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7736 |
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Wednesday, September 13, 2023, Brüssel 9:30 AM Research and Development |
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Implementation of pulsed current on underwater shielded metal arc welding (SMAPUW) |
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Andrés Mauricio Moreno Uribe* / Unterwassertechnikum Hannover UWTH
Leibniz Universität Hannover, Deutschland Leandro Vaccari / Institut für Werkstoffkunde - Unterwassertechnikum Hannover (UWTH), Deutschland Thomas Hassel/ Institut für Werkstoffkunde - Unterwassertechnikum Hannover (UWTH), Deutschland Ivan Lendiel/ Institut für Werkstoffkunde - Unterwassertechnikum Hannover (UWTH), Deutschland Thomas Wolf/ Institut für Werkstoffkunde - Unterwassertechnikum Hannover (UWTH), Deutschland |
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The pulsed welding current is often applied to air welding processes for metal transfer modulation, energy input control, and reduced process disturbances. In underwater wet welding, the water and the water depth are important factors that affect the operational performance of underwater shielded metal arc welding. The arc and melted metal in contact with the water environment promote operational and metallurgical challenges regarding arc instabilities, metal transfer, gas formation, high-cooling rates, and diffusible hydrogen pick-up. On the other hand, the water depth causes losses in consumable fusion efficiency, dropping the voltage, increasing the number of short-circuit events, and consequently decreasing the welded joint's process stability and quality. This study evaluates the operational characteristics of applying pulsed welding current to stick electrode welding. This way, welds were developed with a 3.25 mm commercially available rutile-based electrode using an arc-voltage control system. A target arc voltage of 35 V was defined in all the experiments, and the welding polarity and welding speed were DC- and 0.2 m/min, respectively. For the pulse conditions, two values of pulse current combinations, taking 120 A and 140 A as mean values, were defined (?I of 40 A and 80 A). The same pulse and base duration were chosen (duty cycle of 50%), giving pulsing frequencies of 2.5 Hz and 25 Hz. The voltage and current signals were acquired, and stability factors, short-circuit frequency, and melting rate was calculated by processing the data. The cross-section was also analyzed to assess bead geometry. As a result, welding with lower average welding currents through pulsed current technology was possible. This new technological approach could improve the stability of the process at higher depths of operation and contribute to obtaining better-quality welds. |