Underwater wet welding of S1300 ultra-high strength steel

An expected tendency in marine and offshore structures is an increasing share of steels with high mechanical properties. The necessity to perform the welding work under water leads to a decreasing of the weldability of the steel. It results from the increased susceptibility to form cold cracks, especially in welded structures made of high-strength steel. A potential method, which may improve the problem of limited weldability of steel under water is the use of temper bead welding (TBW) technique. In this paper, the possibility of underwater wet welding by covered electrode S1300 ultra-high strength steel of different thickness (4 mm and 10 mm) has been investigated. The visual, metallographic macro- and microscopic tests, and Vickers HV10 measurements of samples with two nonparallel beads were performed. On the basis of the performed tests, the effectiveness of TBW technique was quantitatively verified. It was proved that TBW leads to positive microstructural changes and reduces the number of cracks in different regions of welded joints. Moreover, it was found that the proposed technique allows to decrease the hardness of S1300 steel joint by 30–80 HV10 in the weld metal and 40–100 HV10 in heat-affected zone. Finally, it was stated that the thickness of the base material does not affect the effectiveness of the TBW technique.