440C is a 400 series stainless steel, and is the highest carbon content from 400 stainless steel series. It is usually heat treated to reach hardness of 58–60 HRC. It is a bearing steel, and used in rolling contact stainless bearings, e.g. ball and roller bearings. It is also used to make knife blades. 440C can be oil quenched to achieve maximum hardness.
Composition
440C has a carbon (C) content of 0.95–1.20%, chromium (Cr) content of 16.00–18.00%, molybdenum (Mo) content of 0.75%, Manganese (Mn) content of 1.0%, and silicon content of 1.0%.
References
440C Wikipedia(Text) CC BY-SA