1. State Key Laboratory of Advanced Metallurgy, University of Science and Techonlogy Beijing, Beijing 100083, China 2. Technology Center, Kunshan Track Co., Ltd., Suzhou 215313, Jiangsu, China
Abstract：In order to identify the fracture failure of B- Cr microalloyed steel, the brittle fracture of track roller during the operation of tracking tractor was taken as the research background. The fracture failure of TiN inclusion on B- Cr microalloyed steel was studied by observing the fracture surface of the central axis and comparing the microstructure and grain size at different positions. The FactSage and Thermo- Calc software were used to calculate the formation and control mechanism of TiN inclusion. The results were as follows. Due to the incomplete dissolution of Ti alloy and irrational control of Ti and N mass fraction in the molten steel, lots of large- size TiN inclusions were formed during the solidification of B- Cr micro- alloyed steel. The addition of Ti element did not play a good role in refining grain, resulting in the large grain size in the center, and further reducing the impact property of B- Cr microalloyed steel. Large- size TiN inclusion acted as the crack origin and the large grain size led to the brittle fracture of B- Cr microalloyed steel. Thermodynamic calculation showed that the TiN inclusion formed during the solidification process and the precipitation temperature of TiN can be effectively delayed with low Ti and N mass fraction in molten steel.Small inclusion size and fine grain size can effectively enhance the crack resistance of the material.
2019, Vol. 29 
