01 Wis5 Defect New

8/9/2019 01 Wis5 Defect New

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Welding InspectionDefects/Repairs

Course Reference WIS 5


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A perfect butt weld joint, when subjected to an external

force, provide a distribution of stress throughout itsvolume which is not significantly greater than parent

metal.

DefinitionDefinition


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DefinitionDefinition

This is achieved as long as the following featuresapply :-

• Welds should consists of solid metal throughout a cross

section at least equal to that of parent metal.• All parts of a weld should be fully fused to the parent

metal.

•Welds should have smoothly blended surfaces.


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Defects which may be detected by visual inspection can

be grouped under five headings

Cracs

!ac of solid metals

!ac of fusion

!ac of smoothly blended surfaces

"iscellaneous

#eld Defects#eld Defects


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CracsCracs


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Classified by Shape

!ongitudinal

$ransverse

%ranched

Chevron

Classified by Position

&A'

Centreline

Crater

(usion )one

*arent metal

CracsCracs

Cracs that may occur in welded materials are caused

generally by by many factors and may be classified byshape and position, cracs are classed as planar.


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*rocess Cracs*rocess Cracs

&A' hydrogen cracing

#eld metal hydrogen cracing

+olidification cracing &ot $earing-

!amellar tearing


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CracsCracs

HAZ hydrogen cracking Weld metal hydrogen cracking

Solidification cracking Lamellar Tearing


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Transverse crack Longitudinal crack


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*R+$0*R+$0Description : Gas pores trapped within the weld metal

Causes

• !am" flu#es$ corroded electrode

•%rease$hydrocar&on$'ater

contamination of "re"ared surface

•Air entra"ment in gas shield

•Too high arc (oltage$arc length

•Incorrect$insufficient deo#idant

in electrode) filler or "arent metal

*re(ention

• +se dry electrodes in good

condition

•,"timise gas flo'

•+se electrode 'ith sufficient

deo#idation acti(ity

•Reduce arc (oltage or arc length


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1as Cavities1as Cavities

%oot piping%oot piping

&orosity&orosity


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Cluster porosity 'erring (one porosity


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Crater *ipeCrater *ipe A shrinkage cavity at the end of a weld run where the arc is

terminated

Causes

•Lack of 'elder skill due to using

"rocesses 'ith too high current-

•Ino"erati(e crater filler . %TAW /

*re(ention

• Retrain 'elder

•+se correct crater fillingtechni0ue


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Crater *ipe/CracsCrater *ipe/Cracs

Crater pipeCrater pipe

Crater CracksCrater Cracks


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RootRoot concavityconcavity

A shallow groove, which may occur in the root of a butt weld

Causes

•Insufficient arc "o'er to "roduce "ositi(e &ead

•1#cessi(e &acking "ressure . %TAW /

•Lack of 'elder skill

•Slag flooding in &acking &ar groo(e

*re(ention

• Raise arc energy

•Reduce gas "ressure

•Retraint 'elder

•Tilt 'ork to "re(ent slag

flooding


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root concavity


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2nderfill2nderfill

A weld with thickness less than that of the parent metal

Causes

•Insufficient 'eld metal

•Irregular 'eld &ead surface

*re(ention

• Increase num&er of 'eld run

•Retrain 'elder


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Inco)plete filled groove


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+lag nclusions+lag nclusions

Slag or other matters trapped during welding. The imperfection is of

an irregular shape and thus differs in appearance from a gas pore

Causes

•Hea(y millscale$rust on 'ork surface

•Incom"lete slag remo(al from

underlying surface of multi"ass 'eld

•Slag flooding ahead of the arc

•1ntra"ment of slag in 'ork surface

•+nfused flu# due to damage coating

*re(ention

• %rind surface "rior 'elding

•Im"ro(e interun slag remo(al

•*osition 'ork to gain control of

slag

•!ress 'ork surface smooth

•+se electrode in good condition


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$longated slag linesInterpass slag inclusions


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nter3 run mperfectionsnter3 run mperfections

