Duplex Steel Hydrogen-Induced Cracking
The damaging accumulation of atomic hydrogen at dislocation and phase boundaries in austenitic-ferritic steels, which can lead to brittle failure under mechanical stress.
Hydrogen is a real problem with duplex steels. It diffuses into the crystal structure and makes the structure brittle. If you don't control it during welding, you'll get cold cracks, often only after hours or days. Therefore, make sure to use dry filler materials and clean edges – grease, rust, or moisture are sources of hydrogen. You must choose the heat input so that the structure transforms properly. If the weld cools too quickly, the structure will transform in an undesirable direction. After welding, a heat treatment may be necessary to remove the hydrogen. But it's not always mandatory – it depends on the material and wall thickness. When in doubt, ask the technologist before doing something wrong.