Austenite grain growth and its effect on splitting fracture property of a V-N microalloyed medium carbon steel connecting rod

The growth behaviour of austenite grain in a V-N microalloyed medium carbon steel and its effect on splitting fracture property were investigated by mechanical tests, fracture morphology and microstructure analysis. When the heating temperature is 800 degrees C, the austenite grain size is 7.6 mu m, and the fracture surface is uneven with the impact energy of 235.9 J. When the heating temperature increases to 1100 degrees C, the austenite grain size grows up to 65.5 mu m and the impact fracture surface is much more even with the impact energy of 13.6 J. It is believed that the coarse austenite grain size of 65.5 mu m is beneficial for the splitting fracture property of V-N microalloyed medium carbon steel connecting rod. In addition, austenite grain sizes of V-N microalloyed medium carbon steel increase with the increasing in heating temperature and holding time. Then, a grain growth model is established to predict austenite grain growth behaviour.