Fatigue properties of Mod.9Cr-1Mo steel; Result of low-cycle fatigue test in air

Furukawa, Tomohiro  ; not registered; Yoshida, Hidekazu; not registered

Mod.9Cr-1Mo steel is a candidate material of once-through type steam generators for the Fast Breeder Reactors, and it is required to clarify low-cycle fatigue properties in air at high temperature on this material for structural design. So the tests were carried out for three heats (12mmt plate, 25mmt plate and 250mmt forged) on conditions that temperature is 450650C and strain range is 0.41.2%. Results obtained are su㎜araized as follows. (1)For cyclic stress-strain behavior of Mod.9Cr-1Mo steel cyclic hardening was. observed in the early stage, and after that changed to softening to failure. The behavior was similar to normalized and tempered 2.25Cr-1Mo steel. (2)Low-cycle fatigue strength of Mod.9Cr-1Mo steel in air was remarkably higher than that of 2.25Cr-1Mo steel, and almost same as much as that of SUS304 steel. Moreover, fatigue life of Mod.9Cr-1Mo steel was longer than that of 9Cr-2Mo or Low C-9Cr-1Mo-Nb-V steel under low strain conditions. (3)In the case of Mod.9Cr-1Mo forged steel, the influence of the sampling position and direction of specimens was not effective. These results were reflected to prepare of tentative material strength standard in 1992.