Sub Critical Annealing or Stress Relieving is undertaken to remove residual stresses generated by processes such as machining, forming, welding etc. These stresses may result in unwanted distortion after further processing. They may also have detrimental effects on fatigue life and stress corrosion. Whilst peak stresses can be relieved at 150-200°C after hardening, to remove all residual stresses, stress relieving is undertaken at temperatures 550-680ºC. Stress relieving at high temperatures may often be referred to as sub-critical annealing or process annealing.