Crucible CPM Rex M4 HC (HS) is a high-vanadium high-speed tool steel made by the Crucible particle metallurgy (CPM) process. This higher-carbon modification of M4 (See Alloy Digest TS-264, November 1973) has high hardening. It also comes with a high-sulfur modification for large cross-section pieces to ease machinability. This datasheet provides information on composition, physical properties, hardness, and elasticity as well as fracture toughness. It also includes information on forming, heat treating, machining, and surface treatment. Filing Code: TS-639. Producer or source: Crucible Service Centers Divisional Headquarters.