Meaning
Weld pool defects occur when molten filler material fails to bond completely with adjacent parent metal or previous weld passes. Unfused boundaries caused by lack of fusion create sharp internal planar voids that degrade the structural integrity of metallic joints and battery module busbar welds. Insufficient heat input or improper torch angles leave cold metal faces unjoined despite surface appearances of a complete weld bead.
The boundary of this defect definition excludes volumetric porosity and solid slag inclusions, applying strictly to planar discontinuities where metallic cohesion is absent.
Detection Reliability
Non-destructive evaluation techniques isolate planar discontinuities through volumetric ultrasonic testing or radiographic inspection. Planar void faces parallel to the inspection beam present minimal cross-sectional reflection, making detection difficult with standard straight-beam transducers. Phased array ultrasonic methods scan multiple angles across the joint to capture planar reflections.
Flaw orientation dictates signal attenuation during acoustic testing.
Formation Mechanism
Improper power settings or excessively high travel speeds prevent adequate thermal transfer into the joint root.
Structural Consequence
Planar defects create severe local stress concentrations under cyclic operational loads. When tensile loads pull across an unfused boundary, stress intensities at the crack tip rise rapidly, promoting premature fatigue failure. Rejecting components with identified planar discontinuities prevents catastrophic joint separation under dynamic working conditions.
