Laser arc weak coupling achieves porosity free welding and stable droplet transfer for high nitrogen steel.

To address the challenge of porosity suppression in laser-arc hybrid welding of high-nitrogen steel, a weakly coupled laser-arc welding method suitable for high-nitrogen steel is proposed. A test platform for composite and "sandwich" welding of high-nitrogen steel was constructed, and this weakly coupled laser-arc welding method was thoroughly analyzed in terms of droplet transfer, arc morphology, keyhole stability, electrical signal stability, weld formation, and porosity rate. The research results show that when the distance between the laser and arc is 6 mm, the droplet transfer mode is jetting, fine droplet, or mixed, with stable, uniform transfer, a stable keyhole, minimal electrical signal fluctuations, and good weld formation quality. The arc is elongated due to laser attraction, increasing the molten pool area and reducing its solidification rate, which provides sufficient time for bubbles to escape, resulting in a pore-free weld. This proves the effectiveness of the weakly coupled laser-arc welding method for high-nitrogen steel, achieving a high-quality, pore-free weld with excellent formation quality. These findings provide guidance and reference for composite welding processes of high-nitrogen steel.