The method of high-pressure hydrogen charging was used to investigate the internal hydrogeneffects on cryogenic mechanical properties of two Cr-Ni-Mn-N austenitic steels, 22-13-5 and21-6-9. Specimens saturated with hydrogen up to 65×10-6～68×10-6 were tested in air attemperatures ranging from 77 to 293 K. Hydrogen caused the increase in cryogenic strength,both yield strength and ultimate tensile strength. Hydrogen decreased cryogenic ductility, andthe maximum hydrogen embrittlement (HE) tendency was found at a certain low temperature.Cr-Ni-Mn-N auStenitic Steels showed the featuref δL > ΨL at low temperatures, here, δL and ΨLare the hydrogen induced loss rates of elongation and reduction of area, respectively. Hydrogenhad less effect on cryogenic Charpy impact toughness and notched tensile strength, however,hydrogen decreased cryogenic fracture toughness of the steels. At temperature below Md, thefracture toughness was obviously decreased due to the formation of strain-induced martensites,whether hydrogen was charged or not.
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