Examination and Testing of Test Pieces
The test suite
After welding, the test piece is examined by a sequence of methods:
- Visual examination (VT) - first and always. Looks for surface defects: cracks, undercut, porosity, incomplete fusion, spatter, profile.
- Radiographic testing (RT) - for butt joints, to detect internal defects.
- Bend tests - root bend, face bend, side bend. Reveal fusion defects and ductility.
- Macro/micro examination - cross-section, for penetration, fusion, heat-affected zone.
- Fracture tests - for fillet welds and some butt tests, to expose lack of fusion.
- Hardness testing - where specified for certain materials.
Order and purpose
VT is a gate: if VT fails, further testing may be pointless. RT and bend tests are complementary - RT finds volumetric defects, bends find planar/fusion defects. Macro is used where RT is impractical (e.g. fillet welds).
Traps
- Thinking RT replaces bend tests - they test different things.
- Forgetting that fracture tests are primarily for fillet welds.
- Assuming all test pieces get all tests - the suite depends on joint type and the part of the standard.
- Confusing macro (low magnification, cross-section) with micro (high magnification, microstructure).
Rule of thumb
Surface first (VT), then internal (RT), then mechanical (bend), then section (macro). Each method answers a different question.
Worked example
A fillet weld test piece is submitted. RT is not practical on a T-joint fillet, so the standard uses a fracture test and macro examination instead. If a question asks "which test for a fillet weld?", fracture/macro is the expected answer, not RT.