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<p>To investigate the effects of post-weld heat treatment on the microstructure and fracture toughness of welded joints in large LCO<sub>2</sub> carrier cryogenic steel, 60&#xa0;mm thick C-Mn steel was chosen as the research subject. Welded joints were prepared using the submerged arc welding method and then subjected to PWHT (580&#xa0;°C for 6&#xa0;hours). The microstructure and fracture toughness of the as-welded (AW) and PWHT welded joints in different regions were studied. The results indicate that after PWHT, the basic types of microstructure in all regions of the welded joint remained largely unchanged, with carbides precipitating at grain boundaries. The hardness in all regions increased by 5-20&#xa0;HV. The average grain size of the base metal near the heat-affected zone increased by 0.32&#xa0;μm, the proportion of high-angle grain boundaries decreased by 16.5%, and the average Kernel Average Misorientation (KAM) value increased by 0.16°. In contrast, the changes in these values within the HAZ itself were minimal. The average crack tip opening displacement (CTOD) characteristic value of the base metal near the HAZ decreased from 2.200 to 1.498&#xa0;mm, indicating a deterioration in fracture toughness.</p>

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Effect of Post-Weld Heat Treatment on Microstructure and Fracture Toughness of Submerged Arc Welded C-Mn Steel Joints

  • 期刊论文

  • 发表日期：

    2025年11月17日

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  • Pei Zou,
  • Zhi-chao Li,
  • Hui-bin Wu,
  • Yu-tang Wang,
  • Heng-kun Li,
  • Ya Gao

摘要

To investigate the effects of post-weld heat treatment on the microstructure and fracture toughness of welded joints in large LCO2 carrier cryogenic steel, 60 mm thick C-Mn steel was chosen as the research subject. Welded joints were prepared using the submerged arc welding method and then subjected to PWHT (580 °C for 6 hours). The microstructure and fracture toughness of the as-welded (AW) and PWHT welded joints in different regions were studied. The results indicate that after PWHT, the basic types of microstructure in all regions of the welded joint remained largely unchanged, with carbides precipitating at grain boundaries. The hardness in all regions increased by 5-20 HV. The average grain size of the base metal near the heat-affected zone increased by 0.32 μm, the proportion of high-angle grain boundaries decreased by 16.5%, and the average Kernel Average Misorientation (KAM) value increased by 0.16°. In contrast, the changes in these values within the HAZ itself were minimal. The average crack tip opening displacement (CTOD) characteristic value of the base metal near the HAZ decreased from 2.200 to 1.498 mm, indicating a deterioration in fracture toughness.