AWS Certified Welding Inspector — FundamentalsWelding MetallurgyEasy
A welding inspector observes a weld discontinuity characterized by small, isolated pockets of gas entrapped within the weld metal. This discontinuity is typically spherical or elongated and can be found either individually or in clusters. Which of the following terms best describes this discontinuity?
- ASlag Inclusion
- BIncomplete Fusion
- CPorosity
- DUndercut
Show answer & explanationAnswer & explanation
Correct answer: C. Porosity
Porosity refers to gas pockets entrapped within the weld metal during solidification. These voids are typically spherical or elongated and are caused by gases failing to escape from the molten weld pool before it solidifies.
Why the other options are wrong
- A. Slag inclusion is entrapped non-metallic solid material, not gas pockets.
- B. Incomplete fusion is a lack of coalescence between the weld metal and the base metal or between adjacent weld beads.
- D. Undercut is a groove melted into the base metal adjacent to the toe or root of a weld and left unfilled by weld metal.
Porosity (Welding)
A weld discontinuity consisting of gas pockets entrapped within the solidified weld metal. It appears as spherical or elongated voids, singly or in clusters.
- Caused by gas entrapment during solidification.
- Can weaken the weld and act as stress concentrators.
- Sources include moisture, contaminants, inadequate shielding gas, or arc instability.
- Can be detected visually or with radiographic testing.
Memory trick: Remember, 'P' for Porosity means 'P' for Pockets of gas.