Common Structural Welding Defects: Identification and Review. This guide explains what a project team should clarify before fabrication or field work.
Porosity
Porosity consists of gas cavities in weld metal. Contamination, moisture or ineffective shielding can contribute. The significance depends on the type, size, distribution and applicable acceptance criteria. Visual appearance alone cannot establish the condition of the entire joint.
Undercut
Undercut is a groove along the weld toe that reduces the local section or creates a stress concentration. Acceptance depends on the applicable standard, loading and detail. Do not use a single generic millimetre limit for every structural weld.
Incomplete fusion and penetration
Fusion and penetration requirements depend on the specified joint. A discontinuity must be assessed against the design and welding requirements; a partial-joint-penetration design should not be confused with an unintended lack of penetration.
Slag inclusions and cracking
Slag inclusions can occur where non-metallic material remains in a weld. Cracking needs prompt technical assessment. Its cause and extent should be established before any repair; simply covering a visible crack with another bead does not resolve the underlying issue.
Inspection and an approved repair plan
The responsible inspector or engineer determines the required evaluation and disposition. Where repair is authorized, define removal limits, preparation, qualified procedure, welding controls and reinspection. Testing methods and acceptance criteria must match the applicable project specification.
Information for an existing-steelwork enquiry
Provide photographs, location, accessible drawings, details of any impact or change in loading, and previous inspection reports. If there is a concern about immediate stability, obtain appropriate site safety and structural assessment before continuing use or attempting repairs.
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Reference: CWB company certification. Confirm applicable standards, editions and project requirements with the responsible professionals.