Research On High-frequency Pulse Micro TIG Spot Welding Power Source And Arc-molten Pool Behavior During Welding Proces

Conventional TIG spot welding in low current welding arc state instability,arc energy unfocused,resulting in poor mechanical properties of welded joints.The addition of highfrequency pulse current can shrink the arc,improve the arc energy density,and effectively solving the shortcomings of conventional TIG spot welding.To clarify the arc-molten pool behavior under the action of high frequency pulses,and reveal the mechanism of high frequency pulse on arc characteristics and molten pool forming process.In this paper,the development of high frequency pulse power supply,characteristics of arc-molten pool behavior and on-line monitoring of molten pool temperature field are studied deeply.Firstly,based on inverter converter technology and high frequency pulse superposition technology,the main circuit topology of high frequency pulse micro-TIG spot welding power supply was designed.Based on the high performance controller,a fully digital control system was designed.The developed welding power supply can realize the output of 0～40 k Hz pulse current,the output current range was 5～60A,and the duty cycle was 10%～90%.Then,based on the developed high-frequency pulsed micro-TIG spot welding power supply,the influence rule of different welding parameters on arc state was studied by combining numerical simulation and experiment.It was found that with the increase of pulse current frequency,arc shrinks significantly and arc stiffness increases.With the increase of pulse current peak value,arc pressure and temperature increases and arc profile becomes larger.The energy density of the arc temperature field was obviously increased by increasing the pulse current duty ratio,but the arc form and arc pressure are basically unchanged.Through the numerical simulation of the molten pool,it was found that the periodic variation amplitude of the molten pool width decreases with the increase of pulse frequency.With the increase of pulse peak current,the molten pool velocity increases.Increasing pulse duty ratio will accelerate the temperature rise rate of molten pool;The welding experiment of stainless steel plate shows that the tensile shear of welded joint increases with the increase of pulse frequency.By observing the structure of fusion zone under different pulse frequency,it was found that pulse current has thinning effect on the structure of joint.Finally,in order to solve the shortcomings of traditional numerical simulation,digital twinning modeling of TIG spot welding pool temperature field under varying working conditions was studied based on digital twinning technology and machine learning algorithms.The improved sparrow search algorithm was used to find the optimal parameters of the digital twin mechanism model under different working conditions.BP neural network was used to learn the model parameters and build the model parameter prediction model to realize the rapid update of the digital twin model.By evaluating the twin model,it can accurately simulate the change of temperature field in TIG spot welding pool under varying conditions,which has great significance for real-time simulation of temperature field change and on-line evaluation of welded joint quality.