Lack of Fusion
A weld defect where fusion did not occur between the weld and base metal (at the sides of the weld) or between weld passes. Lack of fusion creates a linear discontinuity parallel to the weld surface. It significantly reduces weld strength and is a critical rejectable defect. Lack of fusion is best detected by angle-beam ultrasonic testing from the side. Proper arc voltage and technique prevent lack of fusion.
A weld defect where fusion did not occur between the weld and base metal (at the sides of the weld) or between weld passes. Lack of fusion creates a linear discontinuity parallel to the weld surface. It significantly reduces weld strength and is a critical rejectable defect. Lack of fusion is best detected by angle-beam ultrasonic testing from the side. Proper arc voltage and technique prevent lack of fusion.
Detection and Assessment
Lack of Fusion must be detected early and accurately characterized to determine safety implications. Multiple NDT methods may be required for comprehensive evaluation.
Acceptance Criteria
Industry standards such as ASME Section V, AWS D1.1, and API standards provide specific acceptance limits. Whether a detected lack of fusion is acceptable depends on material, component function, and applicable code.
Best Practices
- Always follow applicable NDT standards and procedures
- Use properly calibrated and maintained equipment
- Ensure personnel are properly trained and certified
- Document inspection procedures and results completely
- Keep current with industry standards and best practices
Type
Defects
Material discontinuities and flaws detected by NDT
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