Relaxation of Residual Stresses
Stress relief is the process by which internal stresses in metals decrease over time and temperature. This occurs through thermal activation or plastic flow, stabilizing component geometry.
Physical-Chemical Mechanism of Action
Residual stresses in metals come from an incomplete crystal structure or mechanical loading. These stresses can relax over time and temperature as the atomic structure adjusts. Thermal activation increases atom mobility, while plastic flow changes their position to relieve stress.
Metallurgical Relevance & Welding Risks
If relaxation is insufficient, residual stresses after welding can cause cracks or distortion. This is especially a risk in highly stressed parts and in materials under high stress states. Cooling too fast can prevent relaxation, which is a risk to part integrity.
Workshop Practice & Action Guidelines
To ensure effective relaxation of residual stresses, control the cooling after welding. You can do this with a cooling curtain or by using cooling gases. Set the cooling rate to match the specific material requirements. For critical parts, it's best to cool slowly to make sure all stresses are relieved.