A split-type multifunctional underwater arc welding power supply including a shore power supply module and an underwater power supply module is provided. The shore power supply module comprises a shore power supply main circuit unit and a shore power supply control unit. The shore power supply main circuit unit comprises an input filter circuit, an IGBT full-bridge inverter circuit, an intermediate frequency transformer, and an output rectification filter circuit. The underwater power supply module comprises an underwater power supply main circuit unit and an underwater power supply control unit. The shore power supply module is provided on the shore, and the underwater power supply module is carried underwater.

A water-degradable welding purge dam apparatus for purging a weld zone of a pipe assembly having first and second pipes having respective first and second pipe ends to be welded together at a root gap. The purge dam apparatus includes a blocking plate assembly having an outer blocking plate, an inner blocking plate, and zero or more interior blocking plates. The blocking plate assembly may be formed from one or more water degradable materials to facilitate removal of the purge dam apparatus from the pipe assembly using an aqueous fluid following welding. At least one of the blocking plates may include a plurality of fluid flow apertures to aid distribution of the aqueous fluid through the blocking plate assembly. If desired, first and second ones of the blocking plate assembly may be ganged together by an interconnection assembly to form a ganged set of blocking plate assemblies.

A underwater cutting torch having a control valve assembly, a check valve assembly and a torch head all positioned within a housing. The control valve assembly and check valve assembly include a passageway for gasses to flow that includes a coupler formed of PTFE material to inhibit combustion within the handle of the underwater cutting torch.

A solid wire for submerged arc welding, in which a chemical component of the solid wire includes, by mass %, C: from 0% to 0.650%, Si: from 0.03% to 0.50%, Mn: from 4.1% to 30.0%, P: from 0% to 0.050%, S: from 0% to 0.050%, Cu: from 0% to 5.0%, Ni: from 1.0% to 30.0%, Cr: from 0% to 10.0%, Mo: from 0% to 10.0%, Nb: from 0% to 1.00%, V: from 0% to 1.00%, Co: from 0% to 1.00%, Pb: from 0% to 1.00%, Sn: from 0% to 1.00%, Al: from 0% to 0.10%, Ti: from 0% to 0.10%, B: from 0% to 0.1000%, N: from 0% to 0.5000%, O: from 0% to 0.0050%, and balance: Fe and impurities, (Mn+Ni) is 5.0% or more, (Mn+Ni+Cr) is 15.0% or more, and a fraction of fcc is 70% or more.