Cryogenic fracture toughness of high manganese steel joint and 7 %Ni steel joint welded with nickel-based filler metal

The high manganese steel (HMS) joint and 7 %Ni steel joint were fabricated using ENiCrMo-6 nickel-based electrodes. The cryogenic fracture toughness of both joints was investigated by Crack Tip Opening Displacement (CTOD) tests at 77 K. The results showed that the fracture toughness of both joints satisfied DNV requirements of 0.15 mm. The CTOD values of weld metal (WM) and heat affected zone (HAZ) in HMS joint were approximately 36.5 % and 33.5 % lower than those of corresponding areas in 7 %Ni steel joint, respectively. In the HMS joint, the presence of more large-sized precipitates in WM and segregations in HAZ had negative effects on the fracture toughness. Compared to other test locations, the HAZ of 7 %Ni steel joint contained local hard-brittle zones, resulting in more discrete CTOD values.