Official Answer
Answer
탈탄은 산소가 풍부한 분위기에서 열처리하는 동안 강철 표면층에서 탄소가 손실되는 현상입니다. 이는 코어보다 항복 강도가 훨씬 낮은 부드러운 '페라이트' 스킨을 생성합니다. For a 웨이브 스프링, which relies on surface fiber stress $\sigma = \frac{3 \pi P D_m}{2 N^2 b t^2}$, decarburization leads to immediate 'setting' (permanent loss of free height) upon the first compression. Metallographic examination (per ASTM E1077) would reveal a lighter-colored surface layer. This is avoided by using 'atmosphere-controlled' furnaces or vacuum heat treatment for high-reliability parts.
