Study On The Characteristic Of LB-VPPA Hybrid Heat Source And Welding Process On Aluminum Alloy

Aluminum alloys due to fast thermal conductivity and big linear expansion coefficient,so the problem of welding joint softening is appeared easily on the thick plate structure.While traditional laser welding and double wire MIG welding multichannel failed to solvethe problem of aluminum alloy welded joint softening. Arc energy concentration of VPPAwelding has a certain advantage in the thick plate of Aluminum alloy weld. Join the lasercan further improve VPPA arc energy density and reduce VPPA welding negative polaritycurrent amplitude. It is good to reduce the burning of tungsten electrode and improve thestabling of VPPAarc.Therefore, with the LB-VPPA hybrid welding to improve the quality of welding andwelding efficiency on aluminum alloy, the thick plate is widely used on tanks, armoredvehicles, aeronautics and astronautics etc fields are that has a large scientific researchsignificance and engineering application value. Currently, aluminum alloy laser-arc hybridwelding is given priority to laser-MIG hybrid welding and laser-TIG hybrid welding, butheat source characteristics and process of laser-VPPAhybrid welding researching is less.This article based on the domestic and international laser-arc hybrid welding literaturea lot of reading and the VPPA welding system is developed by laboratory and thelaboratory existed of a CO2laser welding system, first a paraxial laser-VPPA hybridwelding system was set up and produced bead–on–plate runs on3003aluminum alloyunder different welding conditions. The feature detection system including high speedcamera, HANNVOER welding quality analyzer. Then a laser–VPPA hybrid weldingsystem was used to study the relationship between hybrid welding parameters and arcshape, arc voltage, welding current, probability density distribution, the parameters likelaser power, arc power, heat source space etc greatly influenced the weld bead. Influence ofinteraction between laser and arc energy on bead geometry was analyzed.The results show that under stated condition，VPPA arc is attracted by laser andmechanism which laser act on arc is different in both positive polarity and negativepolarity periods. Laser is concentrated on the roof of arc in positive polarity, and there is aprotuberance-like plasma cylinder in negative polarity period. Roof plasma of VPPA arcabsorbs laser by inverse bremsstroblung, and cross sectional area of arc becomes large as temperature increase. Meanwhile, laser provides plenty of free electrons to VPPA arc, thuscurrent density and conductivity increase. Arc voltage decreases about3-4volts asresistance decreases. With the increasing of laser power, it obviously enhances the effectson VPPAarc.The application of laser-VPPA hybrid welding on3003aluminum alloy is realized onthe6mm thick plate butt joints. Basic a certain total power of heat source under LB-VPPAhybrid welding, the CO2laser power is1500W, the positive and negative polarity of VPPAwelding current is115A,155A, the welding speed is140mm/min, can get a good formingflat punch welding of weld.