Effect of Alternating Magnetic Field on Arc Plasma Characteristics and Droplet Transfer during Narrow Gap Laser-MIG Hybrid Welding

Abstract

In this paper, the morphological characteristics of arc plasma and droplet transfer during the alternating magnetic field-assisted narrow gap groove laser-MIG (metal inert gas) hybrid welding process were investigated. The characteristics of arc plasma and droplet transfer, electron temperature, and density were analyzed using a high-speed camera and spectrum diagnosis. Our results revealed that the arc maintained a relatively stable state and rotated at a high speed to enhance the arc stiffness, and further improved the stability of the arc under the alternating magnetic field. The optimum magnetic field parameters in this experiment were B = 16 mT and f = 20 Hz, the electron temperature was 9893.6 K and the electron density was 0.99 × 1017 cm−3 near the bottom of the groove, which improved the temperature distribution inside the narrow gap groove and eliminated the lack of sidewall fusion defect. Compared to those without a magnetic field, the magnetic field could promote droplet transfer, the droplet diameter decreased by 17.6%, and the transition frequency increased by 23.5% (owing to the centrifugal force during droplet spinning and electromagnetic contraction force). The width of the weld bead was increased by 12.4% and the pores were also significantly reduced due to the stirring of the magnetic field on the molten pool.

Effect of Alternating Magnetic Field on the Organization and Corrosion Resistance of 2205 Duplex Stainless Steel Narrow-Gap Laser-MIG Hybrid Weld Head

“…At the same time, the magnetic field increases the plasma temperature, which effectively reduces the generation of unfused defects. This has been pointed out in the study of Cai et al [32].…”

“…At the same time, the magnetic field increases the plasma temperature, which effectively reduces the generation of unfused defects. This has been pointed out in the study of Cai et al [32]. Narrow-gap laser arc hybrid welded joints for thick plates can be divided into four areas: the cosmetic bead, the filling bead, the overlapping bead, and the heat-affected zone.…”

Effects of Magnetic Fields in Arc Welding, Laser Welding, and Resistance Spot Welding: A Review

“…Under the combined action of the laser and magnetic field, charged particles accumulate at one side, which results in asymmetry and oscillation of arc along welding direction. Cai et al [ 104 ] also investigated the droplet transfer and arc plasma characteristics during alternating magnetic field‐assisted narrow gap laser‐MIG hybrid welding of 2205 duplex stainless steel. Under the action of alternating magnetic field, the laser‐induced plasma weakens with the increase of magnetic flux density, while the arc remains relatively stable and rotates at a high speed to improve the arc stiffness, thus further improving the stability of the arc.…”

“…In addition, under the magnetic field condition, the electromagnetic force near the droplet bottom moves downward and inward, resulting in the decrease in the droplet diameter and transfer period time, i.e., the transfer frequency increases, which is consistent with the results of Chen et al [ 26 ] Due to the stirring effect of magnetic field on molten pool, weld width increases and porosity decreases, which is consistent with the results provided by previous researchers. [ 89,100,104 ]…”

Dynamic Characteristics of Plasma in Ultrasonic-Assisted Narrow-Gap Laser Welding with Filler Wire

“…Compared with traditional welding methods, narrow-gap welding sharply decreases the filling quantity and enhances the efficiency. For high-strength steel, narrow-gap laser welding can meet the requirements of processing and assembly precision of the component welding application and, at the same time through the filling of welding wire, can carry out metallurgical control on the weld, refine the microstructure grain, and can use a low-power laser to achieve the welding of a medium and thick plate so as to reduce the dependence on high-power lasers [ 4 , 10 , 11 , 12 , 13 , 14 , 15 ].…”