24605520 welding science and technology
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ISBN (13) : 978-81-224-2621-5
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Classification of Welding Process
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Introduction to Welding Technology 3
1.2.2 Surface Contaminants
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Solidstate
weldingISSWI
Arcwelding
(AW)
Brazing(B)
Weldingprocesses
Soldering(S)
Otherwelding
Resistancewelding(RW)
Oxyfuelgas
welding(OFW)
Thermalspraying(THSP)
Alliedprocesses
Adhesivebonding(ABD)
Oxygencutting(OC)
Thermalcutting(TC)
Arccutting(AC)
Othercutting
atomic hydrogen welding.........AHWbare metal arc welding............BMAWcarbon arc welding..................CAW
–gas.....................................CAW.G–shielded..............................CAW.S–twin.....................................CAW.T
electrogas welding...................EGWflux cored arc welding..............FCAW
coextrusion welding............CEWcold welding........................CWdiffusion welding.................DFWexplosion welding...............EXWforge welding......................FOWfriction welding....................FRWhot pressure welding..........HPWroll welding..........................ROWultrasonic welding...............USW
dip soldering........................OSfurnace soldering.................FSinduction soldering...............ISinfrared soldering.................IRSiron soldering.......................INSresistance soldering.............RStorch soldering.....................TSwave soldering.....................WS
flash welding.....................FWprojection welding.............PWresistance seam welding..RSEW
–high frequency............RSEW.HF–induction......................RSEW.I
resistance spot welding.....RSWupset welding....................UW
–high frequency............UW.HF–induction......................UW.I
electric arc spraying........EASPflame spraying.................FLSPplasma spraying..............PSP
chemical flux cutting...........FOCmetal powder cutting..........POCoxyfuel gas cutting..............OFC
–oxyacetylene cutting.....OFC.A–oxyhydrogen cutting.....OFC.H–oxynatural gas cutting..OFC.N–oxypropane cutting.......OFC.P
oxygen arc cutting..............AOCoxygen lance cutting..........LOC
gas metal arc welding.............GMAW–pulsed arc.........................GMAW.P–short circuiting arc.............GMAW.S
gas tungsten arc welding........GTAW–pulsed arc.........................GTAW.P
plasma arc welding.................PAWshielded metal arc welding.....SMAWstud arc welding......................SWsubmerged arc welding...........SAW
–series.................................SAWS
arc brazing......................ABblock brazing..................BBcarbon arc brazing.........CABdiffusion brazing.............DFBdip brazing......................DBflow brazing....................FLBfurnace brazing..............FBinduction brazing............IBinfrared brazing...............IRBresistance brazing..........RBtorch brazing...................TB
electron beam welding......EBW–high vacuum................EBW.HV–medium vacuum..........EBW.MV–nonvacuum.................EBW.NV
electrostag welding...........ESWflow welding......................FLOWinduction welding..............IWlaser beam welding...........LBWpercussion welding...........PEWthermit welding..................TW
air acetylene welding......AAWoxyacetylene welding.....OAWoxyhydrogen welding.....OHWpressure gas welding.....PGW
air carbon arc cutting..........AACcarbon arc cutting...............CACgas metal arc cutting..........GMACgas tungsten arc cutting.....GTACmetal arc cutting.................MACplasma arc cutting..............PACshielded metal arc cutting..SMAC
electron beam cutting..........EBClaser beam cutting...............LBC
–air...................................LBC.A–evaporative....................LBC.EV–inert gas.........................LBC.IG–oxygen...........................LBC.O
Fig. 1.1 Master Chart of Welding and Allied Processes
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1.2.3 Protecting Metal From Atmospheric Contamination
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C2H2 + O2 → 2 CO + H2 2CO + O2 = 2CO2 + 570 kJ/mol of acetylene
Total heat liberated by 1st reaction H2 + 1
2O2 = H2O + 242 kJ/mol
(227 + 221) = 448 kJ/mol C2H2 Total heat by second reaction = (570 + 242) = 812 kJ/mol of C2H2
Total heat supplied by the combustion = (448 + 812) = 1260 kJ/mol of C2H2
Fig. 2.2 Schematic sketch of oxyacetylene welding torch and gas supply [1].
