical crack height to give limiting condition for
embedded defects (with p+2a=16.7 mm) in unrepaired PWHT and as-repaired plate
subjected to 225 MPa overload stress
160
Jc
fra
ctu
re t
ou
gh
nes
s, K
. M
Pa
m
Plate Repaired weld, Embedded crack, Op=180MPa,
Max=225MPa Plate PWHT weld, Embedded crack, Op=180MPa, Max=225MPa
140
120
100
80
60
40
20
4 5 6 7 8 9 critical crack height 2ac, mm
1/2
Figure 53 Fracture toughness versus critical crack height to give limiting condition for embedded defects (with p+2a=10.8 mm) in unrepaired PWHT and as-repaired plate
subjected to 225 MPa overload stress
0.0
0.5
1.0
1.5
Nf
f(r
epa
ired
)/N
(un
rep
air
ed)
deltaKJ, KJc=110
deltaKJ, KJc=100
deltaKJ, KJc=90
deltaKJ, KJc=80
deltaKJ, KJc=70
deltaKJ, KJc=60
deltaKJ, KJc=50
deltaKJ, KJc=40
deltaKJ, KJc=30
0 2 4 6 8 10 12 14 16 initial crack height 2a0, mm
Figure 54 Ratio of cycles to limiting condition for embedded defects in as-repaired and
unrepaired PWHT plate for various initial heights of embedded crack (with p+2a=16.7
mm) and fracture toughness
0.0
0.5
1.0
1.5
Nf
f(r
epa
ired
)/N
(un
rep
air
ed)
deltaKJ, KJc=60
deltaKJ, KJc=55
deltaKJ, KJc=50
deltaKJ, KJc=45
deltaKJ, KJc=40
deltaKJ, KJc=35
deltaKJ, KJc=30
0 1 2 3 4 5 6 7 8
initial crack height 2a0, mm
Figure 55 Ratio of cycles to limiting condition for embedded defects in as-repaired and
unrepaired PWHT plate for various initial heights of embedded crack (with p+2a=10.8
mm) and fracture toughness
(a)
0.0
0.5
1.0
1.5
2.0
0 10 20 30 40 50 60 70 80 90
% reduction of repaired toughness from original PWHT value
Nf(
rep
air
ed)/
Nf(
un
rep
air
ed)
KJc(orig)=110, 2ao_unr=5.00, 2ao_rep=5.00
KJc(orig)=110, 2ao_unr=5.00, 2ao_rep=4.17
KJc(orig)=110, 2ao_unr=5.00, 2ao_rep=3.33
KJc(orig)=100, 2ao_unr=5.00, 2ao_rep=5.00
KJc(orig)=100, 2ao_unr=5.00, 2ao_rep=4.17
KJc(orig)=100, 2ao_unr=5.00, 2ao_rep=3.33
KJc(orig)=90, 2ao_unr=5.00, 2ao_rep=5.00
KJc(orig)=90, 2ao_unr=5.00, 2ao_rep=4.17
KJc(orig)=90, 2ao_unr=5.00, 2ao_rep=3.33
KJc(orig)=80, 2ao_unr=5.00, 2ao_rep=5.00
KJc(orig)=80, 2ao_unr=5.00, 2ao_rep=4.17
KJc(orig)=80, 2ao_unr=5.00, 2ao_rep=3.33
KJc(orig)=70, 2ao_unr=5.00, 2ao_rep=5.00
KJc(orig)=70, 2ao_unr=5.00, 2ao_rep=4.17
KJc(orig)=70, 2ao unr=5.00, 2ao rep=3.33
(b)
0.0
0.5
1.0
1.5
2.0
0 10 20 30 40 50 60 70 80 90
% reduction of repaired toughness from original PWHT value
Nf(
rep
air
ed)/
Nf(
un
rep
air
ed)
KJc(orig)=110, 2ao_unr=6.67, 2ao_rep=6.67
KJc(orig)=110, 2ao_unr=6.67, 2ao_rep=5.00
KJc(orig)=110, 2ao_unr=6.67, 2ao_rep=4.17
KJc(orig)=100, 2ao_unr=6.67, 2ao_rep=6.67
KJc(orig)=100, 2ao_unr=6.67, 2ao_rep=5.00
KJc(orig)=100, 2ao_unr=6.67, 2ao_rep=4.17
KJc(orig)=90, 2ao_unr=6.67, 2ao_rep=6.67
KJc(orig)=90, 2ao_unr=6.67, 2ao_rep=5.00
KJc(orig)=90, 2ao_unr=6.67, 2ao_rep=4.17
KJc(orig)=80, 2ao_unr=6.67, 2ao_rep=6.67
KJc(orig)=80, 2ao_unr=6.67, 2ao_rep=5.00
KJc(orig)=80, 2ao_unr=6.67, 2ao_rep=4.17
KJc(orig)=70, 2ao_unr=6.67, 2ao_rep=6.67
KJc(orig)=70, 2ao_unr=6.67, 2ao_rep=5.00
KJc(orig)=70, 2ao unr=6.67, 2ao rep=4.17
Figure 56 Ratio of cycles to limiting condition for different height embedded defects (with
p+2a=16.7 mm) in as-repaired and unrepaired PWHT plate as a function PWHT
fracture toughness and percentage toughness reduction in repaired state,
for height before repair of (a) 5 mm, (b) 6.7 mm
(c)
0.0
0.5
1.0
1.5
2.0
0 10 20 30 40 50 60 70 80 90
% reduction of repaired toughness from original PWHT value
Nf(
rep
air
ed)/
Nf(
un
rep
air
ed)
KJc(orig)=110, 2ao_unr=9.17, 2ao_rep=9.17
KJc(orig)=110, 2ao_unr=9.17, 2ao_rep=6.67
KJc(orig)=110, 2ao_unr=9.17, 2ao_rep=5.00
KJc(orig)=100, 2ao_unr=9.17, 2ao_rep=9.17
KJc(orig)=100, 2ao_unr=9.17, 2ao_rep=6.67
KJc(orig)=100, 2ao_unr=9.17, 2ao_rep=5.00
KJc(orig)=90, 2ao_unr=9.17, 2ao_rep=9.17
KJc(orig)=90, 2ao_unr=9.17, 2ao_rep=6.67
KJc(orig)=90, 2ao_unr=9.17, 2ao_rep=5.00
KJc(orig)=80, 2ao_unr=9.17, 2ao_rep=9.17
KJc(orig)=80, 2ao_unr=9.17, 2ao_rep=6.67
KJc(orig)=80, 2ao_unr=9.17, 2ao_rep=5.00
KJc(orig)=70, 2ao_unr=9.17, 2ao_rep=9.17
KJc(orig)=70, 2ao_unr=9.17, 2ao_rep=6.67
KJc(orig)=70, 2ao unr=9.17, 2ao rep=5.00
(d)
0.0
0.5
1.0
1.5
2.0
0 10 20 30 40 50 60 70 80 90
% reduction of repaired toughness from original PWHT value
Nf(
rep
air
ed)/
Nf(
un
rep
air
ed)
KJc(orig)=110, 2ao_unr=10.83, 2ao_rep=9.17
KJc(orig)=110, 2ao_unr=10.83, 2ao_rep=6.67
KJc(orig)=110, 2ao_unr=10.83, 2ao_rep=5.00
KJc(orig)=100, 2ao_unr=10.83, 2ao_rep=9.17
KJc(orig)=100, 2ao_unr=10.83, 2ao_rep=6.67
KJc(orig)=100, 2ao_unr=10.83, 2ao_rep=5.00
KJc(orig)=90, 2ao_unr=10.83, 2ao_rep=9.17
KJc(orig)=90, 2ao_unr=10.83, 2ao_rep=6.67
