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M.S.Trần Ngọc Dân
19 Sep 02
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Welding InspectionDefects/Repairs
Course Reference WIS 5
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Weld DefectsDefects which may be detected by visual
inspection can be grouped under five headings
Cracks
Surface irregularities
Contour defects
Root defects
Miscellaneous
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Weld Defects
Other associated defects
Cavities
Solid inclusions
Set up irregularities
Parent material defects
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Cracks
Hydrogen (HICC)
Solidification (Hot tears)
Reheat cracks
Lamellar tearing
The four essential crack mechanisms
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Cracks
Longitudinal parent metal crack Transverse weld metal crack
Longitudinal weld metal crack Lamellar tearing
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19 Sep 02 Transverse crack Center line crack
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Surface Irregularities
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UndercutAn irregular groove at the toe of a weld run in
the parent metal
Excessive amps/volts
Excessive travel speed
Incorrect electrode angle
Excessive weaving
Incorrect welding technique
Electrode too large
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Cap Undercut
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19 Sep 02 Cap undercutRoot undercut
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OverlapAn imperfection at the toe or root of a weld caused by
metal flowing on to the surface of the parent metal
without fusing to it
Contamination
Slow travel speed
Incorrect welding
technique
Current too low
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Overlap
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Crater Pipe
Crater pipe is a shrinkage defect and not a gas defect, it
has the appearance of a gas pore in the weld crater
Too fast a cooling rate
Deoxidization
reactions and liquid to
solid volume change
Contamination
Crater crack
(Star crack)
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Crater Pipe
Crater pipe
Weld crater
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Contour Defects
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Contour Defects
Incomplete filled groove Poor cap profile
Excessive cap heightIncomplete filled groove
+ Lack of sidewall fusion
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Root Defects
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Root Defects
Incomplete root fusion
Incomplete root penetration
Low Amps/volts
Large Root face
Small Root Gap
Fast Travel Speed
Incorrect Electrode
Angle
Contamination
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Root Defects
Lack of root fusionLack of root Penetration
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19 Sep 02Lack of root fusionLack of root penetration
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Concave root
Root Defects
Root faces too large
Root gap too large
Excessive back purge
pressure during TIG welding
Excessive root bead grinding
before the application of the
second pass
A shallow groove, which may occur in the root of a butt weld
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Concave Root
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Excessive root penetration
Root Defects
Root faces too small
Root gap too large
Excessive amps/volts
Slow travel speed
Root penetration bead in excess in accordance with the
relevant specification being used
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Excessive Root Penetration
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19 Sep 02Concave root Excessive root penetration
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Shrinkage groove
Root Defects
Insufficient weld metal
deposited in the root
pass
Too fast a cooling rate
during the application of
the root bead pass
Poor welding technique
A shallow groove caused by contraction in the weld
metal along each side of the penetration bead
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Root Defects
Burn through
High Amps/volts
Small Root face
Large Root Gap
Slow Travel Speed
A localized collapse of the weld pool due to excessive
penetration resulting in a hole in the root run
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Burn
Through
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Root Coking/Oxidized Root
Loss or insufficient
back purging gas
Most commonly
occurs when welding
stainless steels
Purging gases
include argon, helium
and occasionally
nitrogen
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Miscellaneous Defects
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Miscellaneous Defects
Arc strike
Accidental striking of
the arc onto the parent
material
Faulty electrode holder
Poor cable insulation
Poor return lead
clamping
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Spatter
Excessive current
Damp electrodes
Contamination
Incorrect wire feed
speed when welding
with the MAG welding
process
Miscellaneous Defects
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Inclusions
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Gas Cavities
Cluster porosityGas pore
Blow hole
Herringbone porosity
Root piping
Loss of gas shield
Damp electrodes
Contamination
Arc length too large
Damaged electrode flux
Moisture on parent material
Welding current to low
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Gas Cavities
Root piping
Porosity
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19 Sep 02 Single gas poreCluster porosity
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Solid Inclusions
Slag originates from welding
flux
MAG and TIG welding
process produce silica
inclusions
Slag is caused by
inadequate cleaning
Other inclusions include
tungsten and copper
inclusions from the TIG and
MAG welding process
Lack of sidewall fusion with
associated slag
Slag inclusions
Parallel slag lines
Slag inclusions are defined as a non-metallic inclusion
caused by some welding process
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19 Sep 02Elongated slag linesInterpass slag inclusions
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Set-up Irregularities
Plate/pipe Linear Misalignment
(Hi-Lo)
Poor fit-up
Angular Misalignment
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Linear Misalignment
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Parent Material Defects
A welding inspector should also inspect the parent
material for any visible defects
Lamination
Mechanical damage Lap
Segregation line
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Plate Lamination
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Weld Repairs
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A weld repair may be used to improve weld profiles
or extensive metal removal
Repairs to fabrication defects are generally easier
than repairs to service failures because the repair
procedure may be followed
The main problem with repairing a weld is the
maintenance of mechanical properties
During the inspection of the removed area prior to
welding the inspector must ensure that the defects
have been totally removed and the original joint
profile has been maintained as close as possible
Weld Repairs
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The specification or procedure will govern how the defective areas are to be removed. The
method of removal may be Grinding
Chipping
Machining
Filling
Arc air gouging
Oxy-gas gouging
Weld Repairs