THERMOLD H12 (formerly Thermold B) is a hot-work tool steal offering very high hardenability with good toughness and resistance to softening in service. It is readily heat treated to produce a uniformly fine-grained microstructure, resulting in longer die life. This datasheet provides information on composition, physical properties, hardness, and tensile properties as well as fracture toughness. It also includes information on high temperature performance as well as forming, heat treating, machining, and joining. Filing Code: TS-239. Producer or source: Cyclops Corporation.