Naberezhnye Chelny Institute (Branch) of Kazan (Volga Region) Federal University (Naberezhnye Chelny, Russia)

V. I. Astashchenko, Dr. Eng., Prof.
T. V. Shveyova, Cand. Eng., Associate Prof., asttv@mail.ru
D. A. Bashmakov, Cand. Eng., Associate Prof., Head of the Dept. of Electric Power and Electrical Engineering
T. E. Panfilov, Postgraduate Student
D. T. Safarov, Cand. Eng., Associate Prof.

An analysis of authoritative sources regarding the enhancement of toughness and fracture resistance of structural steels at low temperatures was conducted. Data are presented on the strength and ductility of 40Kh steel components manufactured using various technological processes, including different semi-finished product forms and heat treatment methods. The microstructural states of 40Kh and 42KhMFA steels were investigated following various treatments, and impact bending tests were performed at temperatures ranging from +20 °C to –60 °C. Certified equipment and standard testing methods were employed to determine chemical composition, conduct metallographic analysis, and perform impact toughness testing. The study demonstrates that steels with a sorbitic structure exhibit superior impact toughness compared to those with a ferrite-pearlite structure across the +20 °C to –60 °C temperature range. Following quenching and tempering, 42KhMFA steel exhibits higher resistance to fracture under impact bending than 40Kh steel at all tested temperatures. Using aqueous polymer solutions as a quenching medium instead of oil during the hardening stage of steel heat treatment makes it possible to further enhance the steels’ resistance to fracture at sub-zero temperatures. Fractographs of the fracture surfaces of specimens tested for impact toughness at various temperatures are presented.
This work was carried out within the framework of the state assignment dated January 17, 2025 (No. 75-03-2025-426), on the topic “Development of a prototype automated line for the heat treatment of fasteners.”

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