High-Cycle Fatigue Properties of Medium-Carbon Microalloyed Bainitic Steels for Steering Knuckle
HU Fang-zhong1,2，HUI Wei-jun1,2，YONG Qing-long1,2，ZHANG Ying-jian2，CHEN Si-lian2
1. Faculty of Materials and Metallurgical Engineering, Kunming University of Science and Technology, Kunming 650093, Yunnan, China 2. National Engineering Research Center of Advanced Steel Technology, Central Iron and Steel Research Institute, Beijing 100081, China
Abstract：High-cycle fatigue properties of two newly developed medium-carbon microalloyed bainitic steels for steering knuckle were investigated using rotating-bending fatigue test. The results show that the developed two bainitic steels have fine granular bainitic structure and therefore comparable strength level and fatigue property in both as-forged and as-normalized conditions. However, the fatigue properties of the two bainitic steels are lower than that of the quenched and tempered steel. Compared to as-forged condition, both tensile strength and fatigue limit decrease, whereas both yield strength ratio and fatigue limit ratio increase when the steels were normalized. Further SEM examination of fatigue specimen fracture surfaces revealed that all the fatigue cracks initiated form specimen surface matrix and propagated in forms of quasi-cleavage. The fatigue crack growth rate da/dN of the lower cabon content steel is slower than that of higher carbon content.
2012, Vol. 47 
