Study on in-situ fracture toughness evaluation methods for cryogenic pressure vessel-grade high manganese steels

High manganese austenitic steel, with its excellent cryogenic properties and cost-effectiveness, is considered a promising material for next-generation LNG storage and transportation equipment. However, due to the ultra-low temperature (-163°C) and high-pressure service environment, in-situ mechanical property testing is critical to prevent sudden failure caused by material degradation. This study addresses the risk of cracking failure in cryogenic pressure vessels due to reduced fracture toughness. By applying the energy release rate theory and spherical indentation test, the fracture toughness of high manganese steel was measured at both room temperature (25°C) and service temperature (-163°C). The results were compared with conventional three-point bending tests, validating the effectiveness of the spherical indentation method for insitu fracture toughness evaluation.