Intercrystalline hot crack
A crack in the weld metal or HAZ during solidification, caused by low-melting grain boundary eutectics under shrinkage stresses.
Physical-Chemical Mechanism of Action
During cooling, low-melting phases such as silicon or carbon form at the grain boundaries in the weld. These phases grow during solidification and lead to local stresses that can cause cracking at high shrinkage stresses.
Metallurgical Relevance & Welding Risks
An intercrystalline hot crack can lead to fine, invisible destruction of the weld. This can cause failure under mechanical load and become a critical safety risk in the component's service.
Workshop Practice & Instructions
To avoid intercrystalline hot cracks, it is important to cool the weld as quickly as possible. This can be achieved by carefully selecting the shielding gas and cooling techniques. A high cooling rate (t8/5 < 10 s) prevents the formation of low-melting grain boundary eutectics and reduces the risk of cracking.