Heat treatment and properties of high performance hot working tool steel

摘要

The properties, in the as hardened condition or after nitriding treatment, of a new Cr hot working tool steel, having a composition similar to AISI H10 but with reduced Mo and V contents, have been studied on KCU test bars, taking into account the effects of the metallurgical directions and of the position at the surface or at the core of the steel block, from which the test specimens have been machined. In the as hardened condition, the steel guarantees good isotropic properties, whilst nitriding induces brittle behaviour in the KCU samples taken from the core of the steel block, caused by small microstructural differences between the surface and the core ofthe material. The morphology of the surface of the fracture confirms the presence of brittle zones in the material at the center of the block, whilst the fracture always exhibits toughness at the block surface. However, the presence of brittle and tough mixed structures in the zones at the core of the steel block enables the die to absorb and redistribute the tension which has been applied.