Numerical simulation and experimental verification of droplet transfer during local dry underwater MIG welding process of SUS304

Based on the fluid mechanics and electromagnetic theory, a numerical simulation model of droplet transfer during local dry underwater MIG welding (LDU-MIG) of SUS304 was established by using fluid dynamics software FLUENT. The effects of gas pressure, wire feeding speed (WFS) and pulse peak current on the whole droplet transfer process in LDU-MIG were simulated and investigated. The simulation results indicated that the increase of gas pressure reduced the plasma flow force and enlarged the pressure gradient in the local dry cavity, which hindered the droplet transfer process and led to the larger droplet diameters and longer transfer periods. The increase of WFS decreased transfer period in lower current, but it changed the droplet transfer modes in larger current. With the increase of pulse peak current, the droplet transfer modes changed from globular transfer (200 A) to projected transfer with one pulse one droplet (280 A), then to streaming transfer with one pulse multiple droplets (360 A). Finally, the droplet transfer process was captured by high-speed photography technology in LDU-MIG welding experiments, the simulation results were in good agreement with the experimental results, which provided theory guidance and data supports for manufacturing and remanufacturing of underwater structure.