Defect name Description Causes

Lack of side wall fusion

Failure of weld metal to fuse to weld preparation

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

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

Current too low, travel speed too high, incorrect torch angle, inadequate inter-run cleaning.

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

Current too low, voltage too low, travel speed too high, root face too thick, root gap too wide, incorrect touch angle, inadequate cleaning.

Poor restart (cold start) Lack of fusion beneath weld start position

Incorrect welder technique (see section 7.4.1),poor earthing.

Lack of penetration Failure to achieve the minimum penetration specified by design

Current too low, travel speed too high, incorrect torch angle, incorrect weld prep.

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

Current too low, travel speed too fast, root face too thick, root gap too small, incorrect torch angle, misalignment

Excess penetration Unacceptable protrusion of the root bead

Current too high, travel speed too slow, root gap too wide, root face too thin

Root or face undercut Notch parallel to weld at weld at weld toe. Prevalent at top edge of PB fillet

Current too low, travel speed too fast ,incorrect torch angle, inadequate cleaning

Excess convexity Excess weld metal on the face of a

Current too low, voltage too low,

Excess weld metal (excess cap height) Butt or fillet weld Incorrect torch manipulationIncomplete fill (face concavity or missed edge). Insufficient throat in fillet welds

Insufficient weld metal fill giving groove on weld face resulting in insufficient throat

Poor welder technique, travel speed too fast, current too low, incorrect torch positioning

Root concavity Root pass ‘sucked back’ to give a shallow groove

Current too high, root gap too wide, root face too thin

Burn-through Localised loss of weld pool in root

Current too high, travel speed too slow,root face too thin, root gap too large

Overlap (roll-over) Weld metal that has rolled over at the edges and not fused to the parent metal. May be face or root

Weld bead too large, current too high, travel speed too slow, prevalent in horiz. Vert. Welds, inadequate cleaning

Porosity Gas entrapped in weld metal giving a cavity. May be face or root

Dirty consumable, 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 joint design trapping gas (see chapter 2)

Worm-hole (piping) Elongated gas cavity formed by solidification of large weld pool

Excessive current, travel speed too slow

Crater pipe Elongated cavity in the weld finish

Incorrect welder technique-lack of crater fill

Solidification cracking Cracks in weld produced during welding

Incorrect choice of filler metal, failure to pre parathion, crack susceptible parent

Crater cracking Short longitudinal or star-shaped crack in finish crater

Incorrect welder technique, lack of crater fill

Liquation cracking Cracking In the HAZ or in previously deposited weld metal

Incorrect Filler metal, crack sensitive parent metal, high restraint ,high heat input (see chapter 2)

Oxide entrapment Oxide films trapped within the weld metal

Oxide films in or on parent metal, oxide films in or on filler metal ,oxygen in shield gas, poor gas shielding, inadequate cathodic cleaning

Puckering Excessive oxide entrapment from weld pool turbulence

Poor gas cover, very high weld current

Tungsten or copper inclusions Accidental contact of the electrode (TIG) or contact tip(MIG)

Poor welder gas technique, incorrect mechainsed set-up

Stray arc strike Accidental arcing outside weld prep.

Welder carelessness

Spatter Droplets of weld metal expelled from weld pool

Poor welder technique, incorrect weld parameters

Under flushing Thinning below design thickness

Excessive grinding