Practical · 5 samples · 45 min
Fault bay
Name it, locate it, size it, compare it to the supplied spec. The exam hides trouble at toes and craters.
surface
Crack
A fracture in weld metal, HAZ, or base metal. Hot (solidification, crater) or cold (hydrogen, toe, underbead).
Looks like
A sharp linear indication, often at the toe, centreline, or crater. May need magnification and side light. Rust can highlight it the next morning.
Causes
- Hydrogen + hard HAZ + restraint
- Crater left unfilled
- Excessive width-to-depth, sulphur/phosphorus
- Arc strike
- Excessive heat input then rapid cool on hardenable steel
Prevent
- Low-hydrogen practice and preheat
- Fill craters, use back-step at stops
- Correct bead shape
- No stray arcs
- Follow WPS interpass
Almost always a defect in structural work. Repair by remove-and-reweld to an approved procedure. Do not peen a crack shut.