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Open Access Article

13 pages 1627 KB

Impact of Welding Standards on Heat Affected Zone: A Critical Review of the Methods, Consumables, and Environmental Degradation on the Performance of API 5L X52 in Sour Service

Abid Ur Rehman, Muhammad Arsalan Khan

Online Journal of Engineering Sciences 5(1); 10.31586/ojes.2026.6316 - April 15, 2026

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Abstract

The Heat-Affected Zone (HAZ) is one of the major parameters which determines the structural integrity in welded API 5L X52 pipelines, especially in a sour gas service containing Hydrogen Sulphide (H2S) [1]. This thorough review paper performed the analysis of different international standards including Det Norske Veritas Germanischer Lloyd DNVGL-ST-F101, American Petroleum Institute API 1104, National Association of Corrosion Engineers NACE MR0175 and American Society of Mechanical Engineers ASME B31.8. The researcher analysed the governing and regulation of Heat Affected Zone microstructure and associated properties including strength, hardness and toughness through the specifications like heat values, time between passes and Post Weld Heat Treatment (PWHT), welding specifications and qualification of welding procedures, welders and consumables [2]. By collecting and analysing the data from recent studies (2018-2025), the researchers found out that the standards focusing on prescribing strict recipes for welding and qualification procedures like DNVGL-ST-F101, including explicit heat input limits (typically 1.0-2.0 kJ/mm), obligatory post-weld heat treatment (PWHT), and rigorous consumable qualifications, perform well in Heat Affected Zone in sour gas service. The maximum hardness retirement i.e. 22 HRC (248 HV) obligated for sour media creates a critical limitation that forces optimization of welding procedures. The standards which focus on final quality or the end results rather than prescribing any specific method for producing the weld (Performance-based standards) like API 1104 remains less stringent which results in greater variation in properties around the weld i.e. the HAZ area impacting the service reliability in a worse manner during the sour media [3]. Contemporary world adopting new digital welding techniques for monitoring during weld production, prediction of the microstructural properties of HAZ based on machine learning and other advanced methods like hybrid welding processes which combines different precision welding techniques provide promising results for production of high quality and reliable welds which offer enhanced safety and reliability during sour service [4].

Figure 1. Temperature distribution across the fusion and heataffected zone (HAZ) during a welding thermal cycle, showing the influence of thermal gradients on microstructural evolution in welded joints [7].

Figure 2. A representation of the HAZ sub-zones (CGHAZ, FGHAZ, and ICHAZ) [17].

Figure 3. Schematics of the Sulfide Stress Cracking (SSC) in steels [23].

Figure 4. Heat input vs. HAZ properties regression analysis showing the linear increase in HAZ width with welding heat input and the inverse trend of maximum hardness with heat input [3], [18].

Figure 5. Schematic illustration of machine learning and digital twin–based modeling approaches for monitoring and control of friction stir welding (FSW), showing integration of realtime sensor data, predictive machine learning models, and digital twin simulation for HAZ property prediction and process optimization [4].

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