The method of high-pressure hydrogen charging was used to investigate the internal hydrogen effects on cryogenic mechanical properties of two Cr-Ni-Mn-N austenitic steels, 22-13-5 and 21-6-9. Specimens saturated with hydrogen up to 65×10-6~68×10-6were tested in air at temperatures ranging from 77 to 293 K. Hydrogen caused the increase in cryogenic strength, both yield strength and ultimate tensile strength. Hydrogen decreased cryogenic ductility, and the maximum hydrogen embrittlement (HE) tendency was found at a certain low temperature. Cr-Ni-Mn-N austenitic steels showed the feature: δL>ΨL at low temperatures, here, δL andΨL are the hydrogen induced loss rates of elongation and reduction of area, respectively. Hydrogen had less effect on cryogenic Charpy impact toughness and notched tensile strength, however, hydrogen decreased cryogenic fracture toughness of the steels. At temperature below Md, the fracture toughness was obviously decreased due to the formation of strain-induced martensites, whether hydrogen was charged or not.
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