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.
Highlights
Laser MIG hybrid welding couples a laser beam and an arc into one process
Chen et al [11,12,13] studied the interactions between laser and arc plasma during laser MIG hybrid welding, and the results showed that coupling discharge between the laser keyhole plasma and arc occurs
The results showed that the magnetic field plays a significant role in determining the arc plasma, melt flow, and the stability of the keyhole in laser MIG hybrid welding [24,25]
Summary
Laser MIG hybrid welding couples a laser beam and an arc into one process. It gives full play to their respective advantages and makes up for the shortcomings of a single heat source, which is a more efficient form of heat source [1,2,3,4]. Compared to conventional laser welding, laser MIG hybrid welding can effectively improve the gap bridging capability, obtain greater weld penetration under the condition of lower laser power, and realize a stable and high-efficiency welding process. It has been widely used in different industries such as the vehicle, aerospace, shipbuilding, and pressure vessel industries [5,6]. The results showed that the magnetic field plays a significant role in determining the arc plasma, melt flow, and the stability of the keyhole in laser MIG hybrid welding [24,25]. The effect of the alternating magnetic field parameters on the droplet transfer behavior and arc plasma characteristics in the laser MIG hybrid welding process was discussed. The optimized alternating magnetic field parameters were obtained by observing and analyzing the morphology of the weld cross-section during narrow gap laser MIG hybrid welding
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