OBRABOTKAMETALLOV Vol. 26 No. 2 2024 technology Electrodes TMU-21U Welding a specimen using electrodes produced by “Sudislavsky Welding Materials Plant”, LLC Before welding the test specimens, the electrodes were calcined in a furnace at a temperature of 350 ± 10 °C for an hour; this calcination mode is recommended by the manufacturer on the packaging of the electrodes. There was no index on the packaging for the hydrogen content in the weld overlaid metal according to the requirements [18]. After calcination, the electrodes were subjected to coating testing [1]. After lifting the electrode to a height of 1 meter, it was dropped in free fall onto a smooth steel plate. Welding a specimen with electrodes produced by CJSC “Elektrodnyi zavod”. Before welding the test specimens, the electrodes were calcined in a furnace at a temperature of 400 ± 20 °C for an hour; this calcination mode is recommended by the manufacturer on the packaging of the electrodes. There was no index on the packaging for the carbon content according to the requirements [18]. Note that the calcination mode differs from the electrodes produced by “Sudislavsky Welding Materials Plant”, LLC. After calcination, the electrodes were subjected to coating testing. After lifting the electrode to a height of 1 meter, it was dropped in free fall onto a smooth steel plate. Welding a specimen with electrodes produced by ESAB-SVEL. Before welding the test specimens, the electrodes were calcined in a furnace at a temperature of 359– 400 ± 20 °C for two hours; this calcination mode is recommended by the manufacturer on the packaging of the electrodes (see Fig. 6), and the hydrogen index is also indicated in the range from 5 to 10 cm3/100 g. Note that the calcination mode differs from the electrodes produced by “Sudislavsky Welding Materials Plant”, LLC and CJSC “Elektrodnyi zavod”. Research results Electrodes TMU-21U. Welding a specimen using electrodes produced by “Sudislavsky Welding Materials Plant”, LLC The results of the electrode coating quality tests were examined under a magnifying glass. Chipping of the coating was 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]. 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 (Fig. 2). 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. During welding of the specimens, there was unstable arcing a 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. A gap of 2 mm was set using welder’s gauge Fig. 1. Plates to be welded
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