Organic adhesive assisted underwater submerged-arc welding

Underwater welding technology has become indispensable to the construction, maintenance, and repair of many offshore structures in oceanographic engineering industry. However, the existing disadvantages of current underwater welding technologies make them be unpopular and limited. An innovative organic adhesive assisted underwater submerge-arc welding was proposed to avoid the water disturbances to the maximum extent in wet condition. The mixture composed of bisphenol-A epoxy resin (EP) and welding flux in a weight ratio of 4:6 was placed on the metal surface before welding. Welding arc totally submerged in the mixture and maintained stable burning between the wire and base metal. The coverage effectively isolated the serious direct disturbances from surrounding water and greatly reduced the cooling rate of the welded joints to 19.57 °C/s. High-performance and defect-free welded joints were achieved with fine microstructures. The average tensile strength and maximum bending angle of the welded joints obtained by underwater submerged arc welding reached 463 MPA and 180°, respectively. Especially, low temperature impact toughness still keep 63 J/cm2 in 0 °C, which means far better mechanical properties compared with underwater wet welding. For the wet condition, this provides a possibility to acquire high-quality underwater welded joints comparable to that in air.