Effect of cryogenic environment on the low cycle fatigue properties of 9%Ni steel made by SMAW

In this paper，low cycle fatigue property of 9%Ni steel joint by shielded metal arc welding was tested，and the strain-cycle curve at room temperature was drew．Low cycle fatigue cycle of high strain amplitude(0．6%)at low temperature(－180℃)was tested．fractures at different test temperatures were inspected，and the influence of low temperature environment on crack initiation and crack propagation process were analyzed．The conclusion is that cyclic hardening effect occurs in 9%Ni steel joint performances at low temperature environment under the effect of high strain amplitude loop，while cyclic softening effect appears at room temperature．It shows that low temperature environment helps to slow down the process of 9%Ni steel joint crack initiation and increase crack extension rate．