Heat Treatment - Stress Relieving

Engineering Materials
Manufacturing Processes

Heat treating stress relief is used to reduce the internal material stresses within a part or assembly as a consequence of manufacturing processes. Following manufactuirng processes that include forming, machining, cut, or are assemblies fabricated by welding, will have internal stresses that may cause distorsions. By heating the component or assembly materials to an appropriate temperature and holding for a known period of time to allow the entire part to reach this temperature, most of the interneal stresses can be relieved.

The resultant end item will then be less prone to dimensional variation by post manufacturing. Typically, parts that benefit from stress relieving are large and complex weldments, castings which have had a lot of machining, parts with tight dimensional tolerances and machined parts that have had a lot of stock removal performed.

Carbon steels may be stress relieved by holding a temperature at 1,100 to 1,250°F (600 to 675°C) for 1 hour per inch (25 mm) of thickness. Stress relieving offers several benefits. For example, when a component with high residual stresses is machined, the material tends to move during the metal removal operation as the stresses are redistributed. After stress relieving, however, greater dimensional stability is maintained during machining, providing for increased dimensional reliability.

In addition, the potential for stress corrosion cracking is reduced, and the metallurgical structure can be improved through stress relieving. The steel becomes softer and more ductile through the precipitation of iron carbide at temperatures associated with stress relieving.

Heating Treat - Stress Relieving Cycle

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