KJc(orig)=90, 2ao_unr=10.83, 2ao_rep=5.00
KJc(orig)=80, 2ao_unr=10.83, 2ao_rep=9.17
KJc(orig)=80, 2ao_unr=10.83, 2ao_rep=6.67
KJc(orig)=80, 2ao_unr=10.83, 2ao_rep=5.00
KJc(orig)=70, 2ao_unr=10.83, 2ao_rep=9.17
KJc(orig)=70, 2ao_unr=10.83, 2ao_rep=6.67
KJc(orig)=70, 2ao unr=10.83, 2ao rep=5.00
Figure 56 (cont’d) Ratio of cycles to limiting condition for different height embedded defects
(with p+2a=16.7 mm) in as-repaired and unrepaired PWHT plate as a function PWHT
fracture toughness and percentage toughness reduction in repaired state,
for height before repair of (c) 9.2 mm, (d) 10.8 mm
(a)
0.0
0.5
1.0
1.5
2.0
0 10 20 30 40 50 60 70 80 90
% reduction of repaired toughness from original PWHT value
Nf(
rep
air
ed)/
Nf(
un
rep
air
ed)
KJc(orig)=60, 2ao_unr=5.00, 2ao_rep=5.00
KJc(orig)=60, 2ao_unr=5.00, 2ao_rep=4.17
KJc(orig)=60, 2ao_unr=5.00, 2ao_rep=3.33
KJc(orig)=55, 2ao_unr=5.00, 2ao_rep=5.00
KJc(orig)=55, 2ao_unr=5.00, 2ao_rep=4.17
KJc(orig)=55, 2ao_unr=5.00, 2ao_rep=3.33
KJc(orig)=50, 2ao_unr=5.00, 2ao_rep=5.00
KJc(orig)=50, 2ao_unr=5.00, 2ao_rep=4.17
KJc(orig)=50, 2ao_unr=5.00, 2ao_rep=3.33
KJc(orig)=45, 2ao_unr=5.00, 2ao_rep=5.00
KJc(orig)=45, 2ao_unr=5.00, 2ao_rep=4.17
KJc(orig)=45, 2ao_unr=5.00, 2ao_rep=3.33
KJc(orig)=40, 2ao_unr=5.00, 2ao_rep=5.00
KJc(orig)=40, 2ao_unr=5.00, 2ao_rep=4.17
KJc(orig)=40, 2ao unr=5.00, 2ao rep=3.33
(b)
0.0
0.5
1.0
1.5
2.0
0 10 20 30 40 50 60 70 80 90
% reduction of repaired toughness from original PWHT value
Nf(
rep
air
ed)/
Nf(
un
rep
air
ed)
KJc(orig)=60, 2ao_unr=6.67, 2ao_rep=6.67
KJc(orig)=60, 2ao_unr=6.67, 2ao_rep=5.00
KJc(orig)=60, 2ao_unr=6.67, 2ao_rep=4.17
KJc(orig)=55, 2ao_unr=6.67, 2ao_rep=6.67
KJc(orig)=55, 2ao_unr=6.67, 2ao_rep=5.00
KJc(orig)=55, 2ao_unr=6.67, 2ao_rep=4.17
KJc(orig)=50, 2ao_unr=6.67, 2ao_rep=6.67
KJc(orig)=50, 2ao_unr=6.67, 2ao_rep=5.00
KJc(orig)=50, 2ao_unr=6.67, 2ao_rep=4.17
KJc(orig)=45, 2ao_unr=6.67, 2ao_rep=6.67
KJc(orig)=45, 2ao_unr=6.67, 2ao_rep=5.00
KJc(orig)=45, 2ao_unr=6.67, 2ao_rep=4.17
KJc(orig)=40, 2ao_unr=6.67, 2ao_rep=6.67
KJc(orig)=40, 2ao_unr=6.67, 2ao_rep=5.00
KJc(orig)=40, 2ao unr=6.67, 2ao rep=4.17
Figure 57 Ratio of cycles to limiting condition for different height embedded defects (with
p+2a=10.8 mm) in as-repaired and unrepaired PWHT plate as a function PWHT
fracture toughness and percentage toughness reduction in repaired state:
for height before repair of (a) 5 mm, (b) 6.7 mm
Fig
ure
58
Cra
ck d
ep
th v
ers
us n
um
ber
of
cycle
s f
or
cra
ck d
ep
ths o
f 3.3
3 m
m,
10 m
m a
nd
16.6
7 m
m i
n p
late
su
bje
cte
d t
o 1
80 M
Pa
cycli
c p
rim
ary
str
ess –
un
rep
air
ed
PW
HT
– B
S 7
910 c
alc
ula
ted
co
mp
are
d w
ith
th
ose o
f F
E (
Fig
ure
39(a
))
02468
10
12
14
16
18
20
010000
20000
30000
40000
50000
60000
70000
Nu
mb
er
of
Cycle
s,
N
Crack Depth (mm)
FE
, P
WH
T,
DK
, a0-3
.33m
m
FE
, P
WH
T,
DK
, a0=
10.0
0m
m
FE
, P
WH
T,
DK
, a0=
16.6
7m
m
FE
, P
WH
T,
DK
J,
a0=
3.3
3m
m
FE
, P
WH
T,
DK
J,
a0=
10.0
0m
m
FE
, P
WH
T,
DK
J,
a0=
16.6
7m
m
BS
7910,
PW
HT
, a0=
3.3
3m
m
BS
79810,
PW
HT
, a0=
10.0
0m
m
BS
7910,
PW
HT
, a0=
16.6
7m
m
Fig
ure
59 C
rack d
ep
th v
ers
us n
um
ber
of
cycle
s f
or
cra
ck d
ep
ths o
f 3.3
3 m
m,
10 m
m a
nd
16.6
7 m
m i
n p
late
su
bje
cte
d t
o 1
80 M
Pa
cycli
c p
rim
ary
str
ess –
rep
air
ed
co
nd
itio
n –
BS
7910 c
alc
ula
ted
co
mp
are
d w
ith
th
ose o
f F
E (
Fig
ure
39(b
))
02468
10
12
14
16
18
20
010000
20000
30000
40000
50000
60000
Nu
mb
er
of
cycle
s,
N
Crack Depth (mm)
FE
, R
epair
ed,
DK
, a0=
3.3
3m
m
FE
, R
epair
ed,
DK
, a0=
10.0
0m
m
FE
, R
epair
ed,
DK
, a0=
16.6
7
FE
, R
epair
ed,
DK
J,
a0=
3.3
3m
m
FE
, R
epair
ed,
DK
J,
a0=
10.0
0m
m
FE
, R
epair
ed,
DK
J,
a0=
16.6
7m
m
BS
7910,
Repair
ed,
a0=
3.3
3m
m
BS
7910,
Repair
ed,
a0=
10.0
0m
m
BS
7910,
Repair
ed,
a0=
16.6
7m
m
0
20
40
60
80
100
120
140
160
180
IC (MPam) Fracture Toughness, K 1/ 2
BS
7910,
As-W
eld
ed
BS
7910,
PW
HT
BS
7910,
Repair
ed
0
2
4
6
810
12
14
Cri
tical
Cra
ck D
ep
th (
mm
)
Fig
ure
60
Fra
ctu
re t
ou
gh
ness v
ers
us c
riti
cal
cra
ck d
ep
th f
or
ed
ge d
efe
cts
su
bje
cte
d t
o 2
25 M
Pa o
verl
oad
str
ess –
BS
7910 r
esu
lts
fo
r th
ree d
iffe
ren
t w
eld
co
nd
itio
ns
0
20
40
60
80
100
120
140
160
180
IC (MPam) Fracture Toughness, K 1/ 2
FE
, P
WH
T
BS
7910,
PW
HT
BS
7910 R
efined,
PW
HT
0 2
4 6
8 10
12
14
16
18
Cri
tical
Cra
ck D
ep
th (
mm
)
Fig
ure
61
Fra
ctu
re t
ou
gh
ness v
ers
us c
riti
cal
cra
ck d
ep
ths f
or
ed
ge d
efe
cts
su
bje
cte
d t
o 2
25 M
Pa o
verl
oad
str
ess –
un
rep
air
ed
PW
HT
– B
S 7
910 r
esu
lts c
om
pare
d t
o t
