Different Types of Welding Defects : Causes and Remedies

 

     A list of weld defects and their causes is given below.

     Other defects not listed are mainly those of geometry and include misshapen and incorrectly sized welds, variable cap width and height, weld face roughness, incomplete weld fill and asymmetry of fillet welds.

     These are all welder-induced problems, requiring improved shop-floor discipline and/or welder retraining.

Defect Name: Lack of side wall fusion

ISO 6520 Defect No: 4011 (Fig – 11.1)

Description of Lack of side wall fusion: Failure of Weld Metal to fuse to weld preparation.

Causes of Lack of side wall fusion:

  • Current too low,
  • travel speed too high,
  • incorrect torch angle,
  • oxide film on prep. Surfaces,
  • inadequate join cleaning,
  • weld preparation too narrow.

Defect Name: Lack of inter-run fusion

ISO 6520 Defect No: 4012 (Fig – 11.1)

Description of Lack of inter-run fusion: Failure of weld metal to fuse to preceding run

Causes of Lack of inter-run fusion:

§  Current too low,

§  travel speed too high,

§  incorrect torch angle,

§  inadequate inter-run cleaning



Defect Name: Lack of root fusion

ISO 6520 Defect No: 4013 (Fig – 11.1)

Description of Lack of root fusion: Root bead fully penetrated but not fused to root face

Causes of Lack of root fusion:

§  current too low

§  voltage too low

§  travel speed too high

§  root face too thick

§  root gap too wide

§  incorrect torch angle

§  inadequate cleaning

Remedies of Fusion Related Weld Defects:

§  use a sufficiently wide joint preparation

§  select welding parameters (high current level, short arc length, not too high a welding speed) to promote penetration into the joint side wall without causing flooding

§  ensure the electrode/gun angle and manipulation technique will give adequate side wall fusion

§  use weaving and dwell to improve side wall fusion providing there are no heat input restrictions

§  if arc blow occurs, reposition the current return, use AC (in MMA [SMA] welding) or demagnetize the steel

Defect Name: Poor restart (Cold start)/Lack of fusion

ISO 6520 Defect No: 517

Description of Poor Restart: Lack of fusion beneath weld start position.

Causes of Poor Restart:

§  Incorrect welder technique

§  Poor earthing



Defect Name: Lack of Penetration

ISO 6520 Defect No: 402

Description of Lack of Penetration: Failure to achieve the minimum penetration specified by design.

Causes of Lack of Penetration:

§  Current too low

§  Travel speed too high

§  Incorrect torch angle

§  Incorrect weld prep.

Defect Name: Insufficient (lack of) root penetration

ISO 6520 Defect No: 4031 (Fig – 11.2)

Description of Insufficient (lack of) root penetration: Failure of weld metal to penetrate fully root faces.

Causes of Insufficient root penetration:

§  Current too low

§  Travel speed too fast

§  Root face too thick

§  Root gap too small

§  Incorrect torch angle

§  Misalignment

Defect Name: Excess Penetration

ISO 6520 Defect No: 504 (Fig – 11.3)

Description of Excess Penetration: Unacceptable protrusion of the root bead.

Causes of Excess Penetration:

§  Current too high

§  Travel speed too slow

§  Root gap too wide

§  Root face too thin

Defect Name: Root or face undercut

ISO 6520 Defect No: 501 (Fig – 11.4)

Description of Root or Face Undercut: Notch parallel to weld at weld toe. Prevalent at top edge of PB fillet.

Cause of Root or Face Undercut:

§  Current too high

§  Travel speed too fast

§  Incorrect torch angle

§  Inadequate cleaning

Defect Name: Excess Convexity

ISO 6520 Defect No: 502 (butt) (Fig – 11.5)

Description of Excess Convexity:  Excess weld metal on the face of a butt or fillet weld. Excess convexity can produce notch effect in the welded area and consequently , concentration of stress under load.

Causes of Excess Convexity:

§  Incorrect welding technique

§  Current too high

§  Travel speed too low

§  Incorrect torch manipulation

Defect Name: Excess Weld Metal (Excess cap Height)  

ISO 6520 Defect No: 503 (fillet) (Fig - 11. 5)

Description of Excess Weld Metal:  Excess weld metal on the face of a butt or fillet weld.

Causes of Excess Weld Metal:

§  Incorrect welding technique

§  Current too high

§  Travel speed too low

§  Incorrect torch manipulation

Defect Name: Incomplete fill (face concavity of missed edge). Insufficient throat in fillet welds  

ISO 6520 Defect No: 511 (Fig - 11. 6)

Description of Incomplete fill:  Insufficient weld metal fill giving groove on weld face resulting in insufficient throat.  

