Simulation And Optimization Study On Heat Treatment Process Of Bearing Ring Of Railway Heavy Haul Freight Train

Bearing rings are used to support the journal parts and shaft parts of the rotary parts,widely used in the machinery industry,has become a "mechanical joints." With the rapid development of Chinese high-speed and heavy-duty rail freight,it is imperative to develop high-performance railway bearings.High-speed rail bearings in the use of the process by the extrusion and friction load periodic role,requires it not only have good wear resistance,but also must have a certain toughness and high contact fatigue life,which material selection,heat treatment process have made a very high demand.The mainly aimof this article isat 30 ton axle weight railway freight car bearing ring,according to the research and development of new heat treatment technology,we control the hardness gradient of non-uniform wall thickness bearing ring,ensure its stability and hardness uniformity,and improve the surface hardness,so that bearing ring has good wear resistance and fatigue life,meet the requirements of rolling bearings of heavy axle railway freight cars.Combining with the actual production needs,the chemical composition,surface hardness,carburized layer depth and surface and heart structure of the main shaft heavy spindle bearing rings made of carburizing bearing steel G20CrNi2 MoA were studied by means of simulation combined experiments.The existing problems of the existing heat treatment process were analyzed.The results show that the chemical composition of the test block is qualified,the tissue distribution is reasonable and the grade is qualified,the carburizing layer depth conforms to the national standard,but the value is large,the surface hardness is low and soft point appears in the local.Using Deform software,the distribution of temperature field,carbon atom,hardness,tissue distribution,and the distribution of residual stress after heat treatment were simulated by Deform.The results show that the simulation results of surface carbon content are consistent with the actual situation.The number of microstructure appeared in the middle part of the bearing rings,and the quenching soft points in different degrees are consistent with the actual testing results.Using the above finite element model,the hardness,microstructure and stress distribution of the bearing rings were simulatedwhen the quenching medium with different heat transfer coefficients was used in the two quenching stages.Comparing the two simulated results,it was found that uniform hardness distribution and microstructure distribution can be obtained by using the quenching medium with larger heat transfer coefficient during the two quenching stages.