Machining of pieces can produce internal stresses in several parts. The larger and more complex the work piece, the more tensions will occur. These internal tensions can be detrimental in the long run, creating cracks and other damage. Therefore, the stress relief is often necessary.
The stress relief is a controlled application of heat, before and/or subsequent to deformation and / or machining, which improves the quality of the metallurgical structure, preventing the formation of residual stresses.
Stress relief can be integral or localized. The temperature is adapted to the characteristics of the treated material during a specified time followed by controlled cooling.
Care must be taken to ensure uniform cooling, particulary when the component has different thicknesses. If the cooling rate is not uniform it may generates new tensions.
There are several ways of heating for stress relief such as gas furnaces, electric resistance and induction.
Stress relieving of ends of tube by induction
