Stress relieving

Heating below the transformation temperature in order to reduce or eliminate residual stresses in a component. Because no transformation has taken place, the cooling rate is not critical and is generally fairly rapid.

Castings and welded fabrications generally contain complex internal stress distributions, which arise from the thermal and material transformations which take place during the foundry and welding operations. If they are not rectified, such stress distributions may be disturbed during further manufacturing operations, leading to distortion or cracking of the components produced. With higher alloy steels and cast irons internal stress can cause distortion or cracking even before any further manufacturing operations are commenced. It is possible, by means of a thermal cycle, generally within the temperature range 550-650°C to reduce or remove the internal stress and render the work piece suitable for further manufacturing operations. Close control of the thermal cycle, ensuring temperature uniformity within the furnace and temperature distribution throughout the work piece is vital and multi-point probe thermocouples are routinely used for this.

Sometimes called stress relief annealing.