ho
se o
f F
E (
Fig
ure
41)
20
0
20
40
60
80
100
120
140
160
180
IC (MPam) Fracture Toughness, K 1/ 2
FE
, R
epair
ed
BS
7910,
Repair
ed
BS
7910 R
efined,
Repair
ed
0
2
4
6
8
10
12
14
16
18
Cri
tical
Cra
ck D
ep
th (
mm
)
Fig
ure
62
Fra
ctu
re t
ou
gh
ness v
ers
us c
riti
cal
cra
ck d
ep
ths f
or
ed
ge d
efe
cts
su
bje
cte
d t
o 2
25 M
Pa o
verl
oad
str
ess –
rep
air
ed
co
nd
itio
n –
BS
7910 r
esu
lts c
om
pare
d t
o t
ho
se o
f F
E (
Fig
ure
41)
40
0
30
0
20
0
10
0 0
-10
0
-20
0
-30
0
-40
0
-50
0
-60
00.0
00
0
5.0
00
0
10
.00
00
1
5.0
00
0
20
.00
00
2
5.0
00
0
Str ess Per p en d icular to Weld (MPa)
As-W
eld
ed
As-W
eld
ed
-Re
pa
ir
As-W
eld
ed
-PW
HT
As-W
eld
ed
-PW
HT
-Re
pa
ir
Dis
tan
ce
fro
m S
ide
of
Pla
te (
mm
)
Fig
ure
63
Mo
dif
ied
resid
ual
str
ess d
istr
ibu
tio
ns
0
20
40
60
80
100
120
K1 (MPa m^ 0.5)
As-W
eld
ed
As-W
eld
ed -
Repair
As-W
eld
ed -
PW
HT
As-W
eld
ed -
PW
HT
- R
epair
5
10
15
20
25
Cra
ck
De
pth
(m
m)
Fig
ure
64
Str
ess i
nte
nsit
y f
acto
rs f
or
as-w
eld
ed
, as-w
eld
ed
-rep
air
, as-w
eld
ed
-PW
HT
an
d a
s-w
eld
ed
-PW
HT
-rep
air
cases
0
0
10
20
30
40
50
60
70
80
Bendin
g
K1 (MPa m^ 0.5)
As-W
eld
ed -
PW
HT
Cosim
e D
istr
ibution
Mem
bra
ne
0
5
10
15
20
25
Cra
ck
De
pth
(m
m)
Fig
ure
65
Str
ess i
nte
nsit
y f
acto
rs f
or
as-w
eld
ed
-PW
HT
, sin
uso
idal,
ben
din
g a
nd
mem
bra
ne c
ases
0
50
100
150
200
250
Bendin
g
K1 (MPa m^ 0.5)
As-w
eld
ed-P
WH
T-R
epair
Cosin
e
Mem
bra
ne
5
10
15
20
25
Cra
ck D
ap
th (
a)
Fig
ure
66
Str
ess i
nte
nsit
y f
acto
rs f
or
as-w
eld
ed
-PW
HT
-rep
air
, sin
uso
idal,
ben
din
g a
nd
mem
bra
ne c
ases
0
0
20
40
60
80
10
0
12
0
14
0
16
0
18
0
I) Stress I nt ensi t y Fact or, K (MPam1/2
BS
7910 S
olu
tion
FE
Solu
tion
Sharp
les e
t al S
olu
tion
Rooke &
Cart
wri
ght
Solu
tion,
Restr
ain
ed B
endin
g
Rooke &
Cart
wri
ght
Solu
tion,
Un-R
estr
ain
ed B
endin
g
0
5
10
15
20
25
Cra
ck
De
pth
, a
(m
m)
Fig
ure
67
Co
mp
ari
so
n o
f K
I so
luti
on
s f
or
mem
bra
ne s
tress o
f 220 M
Pa –
ed
ge c
rack
0
10
20
30
40
50
60
I Stress Intensity Factor, K (MPam1/2)
BS
7910 S
olu
tion
FE
Solu
tion
Sharp
les e
t al S
olu
tion
Rooke &
Cart
wri
ght
Solu
tion,
Restr
ain
ed B
endin
g
Rooke &
Cart
wri
ght
Solu
tion,
Un-R
estr
ain
d B
endin
g
0
5
10
15
20
25
Cra
ck D
ep
th,
a (
mm
)
Fig
ure
68
Co
mp
ari
so
n o
f as-w
eld
ed
-PW
HT
resid
ual
str
ess K
I valu
es –
ed
ge c
rack
(No
te:
BS
7910 a
nd
Ro
oke a
nd
Cart
wri
gh
t valu
es a
re f
or
a m
em
bra
ne s
tress o
f 69 M
Pa)
0
50
10
0
15
0
20
0
25
0
30
0
Stress Intensity Factor, KI (MPAm1/2)
BS
79
10
So
lutio
n
FE
So
lutio
n
Sh
arp
les e
t a
l S
olu
tio
n
Ro
oke
& C
art
wri
gh
t, R
estr
ain
ed
Be
nd
ing
Ro
oke
& C
art
wri
gh
t, U
n-R
estr
ain
ed
Be
nd
ing
0
5
10
15
20
25
Cra
ck
De
pth
, a
(m
m)
Fig
ure
69
Co
mp
ari
so
n o
f as-w
eld
ed
-PW
HT
-rep
air
ed
resid
ual
str
ess K
I valu
es –
ed
ge c
rack
(No
te:
BS
7910 a
nd
Ro
oke a
nd
Cart
wri
gh
t valu
es a
re f
or
a m
em
bra
ne s
tress o
f 345 M
Pa)
0
10
20
30
40
50
60
Stress Intensity Factor, KI (MPam1/2
)
BS
7910 S
olu
tion K
FE
Solu
tion K
Rooke &
Cart
wright
0 2
4 6
8 10
12
14
16
Cra
ck D
ep
th, 2a (
mm
)
Fig
ure
70
Co
mp
ari
so
n o
f K
I so
luti
on
s f
or
mem
bra
ne p
rim
ary
str
ess o
f 220 M
Pa –
em
bed
ded
cra
ck
-6-4-202468
10
12
14
0
2
4
6
8
10
12
14
16
I (MPam1/2
) Stress Intensity Factor, K
BS
7910 S
olu
tion
FE
Solu
tion K
FE
Solu
tion K
J
Cra
ck D
ep
th,
2a (
mm
)
Fig
ure
71
Co
mp
ari
so
n o
f as-w
eld
ed
-PW
HT
resid
ual
str
ess K
I valu
es –
em
bed
ded
cra
ck
(No
te:
BS
7910
valu
es a
re f
or
a m
em
bra
ne s
tress o
f 69 M
Pa)
0
10
20
30
40
50
60
0
2
4
6
8
Stress Intensity Factor, KI (MPam)
-20
-10
10
12
14
16
1/ 2
BS
7910 S
olu
tion
FE
Solu
tion K
FE
Solu
tion K
J
Cra
ck D
ep
th,
2a (
mm
)
Fig
ure
72
Co
mp
ari
so
n o
f as-w
eld
ed
-PW
HT
-rep
air
ed
resid
ual
str
ess K
I valu
es –
em
bed
ded
cra
ck
(No
te:
BS
7910 v
alu
es a
re f
or
a m
em
bra
ne s
tress o
f 345 M
Pa)
A1.1 INTRODUCTION
Repair welds may be necessary where flaws or defects have been found in weldments during the
fabrication of vessels or in-service. However, in some cases this process may have a deleterious
effect on the residual lifetime of the component. This can be due to defective repair welds,
inadequate removal of original defects or inappropriate repair weld properties. High residual stresses
may be present in welds that haven’t received sufficient stress-relief. A combination of these factors
can lead to re-cracking of the weld and further losses in productive time or more seriously,
catastrophic failure of the vessel.
