Effects of inclusion and loading direction on the fatigue behavior of hot rolled low carbon steel

The anisotropic fatigue behaviors of hot rolled low carbon steel were investigated for specimens with different angles between the loading and rolling direction. It was found that with the increase of loading angles crack initiation site changed from the matrix of surface to internal inclusions (either alumina or MnS) and fatigue strength decreased significantly. The large difference of the projected area of inclusions was responsible for this anisotropic fatigue strength. A good linear relationship between inclusion area and fatigue life in log–log plot was found. The fatigue limits can be predicted by empirical equation and a modified Murakami’s model.