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
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2
Q

Porosity

A

Entrapped gas

  • spherical
  • elongated =wormhole
  • linear or clustered
  • internal or surface
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3
Q

Undercut

A

Gouging out base metal near a weld

  • parallel to weld
  • can be internal
  • stress concentration when in-service
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4
Q

Lack of Fusion

A

Lack of union between weld metal and parent metal

  • parallel to weld surface
  • associated with slag sometimes
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5
Q

Overlap / Cold lap

A

Form of Lack of Fusion when cap overlaps the parent material

- stress riser or stress notch

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6
Q

Slag Inclusions

A

Slag embedded in weld

  • irregular shape
  • Linear = wagon tracks
  • internal/external
  • from welding with flux
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7
Q

Oxide Inclusions

A

oxides with high melting point on base metal surface

- must be significant size to detect

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8
Q

Tungsten Inclusions

A

Piece of tungsten electrode trapped in weld

  • sharp edge
  • welds from GTAW
  • virtually undetectable
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9
Q

Insufficient Penetration

A

Inadequate penetration of weld joint root

  • root of weld
  • appear similar to subsurface cracks
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10
Q

Hot Cracking

A

Cracks from elevated temperatures

  • jagged
  • in weld or HAZ
  • crater or longitudinal
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11
Q

Cold / Under-bead Cracking

A

Occur right after cooling

  • jagged
  • in weld or HAZ
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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
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