| TIG welding has the advantages of stable welding process and good weld formation,and has a good application in the welding field.Narrow gap welding is mostly used in thick-walled metal structures.However,for the reason of low energy density and small effective melting area,it is difficult to ensure that the side walls of the narrow gap groove are fully heated,and it is easy to cause unfused sidewall defects.Therefore,this topic proposes a central vented hollow tungsten arc,and uses a hollow tungsten electrode as the arc.The internal pressurization structure sends airflow from the inner hole of the hollow tungsten electrode to the center of the arc,increases the internal pressure of the arc,strengthens the radial expansion behavior of the arc plasma,and regulates the arc behavior and energy distribution,so as to improve the peripheral heat distribution and increase the effective heating of the arc regional purpose.In this paper,a central vented hollow tungsten electrode TIG welding system is built.On this basis,a high-speed camera system,an electrical signal acquisition system,and an arc pressure and current density acquisition system are built to analyze the arc characteristics.A high-speed camera system is used to collect and analyze the arc topography.The results show that for center vented hollow tungsten arc,the greater the welding current,the higher the stability of the arc.Compared with the solid tungsten electrode and the hollow tungsten electrode,the arc shape expands and the arc width is larger;the arc height is too high or too low,the arc and the tip of the tungsten electrode will be deflected,resulting in unstable welding process;after the gas is introduced into the inner hole of the tungsten electrode,the arc will expand significantly,and the arc will increase at the tip of the tungsten electrode and near the anode.With the increase of the ventilation flow in the center of the hollow tungsten electrode,the internal pressure of the arc increases,and the arc shape is more expanded.Collect and analyze the static characteristic curve of the central ventilated hollow tungsten electrode arc through the electrical signal acquisition system.The results show that the arc static characteristic curve moves up after the center of the tungsten electrode is ventilated;with the increase of the arc height,the arc voltage increases linearly;after the gas is introduced into the center of the hollow tungsten electrode,the arc voltage increases significantly,and the center ventilation flow increases After reaching0.4L/min,the increase of arc voltage became smaller obviously.When the central ventilation flow increased to 0.8L/min,the arc voltage remained basically unchanged.The arc pressure was collected using the pinhole method,and the arc pressure distribution was studied.The results show that,compared with the solid tungsten electrode and the hollow tungsten electrode,the arc pressure curve of the center vented hollow tungsten arc is smoother and the arc pressure range is larger.The maximum pressure of the booster arc in the tungsten electrode is 0.283 k Pa,which is 0.046 k Pa larger than that of solid tungsten electrode and 0.092 k Pa smaller than that of hollow tungsten electrode.Both the welding current and the arc height will affect the size and distribution of the arc pressure.The increase of the central ventilation flow can increase the peripheral arc pressure.The split anode method was used to study the current density of center vented hollow tungsten arc.The central ventilation increased the current density distribution range and expanded the arc energy distribution.The effect of process parameters on the formation of center vented hollow tungsten arc welds was investigated.The results show that compared with the solid tungsten electrode and the hollow tungsten electrode,the welding seam is well formed,and a larger welding seam width can be obtained.The welding seam has the characteristics of large melting width,shallow penetration and uniform distribution. |
PDF Full Text Request