Hot Deformation Behavior Of Domestic High Speed Train Axle Steel DZ2

As one of the most critical load-bearing components of high-speed train,axle plays an irreplaceable role in improving train speed and ensuring safety performance.However,China's high-speed train axles mainly rely on imports from Europe and Japan.In order to respond to the national development strategy and realize the localization of high-speed train parts,at the same time,for their own development needs,domestic enterprises and scientific research institutions have carried out a series of work on the independent development of high-speed train axle materials and achieved good results.At present,they have the ability to produce high-speed axle steel independently ability.It is very important to study the mechanical behavior and microstructure change of high-speed axle material in the process of hot deformation for regulating the microstructure of the material and optimizing the material production process.Therefore,in this paper,DZ2 steel,a high-speed train axle steel produced in China with completely independent intellectual property rights,is used as the research material,and the high-speed axle steel is hot compressed by using the method of physical simulation The effects of different deformation rates(0.001s^-1,0.01s^-1,0.1s^-1,1s^-1)and different deformation temperatures(850?,920?,990?,1060?,1130?,1200?)on the hot deformation behavior of high-speed train axle steel were studied by scanning calorimetry,metallographic observation,scanning electron microscope and other research methods.The main conclusions are as follows:(1)According to the experimental data of hot compression,the rheological curve is drawn,and the mechanical behavior of the material in the process of hot deformation is analyzed.At the same time,based on Arrhenius hyperbolic sine equation,the constitutive model of the material is established,and the strain compensation correction is made to the model.Through the analysis of rheological curve,it is found that the deformation resistance of high-speed train axle steel decreases with the increase of temperature and increases with the increase of strain rate in the process of hot deformation,and the reduction of deformation resistance is smaller at the same temperature difference;(2)Based on the dynamic material model(DMM),the hot working diagram of high-speed train axle steel was constructed,and the instability zone was analyzed with Prasad instability criterion and microstructure.The instability region of high-speed train axle steel transfers from low temperature and high strain rate region to high temperature region with the increase of strain.In the low temperature instability region,the main instability form is shear band,while in the high temperature instability region,the main instability form is abnormal grain coarsening.At the same time,the optimum processing area is 950?1000?,and the strain rate is about 1s^-1.(3)According to the dynamic recrystallization theory,the dynamic recrystallization critical strain model and dynamic recrystallization dynamic model of high-speed train axle steel during hot deformation are established.The relationship between Z parameter and dynamic recrystallization is explored,and the influence of different deformation conditions on the dynamic recrystallization behavior is analyzed.It is found that the dynamic recrystallization mechanism of the high-speed train axle steel is influenced by the dynamic recrystallization volume fraction.When the temperature is 990?,the strain rate is greater than 1s^-1,and the temperature is above990?,complete dynamic recrystallization occurs.Under other processing conditions,the material did not recrystallize completely.