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Welding
Welding is a fabrication orsculptural process that joins
materials (usually metals) by
causing coalescence. This is
often done by melting the workpieces and adding a filler
material to form a pool of molten
material (the weld pool) that
cools to become a strong joint,
with pressure sometimes used in
conjunction with heat, or by
itself, to produce the weld.
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A Brief History of Welding
Late 19th Century
Scientists/engineers apply advances in electricity to heat and/or
join metals (Le Chatelier, Joule, etc.)
Early 20th Century
Prior to World War I welding was not trusted as a method to jointwo metals due to crack issues
1930s and 40s
Industrial welding gains acceptance and is used extensively in the
war effort to build tanks, ships, etc.
Modern Weldingthe nuclear/space age helps bring welding from an art to a
science
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Welding Processes
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Types of Welding
Fusion Welding
Oxyacetylene Gas Welding
Shielded Metal Arc (SMAW)
Metal Inert Gas (MIG)
Tungsten Inert Gas (TIG)
Submerged Arc Welding (SAW)
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Oxyacetylene Gas Welding
Coalescence is produced by oxyacetylene flame.
It can yield temperature up to 3200 deg C.
Filler metal may or may not be used.
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Shielded Metal Arc Welding
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Metal Inert Gas Welding(MIG Welding)
Coalescence is produced by heating the work piece withan electric arc between a continuously fed metal electrodeand the work piece.
No flux is required.
Shielded by inert gas (Argon, CO2,
Helium or mixture).
GMAW torch nozzle cutaway image.
(1) Torch handle,
(2) Molded phenolic dielectric (white)
and threaded metal nut insert (yellow),
(3) Shielding gas diffuser,(4) Contact tip,
(5) Nozzle output face
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Metal Inert Gas Welding(MIG Welding)
M l I G W ldi
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Metal Inert Gas Welding(MIG Welding)
G T A W ldi
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Gas Tungsten Arc Welding(TIG Welding)
TIG welding is an arc welding process in whichthe heat is produced between a non-consumabletungsten electrode and the work metal.
The arc and adjacent heated areas of the work
piece are protected from atmosphericcontamination by a shield of inert gas.
A filler metal may or may not be used dependingupon the requirement. Because the electrode is
non-consumable, a weld can be made by fusionof the base metal without the addition of fillermetal.
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Gas Tungsten Arc Welding(TIG Welding)
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Gas Tungsten Arc Welding(TIG Welding)
Selection of Inert Gas Shield :Helium and argon gases are mostly used. These do not react
with tungsten or tungsten alloy electrodes and have no
adverse effect on the quality of the weld metal. Argon is more
widely preferred, because it provides a softer arc, which is
smooth and stable. Argon provides greater coverage of theweld puddle at low flow rates. With argon, the flow rate may be
12 to 20 cubic feet per hour.
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SAFETY DURING WELDING
Wear approved safety glasses with side
shields under your welding helmet or face
shield and at all times in the work area.
Wear dry, hole-free insulating gloves
and body protection. Do not touch
electrode with bare hand. Do not wear
wet or damaged gloves.
Do not touch live electrical parts.
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SAFETY DURING WELDING
Arc rays can burn eyes and skin.
Use welding helmet with correct shade
of filter.
Wear welders cap and safety glasses
with side shields. Wear complete body protection.
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SAFETY DURING WELDING
Confined spaces can be hazardous.
Cylinders can explode if damaged.
Magnetic fields can affect Implanted
Medical Devices.
Hot parts can cause severe burns.
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Weldability
Common Name CarbonContent (%)
Weldability
Ingot Iron 0.03 max Excellent
Low Carbon Steel 0.15 max Excellent
Mild Steel 0.15-0.3 Good
Med. Carbon Steel 0.3-0.6 Fair
High Carbon Steel 0.6-2.0 Poor (Difficult to Weld)
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Carbon Equivalent (CE)
Weldability of steel in terms of its susceptibilityto cracking can be roughly estimated by use of acarbon equivalent (CE).
CE= % C + %Mn + % Ni + % Cr + % Cu - % Mo - % V
4 20 10 40 50 10
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Post Weld Heat Treatment
Throughout the cycle of Heat treatment, the portionoutside the heated band shall be suitably wrapped
under insulation to avoid any harmful temperature
gradient at the exposed surface of pipe.
The temperature attained by the portion under heattreatment shall be recorded by means of
thermocouple, pyrometers.
Standard Joint Design For
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Standard Joint Design ForButt Welding
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Welding Electrode
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Welding Electrode
An electrode is a piece of wire or rod (of metal oralloy) with or without flux covering which carriescurrent and also acts as filler material forwelding.
At one end it is gripped in a holder and arc isgenerated at the other end.
Different types of electrodes are available in themarket for different welding processes.
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Welding Electrode
Welding Electrodes for Alloy & Stainless Steel:Sl.No.
Base Metal P.No.
Welding Electrodes Preheat 0C(see note)
Postweld heattreatment 0C (see
note)A.S.M.E.A.W.S
Classification
1 C-1/2 Mo P 3 S.F.A.5.5 E7018 A1 100C Min. 800Cmin for
thickness 1/2or base metalT.S.>71Ksi
None6500C, 1 hr/in, for
thickness >3/4 orbase metal T.S. > 71Ksi
2 1.1/4 Cr-1/2 Mo
P4 S.F.A.5.5 E8016 B2,E8018 B2
1500C Minimum 7200C, 1hr/in, with 2hrs. min., none forthickness
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Welding Electrode
Sl.No.
Base Metal P.No.
Welding Electrodes Preheat 0C(see note)
Postweld heattreatment 0C (see
note)A.S.M.E.A.W.S
Classification
4 5 Cr-1/2 Mo
P5 S.F.A.5.4 E505-16or -15
1800C Minimum 7200C, 1 hr/in. with 2hrs. min.