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2.2.2 Submerged Arc Welding
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2.3.4 Seam Welding
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2.3.7 Percussion Welding
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Fig. 2.17(a) Using a high-frequency current to heat the interface in pressure welding
Review of Conventional Welding Processes 25
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2.4.3 Ultrasonic Welding
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Laminatedcore
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Fig. 3.10 Moving-coil transformer Fig. 3.11 Moveable-core transformer
46 Welding Science and Technology
Mainsinput
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3.3. 2 Direct-Current Welding Power Sources
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Block diagram
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Fig. 3.15 Transisterised power supply unit
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54 Welding Science and Technology
3.7.4 Radiation Losses
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Electrode
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Metal transfer in the spray mode of the pulsed GMAW welding Process
Electrode
Molten metalglobules formspatter
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Fig. 3.19 Horizontally held electrode wires are shown producing globularand spray transfer during gas-metal-arc welding
Welding Science 57
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Fig. 3.19 (c) Dip transfer in MAGS welding
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60 Welding Science and Technology
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Fig. 3.21 (a) Output current wave form of the pulsed current power supply;Metal transfer sequence is also shown
Low-current arc keepsweld pool molten.
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Fig. 3.21 (b) Pulsed transfer in MAGS welding
Welding Science 61
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86 Welding Science and Technology
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88 Welding Science and Technology
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90 Welding Science and Technology
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94 Welding Science and Technology
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96 Welding Science and Technology
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98 Welding Science and Technology
Liquid Liquid
Initial crystals Solid grains Solid grains withgrain boundaries
(a) Initial crystal formation (b) Continued solidification (c) Complete solidification
Fig. 5.1 Pattern of solidification of metals
Fig. 5.2 The three most common crystal structures in metals and alloys. Left: facecentred cubic (FCC) Centre: Body centred cubic (BCC) and right: hexagonal closepacked (HCP).
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Fig. 5.3 Solution. Left: interstitial alloying; Right: Substitutional solid solution
Thermal and Metallurgical Considerations in Welding 99
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100 Welding Science and Technology
1600
1400
1200
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Sub-zero temperature range
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Max. hot working temp.
°C
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Fig. 5.4 Iron-carbon phase diagram
Thermal and Metallurgical Considerations in Welding 101
5.1.4 Critical Range
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102 Welding Science and Technology
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Thermal and Metallurgical Considerations in Welding 103
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°C °F
800
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100
1400
1200
1000
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11
32
38
40
40
41
43
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55
57
66
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Time of transformation
Seconds Minutes Hours
1 2 4 8 15 30 –1 2 4 8 15 30 1 2 4 8 15
M temperaturef
Martensite
Martensite formsinstantly from austeniteon cooling
Martensite formsinstantly from austeniteon cooling
M temperatures
Austenite
Bainite forming from austenite
Bainite forming from austenite
Featherybainite
Fine pearlite
Nose
Austenite
A temperature1Starts Ends
Transformationat 705 °C(1300 °F)
Austenite
Coarse pearlite
Pearlite
Bainite
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Roc
kwel
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rdne
ssof
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tem
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Fig. 5.5. The TTT diagram for the transformation of austenitein a euctectoid (0.8% carbon) plain carbon steel.
Ms = Martensite start temperature
Mf = Martensite finish temperature
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104 Welding Science and Technology
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Fig. 5.6 (a) Temperature variation with time at
various distances from heat source
Thermal and Metallurgical Considerations in Welding 105
Heat-affected zones
Weld
HeatHeat HeatHeatHeatHeat
Meltingpoint
°C
Hea
ting
Cooling
°C
Hea
ting
Cooling
Time Time
Lowest temperaturefor metallurgicalchange
(b) Fusion boundary (c) Outer boundaryof heat-affectedzone
Fig. 5.6 Variation of temperature with time at different distancesfrom the heat source (b) fusion boundary (c) outer boundary of HAZ
5.2.1 Weld-Metal and Solidification
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106 Welding Science and Technology
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Fig. 5.7 Columnar structure of welds Left: Shallow weld;Right: Deep pear-shaped weld.
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Thermal and Metallurgical Considerations in Welding 107
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108 Welding Science and Technology
5.2.5 Macro and Microstructure of Weld, Heat–Affected Zone (HAZ) and Parent Metal
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Fig. 5.9 Characteristics of welded joints in pure metals.
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Thermal and Metallurgical Considerations in Welding 109
Precipitation hardened Overaged
Original precipitationhardened metal
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Strength
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Heat affectedzone
Fig. 5.10 Characteristics of welded joints in precipitation hardened alloy
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110 Welding Science and Technology
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Thermal and Metallurgical Considerations in Welding 111
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1
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1 70000 psi yield strength steel2 500003 30000
70000
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Fig. 5.11. Effect of temperature and time or stress-relief
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112 Welding Science and Technology
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114 Welding Science and Technology
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Fig. 5.12 Shrinkage during solidification
Weld (hot)
On cooling,
tries to go to this
Plates(cold)
Compressive Compressive
Tensile
Weld is stretched by plates.Tensile stresses in weld.Compressive stresses in plateon either side of weld.
Fig. 5.13 Deformation of a weld metal element during cooling.