Causes of Incomplete fill:

§  Poor welder technique

§  Travel speed too fast

§  Current too low

§  Incorrect torch positioning

Defect Name: Root Concavity   

ISO 6520 Defect No: 515 (Fig – 11.7)

Description of Root Concavity:  Root pass ‘sucked back’ to give a shallow groove.

Causes of Root Concavity:

§  Current too high

§  Root gap too wide

§  Root face too thin

Defect Name: Burn – through    

ISO 6520 Defect No: 510

Description of Burn-through:  Localized loss of weld pool in root.

Causes of Burn-through:  

§  Current too high,

§  Travel speed too slow

§  Root face too thin

§  Root gap too large

Defect Name: Overlap (roll-over)   

ISO 6520 Defect No: 506 (Fig – 11.8)

Description of Overlap:  Weld metal that has rolled over at the edges and not fused to the parent metal. May be face or root.  

Causes of Overlap:

§  Weld bead too large

§  Current too high

§  Travel speed too slow

§  Prevalent in horiz.-vert. welds

§  Inadequate cleaning

Defect Name: Porosity   

ISO 6520 Defect No: 201

Description of Porosity:  Gas entrapped in weld metal giving a cavity. May be localized, uniformly distributed or aligned.  

Causes of Porosity:

§  Dirty consumables

§  Poorly cleaned or dirty weld preparations

§  Contaminated shield gas

§  Contaminated ((hydrogen containing) parent metal – especially castings

§  Oxide film on parent metal

§  Porous gas hoses

§  Leaks in gas delivery system

§  Condensation

§  Poor join design trapping gas

Defect Name: Worm-hole(piping)   

ISO 6520 Defect No: 2016

Description of Worm-hole:  Elongated gas cavity formed by solidification of large weld pool.

Causes of Worm-hole:

§  Excessive current

§  Travel speed too slow

Defect Name: Crater pipe   

ISO 6520 Defect No: 2024

Description of Crater pipe:  Elongated cavity in the weld finish crater.  

Causes of Crater pipe:

§  Incorrect welder technique

§  Lack of crater fill

Defect Name: Solidification Cracking   

ISO 6520 Defect No: 100

Description of Solidification Cracking:  Cracks in weld produced during welding.  

Causes of Solidification Cracking:

§  Incorrect choice of filler metal

§  Failure to control dilution

§  Incorrect edge preparation

§  Crack susceptible parent metal

§  High restraint

§  High heat input

Defect Name: Crater cracking   

ISO 6520 Defect No: 104

Description of Crater Cracking:  Short longitudinal or star shaped crack in finish crater.

Causes of Crater Cracking:

§  Incorrect welder technique

§  Lack of crater fill

Defect Name: Liquation Cracking   

ISO 6520 Defect No: 100

Description of Liquation Cracking:  Cracking in the HAZ or in previously deposited weld metal.

Causes of Liquation Cracking:

§  Incorrect filler metal

§  Crack sensitive parent metal

§  High restraint

§  High heat input

Defect Name: Oxide Entrapment    

ISO 6520 Defect No: 303

Description of Oxide Entrapment:  Oxide films are trapped within the weld metal.  

Causes of Oxide Entrapment:

§  Oxide films in or on parent metal

§  Oxide films in or on filler metal

§  Oxygen in shield gas

§  Poor gas shielding

§  Inadequate cathodic cleaning

Defect Name: Puckering   

ISO 6520 Defect No: 3034

Description of Puckering:  Excessive Oxide entrapment from weld pool turbulence.  

Causes of Puckering:

§  Poor gas cover

§  Very high weld current

Defect Name: Tungsten or copper inclusions

ISO 6520 Defect No: 3041 (tungsten), 3042 (copper)  

Description of Tungsten or Copper Inclusions:  Accidental contact of the electrode (TIG) or contact tip (MIG)

Causes of Tungsten or copper inclusions:

§  Poor welder technique

§  Incorrect mechanized set-up

Defect Name: Stray arc strike   

ISO 6520 Defect No: 602

Description of Stray arc strike:  Accidental arcing outside weld prep..

Causes of Stray arc strike:

§  Welder carelessness.

Defect Name: Spatter   

ISO 6520 Defect No: 602

Description of Spatter:  Droplets of weld metal expelled  from weld pool.

Causes of Spatter:

§  Poor welder technique

§  Incorrect weld parameters

Defect Name: Under flushing   

ISO 6520 Defect No: 606

Description of Under flushing:  Thinning below design thickness.  

Causes of Under flushing:

§  Excessive Grinding

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