Hydrogen as Trace Element
Hydrogen diffuses into the metal lattice and forms defects there. This causes stress and pressure buildup, which leads to hydrogen-induced cracking (HIC).
Physicochemical Mechanism of Action
Hydrogen diffuses into the metal lattice and forms defects there. These defects cause local stress and pressure build-up, since hydrogen molecules are smaller than metal atoms in the lattice.
Metallurgical Relevance & Welding Risks
Hydrogen-induced cracking (HIC) occurs due to pressure and stress build-up in the weld. These cracks can lead to hot cracking, fracture, or overall reduction of mechanical properties. High hydrogen content can also impair strength and toughness of the material.
Workshop Practice & Action Guidelines
To avoid hydrogen-induced cracking, thoroughly clean the metal before welding. Use proper shielding during welding and ensure controlled cooling. For high-grade steels, post-weld hydrogen removal can be improved by hydrogen gas treatment or baking.