JSC VNIKTIneftekhimoborudovanie, Volgograd, Russia

M. V. Efimov, Chief Designer, Design Bureau

Volgograd State Technical University, Volgograd, Russia
N. I. Gabelchenko, Cand. Eng., Associate Prof., Dept. of Foundry Machines and Technology, e-mail: ngabelchenko@mail.ru

N. A. Kidalov, Dr. Eng., Prof., Head of the Dept. of Foundry Machines and Technology

OJSC Volgogradneftemash, Volgograd, Russia
D. O. Aliev, Cand. Eng., Deputy General Director for Technical Development and Quality

The paper presents the results of studies on the effect of chemical composition and heat treatment modes on the structure of cast and forged samples made of low-alloy steel 20GML. Using the software and hardware complex Thixomet for analyzing the microstructure of the solid’s surface, the presence of the effect of re-normalization on the appearance of zones of increased concentration of perlite in the structures of cast and forged samples was established. The concentration of pearlite grains is formed in the form of a grid. By the method of quantitative local electron probe elemental determination on a scanning electron microscope Phenom XL, the results of a study of the general and local chemical composition in a section of the sample structure with a zone of increased concentration of perlite and outside it were obtained. A method is proposed for determining the deviation of the content of alloying elements in a local area in the zone of high perlite content from the average content of these elements in the sample area under study. The results of studies to determine the concentrations of manganese, silicon and chromium in the samples are presented. An increase in the concentration of manganese in the zone of pearlite grids and a uniform distribution of the concentration of molybdenum and chromium throughout the structure, including in the zone with a high content of perlite, were found. Temperature ranges for re-normalization have been established, leading to the appearance of a pronounced pearlitic grid. Based on the properties of manganese as an alloying element, a justification for the effect of the appearance of a superstructure in the form of a pearlite grid is presented. It has been established that cast and forged samples with a pearlite mesh in the structure have the highest combinations of strength properties and toughness at negative temperatures.

1. Lashchinsky A. A., Tolchinsky A. R. Fundamentals of design and calculation of chemical equipment: reference book. 4^th edition, reprinted. Moscow : Alyans, 2011. 752 p.
2. Timonin A. S. Fundamentals of design and calculation of chemical-engineering and nature protection equipment: handbook. 2^nd edition, revised and enlarged. Kaluga : Izdatelstvo N. Bochkarevoy, 2002. Vol. 1. 2002. 850 p.
3. Encyclopedic Dictionary of Metallurgy: In 2 volumes. Ed.-in-chief N. P. Lyakishev. Editorial board: S. V. Kolpakov [et al.]. Moscow : Intermet Inzhiniring, 2000. Vol. 1: А–О. 2000. 411 p.
4. Tarasyev Yu. I., Semenova E. S., Kolpishon E. Yu., Nazaratin V. V., Malykhina O. Yu., Nasonovskaya L. B. Mastering of 20GML steel large-sized cast billets for pipeline valve parts. Truboprovodnaya armature i oborudovanie. 2012. No. 1 (58). pp. 36–37.
5. Ayadi S., Hadji A. Effect of chemical composition and heat treatments on the microstructure and wear behavior of manganese steel. Inter Metalcast. 2021. Vol. 15. pp. 510–519.
6. Huang W. A thermodynamic assessment of the Fe–Mn-C system. Metall Trans A. 1990. Vol. 21. pp. 2115–2123.
7. Xiao Z., Tongbang A., Chengyong M., Lixin L. Effect of manganese content on the impact toughness and corrosion resistance of deposited metals of weathering steel. Materials and technology. 2020. Vol. 54. pp. 189–195.
8. Zhide Z., Zhongran S., Zemin W., Wenjing L., Zuoning C., Dian Z., Feng C., Xiaobing L. Effect of manganese on the strength–toughness relationship of low-carbon copper and nickel-containing hull steel. Materials. 2024. Vol. 17, Iss. 5. 1012.
9. Efimov M. V., Gabelchenko N. I., Kidalov N. A. et al. Optimization of heat treatment modes for 20GML steel billets operating at temperatures down to minus 40 °C. Tekhnologiya metallov. 2023. No. 11. pp. 2–9.
10. GOST 54153-2010. Steel. Method of atomic emission spectral analysis. Introduced: 01.01.2012.
11. GOST 22536.1-88. Carbon steel and unalloyed cast iron. Methods for determination of general carbon and graphite. Introduced: 01.01.1990.
12. GOST 2236.2-87. Carbon steel and unalloyed cast iron. Methods for determination of sulphur. Introduced: 01.01.1988
13. GOST 10243-75. Steel. Methods of testing and estimation of macrostructures. Introduced: 01.01.1978.
14. GOST 5640-2020. Steel. Metallographic method for determination of microstructure of flat rolled product. Introduced: 01.01.1921.
15. GOST 5639-82. Steels and alloys. Methods for detection and determination of grain size. Introduced: 01.01.1983
16. GOST 8233-56. Steel. Microstructure standards. Introduced: 01.07.1957.
17. Dobrynina A. V., Khramovsky Yu. V. The influence of manganese on the mechanical properties of low-carbon cast steels. Liteyshchik Rossii. 2010. No. 3. pp. 29–31.
18. Babkin V. G., Dobrynina A. V., Baranov V. N. Optimization of the composition of low-carbon steel. Liteynoe proizvodstvo. 2003. No. 2. pp. 8–10.
19. Silman G. I. Alloys of the Fe-C-Mn system. Part 4. Features of structure formation in manganese and high-manganese steels. Metallovedenie i termicheskaya obrabotka metallov. 2006. No. 1 (607). pp. 3–7.