OBRABOTKAMETALLOV Vol. 26 No. 2 2024 technology The specimen was assembled on a flat surface. A gap of 2 mm was set using welder’s gauge UShS-3. The root seam was welded without separation using a reverse polarity welding current of 90 A (see Fig. 8, a). As can be seen from the photo of the root seam (see Fig. 8, a) there is no spattering of metal on the specimen; slag is difficult to remove only after cooling using an angle grinder. The next layer of the weld is the filling layer. Welding was carried out with the same current parameters as when welding the root seam. It took two electrodes to fill, which allows us to conclude that welding was carried out with separation (see Fig. 8, b). When welding the filler layer, a minimal amount of spattering of molten metal is visible. Removing flash spatter using a welder’s hammer is easy. Slag after welding can only be removed mechanically. a b c Fig. 8. Appearance of the welded seam after filling with TMU-21U electrodes ESAB-SVEL St. Petersburg: a – the root of the seam; b – the filling seam; c – the facing seam Before welding the facing seam, the specimen was completely cleaned of flash sputter. When making a facing seam, the arc, as well as during the root and filling seams forming, burned unstable. The facing seam required 3 electrodes (see Fig. 8, c). As in the case of the filling layer of the seam, welding was carried out with a separation between electrode replacements. The current parameters were the same as in the case of welding the root and filling layers of the seam. On the facing seam, as well as on the filling seam, a fairly large amount of sputtering is visible, which is also a signs of a defect. At the same time, flash sputter was removed from the specimen using a welder’s hammer and a metal brush. The slag on the facing seam was easily removed using a welder’s hammer. Preparation for further testing for the mechanical properties of the weld overlaid metal was carried out only with the help of an angle grinder. Similar work was carried out for TsU-5 electrodes. The results for determining the “fingernail” are negative for the specimens using electrodes produced by “Sudislavsky Welding Materials Plant”, LLC. The welding engineering properties of the studied electrodes are presented in Table 1. The assessment was carried out on a five-point scale [1]. The results of determining the chemical composition and mechanical properties of the weld overlaid metal are given in Tables 2–7. The results of experiments to determine diffusion-mobile hydrogen in the weld overlaid metal are presented in Figs. 9 and 10 for positive temperatures without calcination and with calcination of the electrodes, respectively. A comparative analysis of the diagrams shows that electrodes after calcination produce much less diffusion hydrogen in the weld overlaid metal, which is an indicator of a high-quality weld. The results of assessing the effect of negative temperatures on the desorption of hydrogen from the weld overlaid metal are presented in Figs. 11–14. The total content of diffusion-mobile hydrogen in the weld overlaid metal without calcination of the electrodes when the condition is maintained at −25 °C for 3 days, followed by moving the eudiometers to a warm room and holding for 3 days is shown in Figs. 11–14.
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