Nosov Magnitogorsk State Technical University, Magnitogorsk, Russia:

P. P. Poletskov, Dr. Eng., Prof., Dept. of Metal Processing Technology
A. S. Kuznetsova, Dept. of Metal Processing Technology, e-mail: allakuznetsova.mgtu@mail.ru
N. V. Koptseva, Dr. Eng., Prof., Dept. of Casting Processes and Materials Science
O. A. Nikitenko, Cand Eng., Associate Prof., Dept. of Metal Processing Technology, e-mail: o.nikitenko@magtu.ru

M. N. Mikheev Institute of Metal Physics of Ural Branch of RAS, Ekaterinburg, Russia:

I. L. Yakovleva, Dr. Eng., Chief Researcher, Laboratory of Physical Metal Science

The conditions of heat treatment, providing achievement of high strength characteristics (σ_0,2 ≥ 600 N/mm²) in combination with low-temperature impact strength (KCV−60 ≥ 50 J/cm²) and plasticity (δ₅ ≥ 17 %), were determined for the new weldable sparingly alloyed steel 20G2SMRA. Steel structure was formed after hot rolling, quenching from the temperature 860 °С and consequent high tempering at the temperature 600 °С (which determined the obtained complex of steel properties) and then was examined via the method of scanning electronic microscopy. The results of energy-dispersion analysis of carbide particles which were extracted during tempering of quenched steel are presented. It is shown that the required level of strength and cold resistance is provided due to forming of mainly finedispersed lath martensite (with α-phase lath width 0.2–0.7 μm) and with small part of residual austenite (about 1 %), as well as dislocation high-temperature martensite. Sub-grain α-phase structure (with size of single sub-grains 0.1–0.7 μm) and cementite-type of carbide particles are formed during tempering.

The research was carried out under financial support of the RF Ministry of Education and Science within execution of the RF President’s grant (Agreement No. 075-15-2020-205/1 dated 29.03.2021 (int. No. MK-1979.2020.8/1)).
Electron microscope examination of foils for clearance were conducted within the boundaries of the State assignment for the theme “Structure”, State reg. No. АААА-А18-118020190116-6.

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