Research On The Arc Shape Under High Air Ambient Pressure

With the global continued consumption of land resources, it has become the alternative of exploring the ocean. In recent years China's repairing demand of deepwater structure increase with the rapid growing of marine structures. Puddle welding becomes the most widespread underwater welding technology for its wide range of application, and most studies focuses on puddle welding.But the high pressure of underwater will affect the welding arc and welding procedure, and if we want to obtain the welding process which can be used in industrial practice, we must know more about hyperbaric welding arc.The paper has studied the arc shape of hyperbaric TIG welding, hyperbaric pulsed MIG welding and magnetic welding in-depth with the help of hyperbaric welding research testing chamber, synchronous multi-information acquisition system and high-speed camera system which were built previously, the paper also discussed the effect of pressure and longitudinal magnetic field for the hyperbaric welding procedure.Experimental studies have shown that: (1)With the increase of ambient pressure, TIG welding arc and MIG welding arc both appear a phenomenon of shrinkage and get unstable. The MIG welding arc also present an appearance that arc length turns short which can be solved by increasing the welding voltage. Though this solution is feasible at different pressure, its effect becomes unconspicuous at larger pressure such as 0.7MPa.(2)TIG welding arc shape transforms from a bell to a cone on the effect of longitudinal magnetic field. The taper angle increases and the lighteness of arc anode center decreases with the increasing of magnetic field intensity. Applying longitudinal magnetic field at hyperbaric environment, the arc moving spirally and its stability increases.(3)Increasing the magnetic field intensity at hyperbaric environment will increases the MIG welding arc length which is similar with the situation of increasing the welding voltage. But it also can aroses arc blowout which frustrate the welding process. So the longitudinal magnetic field is not recommended to apply in hyperbaric pulse MIG welding.The paper also established the mathematic model of arc by means of finite element analysis under the base of the experiences of predecessors, and analyzed the effect of pressure that imposed on TIG arc, longitudinal magnetic field imposed on barometric pressure TIG arc and hyperbaric TIG arc, which for testing the experiment result. These effects contains temperature field of arc, flow velocity of arc plasma and other aspects. This paper carried out the first detailed simulation and calculation of TIG welding arc at different pressures that below 10MPa in China, which becomes the theoretical foundation for the application of hyperbaric MIG welding in domestic offshore oil and other areas...