Research On Fiber Laser-MIG Hybrid Welding Heat Sources Characteristics And Welding Process Of Aluminum Alloy

With the continuous development of industry,high-strength aluminum alloy is widely used in aerospace,automobile and ship.Aluminum alloy has the characteristics of high thermal conductivity,so it is very important to study the high quality and high efficiency welding method for medium and thick plate aluminum alloy.The optical fiber laser MIG hybrid welding method greatly increases the adaptability of the welding process,improves the weld formation,improves the quality of the welding joint,and improves the welding efficiency.In recent years,with the development of high-power fiber laser,the technology has been widely concerned and studied.In-depth study of the coupling mechanism between laser and arc is of great significance to optimize the welding process and improve the welding quality.The effect of laser on pulsed MIG arc in laser-MIG welding of high strength aluminum alloy was studied.The results showed that when the welding current I_M=150A,the hybrid transition mode dominated by short circuit transition occurred.Laser keyhole formed in the molten pool in front,according to the principle of minimum voltage,due to the effect of continuous of the laser keyhole to become a constant source of electron emission,near the keyhole will form a relatively stable cathode spots,cathode spots formed between the end of the wire anode area with a parabolic conductive path,maintain a base value condition of arc burning.With the increase of laser power,the phenomenon of short circuit transition almost disappears,reducing the overflow of molten pool and welding spatter.The stability of optical fiber laser MIG hybrid welding process is discussed.The stress models of keyhole in optical fiber laser welding and optical fiber laser MIG hybrid welding are established.The results show that the voltage standard deviation of the hybrid welding arc is smaller than that of the MIG welding arc,which indicates that the hybrid welding process is more stable.The angle between the front wall of keyhole and the vertical direction becomes larger during the fiber laser MIG hybrid welding.The increase of this angle makes the dynamic vapor pressure on the back wall of keyhole decrease uniformly,so that the back wall of keyhole becomes smooth,the stability of keyhole is improved,and the keyhole will not collapse.The effects of various welding parameters on weld forming were studied,and the 8 mm thick 7075-T6 high-strength aluminum fiber laser-MIG hybrid welding process was tested.Test showed that the arc energy is given priority to,when to keep welding speed v=0.51 m/min,the total energy P=6892W,the energy ratio?is between 1.23 and 1.65,get the optimal weld surface of the negative and positive the forming quality,achieve penetration,reach the threshold of deep penetration.Laser energy is given priority to,v=2 m/min,total energy P=9842W,the energy ratio?is between 0.64-0.93 range of welds shall implement penetration,deep penetration to the threshold.Further to 8 mm7075-T6 high-strength aluminum alloy laser-hybrid MIG welding process parameters optimization,get 8 mm7075-T6 high-strength aluminum alloy laser-hybrid MIG welding process interval,based on the optimized the butt weld of X-ray detection,can draw from the result of X-ray detection,when MIG arc energy is given priority to,welding current I_M for 170A-190A,laser power P_L in2.7-3.1k W,when the welding speed v=0.51 m/min to get butt weld porosity is less;When the laser energy is dominant,the welding current is 190A-210A,the laser power is 5.1-5.3k W,and the welding speed v=2m/min,so as to obtain the butt weld without pores.When arc energy was dominant,welding I_M=230A,P_L=4.2k W,L_DF=-3mm,L_LA=3mm,and v=0.6m/min were welded to obtain a well-formed butt weld,with tensile strength up to 345 MPa,welded joint coefficient of 62.73%,and elongation after fracture of 1.04%.When the arc energy is dominant,the heat input is larger,the temperature gradient is smaller,and the cooling rate is slower,which is conducive to the growth of columnar crystals.When the laser energy was dominant,when the welding current I_M=210A,the laser power P_L=5.1k W,and v=1.6m/min,the surface quality of the weld was good,without obvious welding defects.The tensile strength was up to 365MPa,the welded joint coefficient was 66.36%,and the elongation after fracture was1.24%.When the laser energy is the main factor,the columnar crystal is thinner and shorter.