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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contains a small of pearlite structure and enlarged ferrite growth, as shown in figure 4. It means Ferrite structure is brighter than the Pearlite (Hamid et al., 2018). The ferrite phase is softer than the Pearlite. The Ferrite phase causes the properties of the material to soft and ductile, while the Pearlite is hard and brittle. The ductility of material is the main reason for the improvement of impact toughness (Cui et al., 2014). If the impact toughness improves that more energy will consume in the process of crack propagation (Dong et al., 2020). So, fatigue resistance will increase. a. b.

Fig. 4. Microstructure test of base metal (a) non PWHT, (b) with PWHT (Hamid et al., 2018).

4. Conclusions Underwater welding is the development of the welding process used to repair or maintain the structure of materials in the sea and rivers. This welding process influences underwater welding factors such as level of water depth, humidity around the welding area, and the stability of the arc welding. These factors can affect the emergence of defects, inclusions, and evolution microstructure to increase the rate of fatigue crack propagation. Fatigue failure at the underwater welding joint influenced by the level of water depth. If the level of water depth increase, so the quality of welding results will decrease. The depth of the water causes the formation of fine grains of microstructure. To increase the level of water depth will reduce grain size due to an increase in the rapid cooling rate in the UWW joint. Therefore, to improve the fatigue resistance of the UWW joint can be doing with the Post Weld Heat Treatment (PWHT). It aims to increase the structure size of the Ferrite in the weld metal and HAZ. To improve the structure in the form of PF with a larger grain size can reduce but increase the impact toughness. If the impact toughness is improved that more energy will consume in the process of crack propagation. Moreover, PWHT can increase fatigue resistance in UWW joint. Acknowledgements Authors graefully thank University Sebelas Maret, Indonesia for providing financial support through Mandatory Research 2020 grant with Contract No. 452/UN27.21/PN/2020. References Arias, A.R., Bracarense, A.Q., 2017. Fatigue crack growth rate in underwater wet welds: out of water evaluation. Welding International 31, 348 – 353. Assuncao, M.T., Bracarense, A.Q., 2017. Evaluation of the effect of the water in the contact tip on arc stability and weld bead geometry in underwater wet FCAW. Soldagem e Inspecao 22, 401 – 412. Chen, H., Guo, N., Liu, C., Zhang, X., Xu, C., Wang, G., 2020. Insight into hydrostatic pressure effects on diffusible hydrogen content in wet welding joints using in-situ X-ray imaging method. International Journal of Hydrogen Energy 45(16), 10219 – 10226. Chen, H., Guo, N., Shi, X., Du, Y., Feng, J., Wang, G., 2018. Effect of water flow on the arc stability and metal transfer in underwater flux-cored wet welding. J. Manuf. Process 31, 103 – 115. Chen, H., Guo, N., Xu, K., Xu, C., Zhou, L., Wang, G., 2020. In-situ observations of melt degassing and hydrogen removal enhanced by ultrasonics in underwater wet welding. Materials and Design 188, 108482. Chen, H., Guo, N., Zhang, X., Zhou, L., Wang, G., 2020. Effect of water flow on the microstructure, mechanical performance, and cracking susceptibility of underwater wet welded Q235 and E40 steel. Journal of Materials Processing Technology 277. Cui, L., Yang, X., Wang, D., Hou, X., Cao, J., Xu, W., 2014. Friction taper plug welding for S355 steel in underwater wet conditions: Welding performance, microstructures and mechanical properties. Materials Science and Engineering A. 611, 15 – 28. Di, X., Ji, S., Cheng, F., Wang, D., Cao, J., 2015. Effect of cooling rate on microstructure, inclusions and mechanical properties of weld metal in simulated local dry underwater welding. Materials and Design 88, 505 – 513.