STRESS RELIEVING

Stress relieving is carried out on metal products in order to minimise residual stresses in the structure thereby reducing the risk of dimensional changes during further manufacturing or final use of the component.

Typically, the parts that benefit from stress relieving are large and complex weldments, castings with a lot of machining, parts with tight dimensional tolerances and machined parts that have had a lot of stock removal performed.

Stress relieving is done by subjecting the parts to a temperature of about 75 ºC (165 ºF) below the transformation temperature,line A1 on the diagram, which is about 727 ºC (1340 ºF) of steel—thus stress relieving is done at about 650 ºC (1202 ºF) for about one hour or till the whole part reaches the temperature. This removes more than 90% of the internal stresses. Alloy steels are stress relieved at higher temperatures. After removing from the furnace, the parts are air cooled in still air.