Thermal and Metallurgical Considerations in Welding 115
3 mm
cb
a
5 mm
45°
Direction oftransverseshrinkage
t = 12 mm
Fig. 5.14 Estimation of transverse shrinkage in ‘T’ butt joint
w
Single-V Double-V
Averagewidth
Fig. 5.15 Transverse shrinkage in ‘V ’ butt welds.
5.4.3 Transvers Shrinkage
& #
5 5
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116 Welding Science and Technology
)"*+,&-.'
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5.4.4 Angular Distortion and Longitudinal Bowing
(% " #% %%"
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# "# # %
%% '
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Afterwelding
Original
(a) Changes in shape resulting fromshrinkage which is uniform throughout the thickness
(b) Asymmetrical shrinkage tends toproduce distortion.
Fig. 5.16 Change in shape and dimensions in butt-welded plate.
2 % A8: #
5 %
Thermal and Metallurgical Considerations in Welding 117
& #
2 "# % #
( ")
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Original preparation
Neutralaxis
(a)
Original preparation
2t/32ndside
1stsidet/3
t(b)
(c)
10° 10°
Fig. 5.17 Edge preparation designed to reduce angular distortion
(a) Double-V joints balance the shrinkage so that more or less equal amounts of contractionoccur on each side of the neutral axis. This gives less angular distortion than a single ‘V’.
(b) It is difficult to get a completely flat joint with a symmetrical double ‘V’ as the first weld runalways produces more angular rotation than subsequent runs; hence an asymmetrical prepa-ration is used so that the larger amount of weld metal on the second side pulls back thedistortion which occurred when the first side was welded.
(c) Alternatively, a single-U preparation with nearly parallel sides can be used. This gives anapproach to a uniform weld width through the section.
118 Welding Science and Technology
Direction of welding
Longitudinaldistortion
Fig. 5.18 Longitudinal bowing or distortion in a butt joint
12
34
56
25
36
41
Fig. 5.19 Sequences for welding short lengths of joint to reduce longitudinal bowing
Longitudinla distortio
n
Fig. 5.20 Longitudinal bowing in a fillet-welded ‘T’ joint
(a) Distortion causedby fillet weld
(b) Use of presetting to correctdistortion in fillet welded 'T' joint
1st weld2ndweld
1 3 2
(c) Distortion offlange
1 = plate centre-line beforewelding
2 = plate centre-line afterfirst weld
3 = plate centre-line aftersecond weld
Fig. 5.21 Distortion in fillet welding of ‘T’ joints
Thermal and Metallurgical Considerations in Welding 119
%# #
5# % %#
%$ ' # 5% %
B8: %
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5.4.5 Effect of Heat Distribution
)#
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5.4.6 Residual Stresses
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120 Welding Science and Technology
% " "" #
" # %
( ' "
"% " 5#%#
#, "' 5%
WeldYieldstress
Tensilestress
Compressivestress
0
Distance fromweld centre-line
Fig. 5.22 Distribution of residual stresses in a butt-welded joint
2 ", %#
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Thermal and Metallurgical Considerations in Welding 121
5.4.7 Stress Relieving
F "% " 5
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122 Welding Science and Technology
t
R
Heated band
Tem
pera
ture
q
q2
5 Rt2
5 Rt2
Weldcentre-line
0
Heated-band width 5 RtR =t =
=q
radius of pipewall thicknessstress relievingtemperature
Fig. 5.23 Typical specification for temperature distribution duringlocal stress relief of welded butt joints in pipe
) '"%'
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124 Welding Science and Technology
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Analytical and Mathematical Analysis 125
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Fig. 6.1 Plate geometry for calculating the heat input rate
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126 Welding Science and Technology
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Analytical and Mathematical Analysis 127
Travel speed v
Solidified weld bead
WHeat source
H
Y Z
2B
Moving co-ordinate (W, Y, Z).
