Numerical Analysis Of Complicated TIG Arc Of Fully Coupled Multi-physics

Double TIG (tungsten argon arc) welding as a new type of high efficient welding method, overcome many shortcomings of the single TIG welding:heat input required by the small volume; low deposition efficiency; welding speed is slow. This method can be maintained small arc pressure at high current, avoiding the increase in deposition rate at the same time. The excessive electric arc pressure caused the melt-through, bite edge of weld defects. Therefore, double TIG welding in the welding quality and welding efficiency have strict requirements of occasions has wide application prospect.In the welding process, using a mixture of two or more protective gas overcomes the limitations of a single gas action process, and giving full play to the advantages of each component in the mixed gases, ensure the welding quality, improve the welding efficiency, also make the weld is improved.The topic for thermal physical phenomena in the process of double TIG welding, and all kinds of behavior under the double gas TIG arc carried out the following several aspects of research work.First of all, according to the continuity equation, momentum conservation equation, energy conservation equation and maxwell’s equations, established the double TIG arc all coupling solving conditions of three-dimensional steady-state model, study the coupling mechanism between arc temperature field, flow field and electromagnetic field. In the establishment of the model, based on double TIG arc physics involved in the actual welding process and internal more field coupling principle respectively selected corresponding control equation on the temperature field, flow field and electromagnetic field, and according to the actual situation of each control equations to determine the appropriate boundary conditions, so double TIG arc fully coupled finite element model is established. Based on the large finite element analysis software COMSOL Multiphysics to solve the model, and got the distribution characteristics of temperature field, flow field, electromagnetic field, arc pressure, current density and electromagnetic force from the internal arc under the condition of the different tungsten electrode spacing and arc length. In addition, these results were compared and analyzed. The results showed that:a) For single TIG arc. under the condition of the full coupling, the arc temperature, current density, the maximum speed of plasma appears near the cathode, and in the process of near anode gradually reduced. The temperature field is a typical bell shape, and the highest temperature is close to20000K. The calculated results agreed well with previous experimental results. b) Compared with the single TIG arc, the highest temperature, velocity of arc plasma. current density and arc pressure of the coupling arc were significantly reduced. The distribution of arc pressure and current density from the surface of the anode cannot be described in Gaussian distribution. The distribution of the electromagnetic force near the cathode is also different. c) With the increasing of tungsten electrode spacing, two arc beam of coupling degree is more and more weak. When the tungsten electrode spacing increases to a certain value, two beams arc will remove coupling, and become two separate arc beam. In addition, with the increasing of tungsten electrode spacing, the highest temperature, current density, the plasma arc velocity and the arc pressure will reduce first and then increases. Moreover, the arc pressure there will be a bimodal distribution. d) Under the condition of asymmetric current, arc temperature fiele, current density, electromagnetic lines, electromagnetic force, arc pressure and plasma velocity field no longer appear symmetry distribution, and the bias current is larger. With the greater difference between the currents, this trend will lead to greater. e) Under the condition of different arc length, the highest temperature, current density, the plasma arc current and electromagnetic force were slightly increased, but their influence is not very big. Arc stretched or shortened made the formation distribution of arc more and more concentrated or extension, and thus influenced the distribution of the arc pressure, and made its have increased with the decrease of the length of the arc.Secondly, the process gas mixture, using a layering process. Different from the traditional processing method, this text divided into two layers, alayer of argon filling inside and outside a layer of helium, so as to study the interaction between the different gases. In the process of establishing the model, in addition to the continuity equation, momentum conservation equation, energy conservation equation and maxwell’s equations, also with the diffusion and mass transfer equations. In the calculation of the protection of double gas TIG arc behavior, the result is:a) The effect of outer helium obvious the shape of the arc, and made it no longer presenting typical bell shape distribution. The highest temperature of arc was reduced, but the overall distribution basically unchanged. b) The distribution law of arc current density, plasma velocity and electromagnetic force were changed, but not very big. in addition to relate to the accuracy of the model, and also related to the size of the delamination area. c) Since the flow rate of the arc plasma was reduced, so that the lower of the arc pressure on the surface of the anode of the double gases protected by TIG.