For defects found during fabrication, standards such as BS5500 (Reference A1.1) require repair welds
to be carried out to an approved procedure and that they are subjected to the same acceptance criteria
as the original work. For defects found in-service there are no specific standards available that
provide guidance on the necessity to repair.
This Appendix is a review of current industrial practices and previous problems contained in the open
literature.
A1.2 LITERATURE SURVEY
A literature search for papers related to repair welds initially identified over 100 abstracts for
references dated from 1976. Following a review of these abstracts, twenty-five papers were identified
as of possible interest. A list of all these papers is given in Annex 1 of this Appendix.
The papers reviewed can be categorised by the following:
- Numerical analysis: These relate to the prediction of residual stresses in weldments.
- Case Studies: These papers discuss the metallurgical examination of repair welds and the
evaluation of found defects.
- Weld Repair Procedures and Techniques: These papers present weld repair techniques
- Performance of Repair Welds: An assessment of how various weld repairs have performed in
service.
The papers are briefly described in this next section with the aim of seeking information on current
practices dealing with weldment flaws, which will be useful for later stages in the project.
A1.2.1 Numerical Analysis
Eight references were identified relating to the prediction of residual stresses using numerical
techniques. The papers are briefly described in chronological order to illustrate the increase in
complexity of the numerical analysis that is now used to predict residual stresses in repair welds.
Rybicki and Stonesifer (References Annex1.1 - Annex1.3) describe the analysis of weld repairs of
heavy section steels. The vessel analysed was one of the intermediate pressure vessels used as part of
the Heavy Section Steel Technology (HSST) program at Oak Ridge National Laboratory (ORNL)
(Reference Annex1.4). This program looked at repair weld residual stresses in thick –walled steel
pressure vessels. The repair welds were performed in accordance with Section XI of the American
Society of Mechanical Engineers (ASME) boiler and pressure vessel code. The repair procedure
employed, known as the half-bead or temper-bead technique, was devised for repair welds that for
A1.1
practical considerations could not undergo routine high temperature thermal post weld heat treatment
(PWHT).
These papers may now be considered ‘dated’ considering the progress that has been made in the use
of finite element techniques to predict residual stresses. Nevertheless, they did illustrate the feasibility
of developing an efficient residual stress model to understand the complexity of residual stresses due
to weld repairs.
Further numerical techniques are described from simple approximations of residual stress patterns
(Reference Annex1.5) to three dimensional analysis (Reference Annex1.6) which examine the effects
of residual stresses and mechanical characteristics of repair welds. A further complexity of predicting
residual stresses is described by Oddy et al (Reference Annex1.7), which is the effect of
transformation plasticity on the magnitude of residual stresses in welds which undergo phase
transformation during cooling of the weld.
Leggatt describes a one-dimensional computer model (Reference Annex1.8) used to evaluate
transverse residual stresses in repair welds. However, the finite element analysis of residual stresses
in repair welds (Reference Annex1.9) describe the importance of using three dimensional models in
order to obtain valid residual stress information at the weld end regions where crack initiation is often
observed.
A1.2.2 Case Studies
Only two references were identified which describe the analysis carried out for components with weld
repairs. Each of the references has been briefly described highlighting the analysis used in assessing
the components structural integrity.
Chowdhury et al (Reference Annex1.10) describes the analysis of a failure in a weld repaired turbine
casing. The turbine casing operates at a temperature of 600oC and a pressure of 10-18 MPa. After 25
years of service, a crack was detected and repaired by welding. However, after 5 years of service,
since the repair, a crack was again detected in the weld. The casing was weld repaired by a high Cr-
Ni weld metal (24Cr-32Ni-4Mn-Fe). The base metal is low alloy ferritic steel (1Cr -0.5Mo steel).
The paper describes the analysis carried out to examine the cause of cracking and the metallography
of the base metal used to assess whether the turbine could be re-employed again after repairing the
new crack.
An experimental procedure is described whereby a sample, cut from the weld repair region, was
subject to visual examination, chemical analysis, microstructure and fractography analysis using a
scanning electron microscope and hardness testing. This analysis was used to consider whether the
base and weld metal was still in good metallurgical condition and if the choice of filler metal in the
weld repair was the correct choice. This analysis showed that holes and cavities were present in the
weld, which were responsible for initiating the cracks. The choice of filler metal was incorrect which
led to higher stresses due to the large difference in the thermal expansion coefficient of the weld and
base metal.
The paper highlights the consequences of using improper filler metal in weld repairs and that
appropriate advice should be sought when making a weld repair. The value of good metallographic
analysis is well described, however the basis for the initial weld repair is not given.
Corbit et al (Reference Annex1.11) describes the justification for continued service of a HP turbine
steam chest subject to a weld repair. The operating temperature is 538oC (1000
oF) and pressure is
1450 psig. Numerous cracks were found in the steam chest weld HAZ of the turbine shell during a
A1.2
scheduled outage. Replication was used to determine crack propagation along the surface and a boat
sample was removed to observe the crack path into the steam chest as well as checking the chemistry
of the weld metal.
Cracks were sized using ultrasonic inspection to determine the extent of the grinding and weld repair
necessary. Excavations were made to a maximum depth set by the turbine manufacturer. This left
cracks below the surface of the excavation. The cause of cracking was determined to be creep or
creep-fatigue related. An analysis was then performed to determine whether a repair weld was
required. Since cracks were left below the excavation, a remaining life assessment was carried out to
demonstrate the continued operation of the steam chest. A leak-before-break evaluation was also
carried out to demonstrate that leaking would develop before a catastrophic rupture.
A detailed repair procedure was then developed to address the creep damage found in the HAZ of the
weld. The repair process utilised a half-bead temper technique in order to minimise the need for a full
PWHT. The weld repair was carried out using the shielded metal arc welding (SMAW) process. A
controlled pre-heat was used before welding commenced and magnetic particle (MT) inspection was
performed to verify that no additional cracking or growth of the remaining cracks had not occurred.
MT inspections were carried out after each weld pass to confirm that cracking had not occurred in the
weld metal.
This paper provides a good illustration on the decisions that need to be carried out when carrying out
the successful repair of defects found in situ.
A1.2.3 Weld Repair Procedures and Techniques
An overview of weld repair techniques was described by Jones (Reference Annex1.12) in 1994.
General principles are defined which consider the questions that need to be asked before carrying out
a repair. They provide practical considerations that need to be considered when evaluating the need
to repair and are repeated below:
· Is welding the best method of repair?
· What is the composition and weldability of the base material?
· Is the repair location accessible?
· Can preheat be tolerated?
· Which welding procedure should be applied?
· Is PWHT necessary?
· Will the repair be fit for purpose?
· Can the repair be inspected and tested?
Several weld repair techniques are available, the choice of which rests on the consideration of a
number of factors. These are:
· Conventional buttering
· Half-bead
· Two-Layer
· Six-Layer
Factors influencing the choice of method are summarised in Table A1.1. The paper reflects that each
weld repair is usually unique, and whilst definitive rules are not possible, similar criteria need to be
considered when assessing the feasibility of a weld repair and deriving an appropriate weld procedure.
This can be achieved by guidelines that consider the general principles highlighted above.
A1.3
The half-bead weld or temper bead repair technique as outlined in ASME XI, was employed in the
HSST program (References Annex1.4, Annex1.13, and Annex1.14) examining repair weld residual
stresses. The procedure was developed for repair welds that for practical reasons could not undergo
routine PWHT. Whilst the adequacy of the technique was demonstrated by the results of destructive
and non-destructive testing the main concern were the high values of residual stresses associated with
very deep repairs.
The six-layer GTAW repair procedure is described by Alberry and Feldstein (Reference Annex1.15)
as an alternative to the ASME XI half-bead repair procedure. The need was for an in-service repair
capability, for use on light water reactor pressure components, which avoided the major disadvantage
of the half-bead technique. This was the heavy reliance on manual activities, notably the need to
remove, by grinding, the half of the first layer thickness deposited by welding.
