Answer
SAE 1070 carbon steel is commonly used for cost-effective wave springs, but the cold-forming process introduces significant residual tensile stresses at the wave crests. Without a proper stress-relief heat treatment (typically $600-650^°F$ for 30 minutes), these residual stresses combine with operational loads to exceed the material's yield strength, leading to 'set' or premature fatigue failure. Furthermore, if the spring is electroplated for corrosion resistance (e.g., zinc plating), it is highly susceptible to hydrogen embrittlement. Atomic hydrogen can migrate into the high-stress areas of the grain boundaries, causing sudden, brittle fracture. A baking cycle at $375^°F$ for at least 4 hours immediately following plating is mandatory to drive out the hydrogen.
