Effects of niobium additions on the properties and life cycle of steels for hot working tools

Mechanical, thermal, and chemical loads influence the life cycle of hot working tools. For economic hot forming processes, tools and dies are made from classical hot work steels of the CrMoV and NiCrMoV steel groups. The CrMoV steels, with a secondary hardening effect, are mainly used in the die-casting industry and as high stressed dies in drop forging presses. Hammer dies have a higher demand on toughness, so NiCrMoV grades are used. In every case, tool properties depend on the steelmaking processes and the final heat treatment. Increasing demands on tools are created by changes in process technologies, such as using bigger tools and dies or critical cavity geometries. In this case, there is a need for a further optimization of classical tool steels in view of the toughness behavior. This paper shows one way to increase mechanical-technological properties through small additions of niobium that lead to a higher toughness of existing steels grades. Thus, microalloying can be used for alloy design of new hot work steels. (AU) Copyright © 2018 Companhia Brasileira de Metalurgia e Mineração (CBMM)All rights reserved