The six-layer methodology uses the principle of controlling individual layer thicknesses of weld metal
to promote high levels of refinement and tempering in the underlying HAZ. The method has been
validated experimentally for a wide range of welding parameters for SA508 Class 2 steels. In
particular, it has been shown to accommodate variations in wire speed of up to ±30%, which makes
the technique suitable for all positional welding.
An as-welded repair procedure for C-0.5Mo coke drums is described by Moore (Reference
Annex1.16). The procedure was developed to allow through wall repairs of coke drums of up to 1-
inch thickness without PWHT. A preheat is applied before the first pass. Unlike the half-bead
procedure the grinding of the first pass is not required. Instead the electrode size is increased to
temper and refine the HAZ of the first pass, but precise heat input control and bead placement typical
of controlled deposition repairs are not used. On completion of welding, the preheat temperature is
increased, and the welds are post heated for 2 hours to allow hydrogen to diffuse.
In order to improve productivity by reducing time due to the manual labour required for grinding and
SMAW repairs, an automatic arc gouging and GMAW was developed. No experience of re-cracking
had been observed in service for either of the two procedures. The main benefits of the two
procedures compared with repairs with PWHT were lower repair costs and decreased repair time.
A1.2.4 Performance of Repair Welds
The effect of repair welds on various aspects of service performance is considered in several of the
references. Slater (Reference Annex1.17) describes a literature search relating to repair welding in
the structural steel industry in 1985. Problems associated with poor weld repairs were listed:
· Incomplete removal of defect being repaired
· Introduction of further defects
· Microstructure, material or toughness degradation
· Increased residual stresses and distortion
· Unfavourable environmental conditions
It was recognised that a fracture mechanics approach was required to assess the initial need to repair
and that guidance was needed on how to repair when necessary.
Booth, Threadgill and Wylde (References Annex1.18 and Annex1.19) observed a significant number
of service failures in welded structures involving weld repairs. These failures fell into three
categories:
· Defective repair welds
A1.4
· Inadequate removal of original defects
· Inappropriate repair weld properties
The importance of evaluating whether a repair is necessary was again recognised. It was estimated
that 'over 90 per cent of weld repairs carried out in some industries was unnecessary' because
‘workmanship’ acceptance criteria were used instead of a quantitative fitness-for-purpose concept.
Lai and Fong (Reference Annex A1.20) examined the fatigue performance of repaired pipeline steel
welds. Evaluating three welding processes, SMAW, GMAW and inner-shield welding (IW), only the
GMAW repairs exhibited a reduction in the fatigue life whereas the other repairs appeared to give
better fatigue resistance. This fatigue resistance of the repair weld was clearly dependent up on the
quality of the repair.
Evans et al (Reference Annex1.21) examined the performance of structural steel after multiple weld
repairs. It was shown that satisfactory multiple repairs are possible as long as the process is carefully
controlled. However, a review of weld repair by Prosser and Boothby (Reference A1.2) concluded
that through thickness and part wall repairs should be limited to one or two attempts respectively.
The application of the temperbead technique weld repair has been demonstrated by Viswanathan et al
for ferritic steel piping girth welds (References A1.3, A1.4, Annex1.22) and ferritic header welds
(Reference A1.5). In 1994, the US National Board Inspection Code (NBIC) reconsidered the
requirement of PWHT of weld repairs on 1.25Cr-0.5Mo and 2.25Cr-1Mo steels. It recognised that the
requirement to PWHT in accordance with the original code of construction may be inadvisable or
impractical, and thus allowed for alternative repair methods to be used. To address this a
comprehensive R&D study, co-ordinated by EPRI was performed to address these issues. A repair
guideline document was prepared based on the current state-of-the-art (This is not available in the
open literature). Secondly, a detailed survey was carried out to document industry experience and
practices with respect to weld repair. This is discussed further in the next section. Lastly a major
experimental program was conducted on repair welds to aged CrMo piping.
The tests have compared Shielded metal arc weld (SMAW) repairs with PWHT, Gas Tungsten arc
weld (GTAW) with PWHT and SMAW using the temperbead technique. The welds have been
evaluated prior to and after repair to study the effects of degradation on repairability, the effectiveness
of temperbead repairs and the remaining life achieved by the weld repair. The overall results of the
study indicated that service aged piping systems can be successfully repaired with or without PWHT
and that life extension by several decades may be achieved under design conditions.
Brett and Jones (Reference A1.6) reviewed the development of repair procedures without PWHT in
the power plant industry. Commercial pressures are now dictating that repairs without PWHT are
carried out as long as appropriate safety criteria are met. This includes an appraisal of the nature of
the repair that is required, consideration of the consequences of repair welding without PWHT, close
supervision of the repair welding and monitoring of the subsequent service performance of the
repaired plant.
A1.2.5 EPRI Survey
EPRI has carried out an industrial survey (Reference A1.7) on the weld repair technologies currently
used by utilities and repair organisations to extend the life of high temperature, high pressure
components. The responses that may be pertinent to the UK industry are related to here. The
components of most concern were steam turbine casing, piping and headers.
A1.5
Most of the utilities indicated that a cost-benefit analysis played a major role in their repair decision
process. The utilities usually rely on the original equipment manufacturer and/or specialist consultant
for repair methodologies. Interestingly, only 50% of the utilities that responded indicated that they
used some form of life assessment program or methodology to determine if and when repairs should
be performed. Most repair decisions were made on a case-by-case basis with no specific methodology
employed.
Most repairs are carried out in-situ, which is the preferred situation, again to reduce costs.
Recurrence of cracking was particularly observed where dissimilar weld metal was used. In headers
and piping, half of the reported cracking observed re-cracking within one year.
Over 70% of the utilities stated that repairs had been conducted without implementing PWHT, i.e.
temperbead techniques were employed. Grinding, machining or gouging were used for defect
removal. The SMAW welding process is the most common for weld repair.
A1.3 DISCUSSION
Defects in welded structures can occur during the fabrication process due to ‘workmanship’ or in-
service due to working conditions. During fabrication, BS5500 states that ‘unacceptable
imperfections shall be either repaired or deemed not to comply with this standard’. Repair welds have
to be carried out to an approved procedure and subjected to the same acceptance criteria as the
original weld. Thus all welds have to satisfy the requirements of the design specification before
acceptance by the purchaser or inspecting authority.
For defects found in-service there are no standard guidelines available for utilities to use to make a
decision on the need to carry out a weld repair. The industrial survey carried out by EPRI for utilities
in the United States has shown that utilities will rely on the original manufacturer or outside vendors
to assist on this decision. However, it is not clear that the assessment procedures used are consistent
or are indeed reliable. In the UK, the repair of welds appears to rely on in-house experience in the
absence of guidelines to follow. However, this review shows that re-cracking of repair welds still
occurs due to lack of understanding on why original defects have occurred and how they should be
repaired.
Whilst the decision to repair a defect may be aided using an assessment procedure the practical
considerations identified by Jones [A1.12] should also be considered. These show that repair welds
should be considered on a case-by-case behaviour, therefore a definitive set of ‘rules’ can not be
given. Instead, the guidelines need to be produced which provide good practice in assessing defects
in welds and the requirements for carrying out a ‘safe’ repair.
A number of references have been found illustrating the capabilities of performing a repair weld
without the need for PWHT. This was introduced by the half-bead technique defined in ASME XI
primarily for the nuclear industry. This has been superseded by other temperbead techniques, which
are all aimed at improving the properties within the weld HAZ, whilst saving time and costs by
precluding the time for PWHT. There is evidence that this method is employed by other industries in
the USA, but it is unclear on the use of this practice in the UK.
In the references associated with case studies and the performance of weld repairs, only a few
references have related to residual stresses. These papers have indicated that the magnitude of
residual stresses in repair welds can be of yield magnitude. The most recent advances in welding
simulation were presented at the IMechE conference (Reference A1.8) in November 1999. The
conference demonstrated the developments that had been made, mainly in the use of FE, to predict
A1.6
residual stresses. Sufficient confidence in numerical analysis needs to be demonstrated by
comparison with measurement methods.
