Effect of Water Depth and Flow Velocity on Microstructure, Tensile Strength and Hardness in Underwater Wet Welding

Abstract

Wet underwater welding is a welding process carried out under water. The depth and water flow velocity greatly affect the welding results. Thus, a further research needs to be done about the effect of the depth and water flow velocity of underwater wet welding. The research aimed to determine the effect of depth and velocity of water flow on underwater wet welding on physical and mechanical properties. The welding process is carried out by using SMAW method at a depth of 2.5 m and 5 m with variations in water flow velocity of 0, 1, and 2 m/s. Land welding is performed as a comparison. X-ray radiography, micro-structure, tensile strength, and Vickers hardness test were performed to determine the type of welding defects. Radiographic test results indicate an incomplete penetration defect (I), spatter (S), porosity (P), undercut (U), concavity (V), and irregular surface (Z). The results of the micro-structure test show that the grain size is fine and coarse as the depth and velocity of the water flow increase. Tensile strength and micro-hardness testing increase along with an increasing depth and velocity of water flow.

Effect of water flow and depth on fatigue crack growth rate of underwater wet welded low carbon steel SS400

“…Macro and micro structures of underwater wet welded joints related to water depth and flow have been discussed in our previous papers [18,19]. There are differences in weld penetration depth and porosity due to differences in water depth and water flow speed of underwater wet welding.…”

“…It means that the crack in on land weld metals will propagate faster than in underwater wet weld metals. Based on our previous research [19,32], the main microstructure of underwater wet weld metal was acicular ferrite which had small grain and good toughness. It will resist the movement of propagation crack.…”

“…During taking data analysis of underwater wet welded joint test, it is found that there was interesting relationship between tensile strength and fatigue crack growth rate. By taking the tensile test of underwater welded joints [19], the relationship between tensile strength and fatigue crack growth rate represented by Paris constant can be illustrated in Figure 15. It shows that there is a proportional relationship between tensile strength and fatigue crack growth rate.…”

“…Even though in its application, underwater wet welding is carried out at a water depth of more than 1 meter and a sea water wave causes water to flow around the welding environment. Yasinta et al [18] and Paundra et al [19] have conducted research on underwater wet welded joints with varying water depth and speed of water flow, but the characterization of underwater wet welded joints was still limited to physical properties and basic mechanical properties including hardness and tensile strength. Because underwater construction experiences dynamic loads caused by sea waves, it is very important to continue the research on the fatigue crack growth rate of underwater wet welded joints.…”

Underwater Local Cavity Welding of S460N Steel

“…Klett et al [14] reported that the amount of hydrogen increases with increasing water depth. The water depth is also responsible for the properties of underwater welded joints, which was studied by Paundra et al [15]. It was stated that the increase of the water depth causes higher hardness in the HAZ.…”