Research On Study On Service Performance Improvement And Microstructure Regulation Of Metro Wheels

As an important part of the close connection between the locomotive and the track,the wheel is the component with the highest load borne by the train,and its reliability is also closely related to the safe operation of the whole train.To further improve the safety and reliability of wheels has always been the goal pursued by rail transit R & D workers all over the world.Heat treatment plays a very important role in the whole wheel forming process.The correct heat treatment process can make the composition of the wheel uniform,the stress distribution reasonable and the deformation small,and then change its machinability and service life.It is of great significance for the design of alloy elements and the study of reasonable heat treatment process.Through composition design,organization design and process design,the corresponding mechanical properties and service characteristics can be improved.Comprehensive and systematic research on wheel steel materials can improve its scientific research value and application value,and provide basic help for the further development of China’s future Metro system.n this study,CL60 wheel steel was taken as the research object.The comprehensive properties of CL60 wheel steel with different chemical compositions were tested by Gleeble simulator,metallographic microscope and scanning electron microscope.Firstly,JMat Pro is used to predict the effect of different content of alloy elements on the phase equilibrium of CL60 wheel steel,and the curve of precipitation amount of each phase with temperature is obtained.It is found that the reduction of Cr content will reduce the temperature of transformation from cementite to M7C3.Then,the properties of wheel steel at different cooling rates were investigated by tensile and impact tests.Then the properties and microstructure of the new high hardness Metro wheel were studied.The tensile test,hardness test and impact toughness test were carried out,and the relevant mechanical properties were measured.At the same time,through the thermal expansion test,the test results of the transformation point of the new ratio CL60 steel are ac1=746 ℃,ac3=771 ℃,ms=259 ℃.It is found that with the increase of cooling rate,ferrite pearlite transformation,bainite transformation and martensite transformation are carried out in turn.The transformation amount of pearlite and bainite first increases and then decreases with the increase of cooling rate.The initial transformation temperature of martensite gradually increases and the content also gradually increases.In order to obtain ideal strong hardness and ensure fine grains,870 ℃ should be used as the ideal temperature for wheel quenching and heating,and the cooling rate in the wheel rim area should be controlled within 5 ℃ /s.