Stress relieving is differentiated from other slow-cooling processes (e.g., annealing, normalizing) primarily by the temperature at which it is performed. Unlike tempering, microstructural phase changes do not occur during stress relieving. Stress relief benefits from a still-air cool.

Stress relieving can be done in an industrial furnace or an oven. In stress relief both temperature and time are important, but cooling rate is critical to prevent the reintroduction of stress.

Source: Dan Herring, The Heat Treat Doctor®, Atmosphere Heat Treatment, Volume 1, pages 421–428.