When developing guidelines for the assessment of defects in repair welds sufficient advice needs to
be given to the user as to when residual stresses need to be considered in the assessment. Advice also
needs to be provided on when the user should use simple approximations of the residual stress pattern,
e.g. R6 residual stress compendium (Reference A1.9), or to use finite element analysis techniques to
predict the complex behaviour of the material during welding.
A1.4 RECOMMENDATIONS
The literature review has re-affirmed that an assessment procedure is required to enable users to
evaluate if a defect needs to be repaired. This needs to consider the magnitude of residual stresses,
not only in the as-welded condition but also after temperbead welding or PWHT.
Practical guidelines are also required which give guidance on how the weld repair should be carried
out and the necessary requirements that it needs to meet.
Further information needs to be sought from appropriate industrial companies in the UK in order to
ascertain their current practices dealing with weldment flaws.
A1.5 REFERENCES
A1.1 British Standard BS 55000:1994, ‘Specification for unfired fusion welded pressure vessels’.
A1.2 K Prosser and P J Boothby, ‘Weld repair of pressurised equipment’, Conference
Proceedings, Developments in Materials Usage for Pressure Systems, IMechE, November
1999.
A1.3 R Viswanathan and D W Gandy, ‘Performance of repair welds on aged Cr-Mo piping girth
welds’, Conference Proceedings, International Conference on Integrity of High Temperature
Welds, 3-4 November 1998, IOM Communications, ISBN 1 86058 149 8.
A1.4 R Viswanathan, D W Gandy and S Findlan, ‘Weld repair of 1-¼Cr-½Mo steel piping girth
welds’, PVP-Volume 388, Fracture, Design Analysis of Pressure Vessels, Heat Exchangers,
Piping Components, and Fitness for Service –1999, ASME 1999 p 373-382.
A1.5 R Viswanathan, D W Gandy and S Findlan, ‘Weld repair of 2-¼Cr-1Mo service-aged header
welds’, Journal of Pressure Vessel Technology, Volume 121, November 1999 p345-352.
A1.6 S J Brett, D J Abson and R L Jones, ‘The repair welding of power plant without post-weld
heat treatment’, Conference Proceedings, International Conference on Integrity of High
Temperature Welds, Professional Engineering Publications, ISBN 1 86058 149 8, 1998.
A1.7 D W Gandy, S J Findlan and R Viswanathan, ‘Weld repair of steam turbine casings and
piping – An industry survey’, PVP-Volume 388, Fracture, Design Analysis of Pressure
Vessels, Heat Exchangers, Piping Components, and Fitness for Service –1999, ASME 1999
p 355-359.
A1.8 Recent Advances in Welding Simulation, Proceedings of the Conference organised by the
Materials and Mechanics of Solids Group of the IMECHE, IMECHE headquarters, 26
November 1999.
A1.7
A1.9 S K Bate, ‘Compendium of residual stress profiles for R6’, AEAT/NJCB/000006/00, March
2000.
A1.8
Tab
le A
1.1
A
pp
licati
on
Ch
ara
cte
risti
cs o
f A
s-W
eld
ed
Rep
air
Tech
niq
ues [
A1.1
2]
C
on
ven
tio
nal
Bu
tter
ing
H
alf-
Bea
d
Tw
o-L
ayer
S
ix-L
ayer
Mo
de
of
app
lica
tio
n
SM
A
SM
A
Mai
nly
SM
A b
ut
mec
han
ised
GM
A p
oss
ible
Mec
han
ised
GT
A o
nly
Deg
ree
of
HA
Z
mic
rost
ruct
ura
l co
ntr
ol
Hig
h r
efin
emen
t p
oss
ible
(80
% m
ax)
lim
ited
tem
per
ing.
Hig
h r
efin
emen
t p
oss
ible
(9
5%
max
) li
mit
ed t
emp
erin
g
Fu
ll r
efin
emen
t p
oss
ible
, li
mit
ed
tem
per
ing u
sin
g t
wo
-lay
ers.
Mo
re e
ffec
tive
tem
per
ing p
oss
ible
usi
ng t
hre
e la
yer
s.
Fu
ll r
efin
emen
t an
d
tem
per
ing p
oss
ible
.
Pro
ced
ure
Co
ntr
ol
Lo
w t
ole
ran
ce
Hig
h w
eld
bea
d o
ver
lap
(60
%)
must
be
ob
tain
ed
Mo
der
ate
tole
ran
ce
Gri
nd
ing t
ole
ran
ces:
- 0.6
mm
+ 1
.1 m
m
Go
od
to
lera
nce
to
wel
d b
ead
over
lap
an
d w
eld
ing p
aram
eter
s
(typ
ical
ly ±
15
%)
Hig
hly
to
lera
nt
to
var
iati
on
s in
wel
din
g
par
amet
ers
eg.
±3
0%
on
wir
e fe
ed s
pee
d
Pro
du
ctio
n F
acto
rs
Rel
ativ
ely e
asil
y a
nd
rap
idly
app
lied
Co
ntr
ol
of
gri
nd
ing i
s d
iffi
cult
N
eed
fo
r la
rge
rep
air
pre
par
atio
ns.
D
etai
led
wel
din
g
tria
ls a
nd
wel
der
tra
inin
g m
ay b
e
nee
ded
Slo
w a
nd
co
stly
.
Su
itab
le f
or
rem
ote
op
erat
ion
. S
imp
le r
epai
r
wel
d g
eom
etri
es o
nly
e.g
.
pip
ewo
rk
A1.9
ANNEX 1 OF APPENDIX 1
LIST OF REFERENCES FROM LITERATURE REVIEW
Annex 1.1 Rybicki E F and Stonesifer R B, ‘Residual stresses at weld repairs in pressure vessels’,
Report NUREG-CR-0078 (PB-281853 / 25L)9, Publ. Washington DC, Nuclear
Regulatory Commission, Division Of Reactor Safety Research, April 1978.
Annex 1.2 Rybicki E F and Stonesifer R B, ‘Development of a computational model for residual
stresses due to weld repairs in pressure vessels’, Repair Aspects and Procedures.
Proceedings, International Working Group on Reliability of Reactor Pressure
Components Technical Committee Meeting, Riso, Denmark, 13-15 Sept.1978. Report
IWG-RRPC-79 / 1. Publ. Vienna, Austria, International Atomic Energy Agency
(IAEA), July 1979, pp221-231.
Annex 1.3 Rybicki E F and Stonesifer R B, ‘An analysis procedure for predicting weld repair
residual stresses in thick walled vessels’, Transactions of the ASME, Journal of
Pressure Vessel Technology, Vol.102, No.3. Aug.1980, pp.323-331.
Annex 1.4 Smith G C and Holz P P, ‘Repair induced residual stresses in thick walled steel
pressure vessels’, ORNL / NUREG / TN-153 (NUREG / CR-0093). Publ. Oak Ridge,
Tenn. 37830; Oak Ridge National Laboratory, June 1978, 130pp.
Annex 1.5 Bloom J M, ‘An analytical assessment of the effects of residual stresses and fracture
properties on service performance of various weld repair processes’, Transactions of
the ASME, Journal of Pressure Vessel Technology, Vol.103, No.4. Nov.1981, pp373-
379.
Annex 1.6 Ueda Y, Kim Y C, Garatani K, Yamakita T and Bang H S, ‘Mechanical characteristics
of repair welds in thick plate. Report 1: Distributions of three-dimensional welding
residual stresses and plastic strains and their production mechanisms’, Transactions of
JWRI, Vol.15, No.2. Dec.1986, pp359-368.
Annex 1.7 Oddy A S, Goldak J A and Mcdill J M J, ‘Transformation plasticity and residual
stresses in single-pass repair welds’, Weld Residual Stresses and Plastic Deformation.
Symposium during 1989 Pressure Vessels and Piping Conference and Exhibition,
Honolulu, HI, 23-27 July 1989.
