Research On Welding Characteristics Of Pulse GMAW At High Pressure

With the rapid development of society and economy,marine oil and gas resources gradually become the focus of competition.The development of marine oil and gas resources depends on the offshore structures and submarine pipelines,so the maintenances of marine equipments become more important.Underwater hyperbaric dry welding can not only get good welding quality,but also be very good to adapt to the underwater environment,so it has become a common means of underwater welding.Among underwater hyperbaric dry welding technologies, the pulse GMAW is paid more attention because of its wide adjustable parameters and better control.Influenced by underwater hyperbaric ambient, the welding at high pressure is not stable.The stability of welding process becomes worse gradually with the increase of the underwater pressure,so the research on the effect of pulse parameters at high pressure is very important.This experiment was done in high pressure chamber through seting different pressures.The Hannover Analysator is used to analysis welding electrical signals,through which we can know the changing trend of electrical signals,to guide the pulse parameters.High speed camera is used to observe droplet transfer situation and different parameters are compared.After welding,through observing the seams under different kinds of welding parameters,the corresponding changing rules are found out.The paper concluded that:Average current mainly affects the deposition rate of welding wire.With the increase of average current,the welding process and weld appearance can be better.The main influences of welding arc voltage are welding arc height and stiffness.Under high pressure environment,voltage can be used to change the weld width and effectively reduce the welding spatters;The main influence of pulse peak time and pulse frequency is welding arc energy which can not only improve the deposition efficiency of welding wire,but also can effectively improve the stability of welding process.The short circuit phenomenon can be effectively controlled with the increase of frequency and peak time;The main influence of transfer current transfer time is droplet transfer and the rational ratio of them can effectively control the size of the spatters ecept for the weld appearances;Welding with DCEN in high pressure environment can effectively improve the weld appearance.When the pressure exceed 0.4MPa,DCEN is effective to reduce welding spatter.Through a series of welding experiments,this paper summarized the influences of pulse parameters on pulse GMAW at different pressures and analyzed the reason of seam shaping under high pressure environment.This paper can lay a theoretical foundation for the development of pulse GMAW welding equipments and provide important reference for underwater welding research in the future.