Irregular along the fusion line between weld beads

Causes

•Lo' arc current resulting in lo'

fluidity of 'eld "ool

•Too high tra(el s"eed

•Inaccurate &ead re"lacement

*re(ention

• Increase current

•Reduce tra(el s"eed

•Retrain 'elder


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!ac of (usion!ac of (usion


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ncomplete root penetrationncomplete root penetration

Failure of the weld metal to extend into root of a oint

Causes

•1#cessi(ely thick root face) insufficient root ga"

or failure to cut &ack sound metal in a 2&ack

gouging3 o"eration

•Lo' heat in"ut

•1#cessi(e inductance in %4AW di" transfer

•S4AW electrode too large. lo' current density /

•+se of (ertical do'n 'elding

*re(ention

• Im"ro(ed &ack gouging and edge

"re"aration

•Increase arc "o'er or decrease tra(els"eed

•Im"ro(e electrical settings and "ossi&ly

s'itch to s"ray transfer

•Reduce electrode sie

•S'itch to (ertical u" "rocedure


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Root DefectsRoot Defects

Lack of root fusion Lack of root &enetration


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!ac of sidewall fusion!ac of sidewall fusion

!ack of fusion between weld metal and parent metal at one side of weld

Causes

•Lo' heat in"ut to 'eld

•4olten metal flo'ing ahead of arc

•,#ide or scale on 'eld "re"aration

•1#cessi(e inductance in %4AW di" transfer

'elding

*re(ention

•Increase arc energy or increase tra(el

s"eed

•Im"ro(e electrode angle and 'ork

"osition

•Im"ro(e edge "re"aration "rocedure

•Reduce inductance) e(en if this increase

s"atter


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!ac of +moothly!ac of +moothly

%lended +urfaces%lended +urfaces


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+urface porosity+urface porosity

"as pores which break the surface of the weld

Causes

•!am" or contaminated surface of electrode

•Lo' flu#ing acti(ity

•1#cess sul"hur . "articularly free 6 cutting steels/

"roducing sul"hur o#ide

•Loss of gas shield gas due to long arc or high

&reees . %4AW /

*re(ention

•Clean surface and dry electrodes

•+se a high acti(ity flu#

•+se high manganese to "roduce 4nS)

note free cutting should not normally &e

'elded

•Reduce arc length


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4xcess #eld "etal Reinforcement -4xcess #eld "etal Reinforcement -

#einforcement is the extra metal which produces convexity in fillet

welds and a welds thickness than the parent metal plate in butt welds.

Causes

•1#cess arc energy . %4AW)SAW /

•Shallo' edge "re"aration

•7aulty electrode mani"ulation

•Incorrect electrode sie

*re(ention

•Reduction of energy in"ut

•!ee"en edge "re"aration

•Im"ro(e 'elder skill

•Reduce electrode sie


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$*cess cap reinforce)ent


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4xcessive *enetration4xcessive *enetration

