Effect of welding structure and delta-ferrite on fatigue properties for tungsten-inert-gas (TIG) welded austenitic stainless steels at cryogenic temperatures.

High-cycle and low-cycle properties of base and weld metals for SUS304L and SUS316L and the effects of welding structure and delta-ferrite on fatigue properties were investigated at cryogenic temperatures in order to evaluate the long-life reliability of the structural materials to be used in liquid hydrogen supertankers and storage tanks and to develop a welding process for these applications. The S-N curves of the base and weld metals shifted towards higher levels, i.e., the longer life side, with decreasing test temperatures. High-cycle fatigue tests demonstrated the ratios of fatigue strength at 10 power 6 cycles to tensile strength of the weld metals to be 0.35-0.7, falling below those of base metals with decreasing test temperatures.