Study On Numerical Simulation Of Dual Pulse Heat Transfer Of High-power Twin-wire Pulsed MIG Welding

Twin-wire pulsed MIG welding has the characteristics of high deposition rate and welding quality, which attracts more and more attention from welding researchers. The current research of twin-wire pulsed MIG welding mainly focuses on single pulse welding with comparative low-power and the study of dual pulsed welding is centered on single-wire welding, but very little attention was paid the research of twin-wire dual pulse welding. The research of high-power twin-wire dual pulsed MIG welding places an important role in improving welding efficiency and quality. This subject researches high-power twin-wire pulsed MIG welding dual pulse power control system and conducts numerical simulation for twin-wire dual pulse welding temperature field and analyzes welding metallographic resulted from different pulse welding methods with the support from National Natural Science Foundation of China(No.51205136) and the Fundamental Research Funds for the Central Universities(Key Program)(No.2013ZZ034).The overall scheme of high-power twin-wire pulsed MIG welding dual pulse control system was proposed. The topology structure, power external characteristic of main circuit and output scheme of multiple-phase were analyzed. The hardware circuit and software program of the control system were designed based on TMS320LF2407 A and digital control of multiple-phase output of high-power twin-wire pulsed MIG welding dual pulse current was realized. The hardware and software anti-disturbance schemes were designed by analyzing the interference sources of welding place. For high-power twin-wire pulsed MIG welding master and slave arcs has the unique external characteristic of constant-current amplitudes at peak stage and base stage(I+I), anti-windup PI algorithm was adopted to come true constant-current control of high-power twin-wire pulsed MIG welding dual pulse power.Finite element software ANSYS was used for numerical simulation of high-power twin-wire dual pulse welding temperature field. By establishing geometric model, generating mesh and making use of secondary development function of APDL language, the program of double ellipsoid moving heat source calculation module that fits for high-power twin-wire dual pulsed MIG welding was wrote. The characteristics of temperature field of high-power twin-wire dual pulsed MIG welding was analyzed according to numerical simulation result. The reliability of temperature field simulation result was verified through measuring welding thermal cycle curve and the dimension of welding seam.Single pulse and dual pulse bead-on-plate welding experiment was made by employing the developed welding power, using the parameters of numerical simulation as the welding process parameters. The experiment result shows that the researched control system of high-power twin-wire dual pulsed MIG welding can meet the design requirement, which made the high-power twin-wire dual pulsed MIG welding process stability come true and appearance of welding seam good. The result that crystal grain size of welding seam of dual pulsed welding is smaller than single pulsed welding was verified trough metallographic comparing analysis of the welding seams resulted from single pulse and dual pulse.