Hydrogen trap in weld metal
Hydrogen traps are lattice defects or precipitates that store hydrogen and delay diffusion-related cracking.
Physico-chemical mechanism of action
Hydrogen sinks are microscopic defects in the metal lattice, such as voids or pores. They can store hydrogen physically (in the lattice structure) or chemically (by adsorption on surfaces). This prevents hydrogen from diffusing into the environment and forming cracks.
Metallurgical relevance & risks in welding
Hydrogen sinks can delay or prevent cracking because they trap free diffusing hydrogen. This is especially important in highly stressed components where hydrogen-induced cracking can be dangerous. However, excessive hydrogen content can also lead to hydride formation and other metallurgical changes.
Workshop practice & instructions
To effectively create hydrogen sinks, it is important to use a clean weld and a good deoxidizer. The melting time should be long enough (approx. 10-20 s) to stabilize the lattice structure. After welding, the workpiece should be cooled well to prevent hydrogen diffusion. For special materials like high-carbon steel, a special hydrogen removal treatment may be required.