Fig. 6.2
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128 Welding Science and Technology
) 4"!$"
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Analytical and Mathematical Analysis 129
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130 Welding Science and Technology
Three dimensional heat flow > 0.9t
Intermediate condition 0.6 < < 0.9t
Two dimensional heat flow < 0.6t
Fig. 6.3 Relative plate thickness factor τ for cooling rate calculations
8559
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Analytical and Mathematical Analysis 131
72 L #
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132 Welding Science and Technology
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Examples for Revision
, 5"
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Analytical and Mathematical Analysis 133
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134 Welding Science and Technology
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135
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7.1.1 Composition of Cast Irons
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7.1.2 Oxy-Acetylene Welding of Gray and Nodular Cast Irons
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136 Welding Science and Technology
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Welding of Materials 137
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138 Welding Science and Technology
800
700
600
500
400
3000.3 0.4 0.5 0.6
Carbon equivalent %
Ulti
mat
ete
nsile
stre
ngth
, MP
a
Normalised andtempered
Water quenchedand tempered
API X65
Fig. 7.1 (a) Effect of carbon equivalent on UTS of X65 pipe steel.(R.G. Baker, Proc. Rosenhain Centinary Conf., Royal Society, 1975)
700
600
500
400
300
2000.3 0.4 0.5 0.6
Carbon equivalent %
Normalised andtempered
API X65
Water quenchedand tempered
Yie
ldst
reng
th,M
Pa
Fig. 7.1 (b) Effect of carbon equivalent on YS of X65 pipe steel.(R.G. Baker, Proc. Rosenhain Centinary Conf., Royal Society, 1975)
Welding of Materials 139
340
320
300
280
260
240
2200.1 0.15 0.2
Pcm
HA
Zha
rdne
ss
X with Bo without B
C = 0.010.04
Fig. 7.2 Effect of Pcm on HAZ hardness for low carbon pipe steel
'
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89 89 89
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140 Welding Science and Technology
*2809
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Welding of Materials 141
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AusteniteAustenite
A+MA+M
MartensiteMartensite
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4+F4+F
No ferrite
No ferrite 5%
ferrite
5%ferri
te
10%ferrit
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e
20%ferrit
e
20%ferrit
e
40% ferrite
40% ferrite
80% ferrite
80% ferrite
100% ferrite100% ferrite
FerriiteFerriiteM
2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40
3028262422201816141210
86420
Chromium equivalent=% Cr+%Mo+1.5×%Si+0.5×%Cb+5×%V+3×%AlNie
quiv
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+0.
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0.21
/0.2
5or
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whe
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0.26
/0.3
5
Fig. 7.3 Schaeffler diagram
142 Welding Science and Technology
AusteniteAustenite
SchaefflerA+M line
SchaefflerA+M line
WRC
Ferrite
number 0
WRC
Ferrite
number 022
44 5566
881010
12121414
16161818
0%ferri
te
0%ferri
te
2%ferri
te
2%ferri
te
4%ferri
te
4%ferri
te
5%ferri
te
5%ferri
te
6%ferri
te
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te
7.6%ferri
te
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te
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te
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te
10.7%ferri
te
12.3%ferri
te
12.3%ferri
te
13.8%ferri
te
13.8%ferri
te
Austenite+ferriteAustenite+ferrite
16 17 18 19 20Chromium equivalent = % Cr+%Mo+1.5×%Si+0.5×%Nb
21 22 23 24 25 26 27
21
20
19
18
17
16
15
14
13
12
11
10
Nic
kele
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t =%
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+30
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Fig. 7.4 De Long diagram
"
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7.5.1 Guidelines for Welding Dissimilar Metals
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Welding of Materials 143
%
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144 Welding Science and Technology
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Welding of Materials 145
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146 Welding Science and Technology
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DC+ –
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Welding of Materials 147
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Welding Procedure and Process Planning 149
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150 Welding Science and Technology
Finish symbol
Contour symbol
Root opening; depth of fillingfor plug and slot welds
Effective throat
F
A
R
Groove angle; includedangle of countersinkfor plug welds
Length of weld
Field weld symbol
Pitch (center-to-centerspacing) of welds
Arrow connecting ref-erence line to arrowside member of joint
Weld-all-around symbol
Reference line
Number of spot orprojection welds
Elements in thisarea remain asshown when tailand arrow arereversed
Depth of preparation size orstrength for certain welds
(Tail omittedwhen referenceis not used)
TailT
S (E)
Specification, process,or other reference
Basic weld symbolor detail reference
(N)(Bot
hsi
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ersi
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rrow
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Fig. 8.1 Standard location of elements on the welding symbol
0
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14
938
8
Size of filletin inches
Depth ofpreparation in inches
Field weldpoints to tail
Length and pitchin inches
2 to 4
Fig. 8.2 Size location, field weld length, and pitch
Fig. 8.3 Arrow side, other side reflection
Welding Procedure and Process Planning 151
Fig. 8.4 Straight line always on left
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0
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Significance
Significance
Significance
Significance
Fig. 8.5 Welding symbols-significance
Significance
Fig. 8.6 Arrow/side-other/side significance
152 Welding Science and Technology
516
516
516
Fig. 8.7 Size of fillet welds
8.2.1 Steps in Preparing Welding Procedure Sheets
0 6
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Welding Procedure and Process Planning 153
$
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8.4.1 Type of Welds
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154 Welding Science and Technology
8.4.2 Joint Preparations for Different Types of Welds
D 7/1/1
8.4.3 Fatigue as a Joint Preparation Factor
7 7 /3)
Fillet welds Butt welds
Lap Butt
Tee fillet Tee butt
Corner fillet Corner butt
7
MMA welds
P
t
g
ga
Fig. 8.9 Manual metal arc welds
Welding Procedure and Process Planning 155
t
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g
g
Low strength
Better strength
Fig. 8.10 Factors affecting joint preparation (contd.)
