Mechanical and Microstructural Properties of A36 Marine Steel Subjected to Underwater Wet Welding

Abstract

Underwater wet welding (UWW) is applied to repair basic offshore structures, underwater pipelines, water transportation, docks, and port equipment. The underwater wet welding method used in the current research was shield metal arc welding (SMAW), and this was conducted on an A36 steel plate. We investigated the effect of a water temperature of 10 ± 5 °C and different types of water flow (without flow, non-uniform flow with baffle bulkhead, and non-uniform flow without baffle bulkhead). The defects found on the specimen included spattering, irregular surfaces, porosity, and undercutting. A high cooling rate led to the formation of more acicular ferrite (AF) phases in the weld metal area than a slow cooling rate. The microstructure of the heat affected zone (HAZ) area led to the formation of finer and small grains. Values of tensile, impact, and hardness strength were greater with higher cooling rates. The highest tensile strength value was 585.09 MPa, and this occurred with non-uniform flow without a baffle bulkhead. The highest values of absorbed energy and impact strength were 41.9 J and 2.05 J/mm2, respectively, and these occurred with a non-uniform flow without a baffle bulkhead. The greatest hardness values were found with a non-uniform flow without a baffle bulkhead in the weld metal area.

Fatigue Behaviour of Offshore T-Weld Connections Repaired by Grinding and Wet Welding

“…Braun et al [8] stated that grinding may be applicable to butt and fillet welded joints with similar effectiveness. In fixed platforms, the effect of water temperature and sea water flows affect the mechanical and microstructural properties of A36 plates steels employed in the welding connections as investigated by Surojo et al [9]. The effect of water flow speed and water depth on the crack growth rate of underwater wet-welded lowcarbon steel was studied by Surojo et al [10], who showed that fatigue crack growth rate in underwater welded joints decreases as water depth and flow rate increase.…”

Application Possibilities of the S960 Steel in Underwater Welded Structures

“…Following this, there are problems with controlling the process, which is the biggest disadvantage of local cavity welding. The third and most used method is wet welding [5]. In wet welding, the welder diver and the whole welding area are in direct contact with water.…”