Research On Influence Mechanism Of Ultranism And Active Flux To Arc Plasma

With the accelerating process of industrialization,welding as a kind of unique material connection technology is more and more attention.TIG welding is widely used for its stable welding process,good appearance of weld and the high quality of weld microstructure.But the shortcomings of the single-channel weld depth,low efficiency of welding limit its application range.Previous studies have shown that ultrasound and active flux showed great advantage in increasing the penetration and improve the welding efficiency,the main reason is improved arc plasma volume density in the process of welding.But at the moment,the research on the improving mechanism of ultrasound and active flux to the arc plasma volume density is less.This paper around the TIG welding arc plasma,with the method of two exposure holographic interferometry,studied the influence mechanism of ultrasound and active flux to the energy density of arc plasma.First of all,conventional TIG arc plasma is studied and selects welding current,arc length and shielding gas as single variable,analyze the effect of parameters on the arc.With the welding current increased,the number of the interference fringes is increase and the fringe spacing is decreases,this phenomenon shows that arc temperature is rise and the energy density distribution of the arc is more concentrated.With the increase of arc length,the outline radius of the interference fringes is increases,shows that the distribution of arc temperature field is more extended.The interference fringes will be disorder when the gas flow rate is too large,instructions that the gas flow is too large to lead the arc unstable.The influence mechanism of active flux on the arc plasma is studied.Selecting oxides（SiO₂,TiO₂,Cr₂O₃）,chlorides（NaCl,KCl）,fluoride（AlF₃）and mixed active flux as test object.Found that the distribution of the interference fringe is more intense and its number is increase after coating SiO₂,Cr₂O₃,Na Cl,KCl,AlF₃ and mixed active flux.This means that the arc contraction after coating active flux and the energy density is more concentrated.The arc voltage is measured after coated with active flux,found that the voltage increase and this phenomenon verified the conclusion of arc contraction.However,the change of arc interference fringes is very small after coated with TiO₂,and the arc voltage basic remains unchanged,it shows that coated with TiO₂ has no effect on arc plasma contraction.The influence mechanism of ultrasonic on the arc plasma is studied.Select the emitter with concave spherical shape,which sound field energy centralized,uniform distribution and almost does not attenuation.The shape of the interference fringes loaded ultrasonic from the side to the middle,and on the contrary of hologram stripe distribution direction with no ultrasonic.The effect of ultrasound for protecting gas motion state was studied,and the protective gas from both sides is affected by the "sound constraint" of the ultrasonic field,which brings t he center of the arc.The energy density of the central arc is more concentrated,which is shown in the form of arc contraction.Finally,the temperature field of arc plasma was calculated.Analyzed the process of using holographic interferometry method measurement arc plasma temperature field and derivation correlation formula,collected the limited holographic interference with welding parameters of current 60 A,arc length 12 mm,shielding gas flow rate of 4 L/min.Calculate the temperature of the cross section away from the cathode 7.92 mm of the conventional TIG and the arc which work piece coated SiO₂ active flux,the highest temperature in the center of the arc column are 12776 K and 13043 K respectively.After coated SiO₂ active flux,the temperature of the cross section has been whole improved,and in the local area near the center of the arc column,with the increase of arc radius,the temperature lower amplitude is smaller.Indicates that active flux has the function of compression arc and improve the utilization ratio of energy.In addition,if ideally to divide the arc into an infinite number cross section along the axial and calculate the temperature,using the holographic interferometry can get each point temperature of arc.