Siberian State Industrial University (Novokuznetsk, Russia):

N. A. Kozyrev, Dr. Eng., Prof., Head of the Dept. of Materials Science, Foundry and Welding Production
R. E. Kryukov, Cand. Eng., Associate Prof., Dept. of Materials science, Foundry and Welding Production
V. E. Gromov, Dr. Phys.-Math., Prof., Head of the Dept. of Natural Sciences named after prof. V. M. Finkel, e-mail: gromov@physics.sibsiu.ru
Yu. A. Shliarova, Postfraduate Student, Dept. of Natural Sciences named after prof. V. M. Finkel

By the methods of scanning and transmission electron microscopy a structural phase state, defect substructure and fracture surface of low carbon alloy steel welds produced with use of carbon-containing addition and without it are investigated. The study of etched metallographic section structure of welds revealed a presence of a large amount of second phase particles (carbides, sulfides, oxides, etc.). It is shown that in weld with a carbon-containing addition the particles locate chaotically, and in weld without addition they decorate boundaries of ferrite grains. Dimensions of second phase particles vary in the limits from 0.8 μm to 5 μm and are identical for both types of welds. Analysis of fracture surface structure of welds is carried out. A presence of nonmetallic inclusions is detected. They are typical of mainly weld produced without a carbon-containing addition which may indicate its increased brittleness. Amount of micropores in fracture of weld with carbon-containing addition is many times greater than that in weld without addition, which is indicative of gas removal in use of carbon-containing addition. The quantitative analysis of structure and dislocation substructure parameters of weld metal is carried out, the estimates of contributions of scalar and excess dislocation density to strength of welds are performed. It is shown that higher values of scalar and excess dislocation density in the weld formed without carbon-containing addition in flux may be responsible for material embrittlement. A large quantity of stress concentrators in the weld without carbon-containing addition may result in material embrittlement.

1. Saini S., Singh K. Recycling of steel slag as a flux for submerged arc welding and its effects on chemistry and performance of welds. International Journal of Advanced Manufacturing Technology. 2021. Vol. 114. pp. 1165–1177.
2. Makienko V. M., Atenyaev A. V., Belous T. V. Development of Welding Fluxes for Hardfacing Based on Mineral Raw Materials of the Far Eastern Region of Russia. Inorganic Materials: Applied Research. 2021. Vol. 12. pp. 558–569.
3. Lee J., Lee K., Lee S., Kwon O. M., Kang W.-K., Lim J.-I., Lee H.-K., Kim S.-M., Kwon D. Application of Macro-Instrumented Indentation Test for Superficial Residual Stress and Mechanical Properties Measurement for HY Steel Welded T-Joints. Materials. 2021. Vol. 14. pp. 2061 (1-13).
4. Bakhmatov P. V., Startsev E. A., Sobolev B. M. Impact and Effect Study of Submerged-Arc Welding Conditions on Structural Changes in Weld Metal. Current Problems and Ways of Industry Development: Equipment and Technologies. Lecture Notes in Networks and Systems. 2021. Vol. 200. pp. 65-76.
5. Lochan S., Rahul C. Study of weld bead chemical, microhardness & microstructural analysis using submerged arc welding fluxes for linepipe steel applications. Ceramics International. 2020. Vol. 45 (15). pp. 24615-24623.
6. Kryukov R. Е., Kozyreva О. А., Kozyrev N. А. The carbon-fluorine additives for welding fluxes. Mechanics, Materials Science and Engineering. 2016. Vol. 2 (2). pp. 5-14.
7. Kozyrev N. A., Kryukov R. E., Kryukov N. E., Kovalskiy I. N., Igushev V. F. Technological aspects of using a carbon–fluorinecontaining addition in submerged-arc welding. Welding International. 2016. Vol. 30 (4). pp. 325-328.
8. Koval N. N., Ivanov Yu. F. Evolution of structure of steel surface layer subjected to electron-ion-plasma methods. Tomsk: NTL, 2016. 304 p.
9. Egerton F. R. Physical Principles of Electron Microscopy. Basel: Springer International Publishing, 2016. 196 p.
10. Carter C. B., Williams D. B. Transmission Electron Microscopy. Berlin: Springer International Publishing, 2016. 518 p.
11. Rotshtein V. P., Proskurovskiy D. I., Ozur G. E., Ivanov Yu. F. Modification of surface layers of metallic materials by low-energy high-current electron beams. Novosibirsk: SB RAS: Nauka, 2019. 348 p.
12. Yuriev A. A., Gromov V. E., Ivanov Yu. F., Rubannikova Yu. A., Starostenkov M. D., Tabakov P. Y. Structure and Properties of Lengthy Rails after Extreme Long-Term Operation. Materials Research Forum LLC, 2021. 193 p.