OBRABOTKAMETALLOV technology Vol. 26 No. 2 2024 The purpose of the work is to determine the content of diffusion-mobile hydrogen in the weld overlaid metal made with electrodes with a basic coating from various manufacturers. In this work, the main objective of the study was to evaluate the welding and technological properties of electrode coatings of the basic type from various manufacturers of electrodes for welding pipe parts made of low-alloy steels and assembly units of heat exchange surfaces of boiler units. Materials and research methods In this work, two brands of electrodes manufactured at different plants were compared, namely at “Sudislavsky Welding Materials Plant”, LLC; imported electrodes manufactured by ESAB; and electrodes produced at CJSC “Elektrodnyi zavod”. Welding of the specimens was carried out with electrodes TsU-5 and TMU-21U from three manufacturers: CJSC “Elektrodnyi zavod”, St. Petersburg and production of “Sudislavsky Welding Materials Plant”, LLC, Kostroma region, Sudislavsky district, Tekotovo village, as well as the plant ESAB-SVEL, St. Petersburg on direct current of reverse polarity 90 A. The stability of the arc was determined using a welding parameters recorder IRSP-11, followed by computer processing of the results. Tests of welding and technological properties were carried out in accordance with the methodology described in RD 03-613-03, GOST 9466 and GOST 25616. The content of chemical elements in the weld overlaid metal was determined according to GOST 1889575, GOST 28033-89 or using special methods that provide the required accuracy and reproducibility. Tests of the mechanical properties of the weld overlaid metal were carried out in accordance with the requirements of RD 03-613-03, GOST R ISO 2560 and GOST R ISO 15792-1. The determination of diffusion hydrogen in the weld overlaid metal, taking into account the specifics of the energy enterprise Novo-Irkutsk Thermal Power Station, was determined directly in the repair shop using the “pencil test” method [25]. The specifics of repair welding under station conditions include welding at both positive and negative temperatures, and this greatly affects the process of hydrogen desorption from the weld [2, 4, 8]. Several sets of experiments were carried out to determine diffusion-mobile hydrogen using the “pencil test” method: – the first set of experiments was carried out with non-calcined electrodes at room temperature, at about 18–20 ºС; – the second set of experiments was carried out with electrodes after calcination at a temperature of 300–400 ºС for two hours at room temperature, at about 18-20 ºС; – the third set of experiments was carried out when weld overlaying specimens at a negative temperature of −25 ºС using calcination; – the set of experiments was carried out by weld overlaying specimens at a negative temperature of −25 ºС without calcination. A PICOTIG-180 welding machine from EWM was used for welding. Before welding, the electrodes were dried and calcined in a PSPE10/400 furnace. The specimens were cleaned from the forming slag using a slag hammer and a metal brush, and an angle grinder Dexter 800AG2-125.5. Two plates made of steel 09G2C with a size of 350×110 mm, 13 mm thick were welded with electrodes TsU-5 and TMU21U, calcined according to the manufacturer’s recommendations indicated on the pack of electrodes (Table 1) for conducting research. Three specimens were welded, one specimen for each electrode of each manufacturer. The plates were made with cutting edges. The edges were prepared using milling. The edges prepared for assembly should be free of burrs, sharp transitions and sharp corners. Immediately before assembly, edges made for welding and adjacent areas of the surfaces of parts should be cleaned to a metallic shine and degreased. The width of the cleaned areas, counting from the cutting edge, should be at least 20 mm on the outside and at least 10 mm on the inside of the specimen (Fig. 1). Since the thickness of the plate is 13 mm, and the diameter of the electrodes is 3 mm, we weld in several layers of the weld. Each subsequent layer is processed with an abrasive tool using an angle grinder to avoid slag inclusions.
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