Assessment of the effect of the steels structure dispersion on its magnetic and mechanical properties

OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 23 No. 4 2021 Assessment of the effect of the steels structure dispersion on its magnetic and mechanical properties Roman Sokolov a,* , Vitaly Novikov b , Kamil Muratov c , Anatolii Venediktov d Industrial University of Tyumen, 38 Volodarskogo str., Tyumen, 625000, Russian Federation a https://orcid.org/0000-0001-5867-8170, falcon.rs@mail.ru , b https://orcid.org/0000-0002-1987-351X , vitaly.nowikov2017@yandex.ru, c https://orcid.org/0000-0002-8079-2022, muratows@mail.ru, d https://orcid.org/0000-0002-6899-4297, annattoliy@gmail.com Obrabotka metallov (tekhnologiya, oborudovanie, instrumenty) = Metal Working and Material Science. 2021 vol. 23 no. 4 pp. 93–110 ISSN: 1994-6309 (print) / 2541-819X (online) DOI: 10.17212/1994-6309-2021-23.4-93-110 Obrabotka metallov - Metal Working and Material Science Journal homepage: http://journals.nstu.ru/obrabotka_metallov ARTICLE INFO Article history : Received: 07 June 2021 Revised: 06 August 2021 Accepted: 23 September 2021 Available online: 15 December 2021 Keywords : SEM Tempering temperature Grain size variation factor Coercive force Internal stresses Grain size Tensile strength ABSTRACT Introduction: The control of the mechanical properties of structural steels is one of the main processes that regulate the service life of equipment. In most technical processes (pressure treatment, welding, rolling, thermal exposure), structure changes both in local areas and in the entire volume. Changes in the steel structure entail changes in its properties and as a result in local areas, at various stages of operation, the likelihood of the occurrence and development of critical defects increases. Its presence signi fi cantly affects the performance of the equipment, and leads to premature aging of the material and its failure. Precisely because the control of the mechanical properties of steel remains one of the urgent problems, new control methods are being developed. It is known that all properties of steel depend on the structure of the substance, however, studies on the effect of the dispersion of the structure under consideration on the mechanical properties are presented in an insigni fi cant amount. Purpose: to analyze from a mathematical point of view the in fl uence of the factor of different grain size, as a parameter re fl ecting the dispersity of the system, on the mechanical properties of structural steel. The paper studies a heat-treated planar samples of steels 15KhSND , 09G2S and St3 . Methods of research: scanning electron and optical microscopes are used to study the grain structure and grain boundaries; SIAMS 700 software package is used for fi nding the boundaries and average data of the grain structure; portable X-ray fl uorescence analyzer of metals and alloys X-MET 7000 is used to determine the chemical composition of the test samples in percentage; tensile testing machine IR-50 is used for measuring the tensile strength of samples; Vickers hardness tester is used to determine the hardness of samples. Results and discussion: it is found that there is a satisfactory correlation for the mechanical properties of structural steels (hardness and ultimate strength) and the grain size factor, which can be used to predict the hazardous states of structures and the operating time. The analysis of variance and regression of the detected dependencies is carried out. It is noted that the dropout of some values from the general regression dependence can most likely be associated with a decrease in the value of internal stresses as a result of a decrease in the distortions of the crystal lattice of steel occurring during heat treatment. It should be noted that the processes occurring and the degree of its in fl uence on the properties of the structural steels under consideration can be different due to the presence of different amounts of alloying elements in the composition of the studied steels. For citation: Sokolov R.A., Novikov V.F., Muratov K.R., Venediktov A.N. Assessment of the effect of the steels structure dispersion on its magnetic and mechanical properties. Obrabotka metallov (tekhnologiya, oborudovanie, instrumenty) = Metal Working and Material Science , 2021, vol. 23, no. 4, pp. 93–110. DOI: 10.17212/1994-6309-2021-23.4-93-110. (In Russian). ______ * Corresponding author Sokolov Roman A. , Post-graduate Student, Assistant Industrial University of Tyumen, 38 Volodarskogo str., 625000, Tyumen, Russian Federation Tel.: 8 (919) 925-88-47, e-mail: falcon.rs@mail.ru Introduction There is a need to determine the value of the steel mechanical properties to predict the residual life in the practice of operating the hazardous production facilities. Mechanical properties are the main characteristics to which strict control requirements should be imposed. They directly determine the service life of equipment and metal structures.