Optimization of underwater welding process in stationary local dry cavity and analysis of welding joint properties

The droplet transfer of flux cored arc welding at normal pressure was investigated with high-speed digital camera system. Based on the experiments under 0.2 MPa pressure in hyperbaric chamber, the welding parameters were optimized. The voltage decrease of cable was compensated. The final current and voltage setting values of the welding machine used for the practical test in Bohai Sea were 175~185 A and 32~34 V, respectively. The test in stationary local dry cavity was carried out at the water depth of 23 m in Bohai Sea. According to AWS D3.6M:2010, the mechanical properties tests were taken. Results indicated that no pores, inclusions and cracks were founded in the welding joints. The microstructures of the weld metals were mainly consisted of acicular-ferrite, ferrite-side-plate and polygonal-ferrite. All the tested mechanical properties reached the requirements of Class A Weld according to the standard. The experimental results indicated that local dry underwater welding based on the stationary drainage cavity can be applied in the repair of DH36 offshore jacket structures.