Mechanical Integrity and Weld Characterization of FCAW and GTAW Joints on API 5L CO2 Fire Suppression Pipes
Abstract
This study investigates the mechanical and macro structural performance of welded joints produced by Flux-Cored Arc Welding (FCAW) and Gas Tungsten Arc Welding (GTAW) on API 5L Grade B low-carbon steel pipes used in marine CO2 fire suppression systems. The experimental work involved tensile, bending, hardness, and macro structural tests to evaluate the influence of each welding process on joint integrity. Both FCAW and GTAW joints exhibited high mechanical strength, with ultimate tensile strengths of 506MPa and 516MPa, respectively, exceeding the minimum requirement for API 5L Grade B steel. Fracture occurred in the base metal rather than the weld zone, confirming the superior strength and sound fusion quality of the joints. GTAW demonstrated slightly higher tensile performance and cleaner weld morphology due to the controlled heat input and stable arc achieved with 100% argon shielding, whereas FCAW produced marginally higher hardness in the heat-affected zone due to CO?-induced cooling effects. Macro structural analysis revealed complete penetration and the absence of porosity, slag inclusions, or cracks in both processes. The results comply with AWS D1.1 and ASME Section IX standards, confirming that both welding methods or their hybrid application are suitable for producing safe, reliable, and regulation-compliant marine fire suppression pipelines.
##Keywords:##
API 5L grade B, Flux-Cored arc welding (FCAW), Gas tungsten arc welding (GTAW), Marine fire suppression systems, Mechanical properties.
Published
Dec 1, 2025
How to Cite
DELPERO, M Arief et al.
Mechanical Integrity and Weld Characterization of FCAW and GTAW Joints on API 5L CO2 Fire Suppression Pipes.
Journal of Ocean, Mechanical and Aerospace -science and engineering-, [S.l.], v. 69, n. 3, p. 216-223, dec. 2025.
ISSN 2527-6085.
Available at: <https://www.isomase.org/Journals/index.php/jomase/article/view/558>. Date accessed: 30 may 2026.
doi: http://dx.doi.org/10.36842/jomase.v69i3.558.
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[4] Arvidson, M., & Westlund, Ö. (2024). The development of automatic sprinkler system concepts for maritime vehicle carriers. Fire Technology, 60(3), 2125–2153. doi: 10.1007/s10694-024-01563-3.
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[6] Moon, H.J., Kim, H.T., & Kim, Y.J. (2013). Design improvement to prevent low-pressure CO2 fire suppression system from plugging up with dry ice. InInternational Congress on Advances in Nuclear Power Plants, ICAPP 2013(pp. 1156–1160). Curran Associates, Inc.
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[8] Lv, H., et al. (2023). Data-driven urban gas pipeline integrity detection and evaluation technology system. Processes, 11(3), 895. doi: 10.3390/pr11030895.
[9] Sam, S., Kant, N., & Hazra, S.S. (2019). Development of API 5L X70 grade steel through thin slab casting & rolling process. InASME 2019 India Oil and Gas Pipeline Conference. ASME. doi: 10.1115/IOGPC2019-4519.
[10] Zhou, Y., Xie, F., Wang, D., Wang, Y., & Wu, M. (2024). Carbon capture, utilization and storage (CCUS) pipeline steel corrosion failure analysis: A review. Engineering Failure Analysis, 155, 107745. doi: 10.1016/j.engfailanal.2023.107745.
[11] Godefroid, L.B., Sena, B.M., & Da Trindade Filho, V.B. (2017). Evaluation of microstructure and mechanical properties of seamless steel pipes API 5L type obtained by different processes of heat treatments. Materials Research, 20(2), 514–522. doi: 10.1590/1980-5373-MR-2016-0545.
[12] Zhao, B., Wang, C., Xie, D., & Chen, K. (2018). Research of anti-H2S corrosion seamless line pipe. Heat Treatment of Metals, 43(3), 25–29. doi: 10.13251/j.issn.0254-6051.2018.03.006.
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[14] Simionescu, D., Mitelea, I., Burc?, M., & Uu, I.D. (2018). Mechanical behaviour of narrow gap MAG welding of API 5L X65M steel pipeline. InIOP Conference Series: Materials Science and Engineering, 416, 012008. IOPScience. doi: 10.1088/1757-899X/416/1/012008.
