Diffusion Coefficient of Hydrogen in Iron
The diffusion coefficient of hydrogen in iron describes how fast hydrogen atoms move in the metal. It is temperature-dependent and influences the formation of cold cracks.
Physicochemical Mechanism of Action
The diffusion coefficient indicates how fast hydrogen atoms diffuse into the iron lattice. As temperature rises, the diffusion coefficient increases, raising the migration speed of hydrogen.
Metallurgical Relevance & Welding Risks
A high diffusion coefficient can lead to rapid hydrogen accumulation in the lattice. This can cause cold cracks, which are especially dangerous because they are prone to stress and temperature equalization processes. Risks increase when welding iron at high temperatures or in environments with high hydrogen exposure.
Workshop Practice & Action Guidelines
To avoid cold cracks, design the welding process to keep the lattice temperature as low as possible. For heavily stressed steels or at high temperatures, it's advisable to degas the iron before welding and perform careful cooling after welding.