Incomplete fusion(superiority is lost)
defect
156 Welding Science and Technology
Distortion
Distortion
Penetration
Backing bars in areasunaccessible for gouging
Backing strip
Backing providedby the part. Italso alligns.
Constraineddistortion canlead to cracks
Fig. 8.10 Factors affecting joint preparation
Welding Procedure and Process Planning 157
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Fig. 8.11 Single V preparations
a
g
s
g
g
g
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b2
b1
s2
s1
a
a
g
158 Welding Science and Technology
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a
gs
g
a
n
g
a
g
a°453020
‘g’ mm66
9.5
Fig. 8.12 Single bevel preparation
Welding Procedure and Process Planning 159
31"#% $ !!
0
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7
α0
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0
0
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Fig. 8.13 Single U preparation and single J-preparation
Suitable only forout-side corner
b2
b1
25 – 20°
5 – 10°
a2
a1
Asymmetric prep. forhorizontal-verticalwelding
Access and economyin deep groovesIncrease = 30 – 40°
remains 20°1
2
a
g
g s
Thickness t
ag
= 19.5 – 38 mm= 20, s = g = 1.6 – 3.2 mm= 6.3 to 9.5 mm
g
s
a
g
160 Welding Science and Technology
a = 20 – 25°
Fig. 8.14 Single J preparation
51($)% & !!
P
P s
g
g
at = 12 50 mm= 60° s = 0 – 1.6 g = 1.6 – 6.3 mma
–
b1 = 10 – 15°
b2 = 45 – 40° b2
b1
a
a
sd2
d1
Unequal preparation for jointsfixed in flat position reducingoverhead welding volume.
Asymmetric preparationfor horizontal-verticalposition welding
Requires less weld metalBalanced welding sequenceControlled distortionLarge solid angleBack gouging needed forefficient high quality joint
g
Fig. 8.15 Double V preparation
)
=
2*
Welding Procedure and Process Planning 161
61($)% ) & % !!
0I1,
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6
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Fig. 8.16 (a) Double bevel preparation
Fig. 8.16 (b) Double bevel preparation
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a
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gs
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b2
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b1 = 5 to 10°b2 = 25 to 20°
t
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38 mm= 20°= 1.6 to 3.2 mm= 1.6 to 3.2 mm= 6.3 to 9.5 mm
³a
g
Fig. 8.17 Double U preparation
s g
g
a
( )a
sd2
d1
a
a
(b)
162 Welding Science and Technology
71($)% !!
2 D
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Fig. 8.18 Double J preparation
-1'8 ( !!"
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Combination of V and bevel where welding
can be done easily from both sides.
Fig. 8.19 Mixed preparations
)#
0 7 =
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0
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K 5 K 5:
=(7/
s
g
g
a
Welding Procedure and Process Planning 163
Flat FlatHorizontal Vertical
Vertical Overhead Overhead Horizontal
Fig. 8.20 Welding positions for butt and fillet welds
Line of root
SlopeSlope
Fig. 8.21 Diagram to illustrate weld slope
:
! (
7/
Rotation of weld 0°
Rotation of weld 150°
150°150°
90°90°
Rotation of weld 90°Rotation of weld 45°
45°45°
180°180°
Rotation of weld 180°
Fig. 8.22 Diagrams to show weld rotation
0
$ (.9 + 3G
+ 3G
164 Welding Science and Technology
$ 9 + 3G#,G
+ 13G
$ :;<&9 + 3G
3G + 13G
$ &9 + #,G
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$ 29 + #,G
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Welding Procedure and Process Planning 165
"$''!*+:!9
0
Materialthickness Manual metal arc Manual CO
DIP transfer2 Manual CO
spray transfer2 Mechanised CO2 Submerged arc
Process
20 S.W.G.
16 S.W.G.1/32 in.
1/8 in.1/16 in.
3/16 in.60°60°
1/16 in.
1/16 in.
1/4 in.60°60°
1/16 in.
1/16 in.
1/32 in.
3/8 in.60°
60°-70°
1/16 in.
1/16 in.
1/16 in.
40°-50°
1/16 in.
40°
1/16 in.
40°
1/16 in.
1/2 in.60°
60°-70°
3/32 in.
3/32 in.
40°-50°
1/16 in.
40°
1/16 in.
40°
1/16 in.1/16 in.
3/4 in.
60°60°-70°
1/8 in.
1/8 in.
50°
1/16 in. 50°
1/8 in.
