Welding Discontinuities (5) Flashcards
1
Q
Discontinuities found with MPI (8)
A
- Porosity
- Lack of fusion
- Inclusions
- Hot/cold cracking
- Undercut
- Overlap / Cold lap
- Insufficient penetration
- Lamellar tearing
2
Q
Porosity
A
Entrapped gas
- spherical
- elongated =wormhole
- linear or clustered
- internal or surface
3
Q
Undercut
A
Gouging out base metal near a weld
- parallel to weld
- can be internal
- stress concentration when in-service
4
Q
Lack of Fusion
A
Lack of union between weld metal and parent metal
- parallel to weld surface
- associated with slag sometimes
5
Q
Overlap / Cold lap
A
Form of Lack of Fusion when cap overlaps the parent material
- stress riser or stress notch
6
Q
Slag Inclusions
A
Slag embedded in weld
- irregular shape
- Linear = wagon tracks
- internal/external
- from welding with flux
7
Q
Oxide Inclusions
A
oxides with high melting point on base metal surface
- must be significant size to detect
8
Q
Tungsten Inclusions
A
Piece of tungsten electrode trapped in weld
- sharp edge
- welds from GTAW
- virtually undetectable
9
Q
Insufficient Penetration
A
Inadequate penetration of weld joint root
- root of weld
- appear similar to subsurface cracks
10
Q
Hot Cracking
A
Cracks from elevated temperatures
- jagged
- in weld or HAZ
- crater or longitudinal
11
Q
Cold / Under-bead Cracking
A
Occur right after cooling
- jagged
- in weld or HAZ
12
Q
Lamellar Tearing
A
Crack in base metal of structural welded shapes
- internal or at edges
- terrace-shaped
- indication like a crack
- parallel to surface
