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A discontinuity is not automatically a defect
In inspection terminology, a discontinuity is an interruption or irregularity in structure or geometry. It becomes a defect when it exceeds the applicable acceptance criteria. This distinction prevents rejecting a joint based only on appearance and also prevents accepting it without comparing the indication with technical limits.
Surface porosity appears as open cavities
Visible pores may appear individually or in clusters on the weld surface. Contamination, inadequate shielding, moisture, or technique can contribute depending on the process. During visual inspection, record the apparent size, distribution, number, and location. Root-cause analysis should consider the actual process and welding conditions.
Undercut is a groove next to the weld toe
Undercut appears as a groove melted into the base metal along the weld toe. Current, travel speed, arc length, and manipulation can influence its formation depending on the process. Inspection should measure depth and length when the governing acceptance criteria set limits for those dimensions.
Cracks require immediate attention
Cracks may appear in weld metal, transition areas, or base material. Because they are critical indications under many codes and specifications, a suspected crack should be documented and evaluated according to the inspection procedure. Grinding it away without first identifying and recording the condition can hide useful evidence about the cause.
Irregular profile can also signal execution problems
Overlap, insufficient fill, excessive convexity or concavity, poor crater fill, and heavy spatter can point to issues in technique, settings, or sequence. Not every irregularity carries the same technical significance. Good inspection separates observation, measurement, acceptance criteria, and root-cause analysis.
Practical checklist
- Identify the indication without judging by appearance alone
- Measure when criteria require a dimension
- Mark and record the location
- Compare with the governing code, drawing, or specification
- Investigate cause before repair
Frequently asked questions
Does visible porosity always reject a weld?
Acceptance depends on the governing code or specification and the size and distribution of the indication.
Can undercut be measured?
Yes. Depth and length are commonly measured where acceptance criteria establish limits.
What should be done when a crack is suspected?
Document the indication and follow the applicable evaluation procedure before removing material or performing repair.
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