40°
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1/4 in.
40°
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1/4 in.
1 in.
60°-70°
1/8 in.
50°
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1/8 in.
60°-70°
60°
1/16 in.
60°
40°
40°
1/4 in.40°
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1/4 in.
1½ in.
60°-70°
1/8 in.
50°
50°
1/8 in.
60°-70°
60°
60°
1/2 in.
60°
60°
1/16 in.
40°
40°
1/4 in.
3 in.
20°
1/8 in.
50°
50°
1/8 in.
60°
1/16 in.20°
1/4 in. r
60°
30°
1/2 in.
30°
1/4 in. r
30°
1/4 in.
30°
1/4 in. r
1/16 in.
166 Welding Science and Technology
%& :
%& < B
%& F L
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8.7.1 Type of Joints
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Welding Procedure and Process Planning 167
%& :
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+
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(A) (B)
(D) (C)
(E) (F)
Fig. 8.23 Major types of joints: (A) Square butt weld (B) Square tee-joint and fillet welds(C) Cruciform joint with four fillet welds (D) Lap joint with single fillet weld (E) Full open corner joint with fillet welds (F) Edge joint with edge weld.
C 7.1$.1
%2.&
8.7.2 Welding Parameters
0
=
!0
%& ! =
*
168 Welding Science and Technology
!A
=
A=!
Included angle
Angle of bevel
Root face
GapGap
Root radiusIncluded angle
Angle of bevel
Root face
GapGap
Included angle
Angle of bevel
Root face
GapGapRoot radius
Land
Fig. 8.24 Terms pertaining to typical weld preparations
7
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Welding Procedure and Process Planning 169
Weld width
Weld face
ToesToes
Toes
Weld face
Toes
Leg (length)
Weld width
Weld face
Toes
Leg
(Length)
Fig. 8.25 Term pertaining to welds
Design throat thickness
Actual throat thickness
Design throat thickness
Fig. 8.26 Actual and design throat thicknesses of welds
( =
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170 Welding Science and Technology
:+
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Welding Procedure and Process Planning 171
+(
Fig. 8.27 Joint and positions suitable for SAW
Second pass
Backing pass
Second pass
Backing pass
Fig. 8.28 Base metal backing for SAW
)):
!%+&(
): !
(): =
0
0
0!
8.8.1 Weld Backing Techniques
0 !%&;L
% &)L%"&: L%#&;L%,&2L%-&7+
L%.&;
-)=/07/ /
0 ! !
2
0
172 Welding Science and Technology
,"=/(
7/ 1(
0
Fig. 8.29 Structure backing for SAW
Fig. 8.30 Weld backing for SAW
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Welding Procedure and Process Planning 173
5 =/7/"" )+
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): D
Backing strip
Fig. 8.31 Backing strip for SWA
(A) (B)
Fig. 8.32 Copper backing for SAW: (A) V-groove butt; (B) Square butt
6)/ 2
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8.8.2 Butt Welds
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174 Welding Science and Technology
D7/"#
0 0/
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Fluxbacking
Flexiblesheetmaterial
Inflatedhose
Trough
Paperinsert(Optional)
Plate
Fig. 8.33 A method of producing flux backing for SAW
g
t
Steel back-upSteel back-up
Fig. 8.34 Joint fit-up for butt welds in sheet metal
=,("!=..=/
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Welding Procedure and Process Planning 175
6 -#$,1 !
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tSecond pass
Backing pass
Close fit-up
Fig. 8.35 Square butt weld in two passes, one from each side
9.5 MM
3.2 MM
19 MM
2ndpass
1st pass1st pass
2nd pass
25.4 MM
9.5 MM
9.5 MM
Fig. 8.36 Parameters for two-pass 19 mm and 25.4 mm t butt welds
=0(.?@=.
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-# #3 #., 1 3 #3 ,., " 3
1, #3 ,33 "" # #3 /,3 ", #
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176 Welding Science and Technology
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70°
60°
16 MM
9.5 MM
3rd pass
2nd pass
1st pass
32 MM
38 MM
1st pass
2nd pass
3rd pass
90°
70°
16 MM
12.7 MM
Fig. 8.37 Parameters for three-pass 32 mm and 38 mm t butt welds
Welding Procedure and Process Planning 177
=4(0,0=.
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" , /,3 ", ,, , 333 "- ,
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6.4 MM
3.2 MM
Fig. 8.38 Joint fit-up for multi-pass butt weld
, !(-
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178 Welding Science and Technology
!
!
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Welding Procedure and Process Planning 179
.!#
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180
(a) Undercut (b) Cracks
(c) Porosity (d) Slag inclusions
(e) Lack of fusion (f) Lack of penetration
Fig. 9.1 Typical weld defects
Weld Quality 181
!
