The drive to minimise ship weight, and hence reduce fuel consumption, has stimulated research into the effects of reducing the plate thickness of the hull structure. However, thinner plate structures significantly increase the risk of major distortion, which can lead to substantial post-welding rework. A number of novel welding techniques have shown potential to reduce welding induced distortion and its associated cost.
Two novel welding processes are of particular interest: Tandem-Gas Metal Arc Welding (T-GMAW) and, so called, GMAW with Dynamically Controlled-Low Stress No Distortion (DC-LSND). Although, both techniques modify the thermal heat fields associated with the welding process, they achieve this aim in fundamentally different ways. The T-GMAW process uses a second welding electrode to introduce a second heat source whilst DC-LSND technique uses a trailing CO2 heat sink nozzle to accelerate the cooling of the GMA weldment. Both techniques have the potential to influence the stresses introduced by the welding process and, thus, the distortion.
In this study, these two processes are applied to both butt weld and fillet welds specimens made of 5mm DH36 steel. A comparison of the measured out-of-plane distortion for both processes is presented and compared to traditionally used processes, such as Submerged Arc Welding or Gas Metal Arc Welding. After considering other influencing factors such as weld mechanical properties and productivity, an assessment is presented of the suitability of both the T-GMAW and DC-LSND processes for use in naval shipbuilding.