Welding Discontinuities (5) Flashcards
Discontinuities found with MPI (8)
- Porosity
- Lack of fusion
- Inclusions
- Hot/cold cracking
- Undercut
- Overlap / Cold lap
- Insufficient penetration
- Lamellar tearing
Porosity
Entrapped gas
- spherical
- elongated =wormhole
- linear or clustered
- internal or surface
Undercut
Gouging out base metal near a weld
- parallel to weld
- can be internal
- stress concentration when in-service
Lack of Fusion
Lack of union between weld metal and parent metal
- parallel to weld surface
- associated with slag sometimes
Overlap / Cold lap
Form of Lack of Fusion when cap overlaps the parent material
- stress riser or stress notch
Slag Inclusions
Slag embedded in weld
- irregular shape
- Linear = wagon tracks
- internal/external
- from welding with flux
Oxide Inclusions
oxides with high melting point on base metal surface
- must be significant size to detect
Tungsten Inclusions
Piece of tungsten electrode trapped in weld
- sharp edge
- welds from GTAW
- virtually undetectable
Insufficient Penetration
Inadequate penetration of weld joint root
- root of weld
- appear similar to subsurface cracks
Hot Cracking
Cracks from elevated temperatures
- jagged
- in weld or HAZ
- crater or longitudinal
Cold / Under-bead Cracking
Occur right after cooling
- jagged
- in weld or HAZ
Lamellar Tearing
Crack in base metal of structural welded shapes
- internal or at edges
- terrace-shaped
- indication like a crack
- parallel to surface