The Effects Of Pressure And Welding Polarity On The Stability Of GMAW

In recent years, a growing number of oil platforms, pipelines and other underwater components need to assemble and repair with the constantly development of marine resources, so the importance of underwater welding technology is increasingly prominent. As the mining depth of marine resources is increasing and the welding environmental pressure is rising, higher requirements are put forward to underwater welding. For this reason, it is significant to research and develop deep-sea underwater welding technology.Underwater hyperbaric dry GMAW is considered one of the most important underwater welding technologies. Compared with normal pressure welding, the welding process will be affected by the hyperbaric environment, but the research of hyperbaric dry GMAW welding is in its infancy. In this paper, the welding experiments were conducted on the hyperbaric welding experimental system, and the impact of pressure on the stability of GMAW welding process was studied. The effects of welding polarity to hyperbaric dry GMAW were also studied by changing welding polarity. The research contents of this paper are as follows:1. The welding experiment platform and welding control system for GMAW welding were designed based on the hyperbaric welding experiment cabin, and the system can realize automation welding under the hyperbaric environment. The welding process information collection system was built, which can collect the information of welding arc shape, droplet transfer behavior and welding electrical signals, etc.2. The experiment scheme was designed based on orthogonal design method. The appropriate welding specimens were selected, and the welding parameters were set. The experimental procedure was planned as requested.3. The hyperbaric GMAW welding experiments were carried out according to the experiment scheme, and the information of the welding process was collected under the pressure of0.1MPa、0.4MPa、0.7MPa、1.0MPa. The influence of pressure on the stability of the welding process were analyzed and summarized.4. The influence of the welding electrical parameters, wire extension, shielding gas composition to the hyperbaric GMAW welding process was studied, and the best welding parameters were obtained according to the welding process and welding results. It provides a reference for relevant engineering applications.5. By comparing the welding process stability, weld appearance and weld sectional shape under DCEP and DCEN condition, the effect of welding polarity to hyperbaric dry GMAW welding was studied.This study shows that for hyperbaric dry GMAW, the welding process stability will gradually decline and splash serious with increasing environmental pressure, but the spatter can be improved by using DCEN. It lays foundation for the further study and application of hyperbaric dry GMAW.