Annex 1.8 Leggatt R H, ‘Computer modelling of transverse residual stresses in repair welds’,
Welding Journal, Vol.70, No.11. Nov.1991, pp299s-310s.
Annex 1.9 Feng Z, Wang X L, Spooner S, Goodwin G M, Maziasz P J, Hubbard C R and Zacharia
T, ‘A finite element model for residual stress in repair welds’, Residual Stresses in
Design Fabrication, Assessment and Repair, ASME 1996 Pressure Vessels and Piping
Conference, Montreal, Canada, 21-26 July 1996. Ed: R W Warke. PVP Vol.327. Publ.
New York, NY 10017, USA; American Society of Mechanical Engineers (ASME),
1996. ISBN 0-7918-1774-1, pp119-125.
A1.10
Annex 1.10 Chowdhury S G, Mukhopadhyay N K, Das G, Das S K and Bhattacharya D K, ‘Failure
analysis of a weld repaired steam turbine casing’ Engineering Failure Analysis, Vol. 5,
No. 3, 1998, pp205-218.
Annex 1.11 Corbit R B and French S M, ‘ Weld repair adds life to power plant turbine’, Welding
Journal, Vol.76, No.1. Jan.1997, pp51-55.
Annex 1.12 Jones R L, ‘Overview of weld repair techniques’, Inspection, Assessment and Repair of
Welded Structures and Components. Proceedings, 10th Annual North American
Welding Research Conference, Columbus, OH, USA, 3-5 Oct.1994. Publ: Abington,
Cambridge CB1 6AH, UK; Abington Publishing, (1994). Session 6. 15pp
Annex 1.13 Goins W and Merrick E, ‘Weld repair of Heavy Section Steel Technology Program
vessel V-7’, DVS Berichte, No.52. 1978. Proceedings, Conference, Welding in
Nuclear Engineering, Hamburg, 28-29 Nov.1978. Publ. Dusseldorf, W.Germany;
Deutscher Verband fur Schweisstechnik, 1978. ISBN 3-87155-353-0, pp164-167.
Annex 1.14 Canonico D A and Whitman G D, ‘Evaluations of half-bead weld repair procedures
with thick-wall pressure vessels’ Jnl. Criteria for Preventing Service Failures in Welded
Structures. Papers presented at JWS 3rd
International Symposium, Tokyo, 26-28 Sept.
1978. Publ. Tokyo, Japan Welding Society, 1978. Paper 3 JWS-24, pp197-202.
Annex 1.15 Alberry P J and Feldstein J G, ‘Weld repair of light water reactor pressure boundary
components’, Welding Journal, Vol.66, No.12. Dec.1987, pp33-42.
Annex 1.16 Moore D E, ‘Weld repair of carbon-moly (molybdenum) coke drums without postweld
heat treatment’, WRC Bulletin 412, 1996, pp70-76.
Annex 1.17 Slater G, ‘The effect of repair welds on service performance’, Welding Journal, Vol.64,
No.3. Mar.1985, pp22-29.
Annex 1.18 Booth G S, Threadgill P L and Wylde J G, ‘Significance of repair welds in service
failures’, ISTFA '87: Advanced Materials. Proceedings, International Symposium,
Testing and Failure Analysis, Los Angeles, CA, 9-13 Nov.1987. Publ. Metals Park,
OH 44073, USA, ASM International, 1987. ISBN 0-87170-312-2, pp.305-308.
Annex 1.19 Wylde J G, Threadgill P L and Booth G S, ‘Service failures associated with weld
repairs’, Weld Failures. Proceedings, International Conference, London, 21-24
Nov.1988. ed: J. D. Harrison. publ: Abington, Cambridge, UK; The Welding Institute;
1989.ISBN 0-85300234-7. Paper 27, pp11-17.
Annex 1.20 Lai M O and Fong H S, ‘Fatigue performance of repaired pipeline steel welds’, Journal
of Materials Science Letters, Vol.7, No.12. Dec.1988, pp1353-1354.
Annex 1.21 Evans C, Apps R L and Fenn R, ‘The performance of structural steel after multiple
weld repair’, International Journal for the Joining of Materials, Vol.10, No.3-4.
Dec.1998, pp63-68.
Annex 1.22 Viswanathan R, Gandy D and Findlan S, ‘Performance of repair welds on service-aged
2.25%Cr-1%Mo girth weldments’, Transactions of the ASME, Journal of Pressure
vessel Technology, Vol. 119, November 1997, pp414-422.
A1.11
Annex 1.23 Minnick W H, ‘Weld repair’, Gas Tungsten Arc Welding Handbook. Publ. South
Holland, IL 60473, USA, Goodheart-Willcox Co., Inc. 1996, ISBN 1-56637-206-2.
Chapter 23, pp235-239.
Annex 1.24 Veron P, ‘Weld repair and life extension’, Engineering Design in Welded
Constructions. Proceedings, International Conference, Madrid, Spain, 7-8 Sept.1992.
Publ. Oxford OX3 0BW, UK; Pergamon Press for International Institute of Welding
(IIW); 1992. ISBN 0-08-041910-0, pp231-239.
Annex 1.25 Smith E, ‘The stresses associated with a crack in a repair weld’, International Journal
of Fracture, Vol.53, No.4. Feb.1992. ppR59-R62
A1.12
APPENDIX 2
MICROSTRUCTURAL EXAMINATION OF WELD SAMPLES UNDERTAKEN BY
SHEFFIELD UNIVERSITY METALS ADVISORY CENTRE (SUMAC)
A2. i
A2.1 SAMPLES PROVIDED
(a) One, approximately 10 mm thick, slice cut from a weld test piece of a double-V
preparation butt weld in 40 mm plate. Designated SISD/SK/1944/3
(b) One, approximately 14 mm thick, slice cut from a weld test piece of a double-V preparation butt weld in 40 mm plate, with a simulated weld repair. Designated SISD/SK/1944/8
A2.2 NOMENCLATURE
In this Appendix the welds will be treated as orientated in the macrographs of Figure
A2.1. The larger V-preparation is at the top and this is designated 'Weld 1'. The smaller
V- preparation is at the bottom and this is designated 'Weld 2' (in the case of sample
SISD/SK/1944/8 this is the weld repair). References to "left hand side' (LHS), 'right
hand side' (RHS), top and bottom are as viewed in Figure A2.1. The final weld runs, on
either side of the plate, which immediately abut the plate surfaces will be designated as
'toe' welds
A2.3 MACROSECTIONS AND BRITISH STANDARD HARDNESS TESTS
One surface of each slice was ground, polished and etched to reveal the weld profile, as
illustrated in Figure A2.1. The welds were clearly sound with no evidence of inter-run
lack of fusion or porosity.
Hardness measurements were made on each sample in accordance with BS EN 288-
3:1992/A1:1997, section 7.4.5 and using the "narrow HAZ" configuration shown in
figure 10 of the standard. The results of these tests are tabulated below.
SISD/SK/1944/3: Hardness (HV10) Tests according to BS EN 288-3
position matrix HAZ Weld HAZ Weld
Top 162, 165, 206,248*,266* 227,209, 254*, 237*, 165:151, 148
167 199, 213, 235, 187
229
Root 163, 195, 201,218,221*, 236, 232, 257*, 240*, 181, 184, 176
187 246*, 216* 231 222*, 248,
209
Bottom 165, 187,
219
228, 274* 281* 242, 253,
259
299*, 310*,
253, 195
179, 168, 154
A2. 1
SISD/SK/1944/8: Hardness (HV10) Tests according to BS EN 288-3
position matrix HAZ Weld HAZ Weld
Top 156, 154, 174 245, 265*, 234, 227, 270*, 261*, 176, 207, 159
247*, 251* 214, 237, 299 274*, 222
Root 161, 179, 177 191, 199, 229, 234, 230 211*, 200*, 177, 177, 163
231*, 222*, 230*, 198,
241* 211
Bottom 159, 162, 176 325*, 335*,
318*, 213
234, 216, 247 318*, 339*,
308*, 268
175, 166, 159
* hardness test within 0.5 mm of fusion line
This hardness survey is within the permitted limits as specified in Table 2 of BS EN 288-
3:1992A1:1997.
