Research On The Design Of Pulse TIG Spot Welding Power Supply And The Control Method Of Power Supply Output Characteristic

TIG spot welding is a special application of traditional TIG welding,which is suitable for micro area connection of thin-walled parts.Under the background of lightweight manufacturing,complex thin-walled parts have great demand for TIG spot welding.Traditional TIG welding has the disadvantages of long single discharge time and low arc energy density,which can not meet the requirements of micro area spot welding.Therefore,it is necessary to design a TIG spot welding power supply which can realize the precise control of welding energy and time,and study the regulation method of arc energy density based on the regulation of electrical characteristics.Firstly,a digital pulse TIG spot welding power supply is designed based on inverter technology and embedded control technology.The main circuit of the power supply includes input rectifier filter circuit,full bridge inverter circuit,high-frequency transformer and full wave rectifier circuit.The high-frequency and high-voltage arc striking circuit is used to realize non-contact arc striking,and the transformer synchronous driving circuit is used to realize MOSFET parallel driving.The power control system is composed of hardware circuit and software system with stm32h745 as the core.The dual MCU architecture is adopted to realize the separation of welding process control and information interactive processing,so as to improve the stability of the system.Then,based on the designed power supply and high-speed camera and other testing equipment,the power supply test and arc regulation platform is constructed,and the arc characteristic regulation method based on the output characteristic regulation of power supply is studied.The power supply has two output modes of DC and pulse.The welding process is controlled by arc striking,slow rise,welding,slow fall and arc maintenance.The arc morphology map is obtained by high-speed camera,and the arc image is analyzed and processed by using algorithms such as image graying,Gabor filtering,median filtering,threshold segmentation and Canny edge detection,which can realize the extraction of arc morphology characteristic parameters.The regulation of the output electrical characteristics of the power supply has an obvious impact on the arc morphology.The arc is more dense in the pulse mode,and the arc bunching is better when the appropriate welding parameters are selected.Finally,through the pulse TIG spot welding process test of stainless steel sheet,the influence law of electrical parameters on the properties of welded joint is studied.In the pulse mode,the pulse modulation function reduces the welding defects,makes the joint shape more beautiful and the combination more dense.Pulse peak current,base current,pulse frequency and duty cycle have great influence on the joint performance,among which the welding current has the greatest influence,followed by frequency and duty cycle.The tensile strength of welded joint increases with the increase of welding peak current,and first increases and then decreases with the increase of base current,power output frequency and duty cycle.