CPM Rex 121 is a super high-speed steel with significantly higher wear resistance and red hardness than other high-speed steels. It is best suited for applications requiring high cutting speeds. It may provide an alternative to carbide where carbide cutting edges are too fragile. The annealed hardness is approximately 350-400 HB, and maximum hardness is approximately 72 HRC. This datasheet provides information on composition, physical properties, microstructure, hardness, and elasticity as well as fracture toughness. It also includes information on high temperature performance and wear resistance as well as heat treating and surface treatment. Filing Code: TS-591. Producer or source: Crucible.