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Crater cracks
Arc strike Toe crack
Underbead crack
Longitudinalcracks
Transversecracks
Toe crack
Fig. 9.2 Types of cracks in welded joints
182 Welding Science and Technology
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Weld Quality 183
A B
Fig. 9.3 Types of lack of fusion
$ #
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Reinforcement of buttsmore than 3.2 mm(1/8 in.) is excessive
Lack of filler metal
Fig. 9.4 Excessive reinforcement, Lack of filler metal
184 Welding Science and Technology
A B
C
D
Size Size
45°
Desirable fillet weld profiles
Convexity Cshall not exceed0.15 + 0.03 in.
SS
S S
C
Acceptable fillet weld profiles
Size Size Size Size Size
Insufficientthroat
Excessiveconvexity
Excessiveundercut
Overlap Insufficientleg
Defective fillet weld profiles
C
Fig. 9.5 Desirable, acceptable and defective fillet weld profiles
")
")
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Weld Quality 185
a. No corrosion b. Uniform c. Galvanic d. Erosion e. Fretting f. Crevice
More noblemetal
Flowingcorrodent
Cyclicmovement
Load Metal ornon-metal
g. Pitting h. Exfoliation
i. Selective leaching j. Intergranular k. Stress cor-rosion cracking
l. Corrosionfatigue
Fig. 9.6 Types of corrosion commonly found in metals and alloys
9.8.1 Galvanic Corrosion
! + !
;
.
! *%6
Large cathodic regionsSmall
anodic region
Large anodic regionsSmall cathodic region
A A
Regions where attack may be serious
Fig. 9.7 Galvanic corrosion in a welded join
Top: weld Metal less noble than base metal
Bottom: Weld metal more noble than base metal
186 Welding Science and Technology
9.8.2 Crevice Corrosion
. 0
<+
+!
9
9.8.3 Intergranular Corrosion
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9.8.4 Stress Corrosion
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Weld Quality 187
APPEARANCE TYPE OF CORROSIONWeld metal
Base metal
a. Uniform
b. Base metalcorrosion
c. Weld metalcorrosion
d. Base metalhigh-temp. HAZcorrosion
e. Base metallow-temp. HAZcorrosion
Fig. 9.8 Types of corrosion in a welded joint
!# (
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9.9.1 Factors Affecting Corrosion Resistance of Welded Joints
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188 Welding Science and Technology
!
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10.1.1 Tension Tests for base metal
$
10.1.2 Weld Tension Test
"
%&'&
$ %&'&
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190 Welding Science and Technology
Longitudinal weldspecimen
Weld 8"
Gage length
1.5"2"
Both plate - typespecimens have iden-tical dimensions
18" min
t
Transverseweld specimenBase metalAll weld
metal
0.252 or 0.505"diam round specimensdepending on t
Fig. 10.1 Typical test specimens for evaluation of welded joints (dimensions in inch units)
T
f
f
W
6.4
6.4
W = 38.1 ± 0.3T = 8 mm. approx.
25.4 approx.
50.8
–50.
6R
6.46.4
Machined by milling
(a) Transverse-weld tension specimen
25.4 ± 1.6
25.4 8
38.1
76.2 63.5 76.2
25R
Machined by milling
(b) Longitudinal-weld tension specimen
Fig. 10.2 Tension test specimens with dimensions in mm
Testing and Inspection of Welds 191
76.231.8
25.4 0.13
4.6 R
9.5
6.4 ± 0.13 6.4
Specimenlocation
(c) All weld metal tension specimen
Fig. 10.2 Tension test specimens with dimension in mm
#
!
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#
* #
*+
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10.1.3 Tension-shear Test
$
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0 1"
192 Welding Science and Technology
A. B.
D. C.
After welding After machining
Fig. 10.3 Various types of tension-shear specimens
10.1.4 Tension Tests for Resistance Welds
#
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Testing and Inspection of Welds 193
"
Edges as sheared Direction ofrolling (preferred)
Spot-weld centeredas shown
Fig. 10.4 Test specimen for tension shear
a.
b.
Thickness up to 4.8 mm (0.19 in.)
Thickness over 4.8 mm (0.19 in.)
Fig. 10.5 Cross-tension test
0
194 Welding Science and Technology
Fig. 10.6 Test jig for cross-tension specimens
78 7!!$0&&
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%&'1 "26%
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Testing and Inspection of Welds 195
%&'9,.
"
*
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(a) (b)
Fig. 10.7 Jig for cross-tension test (t > 4.8 mm)
: %&'5,.
