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<p>This research presented the effect of post-weld heat treatment (PWHT) holding times on the welded pressure vessel steel (SA516-70). Single-V butt joint specimens (thickness 20 mm) were welded using submerged arc welding (SAW) and then subjected to PWHT at 625&#xa0;°C with holding times of 25, 50, 75, and 100 min. The integrity and microstructure of welds were analyzed using PAUT, microscope, SEM-EDS, XRD, and EBSD, while residual stress was measured using XRD. The results exhibited that as-weld specimen&#xa0;showed multiple-shaped ferrite mixed with pearlite, while the increasing PWHT holding time exhibited large-grain ferrite, a reduction in pearlite fraction, and the formation of spherical cementite. PWHT at 25 and 50 min could reduce compressive residual stress to normal levels due to grain growth, but prolonged holding times (75 and 100 min) caused an increase in the tensile residual stress. PWHT with longer times tended to decrease the hardness (25-30%) and tensile strength (4-14%) while increasing dimple fracture with micro-voids, consistent with the observed microstructural changes. The optimal PWHT holding time was 25 min, presenting 95% joint efficiency and the tensile strength compliant with ASME Section IX, indicating an improvement in overall performance for constructing pressure vessels and components.</p> Graphical Abstract <p></p>

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Effect of Holding Time in Post-weld Heat Treatment on Microstructure, Residual Stress, and Mechanical Properties of Welded Pressure Vessel Steel

  • 期刊论文

  • 发表日期：

    2025年7月25日

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  • Jednupong Palomas,
  • Thamrongsin Siripongsakul,
  • Chayanee Tippayasam,
  • Thammanoon Thaweechai,
  • Attaphon Kaewvilai

摘要

This research presented the effect of post-weld heat treatment (PWHT) holding times on the welded pressure vessel steel (SA516-70). Single-V butt joint specimens (thickness 20 mm) were welded using submerged arc welding (SAW) and then subjected to PWHT at 625 °C with holding times of 25, 50, 75, and 100 min. The integrity and microstructure of welds were analyzed using PAUT, microscope, SEM-EDS, XRD, and EBSD, while residual stress was measured using XRD. The results exhibited that as-weld specimen showed multiple-shaped ferrite mixed with pearlite, while the increasing PWHT holding time exhibited large-grain ferrite, a reduction in pearlite fraction, and the formation of spherical cementite. PWHT at 25 and 50 min could reduce compressive residual stress to normal levels due to grain growth, but prolonged holding times (75 and 100 min) caused an increase in the tensile residual stress. PWHT with longer times tended to decrease the hardness (25-30%) and tensile strength (4-14%) while increasing dimple fracture with micro-voids, consistent with the observed microstructural changes. The optimal PWHT holding time was 25 min, presenting 95% joint efficiency and the tensile strength compliant with ASME Section IX, indicating an improvement in overall performance for constructing pressure vessels and components.

Graphical Abstract