Official Answer
Answer
Cryogenic treatment of 302 stainless steel wave springs, involving immersion in liquid nitrogen ($-196^∘C$), promotes the transformation of retained austenite to martensite. This transformation increases the hardness and wear resistance of the wave peaks. More importantly for precision optics or cryo-valves, it improves dimensional stability by relieving internal stresses caused by the edge-winding process. Without cryo-processing, the spring might undergo subtle 'walking' or diameter changes when cycled between ambient and cryogenic temperatures, which would compromise the axial preload on sensitive lens assemblies.
