Research On Hot Deformation Behavior And Impact Performance Of Bainite Bearing Steel

Bearings are an important indicator of a country's science and technology and industrial level,and are considered"joints of high-end equipment."Bearings are subject to various alternating stresses during work.Their life is related to working temperature,humidity,speed,load,lubrication,etc.The harsh working environment requires bearing steel to have high contact fatigue strength,high wear resistance,and high elasticity,limit,suitable hardness and corrosion resistance.Therefore,the performance requirements of bearing steel materials are severe,which brings severe challenges to bearing manufacturing.The high quality and high reliability of bearing steel materials are the determining factors.In this paper,the thermal deformation behavior and impact properties of bainite bearing steels independently developed are studied in order to improve the mechanical properties of traditional martensitic steel bearings.First of all,The Gleeble-3500 thermal simulation test machine was used to perform 24 sets of single-pass thermal compression tests on the new type of bainite bearing steel.The material was investigated at a temperature of 900?1200?and a deformation rate of 0.01?5s^-1,the high-temperature plastic deformation behavior when the compression deformation was 60%,the rheological curve shows a typical dynamic recovery type and dynamic recrystallization type.From the material's true stress and true strain curve,it can be seen that the higher the temperature and the smaller the strain rate,the lower the flow stress of the material.According to the curve obtained from the experiment,the data was linearly fitted to establish a hyperbolic sine form constitutive equation based on the peak stress material.Based on the thermal deformation characteristics of the material,a modified Avrami equation was used to establish a dynamic recrystallization kinetics equation on the material,and the microstructure was analyzed.The material's processing map is an important way to reflect the material's thermal processing stability.The processing map of the material under different true strain conditions was calculated.Based on the distribution area of the power dissipation efficiency parameter?and the rheological instability parameter?,the material was determined in the best area during hot working is:temperature 950?1080?,strain rate is 0.1?0.5s^-1;temperature 1080?1150?,strain rate is 1.4?2s^-1.The MTS810 equipment was used to perform a quasi-static compression test on the material.The yield strength of the material at a strain rate of 10^-3s^-1is 860 MPa,which is improved the new bearing steel has a higher yield strength than the high carbon chromium bearing steel(GCr15).Using a separate Hopkinson pressure bar(SHPB)experimental device,a dynamic impact test was carried out on the material to obtain the true stress and true strain curve under high strain rate to analyze its deformation law.The impacted sample was cut along the axis,polished and etched with4%nitric alcohol.Using optical microscope and scanning electron microscope to observe the microstructure of the material under different impact air pressure provides a theoretical basis for practical application.