5 9 Cr-
1 Mo
P5 S.F.A.5.4 E505-16
or -15
1800C Minimum 7300C, I hr/in. with
two hrs. min.
6 12 CrType 410
P6 S.F.A.5.4S.F.A.5.4
E410-16or15E309-16or -15
2050C Minimum2050C Minimum
7600C, 1 hr/in. with 2hrs. min None
7 12 CrType 405
P7 S.F.A.5.4S.F.A.5.4S.F.A.5.11S.F.A.5.4
E309-16or15ENi CrFe-3E410-16or15
100C Minimum100C Minimum1500C Minimum
NoneNone7300C 1 hr/in. with 2hrs. min.
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Welding Electrode
Sl.No.
Base Metal P.No.
Welding Electrodes Preheat 0C(see note)
Postweld heattreatment 0C (see
note)A.S.M.E.A.W.S
Classification
8 3.1/2 Ni P 9B S.F.A.5.5S.F.A.5.5S.F.A.5.11
E8016-C2E8018-C2E Ni Cr Fe-3
950C Minimum 6200C hr/in. 1 hr
minimum
9 18 Cr-8NiSS Type 304SS Type304L
P8 S.F.A.5.4 E308-16or15E308L-16or -15
100
C min. None
10 18 Cr-8NiStabilisedSS Type 347,321
P8 S.F.A.5.4 E347-16or15
100C min. None
11 18 Cr-10Ni-MoSS Type 316SS Type316L
P8 S.F.A.5.4 E316-16or15E316L-16or15
100C min. None
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Inspection Of Welding
Inspection After Welding:
Destructive Tests (for mechanical properties /chemical analysis / spectro etc).
Non Destructive Tests (NDT).
Checking of distortion.
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Welding Procedure Qualifications
This shall be done as per ASME Section IX Article 2
Welding Procedure Specification (WPS).
A WPS is a written qualified welding procedure prepared to
provide direction for making production welds to Code
requirements. The WPS or other documents may be used to
provide direction to the welder or welding operator to assure
compliance with the Code requirements.
Procedure Qualification Record (PQR).
A PQR is a record of the welding data used to weld a testcoupon.
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Welding Procedure Qualifications
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El d Q lifi i T
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Electrode Qualification Test
FIG. 3 FILLET WELD TEST ASSEMBLY
FIG. 4 TEST ASSEMBLY FOR TRANSVERSE TENSIONAND LONGITUDINAL GUIDED BEND TESTS FORWELDS MADE WITH E6022 ELECTRODES
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Electrode Qualification Test
FIG. 5 GROOVE WELD TEST ASSEMBLY FORMECHANICAL PROPERTIES AND SOUNDNESS OFWELD METAL MADE WITH E7018M ELECTRODES
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Welder Qualification
This shall be done as per ASME Section IX
The performance qualification is done in accordance
with one of any of the qualified Welding Procedure
Specifications (WPS).
When performance qualification is done in
accordance with a WPS that requires Post weld
heat treatment (PWHT), this PWHT may be omitted.
The welded test joints for qualification may be
examined by mechanical tests or by radiography.
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Welder Qualification
W ldi D f t
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Welding Defects
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Welding Defects
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Welding Defects
Defect-
Causes-
Remedies
Crack - Insufficient weld size.- Excessive joint
restraint.
- Poor joint design and/or
preparation.
- Filler metal does notmatch base metal.
- Rapid cooling rate.
- Base metal surface
covered with oil,
grease, moisture, rust,and dirt or mill scale.
- Adjust weld size to part
thickness.
- Reduce joint restraint
through proper design.
- Select the proper joint
design.- Use more ductile filler.
- Reduce cooling rate
through preheat.
- Clean properly base metal
prior to welding.
Welding Defects
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Welding Defects
Defect - Causes - Remedies
Lack of
penetration- Travel speed too fast.
- Welding current too
low.
- Poor joint design
and/or preparation.
- Electrode diameter toolarge.
- Wrong type of
electrode.
- Excessively long arc
length.
- Decrease travels
speed.
- Increase welding
current.
- Increase root
opening ordecrease root face.
- Use smaller
electrode.
- Use electrode with
deeper penetrationcharacteristics.
- Reduce arc length.
Welding Defects
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Welding Defects
Defect - Causes - Remedies
Inclusion - Incomplete slag
removal between
passes.
- Erratic travel
speed.
- Too wide aweaving motion.
- Too large an
electrode.
- Letting slag run
ahead of arc.- Tungsten spitting
or sticking.
- Completely remove slag
between passes.
- Use a uniform travel speed.
- Reduce width of weaving
technique.
- Use a smaller electrodesize for better access to
joint.
- Increase travel speed or
change electrodes angle or
reduce arc length.- Properly prepare tungsten
and use proper current.
Testing of Weld joint
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Testing of Weld joint
Several Techniques are available for testing qualityof a weld:
Visual Inspection
Dye Penetrant Testing
Magnetic Particles Testing
Radiography Testing
Ultrasonic Testing
Destructive Testing
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Radiography Test
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Radiography Test
DISCONTINUITY
METAL
RADIATION SOURCE
FILM
Principle :
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Radiography Test
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Radiography Test
Sample Films :
Tungsten
Inclusion
Transverse
Crack
AUTOMATIC WELDING
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AUTOMATIC WELDING
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CASE STUDIES
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CASE STUDIES
CRACK IN WELD OVERLAY OF RTJ GROOVE IN REACTOR
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CASE STUDIES
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CASE STUDIES
WELD FAILURE OF STUB IN REACTOR INLET LINE
Standard Joint
Improper Fit Up
& Welding
Poor Penetration
& Under cut
Crack
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