Study On The Wire Feeder For Underwater Welding And Process Experiment In Underwater Welding

As the development of underwater welding and ocean resource exploited,in this paper, the underwater welding wire feeder was invented and used for performance test.Process experiment in underwater welding was studied.Bead-on-plate welding and butt welding on Q235A low carbon steel was researched. Better surfacing weld and butt joint was gained with flux-cored wire. The microstructure,microhardness and fracture morphology of the welds were analyzed in detail.The result shows:1.The performance test of underwater welding wire feeder was well, and wire feed speed is controlable,also the sealing property was well.The internal protected shell of wire feeder was choosed reasonable by softwaer simulation.2.The underwater welding wire feeder can matched well with ordinary CO2 shielded power after the electric circuit improvement.Then, carbon steel wire and flux cored wire was used respectively for the surfacing.And the joint formation was good and there was no weld flash and undercutting. The effect of underwater wet welding processes with flux-cored wire on Q235 was well.3. Bead-on-plate welding on Q235A steel by underwater wet welding process with flux-cored wire was researched. The results showed that the maxim hardness(HV) of welds reached 670. The fusion zone of the welds were composed of columnar grain structure.And the structure of the zone near HAZ was widmannstatten,and the structure of the zone near base metal was fine equiaxed ferrite.We also discovered the performance of welds had little change when the deepth of water change small. The processing parameters was discovered by orthogonal test method, and rescaled range analysis was used to analysis the parameters influence on the hardness of welds. The result shows that the primary and secondary order of the three factors which could affect the microhardness of the welds could be to sort as welding speed, welding voltage and welding current.4.The 3mm and 8mm steel plates were used for the butt welding reserch. The joint formation was good and there was no weld flash and undercutting.The microstructure of the welds were not depend on the thickness of plates.The microstructures of the welded seam had a slender columnar crystals within acicular ferrite.The tensile strength of butt weld(3mm) was higher than base metal,and the tensile strength was 299Mpa.But tensile strength was very low when the flaw existed in the seam.There was obvious defects existed in the seam(8mm) because of unreasonable welding parameter. 60-degree V-groove was machined along one side of the samples(8mm),the joint formation was good,the grain of HAZ and seam was fine. The results showed that the strenth of weld reached 415Mpa whitch is higher than base metal.