Hotde Formation Behavior Of GCr15 Bearing Steel

As a very important and widely used metallurgical products-bearing steel,is the basic accessories of mechanical industry and civilian tools and widely used in national defense,industry,agriculture and other fields.Bearings are generally composed of rolling elements,inner and outer rings and other components,these components are all made of bearing steel.As a supporting basic parts,the working environment of bearing is more bad,will suffer from tension,pressure,shear and friction and other alternating stress.In order to ensure the bearing steel to meet the stability of equipment operation safety,we must follow such working conditions: uniformity and high hardness,high flexibility and high toughness,wear resistance,corrosion resistance,good processing performance,high dimensional accuracy and stability.As the representative of the most widely used high-carbon chromium bearing steel-GCr15 bearing steel,its overall performance is good,is widely used in the world of steel.The safety of mechanical operation depends on the life and stability of the parts,which in turn depends on the metallurgical properties of steel,the performance of steel depends on the internal microstructure,the current advancement of controlled rolling and cooling technology in theory,make it possible to obtain the desired properties by controlling the structure of the steel during the hot working.The dynamic recrystallization and static recrystallization behavior of metals during thermal processing are one of the effective methods to improve the microstructure and properties of metals.In order to design the optimum rolling process parameters,it is necessary to study the recrystallization law of austenite during the whole hot working process.In this paper,a single-pass and two-pass thermal compression simulations were carried out in the temperature range of 800~1200?and the strain rate of 0.01~10 s-1 by using the Gleeble-3800 thermal / mechanical simulator,The stress-strain curve of GCr15 bearing steel was studied,and the constitutive model of the steel was established by the multiple regression analysis.The flow stress model can reflect the change of the microstructure of the material to a certain extent,and predict the thermal deformation behavior;Based on the dynamic material model and the instability criterion,the hot working diagram of GCr15 steel was established.The high-temperature deformation characteristics of the alloy were analyzed and the suitable range of high-temperature deformation parameters was optimized.The dynamic recrystallization behavior under different hot deformation parameters was discussed by using the DEFORM software and numerical simulation technique based on cellular automaton method.The softening behavior and recrystallization rule of austenite GCr15 steel during the interval time of deformation were studied.The microstructure and properties of hot work were simulated and the experimental and theoretical foundations for the development of reasonable rolling process were provided.The main results are as follows:(1)The thermal deformation of GCr15 steel under the condition of deformation temperature of 800 ~ 1200?,strain rate of 0.01 ~ 10 s-1 and true strain of 0.7 was studied by Gleeble-3800 thermal simulation experiment.The constitutive equation based on peak stress,critical strain model and dynamic recrystallization kinetics model were established.(2)The stress-strain curves of GCr15 steel under different experimental conditions were obtained on the Gleeble-3800 thermal simulator.The static recrystallization constitutive equation was established,the effects of deformation temperature,strain rate and pass interval time on the static recrystallization behavior were analyzed.The static recrystallization activation energy of the steel was calculated.(3)Based on the dynamic material model and the Prasad instability criterion,the energy consumption efficiency and instability parameters at different deformation temperature and strain rate were calculated.The hot processing map of different strain was analyzed,and the recrystallization region was established.(4)Using the cellular automata method on the DEFORM software,the constitutive model and the dynamic recrystallization kinetics model were used to simulate and analyze the evolution process of the recrystallized microstructure of the test steel,and the visualization of the grain change was realized,the correctness of the recrystallization kinetics model was verified.