$roection of the root penetration bead beyond a specified limit

Causes

•Weld in"ut energy too high

•Incorrect 'eld "re"aration i-e e#cessi(e

root ga") thin edge "re"aration) lack of

&acking

•+se electrode unsuited to 'elding "osition

•Lack of 'elder skill

*re(ention

•Reduce arc "o'er$increase 'eld s"eed

•Im"ro(e 'ork "iece "re"aration

•+se correct electrode "osition

•Retrain 'elder


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$*cessive root penetration


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2ndercut2ndercut

An irregular groove at the toe of a run in the parent metal or in

previously deposited welding, cause by welding

Causes

•4elting of to" edge due too high 'elding

current . es"ecially at free edge/ or high

tra(el s"eed•Attem"ting an H8 fillet 'eld leg length

9:-; 44

• 1#cessi(e$Incorrect 'ea(ing

•Incorrect electrode angle

*re(ention

•Reduce "o'er in"ut) es"ecially

a""roaching a free edge 'here o(erheatingcan occur

•Weld in a flat "osition or use multirun

techni0ue

•!irect arc to'ards thicker mem&er

C 2 d t


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Cap 2ndercutCap 2ndercut

"easured in both !ength 5 Depth"easured in both !ength 5 Depth


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Cap undercut%oot undercut


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verlapverlap

An Imperfection at the toe of a weld caused by metal flowing on to the

surface of the parent metal without fusing to it

Causes

• *oor electrode mani"ulation

• High energy in"ut$lo' tra(el s"eed

causing surface flo' of fillet 'eld

• Incorrect "ositioning of 'eld

• 1lectrode ha(ing too high a fluidity

*re(ention

•Retrain 'elder

•Reduce the heat in"ut or limit sie of

fillet 'eld to :-; mm leg &y using multi

run 'eld

•Change the flat "osition

•Change to less fluid 'eld metal


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*rofile Defects*rofile Defects

&oor stop+starts


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"iscellaneous"iscellaneous


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"isalignment"isalignment

The non % alignment of two abutting edges in a butt oint

Causes

• Inaccuracies in assem&ly "rocedures or

distortion from other 'elds

• 1#cessi(e 2out of flatness< in hot rolled

"late or sections

*re(ention

•Ade0uate checking of alignment "rior to

'elding cou"led 'ith the use of clam"sand 'edges

•Check accuracy of rolled section "rior to

'elding


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Arc stries Arc stries#andom areas of fused metal where the electrode, the holder, or

current return clamp accidentally touched the work and produced a

short duration arc

Causes

• *oor Access to 'ork

• 4issing insulation on electrode holderor torch

• 7ailure to "ro(ide an insulated resting

"lace for the electrode holder or torch

'hen not in use

• Loose current return clam"

*re(ention

•Im"ro(e access . modify assem&ly

se0uence /

•Institute a regular ins"ection scheme for

electrode holders and torches

•*ro(ide an insulated resting "lace

•Regularly maintain current return clam"

+


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+patter +patter

Small droplets of electrode material can be proected clear of the weld

and may fused to the parent metal

Causes

• High arc "o'er

• 4agnetic arc &lo'

• Incorrect setting for %4AW "rocess

• !am" electrodes

*re(ention

•Reduce arc "o'er

•Reduce arc length or s'ith to AC "o'er

•4odify electrical settings . &ut &e careful

to maintain full fusion

•+se dry electrodes

% $h h% $h h


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%urn $hrough%urn $hrough

&igh Amps/volts

+mall Root face

!arge Root 1ap

+low $ravel +peed

%urn through

A locali&ed collapse of the weld pool due to excessive

penetration resulting in a hole in the root run

R t D f t


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,urn through

,urn

Through

Root Defects

R t C i / idi d R tR t C i / idi d R t


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Root Coing/xidi)ed RootRoot Coing/xidi)ed Root

!oss or insufficient bac

purging gas

"ost commonly occurs

when welding stainlesssteels

*urging gases include

argon, helium andoccasionally nitrogen


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"echanical Damage"echanical Damage



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"echanical damage can be defined as any surface material

damage cause during the manufacturing process.$his can included damage caused by6

1rinding

&ammering

Chiselling

Chipping

%reaing off welded attachments torn surfaces-

2sing needle guns to compress weld capping runs

* t " t i l D f t* t " t i l D f t


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*arent "aterial Defects*arent "aterial Defects

A welding inspector should also inspect the parent

material for any visible defects

!amination

"echanical damage !ap

+egregation line

*l t ! i ti*l t ! i ti


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*late !amination*late !amination


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Any uestions.Any uestions.

7 ti7uestions


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7uestions7uestions

72 8. 1ive two main causes for the occurrence of a burn through

72 9. 1ive two main causes for the occurrence of excessive rootpenetration on a single3: butt weld

72 ;. 1ive five defects, which may occur when welding carbon

steel using the ""A welding process with the current settingto low

72


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#eld Repairs#eld Repairs

#elding Repairs#elding Repairs


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#elding Repairs#elding Repairs

Authori)ation for repair

Removal and preparation for repair

$esting of repair 3 visual and >D$

n the event of repair



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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

$he 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




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$he specification or procedure will govern how the defective

areas are to be removed. $he method of removal may be

1rinding

Chipping

"achining

(iling

xy31as gouging

Arc air gouging


Arc air gouging

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