Official Answer
Answer
Austenitic stainless steels like 316 exhibit a high work-hardening rate during the flat-wire rolling and subsequent coiling process. As the wire is shaped into the wave profile, the localized plastic deformation increases the hardness and yield strength but reduces ductility. For very thin sections (e.g., $t < 0.005$ inches), the material can become brittle, leading to micro-cracking at the wave peaks. Process control involves monitoring the 'Springback' angle during coiling, which is a function of the ratio $E/E_{tan}$ (where $E_{tan}$ is the tangent modulus). If the work hardening is inconsistent across the coil, the resulting wave heights will vary, leading to 'cocking' of the spring when under load.
