Effect of pulse current on droplet transfer behavior and weld formation of 304 stainless steel in local dry underwater pulse MIG welding

304 stainless steel, which is widely used in the industrial field due to its excellent thermostability, corrosion resistance, and welding performance, was welded using local dry underwater pulse metal inert gas (LDU-PMIG) welding technology in this study. The effect of different pulse peak currents on droplet transfer behavior and weld formation was investigated. The results show that short circuit transfer, globular transfer, and projected transfer were observed in the LDU-PMIG process. With the peak current of 240 A, the droplet transfer modes were short-circuit transfer and globular transfer; the weld formation was irregular with large particle spatters around the weld. With the peak current increased to 260 A, the droplet transfer mode changed into the globular transfer, and the weld formation quality was improved. With the peak current of 280 A, the droplet transfer mode was projected transfer, the weld formation was satisfied with a few spatters, and the coefficient of weld formation was the largest, and projected transfer was the most stable mode. With the increase of the peak current from 300 to 320 A, the droplet transfer mode did not change, but the instability of the welding arc resulted in poor weld formation with serious spatters and undercuts.