A welding inspector is conducting visual examinations on a newly fabricated pressure vessel made from a carbon-manganese steel. During the inspection, the inspector notices fine, interconnected cracks in the weld metal that appear to follow the dendritic structure formed during solidification. These cracks are often associated with high restraint and specific alloy compositions. What type of cracking is the inspector most likely observing?
- ALamellar tearing
- BSolidification cracking
- CReheat cracking
- DHydrogen-induced cracking (HIC)
Show answer & explanationAnswer & explanation
Correct answer: B. Solidification cracking
Solidification cracking, also known as hot cracking, occurs during the final stages of weld metal solidification. It is characterized by cracks that follow the dendritic structure and are often associated with the presence of low melting point impurities at grain boundaries, high restraint, and specific weld metal compositions. Hydrogen-induced cracking occurs after cooling, lamellar tearing is in the base metal, and reheat cracking occurs during post-weld heat treatment.
Why the other options are wrong
- A. Lamellar tearing occurs in the base metal, parallel to the rolling direction, due to through-thickness stresses and inclusions, not in the weld metal following dendritic structure.
- C. Reheat cracking occurs during post-weld heat treatment (PWHT) or high-temperature service, not during or immediately after solidification, and is typically intergranular.
- D. Hydrogen-induced cracking (cold cracking) typically occurs in the HAZ or weld metal after the weld has cooled, and its morphology is often transgranular or intergranular, not necessarily following dendritic structure.
Solidification Cracking (Weld Metal)
A type of cracking that occurs in the weld metal during the final stages of solidification. It appears as fine, interconnected cracks that typically follow the dendritic grain boundaries.
- Also known as hot cracking.
- Caused by tensile stresses acting on low-melting-point liquid films at grain boundaries.
- Aggravated by high restraint, weld shape, and presence of impurities (S, P).
- Occurs in the weld metal itself, not typically the HAZ or base metal.
Memory trick: Cracks: Hot on dendrites, Cold from H, Lamellar in base, Reheat in oven.