A2.4 MICROSTRUCTURE
The Heat Affected Zone (HAZ) microstructure follows the typical pattern of a multi-pass
weld with a zone of grain growth at the fusion line, backed by a band of recrystallization
followed by a spheroidized/tempered zone before the unaffected matrix. Each weld pass
imposes a further HAZ on the underlying weld (and it's HAZ) leading to a refined
microstructure at the overlap.
The grain growth and recrystallization zones have a microstructure of grain boundary
and Widmanstatten ferrite (the amount depending on the local austentising temperature
and subsequent cooling rate) in a transformed matrix. In carbon and low alloy steels of
this type, the matrix can be a mixture of the phases ferrite, pearlite bainite and
martensite.
With the exception of the 'toe' welds, the grain growth zones in all the weld passes, in
both samples, were similar, with significant amounts of pro-eutectoid ferrite in a
relatively coarse matrix. Figure A2.2 illustrates a typical example of the microstructure,
which is believed to be bainitic in origin.
In sample SISD/SK/1944/8, Weld 2 both the LHS and RHS 'toe' welds were similar as
illustrated in Figure A2.3. There was less pro-eutectiod ferrite and a much coarser
matrix structure. It is believed that this could be a bainite/ martensite mixture. In Weld
1 of the same sample, more ferrite was in evidence and the matrix was a mixture of the
coarse and fine microstructures in Figures A2.2 and A2.3.
In sample SISD/SK/1944/3, all the 'toe' welds were similar, (for both Weld 1 and Weld
2) with pro-eutectoid ferrite and a mixed matrix structure as described in the above
paragraph. The essential difference between the two welds of this sample, was that less
ferrite was evident in the 'toe' welds of Weld 2.
A2. 2
A2.5 MICROHARDNESS SURVEYS
An informal and unrecorded survey was made of the HAZ regions in both samples in
order to assess the areas which may be significant in terms of high hardness. This survey
indicated that, with the exception of the 'toe' welds, all HAZs, in all zones, were well
below any limiting hardness value. The 'toe' welds on Weld 1 in both samples indicated
that, whilst hardness values may be a little higher in the grain growth zone, they would
still fall well within specification.
In sample SISD/SK/1944/8, the indications were that hardness values could be high in
the grain growth zone of the 'toe' welds of Weld 2. For sample SISD/SK/1944/3, it
appeared that hardness values in the grain growth zone of the 'toe' welds could be high,
but not attaining the levels in sample SISD/SK/1944/8.
The survey also showed that, whenever ferrite was visible in the area of microstructure
under test, the hardness value would be low. If ferrite were not visible in the
transformation structure (the centres of grains) then the hardness value would be higher,
but the optical appearance of the phase would be no guarantee that the hardness value
measured would be in a category which could be described as a 'hard spot'.
Recorded hardness measurements were taken and these are given in the attached Tables.
These measurements were mostly confined to the grain growth zones of the HAZs and
specifically sited to avoid visible ferrite. In Tables A2.1 and A2.2, where hardness is
falling rapidly the trace is entering the recrystallized zone. In general these traces
(Tables A2.1 and A2.2) follow the accepted pattern of high values close to the fusion line
which decay gradually into and beyond the recrystallized zone. In Tables A2.3 and
A2.4, the hardness trace follows closely with the fusion line and clearly demonstrates
that high hardness values ('hard spots') are associated with the HAZ of the toe welds on
the lower weld of both samples.
A2.6 MICROANALYSIS USING ENERGY DISPERSIVE X-RAYS
X-ray mapping to demonstrate segregation of the constituent elements of a steel by use
of the scanning electron microscope and energy dispersive x-ray analysis is a long
process with uncertain results. The different areas of the HAZ were assessed by area
scanning for compositional make-up. This process is an order of magnitude quicker,
although the results may be equally uncertain. The most important element, which will
affect hardness is carbon, and this cannot be quantitatively assessed by this technique.
Area scans (approximately 10 x 15 microns) were made in known hard and soft zones in
the grain growth area of the HAZ and an equivalent area, just outside the HAZ (in the
unaffected matrix). The results are given in Tables A2.6 and A2.7.
At this stage, the analytical errors were considered. For the minor elements - chromium,
nickel, copper and molybdenum - the analysis program gave 2sigma as approximately
0.15 wt%, indicating that the majority of the values given were unreliable. Our scanning
electron microscopist estimated that for manganese the error would be at least plus or
minus 0.1 and for silicon about plus or minus 0.05. In light of this, the prospect of
producing a contour map of element concentration, using a grid of analysis spots to cover
a selected area, seemed inappropriate. Furthermore, these errors assume a perfectly
A2. 3
polished surface. Some etching was required in order to identify the fusion zone and, in
analytical terms, this is regarded as undesirable. We are advised that electron probe
microanalysis, which could include carbon analysis, is the only possible route which
might give results of any value.
No more scanning microscopy was carried out.
A2.7 COMMENT
BS EN 288-3 prescribes the areas on which hardness measurements should be made.
These are precisely in the regions where the weld may encounter more rapid cooling
rates than elsewhere. The toe welds cannot be tempered by any further weld runs and the
same may apply in part to the root run. The only tempering that can occur is when
transformation temperatures, within the alloy, are high such that some auto-tempering
can occur after transformation whilst the weld cools to ambient.
With the two samples, the root run area is completely refined and tempered and contains
no 'hard spots'. The macro and micro-hardness testing indicate that the 'toe' welds in
weld 2 of both samples have higher hardness values than elsewhere. The microstructure,
whilst not exhibiting defined 'pools' of hard phase, do show structural refinement and
reductions in pro-eutectoid ferrite that could explain the increased hardness.
Microhardness measurements should be treated with caution. There is not yet a standard
which provides for absolute values when using small indentation loads. For this exercise
we tested calibrated 300 HV10 and 450 HV10 hardness blocks for the readings obtained
at HV300g. We found that the values obtained at the low load were at least 20 hardness
'points high. It would be wise therefore, to regard the microhardness data as comparative.
Both weld samples pass the hardness requirement (HV10) and some potentially high
hardness values obtained by microhardness should not detract from this, particularly as
they are in the areas where this might be expected and are not found elsewhere in the
weld.
A2. 4
Table A2.1 Microhardness traces (HV300g) within 2mm of the plate surface in the grain growth zone of the ‘toe’ welds and running parallel to the plate
surface (d is distance from the fusion line)
A2. 5
Table A2.2 Microhardness traces (HV300g) within 2mm of the plate surface in the grain growth zone of the ‘toe’ welds and
running parallel to the plate surface (d is distance from the fusion line)
A2. 6
Table A2.3 Microhardness traces (HV300g) along the HAZs of weld 2 and within 0.5mm of the fusion line Sample SISD/SK/1944/3
(d is distance from surface around the HAZs)
A2. 7
Table A2.4 Microhardness traces (HV300g) along the HAZs of weld 2 and within 0.5mm of the fusion line Sample SISD/SK/1944/8
(d is distance from surface around the HAZs)
A2. 8
Table A2.6 Microanalysis of HAZ (grain growth zone) and Matrix of weld runs in Weld 2 of Sample SISD/SK/1944/3
A2. 10
Table A2.7 Microanalysis of HAZ (grain growth zone) and Matrix of weld runs in Weld 2 of Sample SISD/SK/1944/8
A2. 11
Figure A2.2 Typical Microstructure in the grain growth zones of the weld pass HAZs
(excluding ‘toe’ welds)
Figure A2.3 Typical Microstructure in the grain growth zones of the ‘toe’ weld HAZ: SISD/SK/1944/8 – Weld 2
A2. 13
Printed and published by the Health and Safety ExecutiveC30 1/98
Printed and published by the Health and Safety ExecutiveC1.10 05/04