Effect of low temperature on fatigue crack propagation rates of DH36 steel and its butt weld

As common marine steel for polar ships, the fatigue crack propagation rates of DH36 steel at low temperature have a crucial influence on the evaluation of the fatigue strength of polar ships. The purpose of this paper is to study the fatigue crack propagation rates of DH36 steel with the different scenarios between the conventional base metal and butt weld specimens at room temperature (RT) and −60 °C. The fatigue crack propagation test and Vickers hardness test of butt weld and base metal were performed. As a result, the fatigue crack propagation test demonstrated a reduced crack propagation rate in both the base metal and the butt weld with a decreasing ambient temperature. For the Vickers hardness, both the welded joint and the base metal at −60 °C presents higher hardness values than RT. Furthermore, the welded joint trends to demonstrates a higher value of Vickers hardness than base metal. Finally, the behavior of fatigue crack propagation in the micro scale between base metal and butt weld at low temperature was described by the fractography.