Research On The Mechanism Of The Hollow Cathode Centered Negative Pressure Arc

Arc welding is the first kind of welding method that appeared as the welding technology,which is widely used in the welding field because of its great adaptability.Conventional GTAW arc welding has good arc stability,but the low energy density of TIG arc leads to a shallow fusion and low welding efficiency.A novel arc source named hollow cathode central negative pressure arc has been proposed in this subject.Hollow cathode is used to ignite arc,and negative pressure is formed in the cavity of cathode,to produce a reverse pressure gradient so that the pressure in the arc increase from the center to the surroundings.Part of arc plasma moves into the cathode cavity to strengthen the electron emission of the electrode,environmental pressure is used to compress the arc,in order to achieve the goal of distributing energy evenly in the center and increasing boundary energy gradient of the arc.Compared with GTAW,the arc morphology,the arc pressure and arc energy density improved enormously.Based on the comprehensive information observation and collection of the novel arc,this subject will study the arc behavior and discharge mechanism of this novel arc,and establish the multi fields coupled model,to explorer the influence law of pressure on the arc and the electron emission mechanism on the interaction between plasma and hollow cathode in low pressure.Arc behaviors were studied and correlated to the process parameters.It was confirmed that the negative pressure constricted the arc and elevated the tungsten temperature.The dynamic change in the arc characteristics reflected in the arc voltage waveform.The reduction control method of arc energy distribution will be set up based on the action mechanism between the arc and the partial negative pressure,in order to control the energy density and gradient in different areas of the arc.This subject will improve the physical properties and the energy distribution of the traditional welding arc,avoid the influence of processing errors and complex coupling mechanism of energy field superposition,and reduce the impact of excess energy from arc on welding formation and structure.