Diagnosis The Physical Characteristics Of Pulsed MIG Welding Arc By Spectrum

The P-MIG welding has been widely used in the welding of carbon steel,stainless steel, aluminum and aluminum alloys, which benefited from itsdroplet transition controllability, high welding quality and productionefficiency. The high voltage between the wire and work piece ionizes theshielding gas to create welding arc. The heat generated by the weld ing arcmelt the wire and work piece, which formats the droplet and molten pool.The stability and performance of the welding arc play key roles in weldingquality and welding efficiency. The physical parameters such astemperature, electron density have a crucial role to study of the mechanismof the welding arc and to improve the welding quality. In this paper, ahigh-speed camera system, Labview signal acquisition system and aspectral acquisition system were used to collect the electric, image andspectral signals. And the temperature, electron density, metal vaporpercentage in both peak and base stages are calculated by the spectral method.Firstly, this paper studied the calculation method of Stark broadening,and the Fourier transform method a signal processing method wassuccessfully applied to calculate the Stark broadening of welding arc. Thismethod, compared with the traditional methods, has a simple principle andhigh accuracy. And the Stark broadening and electron density of the TIGwelding arc were calculated by this method.Secondly, combined with the results of high-speed photography andspectroscopy signal, the distribution characteristics of Ar and metalspectrum of P-MIG both in peak and base were researched.Thirdly, diagnosed the physical parameters of P-MIG welding byBoltzmann, Stark broadening and spectrum simultaneous methods. Whilereconstructed three-dimensional plasma emission coefficient and3DSpectral line by Abel inverse transform method,so that calculated the3Dphysical characteristics of P-MIG welding. The study found that at highvoltage stage, the temperature of P-MIG welding has off-axis distributioncharacteristics, while the maximum electron density and the metal vaporwere in the arc center. At base stage, the temperature, electron density andthe percentage of metal vapor were less than the peak stage, andcontinuously decreased with the increasing off-axis distance. The study also found that, at the peak phase,after Abel transform compared with withoutAbel, the center temperature was lower, but the electron density was muchhigher. At the base stage, after Abel inversion, the electron density andtemperature in the central region were elevated, while the periphery werereduced.