A Study On Conductive Mechanism Of TIG Welding Arc And Its Energy Distribution

Welding plays an important role in modern manufacturing. It has been widelyused in the field of aerospace, shipping, architecture and so on. As first appearredprocess in welding production, arc welding method is more widely used in weldingapplication due to its excellent applicability. Welding arc is the carrier of electricalenergy transfer to thermal energy; therefore, the characteristics of welding arc willhave an important impact on the welding quality. The energy density and controllingof process characteristics of welding arc is taken as the key for “control shape withhigh accuracy” and “control properties with low failure”. The development of thermaland mechanical properties of traditional welding arc and the improvement ofcontrollability of arc energy distribution and transfer is the basis to achievesupernormal welding arc.TIG arc is the primary object for studying the arc physics properties because ofits strong representation and well applicability. Conductive form with traditional TIGarc region changes are different, the difference directly reflects the arc radialinhomogeneity on the aspect of conductive capacity and energy distribution.According to the observations of arc physical processes, the physical meaning of TIGarc conductive regions are defined by basic theory of physics. From center of arccolumn to the position of arc boundry, arc conductive regions are defined in turn asionization region that the ionization of inert gas atom holds the dominant position,recombination region where the recombination of ions and electrons plays thedominant position, and gas fringe region where atoms transition is the main process.Combined arc radiation characteristics, a method of quantitative measurement on arcconductive regions by spectral diagnostic technology is established, this methodovercomes the shortcoming of image method as a qualitative observation method, andrealizes the quantitative measurement of arc boundary.On the basis of accurate cognition of arc conduction region and combined withresult of arc physical parameters, comprehensive determination of energy distributionof arc is gotten. The ionization region carried70-80%energy transfer from theobservation result. Meanwhile, effect factors which related with arc conductive properties are discussed from the aspect of anode metal vapor, arc heat source modeland weld pool form.Methods to improve the ability of arc energy transfer are discussed from aspectsof arc properties and power source: first, changing the energy transformationmechanism to compress arc; second, using suitable welding process to compress arc,and realize increasing of arc energy. The research mainly focuses on process ofcondictive pathway established and physical properties of C-TIG arc. The study foundthat with the same energy power supply conditions, compared with the TIG arc,C-TIG arc energy is much more focused, and with the increase of welding current,energy concentration effect is more apparent. Using synchronous pulse peak power ofthe current period, make the "magnetic contraction" since the effect of arc improvedsignificantly, and improve the energy density of the arc.Effect on conductive ability of C-TIG from electrode gap and pulse technology isstudied. With same average current input, pulse arc not only guarantee energy densityincreasing during the peak period, but also integrated the whole cycle of the averageenergy density is higher than the DC welding process, appropriately increase the pulseduration of peak period, increasing of electron density is more significant; Frequencyof pulse current in the range from2.5-100Hz, with the pulse frequency increasing,electron density of arc ionization region is on rising, the corresponding current densityand energy transmission ability were increased in the same region.C-TIG arc has important engineering application significance. On one side, itimproves energy density of arc region; on the other side, the effective heat input israised in weld process. And C-TIG arc improved the torch current carrying capacity,which helpful to improve weld speed with high current input is provided, and it isuseful to expand the selection range of the welding process parameters.