Stress relieving is an intermediate heat treatment procedure to reduce induced residual stresses as a result of machining, fabrication and welding. The application of heat to the steel during its machining or fabrication will assist in removing residual stresses that will, unless addressed during the manufacturing by stress relieving, manifest themselves at the final heat treatment procedure.

It is a relatively low temperature operation that is done in the ferrite region, which means that there is no phase change in the steel, only the reduction of residual stresses. The temperature region is usually between 800xF to 1,300xF. However, the higher that one goes in temperature, the greater the risk of surface oxidation there is. It is generally better to keep to the lower temperatures, particularly if the steel is a “pre-hard” steel. The hardness will be reduced if the stress relieve temperature exceeds the tempering temperature of the steel.
There is a general rule of thumb for time at temperature. It must be stated that the time is taken when the part is at temperature, not when the furnace is at temperature. The time at temperature for the processes of full anneal (not spheroidize anneal), normalize and stress relieve is 60 minutes at part temperature per one-inch of the maximum cross-sectional area.