Stress relief heat treatment of a specific portion of a structure.
The usual purpose of a postweld heat treatment (PWHT) is to stress-relieve the weld and the heat- affected zone (HAZ). Stress relieving heat treatment is also used when necessary to maintain dimensional stability during subsequent machining operations. Consideration must be given to possible distortion of the structure due to localized stress relief. See STRESS-RELIEF HEAT TREATMENT and HEAT TREATMENT.