OBRABOTKAMETALLOV Vol. 26 No. 2 2024 technology Welding a specimen using electrodes produced by CJSC “Elektrodnyi zavod”. The results of the electrode coating quality tests were examined under a magnifying glass. Chipping of the coating was also normal, partial with a total length of less than 5 % of the length of the coated part of the electrode, and also amounted to no more than 20 mm. Before welding, a “fingernail” check was also carried out [1]. The “fingernail” test was carried out in the same way as with electrodes produced by “Sudislavsky Welding Materials Plant”, LLC; three electrodes were randomly selected from the test package for testing and melted in a vertical position with an angle of inclination of the electrode to the seam of 50–60°. The size of the “fingernail” was measured from the end of the electrode rod to the most distant part of the melted coating. The formation of a “fingernail” from the coating with a size of more than 3 mm and the falling off of pieces of non-melted coating from the rod are signs of a defect. Checking for the “fingernail” showed the presence of a non-melted coating of more than 3 mm, which is already a sign of a defect; the size of the “fingernail” on the other two electrodes was within tolerance and was less than 2.5 mm (Fig. 4). After identifying the “fingernail” we proceed to welding the specimens. During welding, there was unstable arcing in all three layers: root, filling and facing. Also, after welding the root seam, the electrodes were re-calcined, but this did not give positive results for stable arcing. The specimen was assembled on a flat surface. Agap 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. 5, a). As can be seen from the photo of the root seam (see Fig. 5, 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. 5, b). When welding the filler layer, excessive spattering of molten metal is visible. The flash sputter is larger than when welding with electrodes produced by “Sudislavsky Welding Materials Plant”, LLC. Removing flash spatter using a welder’s hammer is difficult. Flash sputter and slag after welding can only be removed mechanically. 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. 5, c). As in the case of the filling layer of the seam, welding was carried out Fig. 4. Formation of the fingernail after welding with TMU-21U electrodes CJSC “Elektrodnyi zavod” St. Petersburg a b c Fig. 5. Appearance of the welded seam after filling with TMU-21U electrodes CJSC “Elektrodnyi zavod” St. Petersburg: a – the root of the seam; b – the filling seam; c – the facing seam
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