[15] Aggarwal, A., Adlakha, D., & Khanna, P. (2023). Development of a mathematical model to predict angular distortion in FCA welded stainless steel 301 plates. In Materials Today: Proceedings, 78, 608–613. doi: 10.1016/j.matpr.2022.11.478.
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[19] Malhotra, M., Kashish, Samridhi, & Khanna, P. (2022). Prediction of angular distortion in flux-cored arc welding of stainless steel 301 plates by mathematical modelling. In Materials Today: Proceedings, 62, 3681–3688. doi: https://doi.org/10.1016/j.matpr.2022.04.426.
[20] Phillips, S., Quintana, M., Jia, D., Wang, J., & Wang, Y.Y. (2022). Self-shielded flux-cored arc welding - practical approaches for improved performance of girth welds in high-strength steel pipelines. InProceedings of the Biennial International Pipeline Conference (IPC). ASME. doi: 10.1115/IPC2022-87290.
[21] Singh, G., Dewangan, A.K., Khan, M.F., & Moinuddin, S.Q. (2025). Fundamental review on gas tungsten arc welding of magnesium alloys: Challenges, innovations, and future perspectives. Welding in the World, 69(9), 2767–2787. doi: 10.1007/s40194-025-02047-w.
[22] Karhu, M., & Kujanpää, V. (2022). Gas tungsten arc process optimization and assessment for robotized position welding of austenitic stainless steel edge joints. CIRP Journal of Manufacturing Science and Technology, 36, 12–22. doi: 10.1016/j.cirpj.2021.10.012.
[23] von Querfurth, B., et al. (2025). AI-driven autonomous adaptative feedback welding machine. Welding in the World, 69(5), 1419–1426. doi: 10.1007/s40194-024-01898-z.
[24] Rathod, D.W. (2021). Comprehensive analysis of gas tungsten arc welding technique for Ni-base weld overlay. InAdvanced welding and deforming (pp. 105–126). Elsevier. doi: 10.1016/B978-0-12-822049-8.00004-9.
[25] PT Steel Pipe Industry of Indonesia Tbk. (n.d.). API 5L grade B material characteristics you must know. https://www.spindo.com/api-5l-grade-b-material-characteristics-you-must-know.
[26] Nikulin, S.A., Rogachev, S.O., Belov, V.A., Turilina, V.Y., & Shplis, N.V. (2025). Effect of high temperature on the strength of the base metal and the weld metal in a welded joint of low-carbon steels. Russian Metallurgy (Metally), 2025(3), 632–637. doi: 10.1134/S003602952570020X.
[27] Zhang, X.A., & Zheng, S.L. (2014). Experimental study in fracture and fatigue property of weld jointing with thick Q345R steel plan. Petrochemical Equipment, 43(1), 17–22.
[28] da Silva, N.N., & Sade, W. (2024). The effects of preheating the shielding gas used in gas tungsten arc welding. Welding Journal, 103(10), 298–307. doi: 10.29391/2024.103.026.
[29] Rathod, D.W. (2021). Comprehensive analysis of gas tungsten arc welding technique for Ni-base weld overlay. InAdvanced welding and deforming (pp. 105–126). Elsevier. doi: 10.1016/B978-0-12-822049-8.00004-9.
[30] Aggarwal, S., Dwivedi, M., & Khanna, P. (2022). Mathematical modelling to predict the dilution in FCA welded low carbon steel plates. In Materials Today: Proceedings, 56, 3512–3519. doi: 10.1016/j.matpr.2021.11.226.
[31] Wei, P., Wu, M., Liu, D., Liang, Y., & Zhao, Z. (2022). Face bend property of 7N01-T4 aluminum alloy MIG welded joint by using different welding wires. Metals, 12(5), 873. doi: 10.3390/met12050873.
[32] Guo, A., Misra, R.D.K., Liu, J., Chen, L., He, X., & Jansto, S.J. (2010). An analysis of the microstructure of the heat-affected zone of an ultra-low carbon and niobium-bearing acicular ferrite steel using EBSD and its relationship to mechanical properties. Materials Science and Engineering: A, 527(23), 6440–6448. doi: 10.1016/j.msea.2010.06.092.
[33] ASME. (2025). 2025 ASME Boiler and Pressure Vessel Code, Section IX: Qualification standard for welding, brazing, and fusing procedures; welders; brazers; and welding, brazing, and fusing operators. American Society of Mechanical Engineers. Available: www.asme.org/cer
[34] American Welding Society. (2020). Structural welding code-steel (AWS D1.1/D1.1M:2020). American Welding Society.
