A Study On Characteristics Of Welding Arc Coupling With High-frequency Pulse And Its Property

Pulse arc welding process has been widely used in manufacturing industrybecause the heat input and weld shape can be controlled precisely. In accordance withthe welding requirement of Aerospace high strength aluminum-alloy materials, theTIG welding system with high frequency pulse coupling has been proposed to adjustthe welding heat source performance in order to improve welding quality of highstrength aluminum-alloy based research of arc-physics and process characteristic.The high frequency current pulse output is difficult to achieve because ofdynamic characteristic limit. The digital control TIG welding system with highfrequency pulse coupling has been established. This system can realize highfrequency pulse current output without limitation because the novel power circuit andspecial external characteristic are adopted. According to strength the flowmanagement and PI arithmetic support by flexible digitalized control system, thewhole system can achieve stable welding process. The circuit parameters, includingcap value, charge voltage and equivalent inductor, have been studied. The result showthe circuit is suitable for working in underdamping pattern.Appearance and electrical parameters of high-frequency pulse arc observed indifferent frequency. The result shows, with the frequency increasing, the differencebetween peak period and base period decreases. In the meanwhile, ball-like shrinkphenomenon arises. Pulse parameters on the effect of arc energy are analyzed basedself-magnetic compress theory and macro high-speed camera photos with multi-cycleexposure. The peak period voltage presents a ascend tendency with the increase ofpulse frequency. The base period voltage shows reverse trends, but when the pulsefrequency surpasses20kHz, base period voltage no longer change significantly. Atransition process from inductor to resistor has been found base the U-I chart analyze.The transient variation process of high-frequency arc can be effectively andaccurately sampled because the dislocation photo take method and softwaresynchronization adopted according to high-frequency arc characteristics. The pulsearc in20kHz presents obviously high-frequency effect on the basis of spectroscopicdiagnosis data. The result of spectroscopic diagnosis in different pulse parameters isbasic same to the arc appearance consequence. This conclusion, as effectivelyevidence, can prove the arc energy variation rules and high-speed camera test result. The results of spectroscopic diagnosis around20k Hz show that the electron densitycan be increased with the pulse amplitude increasing and the duty ratio decreasing. Itindicates arc energy density enhancing during the peak current period and also themain difference between pulse arc and DC arc.The high-frequency pulse energy coupling on DC and AC mixture arc acts thepart in high strength aluminum-alloy welding. The mechanical properties, strengthand ductility of welded joints are all enhanced. The micro-porosity quantity at theboth sides of the fusion line can be significantly decreased. Welding joint fracturemorphology shows that the connections between the cleavage surfaces may bechanged from the secondary cleavage fracture to the shearing fracture. Furthermore, aproposal based on grain-grow mechanism may be put forward to reducecolumnar-dendritic region and increase equiaxed region by experiment of HFcoupling effectivity. It may provide a way to optimize the welding process parameteras well as its quality in industrial application.