What is Weld Seam Inspection?
CT-based weld seam inspection refers to the non-destructive three-dimensional examination of welded joints for imperfections such as cracks, pores, lack of fusion and inclusions. Compared to conventional methods (X-ray film, ultrasound), CT delivers three-dimensional location data of defects and enables quantitative characterisation (size, shape, volume).
Scientific background
Welding defects originate from incomplete fusion (lack of fusion), dissolved gases (gas porosity), shrinkage voids (cavities) or trapped slag (inclusions). CT detects these inhomogeneities via grey-value differences in the volumetric dataset. Detection limits depend strongly on material absorption, wall thickness and achievable voxel size.
Relevant key metrics
- Typical detection limit: pores from ≥ 0.1 mm diameter in steel, depending on wall thickness.
- Linear cracks detectable from ~50 µm width with micro-CT.
- Quantitative evaluation: pore volume fraction, pore distribution, maximum single pore size.
Standards and thresholds
- Standards: ISO 17635 (Non-destructive testing of welds — general rules for metallic materials), DIN EN ISO 5817 (quality levels for imperfections), ISO 10675 (acceptance criteria for butt welds), EN ISO 15614 (welding procedure qualification).
- Typical thresholds (in practice): Quality level B per ISO 5817 for highest requirements; maximum pore ≤ 0.3 × wall thickness, pore area fraction ≤ 2 % in the weld metal.
- Validity: Acceptance criteria depend on quality level (B/C/D), load case and material. Safety-critical assemblies (aerospace, pressure vessels) apply tighter limits.
Application in industrial practice
- Quality inspection of safety-critical weld seams in automotive (body, chassis) and aerospace.
- Analysis of welds in pressure vessels and piping systems.
- Failure analysis after weld seam failure to determine root cause.
Sources and reference date
- ISO 17635:2016.
- DIN EN ISO 5817:2023.
- ISO 10675-1:2016.
- EN ISO 15614-1:2017.
- Reference date: March 2026.