Welding Signal And Simulation Of Microstructure Analysis Of 2219 Aluminum Based On Variable Polarity Gas Tungsten Arc Welding

In recent years,with the continuous development of the aerospace industry,new requirements have been placed on large-sized aluminum alloy components.Doublepulse TP-GTAW(Double-pulse VP-GTAW)as a kind of aluminum alloy welding The improved tungsten argon arc welding technology is suitable for welding 2219 aluminum alloy of medium and heavy plates.In order to improve the welding efficiency and ensure the welding quality of double-pulse variable-polarity tungsten arc welding,the electric signal,thermal cycle and weld formation of the welding process of 2219 aluminum alloy double-pulse variable-polarity tungsten arc welding are analyzed.A study was conducted to analyze the relationship between different welding defects and the electrical signal characteristics of the welding process,and the solidification process of the molten metal in the molten pool under different welding conditions was studied based on the Cellular Automata(CA)algorithm.The electrical signals under different welding parameters were collected.Based on the empirical mode decomposition of the electrical signals,the electrical signal characteristics were analyzed based on the fast Fourier transform spectrum analysis and the Hilbert-Huang transform spectrum.The research showed that the welding signals The less the frequency distribution jumps,the more stable the welding process.The more uniform the amplitude distribution of the Hilbert spectrum,the better the weld formation.The time-frequency entropy is used to characterize the stability of the electrical signal in the welding process.The results of the study indicate that the time-frequency entropy of the well-formed weld is small.The defect detection of welding process based on electric signal is realized.On the basis of obtaining good joint forming,the solidification process of the molten metal in the weld pool during the welding process was studied.The cellular automaton algorithm was used to model the weld pool of the weld,and different subcooling degrees and different Changes in the size of the weld metal grains under heat input.For the double-pulse VP-GTAW of multi-layer and multi-channel of aluminum alloy with medium and thick plates,the effect of the cover layer on the coarsening of the grain size of the bottom bead is studied,and the microstructure changes at the joint surface of the weld are analyzed.Under the conditions of this study,the grain size of the underlying layer increased by about 63% on the cover surface.The simulation of the weld grain size and growth based on the CA method is realized.