Weld Discontinuities & Defects Flashcards

Which weld discontinuity is described as a groove melted into the base metal along the toe of the weld?

Answer: Undercut

Undercut is a groove or channel melted into the base metal at the weld toe or weld root that is left unfilled by weld metal.

What is the primary cause of porosity in a completed weld?

Answer: Entrapped gas in the solidifying weld pool

Porosity is caused by gas that becomes entrapped in the solidifying weld pool before it can escape, forming voids or pockets.

The term 'incomplete fusion' refers to which weld discontinuity?

Answer: A lack of bond between weld metal and base metal or between weld passes

Incomplete fusion (also called lack of fusion) occurs when the weld metal fails to fuse properly with the base metal or with adjacent weld passes.

Overlap in a weld is best described as:

Answer: Weld metal protruding beyond the weld toe onto the base metal without fusion

Overlap is a condition where weld metal flows over the base metal surface beyond the weld toe but does not fuse with it, creating a mechanical notch.

Crater cracks most commonly form at which location?

Answer: In the depression at the end of a weld bead where the arc was extinguished

Crater cracks form in the crater (depression) left at the end of a weld bead when the arc is extinguished, because the small pool cools rapidly under high restraint.

A longitudinal crack in a weld is oriented in which direction?

Answer: Parallel to the weld axis

A longitudinal crack runs parallel to the weld axis (along the length of the weld) and can occur in the weld metal or heat-affected zone.

Underfill is a weld discontinuity that occurs when:

Answer: The weld face or root surface is below the adjacent base metal surface

Underfill occurs when the deposited weld metal is insufficient to fill the groove or joint, leaving the weld face or root surface below the plane of the base metal.