Process of stress relief annealing
Stress relieving is a thermal heat treatment process in which metallic materials are heated to relieve internal stresses that may have arisen during previous processing steps such as welding, forging, casting, or cold forming. For low-alloy steel, the process is typically carried out at temperatures between 550°C and 680°C. For quenched and tempered materials, the stress relieving temperature is generally kept 30°C to 50°C below the tempering temperature to minimize the reduction in strength. Depending on the cross-section, the material is then heated to a specific temperature and then cooled slowly and in a controlled manner to prevent the formation of new stresses. Components are generally treated in air, as the resulting scale (oxidation) on the external surfaces can be removed during further processing. Alternatively, it is also possible to treat components under vacuum or in a protective gas (nitrogen, argon, etc.), with the advantage that the surfaces remain bare or at least scale-free (light tempering colors).