Fig. 10.8 (a) Bend tests
196 Welding Science and Technology
Roller supportor greasedshoulders
A1"4 R
t
1"4A = 1 when t
1"2
A = 2" when t > 1"2
Initial bend for free-bend specimens
Final bend forfree-bendspecimens
Shoulder
Plunger
Roller (alternate)
Specimen
Die
Fig. 10.8 (b) Typical fixtures for free bend testing (top) and guided bend (bottom).(for SI equivalents U.S. customary values)
10.2.1 Procedures of Preparing Test Sample
8 ;
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Fig. 10.13 Fixed box pipe all position test. 1G-1 Flat position root bend 1G-2 Flatposition face bend 2G-3 Horizontal position root bend 2G-4 Horizontal position facebend 3G-5 Vertical position root bend 3G-6 Vertical position face bend 4G-7 Over-head position root bend 4G-8 Overhead position face bend.
as welded
Fig. 10.14 Reinforcement removal
200 Welding Science and Technology
Center lineof weld
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Fig. 10.15 Prepared specimen for bending
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Fig. 10.16 (a) Pipe root and face. Plate root and face
Testing and Inspection of Welds 201
Root Bend
Face Bend
Side Bend
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Fig. 10.16 (b) Relative orientations of face, root, and side-bend tests from a welded plate
Fig. 10.17 Root bend and face bend on small-diameter pipe sample
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Fig. 10.18 Alternating current coil
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Fig. 10.19 Circular magnetization of a shaft
Testing and Inspection of Welds 203
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10.3.2 Radiographic Inspection
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Testing and Inspection of Welds 205
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Fig. 11.3 Examples of fillet-welded joints
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Fig. 11.5 Standard symbols for designating welding position
Welding of Pipelines and Piping 217
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Fig. 11.7 Examples of standard manufactured commercial welding fittings
Welding of Pipelines and Piping 219
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Fundamentals of Underwater Welding Art And Science 247
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Fig. 15.1 Barrel formation during Wet-welding
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Fig. 15.2 Underwater wet-welding
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248 Welding Science and Technology
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Operational Views ‘‘Habitat Welding’’
(a) Ship repairs
Fig. 15.3 Use of Hyperbaric chambers (Habitat welding)
Fundamentals of Underwater Welding Art And Science 249
(b) Hot-tap welding of pipelines
Fig. 15.3 Use of Hyperbaric chambers (Habitat welding)
250 Welding Science and Technology
Umbilical gasand electricity cable
Dryhyperbaricchamber
Controlpanel
Weld-ball
Seal
Pipeline
Removable floor andwall sections
(c) Making Weld-ball pipeline joint
Fig. 15.3 Use of Hyperbaric chambers (Habitat Welding)
15.3.2 Local Chamber Welding (See Figs. 15.4, 15.5 (b) and 15.6)
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Fundamentals of Underwater Welding Art And Science 251
DC power supplyControlunit, gas +wire feed
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UMBILICAL[gas leadspower lead (welding)wire feed drive +control powerleads]
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Fig. 15.4 Schematic diagram of continuous wire MIG welding underwater using local dry environment
15.3.3 Portable Dry Spot (see Fig. 15.5)
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252 Welding Science and Technology
Gas exhaust tube
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"Dry spot" designTube to wire feed
Gas switch
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(a) Portable dry spot (PDS) welding
(b) Example 1Repairing a damaged riser
A. Cut is made below the damaged area,noting location of riser clamps,and the stub and cleaned.
B. Damaged section is removed whilereplacement assembly is madeready on the surface.
C. New section is lowered over theriser stub and the upperconnection is made.
D. Transparent box is put in place,water avacuated, and the weldmade.
(b) Stages in the repair of damaged riser using Local Dry Environment ‘‘Hydrobox’’
Fig. 15.5 Underwater dry welding
Fundamentals of Underwater Welding Art And Science 253
PlatformReplacementriser
Air
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Hydrobox
Weld collar
Fillet weldmade with Hydrobox
Old riser
Hydrobox in use for a Vertical Riser Repair
Fig. 15.5 (c) The Hydrobox Showing Schematic Arrangement for makinga Riser Repair (details) (Kirkley, Lythal, 1974)
Fig. 15.5 Underwater dry welding
15.3.4 Wet Welding
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A. Riser is connected toplatform and pipeline is laidor cut to within one pipediameter of riser end.
Example 2Use of universal assembly
B. Riser is rotated until it iswithin the misalignmenttolerance of 15°.
C. Ball half of the connectoris placed on the pipelineend.
D. Connector halves are movedtogether and a transparentbox placed to cover the weldareas at the joint and therear of the ball half.
Planview
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Fig. 15.6 Use of universal assembly being welded in adry chamber (transparent perspex) (Kirkley, Lythal, 1974)
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256 Welding Science and Technology
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276 Welding Science and Technology
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278 Welding Science and Technology
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