Effect of Microsegregation on Intergranular Fracture Nucleation in Cold Cracking of High‐Strength Flux‐Cored Arc Weld Metal

The effect of microsegregation on the cold‐cracking mechanism in high‐strength flux‐cored arc (FCA) welds is investigated. To examine crack formation and propagation, the secondary crack region of the fracture surface is polished, and microstructural and compositional analyses are performed. The results show that cold cracking in FCA welds consists of intergranular and quasicleavage fracture (QCF) modes. Segregation bands of Mn and Ni are observed in the intergranular regions of weld metal (WM), with more pronounced localized segregation at the crack initiation sites. QCF occurs in regions of nonsegregation, where lower tensile stress is applied owing to the smaller volume fraction of martensite. In contrast, cold cracking occurs in regions with higher Ni and Mn segregation, which exhibit a larger volume fraction of martensite and increased volumetric expansion. This study provides valuable insights into the cold‐crack formation mechanism of high‐strength flux‐cored arc welds, which can facilitate the development of liquefied natural gas ships.