Copy from Welding Inspectionkruwelding.com/expert/WIS5 DEFECT.pdf · Copy from Welding Inspection...

M.S.Trần Ngọc Dân

19 Sep 02

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Welding InspectionDefects/Repairs

Course Reference WIS 5

19 Sep 02

Weld DefectsDefects which may be detected by visual

inspection can be grouped under five headings

Cracks

Surface irregularities

Contour defects

Root defects

Miscellaneous

19 Sep 02

Weld Defects

Other associated defects

Cavities

Solid inclusions

Set up irregularities

Parent material defects

19 Sep 02

Cracks

Hydrogen (HICC)

Solidification (Hot tears)

Reheat cracks

Lamellar tearing

The four essential crack mechanisms

19 Sep 02

Cracks

Longitudinal parent metal crack Transverse weld metal crack

Longitudinal weld metal crack Lamellar tearing

19 Sep 02 Transverse crack Center line crack

19 Sep 02

Surface Irregularities

19 Sep 02

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

19 Sep 02

Cap Undercut

19 Sep 02 Cap undercutRoot undercut

19 Sep 02

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

19 Sep 02

Overlap

19 Sep 02

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)

19 Sep 02

Crater Pipe

Crater pipe

Weld crater

19 Sep 02

Contour Defects

19 Sep 02

Contour Defects

Incomplete filled groove Poor cap profile

Excessive cap heightIncomplete filled groove

+ Lack of sidewall fusion

19 Sep 02Incomplete filled grooveExcess cap reinforcement

19 Sep 02

Root Defects

19 Sep 02

Root Defects

Incomplete root fusion

Incomplete root penetration

Low Amps/volts

Large Root face

Small Root Gap

Fast Travel Speed

Incorrect Electrode

Contamination

19 Sep 02

Root Defects

Lack of root fusionLack of root Penetration

19 Sep 02Lack of root fusionLack of root penetration

19 Sep 02

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

19 Sep 02

Concave Root

19 Sep 02

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

19 Sep 02

Excessive Root Penetration

19 Sep 02Concave root Excessive root penetration

19 Sep 02

Shrinkage groove

Root Defects

Insufficient weld metal

deposited in the root

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

19 Sep 02

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

19 Sep 02 Burn through

Through

19 Sep 02

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

19 Sep 02

Miscellaneous Defects

19 Sep 02

Arc strike

Accidental striking of

the arc onto the parent

material

Faulty electrode holder

Poor cable insulation

Poor return lead

clamping

19 Sep 02

Spatter

Excessive current

Damp electrodes

Contamination

Incorrect wire feed

speed when welding

with the MAG welding

process

19 Sep 02

Inclusions

19 Sep 02

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

19 Sep 02

Gas Cavities

Root piping

Porosity

19 Sep 02 Single gas poreCluster porosity

19 Sep 02

Solid Inclusions

Slag originates from welding

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

19 Sep 02Elongated slag linesInterpass slag inclusions

19 Sep 02

Set-up Irregularities

Plate/pipe Linear Misalignment

(Hi-Lo)

Poor fit-up

Angular Misalignment

19 Sep 02

Linear Misalignment

19 Sep 02

Parent Material Defects

A welding inspector should also inspect the parent

material for any visible defects

Lamination

Mechanical damage Lap

Segregation line

19 Sep 02

Plate Lamination

19 Sep 02

Weld Repairs

19 Sep 02

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

19 Sep 02

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

Copy from Welding Inspectionkruwelding.com/expert/WIS5 DEFECT.pdf · Copy from Welding Inspection...

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