Susceptibility to hydrogen embrittlement in welded joints at ambient temperature for liquefied hydrogen storage tanks

Abstract Liquefied hydrogen storage tanks are poised to play a pivotal role in the realization of a carbon–neutral society. While stainless steel is considered the material of choice for the first 50,000-m 3 tank, there is a potential for carbon steel to be employed as the inner tank material in the future to increase capacity. The welding materials combined with the carbon steel are expected to be Hastelloy and Inconel alloys, which are currently used in LNG (liquefied natural gas) tank construction. However, since some reports have shown that the effect of Ni on hydrogen embrittlement properties deteriorates significantly on the high-Ni side, we conducted evaluation tests that took into account the operating environment. The SSRT (slow strain rate testing) revealed that the GTAW (gas tungsten arc welding) weld metal exhibited severe hydrogen embrittlement, whereas no significant crack propagation was observed in the constant-load CT (compact tension) tests. We analyzed the discrepancies between the two experimental methods and concluded that the differences are largely related to pre-straining and hydrogen diffusion and accumulation. From a FFS (fitness for service) perspective, the results of the CT tests are considered more representative of real-world conditions, indicating that this material combination is suitable for use in liquid hydrogen storage tanks.