Abnormal relation between tensile and fatigue strengths for a high-strength low-alloy steel

The microstructure, tensile and fatigue strengths of the high-strength 35CrMo steel with quenched and tempered (QT) and hot-rolled (HR) states were investigated. There is not a commonly linear relation between tensile and fatigue strengths, namely, the HR steel with higher tensile strength has lower fatigue strength, which is mainly attributed to microstructural inhomogeneity of the steel and different damage mechanisms under fatigue and tensile loads. In this work, an estimation method of fatigue strength for steels with dual phase is suggested.