Orenburg State University (Orenburg, Russia):

S. E. Krylova, Dr. Eng., Prof., Dept. of Materials Science and Technology of Materials, E-mail: krilova27@yandex.ru
E. V. Romashkov, Post-graduate Student, Aerospace Institute, Dept. of Materials Science and Materials Technology

The influence of heat treatment parameters on the structure and properties of the promising 70Cr3Mn2WTiB die steel, which is offered for the manufacture of mold parts for aluminum alloy injection molding machines, is revealed. A rational mode of thermal hardening is recommended for the developed steel, including spheroidizing annealing at a temperature of 780 °C with combined cooling; quenching at 1000 °C with oil cooling; high-temperature tempering at 550–600 °C with cooling in calm air. The structure formation and behavior of carbide phases in microalloyed steels at various stages of heat treatment are evaluated. The features of phase transformations and the mechanism of dispersion hardening during high-temperature tempering that provide the required set of mechanical and technological properties are determined. The influence of heat treatment modes on mechanical and operational properties under cyclic loading and heat exposure at normal and elevated temperatures is evaluated. Fractographic studies of zones of cyclic and static crack growth in fractures of samples after testing for crack resistance under cyclic and static loading were performed. The main regularities of changes in the thermal structural stability of chromium steels under cyclic temperature and force influences, depending on the nature of alloying and heat treatment modes, are substantiated, which made it possible to reasonably recommend the developed 70Cr3Mn2WTiB steel for implementation.

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