Effect of heat treatment process on microstructure and properties of high carbon bainitic steel
MA Yue-jie1,2, KANG Jie1,2, ZHANG Fu-cheng3,4, YANG Zhi-nan3,4, WU Da-yong1,2, SU Ru1,2
1. School of Materials Science and Engineering, Hebei University of Science and Technology, Shijiazhuang 050018, Hebei, China;
2.Hebei Key Laboratory of Material Near-net Forming Technology, Shijiazhuang 050018, Hebei, China;
3. State Key Laboratory of Metastable Materials Preparation Technology and Science, Yanshan University, Qinhuangdao 066004, Hebei, China;
4. National Engineering Research Center for Cold Rolled Strip, Yanshan University, Qinhuangdao 066004, Hebei, China
The effect of different austenitizing temperatures on the structure and properties of high carbon bainitic steel for bearings were investigated by scanning electron microscope (SEM), X-ray diffractometer (XRD) and hardness tester. The optimal austenitizing process was selected, and the mechanical properties of high-carbon bainite steel with or without Ce addition after different bainite isothermal transformation processes were compared. The results show that there are no obvious large undissolved carbides at 950 ℃ austenitizing. For this austenitizing temperature, the microstructure size and hardness performance are moderate and carbon content in retained austenite is the highest. It demonstrates that 950 ℃ is the optimal austenitizing temperature. At the same temperature of austenitizing and bainite isothermal, the addition of rare earth elements can slightly inhibit the growth of grain size, whereas affects little on the size of bainite sheaves, accomplishment ratio of bainitic transformation and tensile properties of steel. It is due to the low content of rare earth elements in solid solution of steel. As the bainite isothermal temperature decreases from 300 ℃ to 220 ℃, the hardness, tensile strength and yield strength of high-carbon bainite steel all increases, while the elongation decreases significantly. It is related to the increased volume fraction of bainitic ferrite, the refined bainite sheaves and increasing of carbon content in retained austenite. The fracture surface of sample after isothermal treatment at 300 ℃ is composed of small dimples and cleavage planes, which is quasi-cleavage fracture mode. The fracture surface of sample treated at 220 ℃ is covered by flat cleavage plane, which is cleavage fracture.
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2022, Vol. 32 
