Research On The Control Of Droplet Transfer Of Laser-enhanced MIG Welding

Offshore oil and gas development and nuclear power are currently the main directions of energy development in China. Repair of marine subsea pipeline and power plant facilities are in urgent need of advanced underwater welding technology as a support. However, with the increasing depth of submarine engineering, the gas pressure in the hyperbaric chamber rises and arc behavior and droplet characteristics of MIG are changed. Controlling metal transfer means improving the welding quality and joint properties. For traditional underwater hyperbaric welding, the way to realize stable projected transfer is to improve the current in order to increase the arc force. Consequently, stress corrosion cracking and great danger come.So this paper launched a research named MIG laser-enhanced welding controlling droplet transfer applied on the field of underwater welding. Laser shot on the neck of droplet and the recoil force weakened the adverse effects of pressure on the droplet transfer. By changing the laser paremeters, the form and frequency of droplet transfer were controlled. Ideal state of droplet transfer and good weld appearance were also obtained in the condition of low current in the hyperbaric welding. Details as follow:For observing the form of droplet transfer and laser’s effects on the arc behavior, an image capture system of metal droplet transfer was presented to meet the clear view in hyperbaric welding.Based on a hyperbaric welding test chamber, an experiment system of underwater MIG laser enhanced welding and a set of multi-information synchronization acquisition and analysis system are established. By using the system, laser from out of high pressure chamber could be located on the solid-liquid junction of welding wire in the high pressure chamber. Consequently, laser technology was introduced in the droplet transfer controlling research of hyperbaric MIG welding. Based on LabVIEW, data acquired synchronously such as current, voltage and droplet transfer images could be displayed in the same time domain at the same time. Statistical analysis were also carried by programmingWelding experiments under different pressure condition were conducted and the influence of ambient pressure on the droplet transfer and arc behavior was studied.Influence factors of MIG laser-enhaced welding were studied and precise control of droplet transfer was realized under atmospheric environment. Based on those, laser was brought into the underwater hyperbaric MIG welding and a series of experiments were conducted. Experiments showed that laser could realize the precise control of droplet transfer under high pressure of 0.2 MPa. While the pressure incresed to 0.3MPa,droplet transfer didn’t improved significantly fot the MIG laser-enhanced welding.The above results have laid a solid foundation for the underwater MIG welding on the field of ocean engineering and have important research significance...