The Influence And Its Control Of Pulse Waveform In Weld Arc Of Pulsed MIG Welding At High Pressure

With the development of the explore of offshore oil and gas, the offshore structure and pipeline maintenance become more and more important. Welding repair is the best methods for the quality. In shallow water, wet weld or local dry weld can meet the maintenance requirements, but with the increasing of the water depth and the high demand of the welding quality, the dry hyperbaric welding is particularly important. However because of the wide range of adjustable parameters, and various control ways in arc burning and droplet transfer, pulsed MIG welding show a great deal of research space.This paper regard pulse MIG welding arc and droplet as the main object of study, firstly exploring the high pressure environment impacts on the stability of welding arc and metal transfer, then studied the pulse waveform control on stability of welding arc and mental transfer in detail.The welding process stability in high pressure environment is damaged, which is manifested in the arc shape, the stability of the arc and mental droplet. As the pressure increases, the arc shape becoming irregular clearly. The stability of the arc is getting worse, while droplet has also undergone great changes: the increasing pressure changes the transfer of the droplet. Because of the energy loss in the arc burning and the change of the force of the mental droplet, except for the original shoot transfer form, there are the short circuiting transition, the big drops of transition and the rejection of the transition in the high-pressure environment. Which is caused poor of the welding quality.The unstable phenomenon in view of the above, this article study of the optimization of these pulse parameters on stability of welding effect, such as pulse frequency, pulse base current, pulse peak current, slope of the pulse rise time and slope of the pulse down time. Experiments confirmed that the optimization of pulse frequency, pulse peak current and pulse base current can make up for the energy loss of the high pressure environment of welding arc, and the optimization of those parameters also has a positive effect on the stability of droplet transfer. In contrast, due to the limitations of the range, the slope of the pulse rise time and slope of the pulse down time had little effect on the stability of welding process.After those parameters optimization, the paper study the greater influence of the factors mentioned above(includes pulse frequency, pulse peak current and pulse base current), then matched them as the way of orthogonal. Through a detailed analysis and comparison, summary the matched with different pressure environments for optimal pulse parameters. In this study of stability of welding in the high pressure environment provided a reliable technical support, it has a meaningful research and engineering applications.