Study on the Tensile and Fatigue Properties of the FH36 Ship Steel Plates at Room and Low Temperatures

This study investigated the tensile properties and fatigue behavior of FH36 steel plates subjected to alternating rolling processes in different directions, as well as their performance at room temperature and −60 °C. The results revealed that by employing sequential rolling in both the rolling and transverse directions, the disparities in the mechanical properties between these two directions were eliminated, resulting in nearly identical tensile performances. The macroscopic features of the high-cycle and low-cycle fatigue fractures at both room temperature and at −60 °C were similar, with high-cycle fatigue fractures exhibiting oblique shear features and low-cycle fatigue fractures exhibiting cup-cone shapes. The crack initiation zones were consistently located on the surface of the specimens. As the maximum stress increased, the area of the high-cycle fatigue crack propagation zone decreased, while the area of the final fracture zone, the number of dimples, and the proportion of low-angle grain boundaries all increased. Under −60 °C conditions, the critical crack length for high-cycle fatigue, the maximum stress limit for the onset of high-cycle fatigue, and the fatigue limit were all higher than those at room temperature, indicating a superior low-temperature fatigue performance.