OBRABOTKAMETALLOV Vol. 24 No. 2 2022 TECHNOLOGY Features of the superposition of ultrasonic vibrations in the welding process Sergey Sundukov * Moscow Automobile and Road Construction State Technical University (MADI), 64Leningradsky prospect, Moscow, 125319, Russian Federation https://orcid.org/0000-0003-4393-4471, sergey-lefmo@yandex.ru Obrabotka metallov - Metal Working and Material Science Journal homepage: http://journals.nstu.ru/obrabotka_metallov Obrabotka metallov (tekhnologiya, oborudovanie, instrumenty) = Metal Working and Material Science. 2022 vol. 24 no. 2 pp. 50–66 ISSN: 1994-6309 (print) / 2541-819X (online) DOI: 10.17212/1994-6309-2022-24.2-50-66 ART I CLE I NFO Article history: Received: 25 March 2022 Revised: 13 May 2022 Accepted: 15 May 2022 Available online: 15 June 2022 Keywords: Ultrasound Welding Vibrations Cavitation Microstructure Dendritic segregation Funding This research was funded by the Russian Science Foundation, grant number No. 21-79-00185, https://rscf.ru/project/21-79-00185/ Acknowledgements Research were partially conducted at core facility “Structure, mechanical and physical properties of materials” ABSTRACT Introduction. The main problem in obtaining welded joints is the nonuniform heating of the joint zone, which leads to differences in the structure and properties of the weld metal and the base metal. One of the ways to intensify the welding process is the use of ultrasonic vibrations. As a result of the analysis of methods for introducing ultrasonic vibrations into the melting zone, a method of superimposing vibrations on the elements to be welded was chosen for experimental studies. This method makes it possible to infl uence the welded elements throughout the entire welding cycle from the melt bath to complete crystallization of the metal. Methods. Experimental studies were carried out on plates made of carbon structural steel St3 (ASTM A568M, AISI 1017, DIN 17100) and aluminum deformable non-hardened alloy AMg4 (EN AW-5086, AW-AL Mg4, 5086). As a source of oscillations, a rod magnetostrictive oscillatory system was used, the end of which was rigidly fi xed on one of the welded plates. To determine the places of application of the oscillation source and the welding zone, a calculation method is proposed based on the equality of the resonant frequencies of the used oscillatory system and the natural frequency of bending vibrations of the welding component. It is shown that the optimal places for the application of vibrations and welding will be the antinodes of oscillations, which have the maximum amplitude. Welds were obtained by the method of semiautomatic gas metal arc welding. Results and Discussion. Microstructural study of obtained samples showed a signifi cant decrease in the proportion of dendritic segregation. The changes in the structure are the result of the effects that occur in the liquid melt when ultrasonic vibrations are introduced. The main effects are sound pressure, cavitation and acoustical streaming. The structure change mechanism consists in the dispersion of growing dendrites and crystallization nuclei under the action of shock waves and cumulative jets that occur when cavitation bubbles collapse. The formed fragments of dendrites are new crystallization nuclei that propagate through the melt pool under the action of acoustic currents. Then the process is repeated. The resulting effects affect the kinetics of the crystallization process – the degree of supercooling increases, the number of crystallization nuclei formed per unit time increases, and the rate of its growth decreases. Changes in the structure of the weld metal lead to an increase in the quality of the welded joint, which reduces welding deformations, increases the tensile strength and signifi cantly increases ductility. For citation: Sundukov S.K. Features of the superposition of ultrasonic vibrations in the welding process. Obrabotka metallov (tekhnologiya, oborudovanie, instrumenty) = Metal Working and Material Science, 2022, vol. 24, no. 2, pp. 50–66. DOI: 10.17212/1994-6309-2022-24.250-66. (In Russian). ______ * Corresponding author Sundukov Sergey K., Ph.D. (Engineering), Associate Professor Moscow Automobile and Road Construction State Technical University (MADI) 64 Leningradsky prospect, 125319, Moscow, Russian Federation Tel.: 8 (926) 369-19-70, e-mail: sergey-lefmo@yandex.ru Introduction Welding is a key method to produce permanent joints in various machine-engineering fi elds. Creating stable bonds between atoms or molecules of surfaces to be joined using heating or surface plastic deformation ensures a high-quality joint of both homogeneous and heterogeneous metals and alloys and its joints with non-metallic materials [1]. Fusion welding dominates today among the existing welding types. The primary issue of this welding type is irregular heating of parts to be connected [2]. Due to the crystallization of molten and mixed base
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