PSI - Issue 27

Ericha Dwi Wahyu Syah Putri et al. / Procedia Structural Integrity 27 (2020) 54–61 Putri et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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1. Introduction Underwater welding is a welding process used to maintain and improve structures on underwater. Underwater welding serves to improve and maintain pipeline system construction, ship components, offshore oil and gas rig, port construction, and also nuclear power plant structures (Labanowski et al., 2012; Guo et al., 2015; Assuncao and Bracarense, 2017; Muhayat et al., 2020). Underwater welding can use to repair and replace some marine construction damage due to corrosion, material fatigue, uncertain factors, problems of construction, problems during the assembly process, and operational overload (Labanowski, 2011). The underwater welding method carried out according to material construction, the welding operator's expertise, and the costs involved. Underwater welding methods common and easy to apply, e.g. Shielded Metal Arc Welding (SMAW), Flux-cored Arc Welding (FCAW), and Gas Tungsten Arc Welding (GTAW) (Majumdar, 2006; Labanowski, 2011; Sabari et al., 2016). Shielded Metal Arc Welding (SMAW) is an electric arc welding process that can heat due to arc welds, which can melt electrodes and welded material. The wire electrode in the SMAW protected by flux. The filler metal can deposit on material by forming a slag that can protect the weld metal during the cooling process. FCAW (Flux-cored Arc Welding) is a welding technique using flux as a protector and the addition of alloying elements to the weld metal, which placed in a wire-shaped electrode. FCAW can be operated in all positions and does not require welding operators with typical expertise. GTAW (Tungsten Arc Welding) or TIG Welding (Tungsten Inert Gas) is a welding technique using electrodes made of tungsten and filler metals added separately during the welding process. GTAW process produces a stable arc weld because this process uses a small current so it can apply to metals and alloys that have poor weldability. Based on its work principle, underwater welding classified into two types, namely dry and wet welding (Guo et al., 2015; Chen et al., 2018). UDW is a method of connecting underwater metals using a weld chamber, which conditioned in a dry environment. Weld chamber serves to change the adverse effects of water and ensure that welding quality is equivalent to welding on land (Rodriguez-Sanchez et al., 2014). UWW is a welding process that combines metals using a particular waterproof stick electrode. UWW process carried out directly underwater so the arc can contact directly with water in the surrounding environment (Majumdar, 2006). UWW has the advantage that the equipment used simpler than other methods so that welder can more easily mobilize welding in water. The preparation required for the UWW process is faster. This welding does not need a particular area, so the operation is easy to move, and the costs required are relatively cheaper (Yang et al., 2019; Chen et al., 2020). However, the UWW technique also has disadvantages, including a decrease in material ductility, increased material hardness in the HAZ area, defects in the weld metal, weld arc flame instability, and the presence of water waves around the welding area. These can be a significant problem and must resolve because it affects the results of underwater weldings, such as susceptibility to crack propagation, high porosity, and relatively low weld yield (Labanowski, 2011). Besides, UWW can also reduce the mechanical properties of the weld joint (Chen et al., 2020). Sea and river is a water environment where it has an underwater structure is not stationary but moves to form waves of water. Water waves are a detrimental factor both during the process and applications of the underwater welding joint. During the welding process, the water wave will affect the results of the underwater welding joint. Water waves continuously can drive underwater welding defects, such as porosity and inclusions (Arias and Bracarense, 2017). Porosity is a defect caused by the presence of hydrogen gas trapping in the weld metal. If the water wave at UWW is increasing so the hydrogen gas content will enhance. (Chen et al., 2020). The hydrogen gas trapping in the weld metal has a damaging effect in the form of cracks, which can reduce the reliability of the welding structure and cause the steel to become brittle and fracture (Swierczynska et al., 2017; Chen et al., 2020). At the time of application of an underwater welding structure, water waves whose magnitude is always changing in the environment around the underwater welding joint structure that will cause a cyclic loading on the structure of the material. Cyclic loading causes welding defects to be an initial crack, propagate, and the structure of the material will be a failure. Besides, welding inclusions in large quantities can increase the rate of fatigue crack propagation (Wang et al., 2019). Based on the illustration above, a comprehensive discussion of the fatigue failure behavior of underwater welding joint is critical. Research on fatigue failure behavior at UWW is still limited, and the focus of the discussion is various. To be comprehensive and easy to understand. Therefore, a review of articles about fatigue behavior in an underwater welding joint is needed. This review expected to be a reference in mapping the development of research on underwater