What is case hardened steel and what is through hardened steel?
In general, steel varieties which can be hardened not just on the surface but also deep hardened by the so-called “through hardening method” are used for the raceways and rolling elements of bearings. Foremost among these is high carbon chromium bearing steel, which is widely used. Case hardened steel has excellent efficiency against shock loads because of its combination of a hard surface layer which has been carburized and hardened to an appropriate depth and a relatively pliable inner core. NTN uses case hardened steel for almost all of its tapered roller bearings and is denoted in NTN nomenclature with 4T- or ET- prefixes.
