Kazan (Volga Region) Federal University, Naberezhnye Chelny, Russia:

V. I. Astashchenko, Cand. Eng., Professor, Dept. of Materials, Technologies and Quality, e-mail: astvi-52@mail.ru
G. F. Mukhametzyanova, Cand. Eng., Associate Professor, Dept. of Materials, Technologies and Quality, e-mail: gulnara-ineka@mail.ru
E. V. Purtova, Postgraduate Student, Dept. of Materials, Technologies and Quality, e-mail: elena.v.purtova@gmail.com

PTS KAMAZ, Naberezhnye Chelny, Russia:

V. V. Makhonin, Head of the Bureau of Heat Treatment, e-mail: vasilii.mahonin@jandex.ru

The mechanical properties, chemical composition, hardenability and resistance to grain growth during heating of steel 18HGR were studied. The steel smelted at the Oskol electrometallurgical plant is characterized by narrow limits on the content of both individual chemical elements and the sum of manganese, chromium, nickel and molybdenum. The stability of boron steel in hardenability and its high strength, ductility and impact hardness are shown. When heated to 1000 °C, the steel retains a fi ne-grained structure. The technology of isothermal annealing of forgings for the formation of a favorable steel structure has been developed and substantiated, for subsequent mechanical and hardening processing. It is emphasized that it is necessary to austenitizing forgings at 940-950 °C, uniform and accelerated cooling-down to 680 ± 20 °C, and isothermal holding with a step-down in temperature according to the scheme 680–660–640–600 °C. The relationship between the durability of case-hardened toothed parts and the microhardness of individual structural components of steel in the core of the product is revealed. A resource-saving technology for thermochemical treatment of alloyed low-carbon steels of various composition is proposed. New criteria are recommended for predicting the stability of the properties of steel by its equivalent carbon content and the resistance of parts in operation by the microhardness of the structural components and the difference in values between them in the core of the product.

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