Moscow Polytechnic University, Moscow, Russia

V. V. Ovchinnikov, Head of the Materials Science Department, Doctor of Technical Sciences, Professor, e-mail: vikov1956@mail.ru
T. K. Akopyan, Associate Professor of the Materials Science Department, Candidate of Technical Sciences, e-mail: aktorgom@gmail.com
A. G. Sbitnev, Associate Professor of the Materials Science Department, Candidate of Technical Sciences, e-mail: artem27@list.ru

Moscow Polytechnic University, Moscow, Russia¹ ; National University of Science and Technology Moscow Institute of Steel and Alloys, Moscow, Russia²
M. A. Barykin, Postgraduate Student, Engineer of the Research Project², Research Engineer of the Materials Science Department¹, e-mail: mr.barykin97.97@mail.ru

The article assesses weldability of sheets, 1.5 mm thick, from alloys Al – 1 Ca – 5.5 Zn – 1.5 Mg – 0.5 Mn and Al – 2 Ca – 2.5 Mg – 0.4 Mn in resistance spot welding according to modes with and without forging force. It has been shown that modes with forging force contributes to almost complete prevention of cracking within the limits of the fusion zone. It has been found that an efficient quality control method for welding spots of the alloys under study is X-ray computer tomography, identifying cracks and pores in metal of the fusion zone. The obtained results were compared with the data of automated control of welding mode parameters installed on resistance spot welding machine МТН-7501. On the one part, the comparison of the data obtained showed efficiency of X-ray computer tomography used to identify defects. On the other part, welding spots marked as defective by the automated control unit of machine МТН-7501 turned out to be defective. The authors plotted the curves showing correspondence between welding spot diameters for the alloys under study and welding current and arc current pulse duration. It has been shown that alloy Al – 1 Ca – 5.5 Zn – 1.5 Mg – 0.5 Mn has proper joints at the following welding parameters: radius of the top electrode surface is 90 mm; arc current flow is 0.26 s; arc current is 25kA; electrode pressure is 360 kg. Regarding alloy Al – 2 Ca – 2.5 Mg – 0.4 Mn, to achieve proper joints, arc current should be increased to 26 kA. The stated parameter values result in forming a fusion zone, 5.0–5.3 mm in diameter. As part of the conducted studies, we tested laser treatment of the surface layer with a scanning beam as a method for the surface preparation for resistance spot welding. It has been shown that contact resistance after laser beam surface treatment of alloys Al – 1 Ca – 5.5 Zn – 1.5 Mg – 0.5 Mn and Al – 2 Ca – 2.5 Mg – 0.4 Mn is 12.5–13.2 microohm, corresponding close to contact resistance after chemical etching and mechanical cleaning with a metal brush. It should be noted that laser treatment of the surface did not result in a considerable increase in contact resistance in 72 h after treatment, and chemical etching — in 36 h. The alloys under study showed correspondence between shear resistance and tear strength of the welding spot, and the fusion zone diameter. Regarding the single-point samples at a fusion zone diameter of 6.2–6.5 mm for alloys Al – 1 Ca – 5.5 Zn – 1.5 Mg – 0.5 Mn and Al – 2 Ca – 2.5 Mg – 0.4 Mn, shear resistance was 2200–2350 N and 2050–2180 N, respectively, and tear strength — 3200–3550 N and 2900–3250 N, respectively.
The research was funded by the grant of the Russian Science Foundation, No. 22-19-00121, https://rscf.ru/project/22-19-00121/.

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