Answer
After the cold-winding process, spiral retaining rings contain significant internal residual stresses. If left untreated, these stresses can cause the ring to 'warp' or change diameter over time, especially if exposed to heat. Stress relieving involves heating the rings to approximately $650-750^{\circ}F$ ($340-400^{\circ}C$) for a specific duration. This temperature is below the transformation range, so it doesn't affect the hardness but allows the internal dislocations to rearrange and the residual stresses to dissipate. This ensures that the ring maintains its 'cling-fit' diameter and remains flat. For precision assemblies like optical lens mounts, an improperly stress-relieved ring can introduce tilt into the lens over time as the ring 'settles' into its final shape.
