Effect Of Pre-Heat Treatment On Microstructure And Properties Genetic Evolution Mechanism Of High Performance Automobile Bearing

GCr15 steel is the representative of bearing steel,various mechanical transport equipment runs smoothly because of the bearings,thus the bearings are known as the mechanical joints.Bearing ring was one of the components of the bearing,it was subjected to alternating loads in work condition,so it should have high strength,ductility and fatigue strength,especially for the high-performance automobile bearing rings.It was of great significance to study the pre-heat treatment which could improve the mechanical properties of bearing steels.In this study,the hot-rolled GCr15 bearing rings were firstly carried out pre-heat treatment and final heat treatment,then the experimental results were analyzed and discussed in theory by means of thermodynamics,materials science,plastic mechanics and other multidisciplinary cross research methods.In this way,the effect of pre-heat treatment on microstructure and properties of automobile bearing rings was revealed,as well as the genetic evolution mechanism of microstructure and performance,which would provide a scientific basis for manufacturing forming of high-performance automobile bearing rings.In terms of the effect of pre-heat treatment on microstructure and properties,firstly the hot-rolled GCr15 bearing rings were conducted different pre-heat treatment process,then the materials SEM morphology was observed using scanning electron microscope.The original microstructure of the hot-rolled GCr15 bearing steel was lamellar pearlite,after pre-heat treatment,the lamellar pearlite was transformed into granular pearlite.The pre-heat treatment made a difference in the spheroidization effect,the annealing temperature and holding time mainly affected the carbide particles morphology and size,and the cooling rate affected the size only.Also a series of mechanical properties tests were conducted by micro tensile testing machine and micro hardness tester,the results showed that proper pre-heat treatment process could improve the spheroidizing quality,which was good for increasing the strength,the plasticity and decreasing the hardness of the bearing rings.In the area of the genetic evolution of pre-heat treatment on microstructure and properties.Firstly all of the bearing rings were carried out the same quenching and tempering heat treatment after pre-heat treatment.Then the carbide particles morphology and size after final heat treatment were count in coMParison with the spheroidizing carbides longitudinally.The results showed that the carbide particles morphology and size had a certain heredity in the pre-heat treatment and final heat treatment process.The carbide particles heredity would cause the mechanical properties consistent in the heat treatment process.Adopting reasonable pre-heat treatment,the mechanical properties of the bearing rings would be fine,after the final heat treatment,the mechanical properties of the bearing rings would be more excellent.Considering the energy-efficiency and the optimization of microstruture and performance,it was essential to select the appropriate heating temperature of 710 ℃,suitable holding time of 6h and faster cooling rate.The better spheroidizing microstructure would be passed in the final heat treatment,so the mechanical properties of bearing rings would be excellent.