On the Understressing Effect of the Eutectoid Steel at -60°C

Torsion fatigue tests at -60°C are made to examine the understressing effect of the eutectoid steel, based on the assumption that the strain ageing occurring in the specimens during the fatigue tests is restrained at -60°C. The specimens tested are cooled by gasifying liquid nitorogen, in order to hold the designated temperature. It is found that the main cause of the understressing effect of the eutectoid steel is work hardening at -60°C against both work hardening and strain ageing at room temperature, and the fatigue life of eutectoid steel is mainly controlled by the hardness of the material before fatigue test at -60°C.