Effect Of Prior Cold Deformation On Microstructure And Properties Of GCr15Si1Mo Bearing Steel

Nano-bainite bearing steel has attracted widely attention in the bearing industry due to its excellent comprehensive properties.Cold rolling is one of the important processing methods in bearing ring production in recent years,but how cold deformation pretreatment affects nano-bainite bearing steel has not been studied yet.In this paper,cold deformation processes with different deformation quantities are used to cold rolling process,and three quenching processes are designed for comparative test.The structure and phase transition process were characterized by DIL,EPMA,SEM and TEM.The influence of pre-cooling deformation on the structure and properties of nano-bainite bearing steel was revealed by hardness,impact toughness,tensile property and wear resistance tests.The following conclusions are drawn:The pre-cooling deformation treatment reduces the temperature of A_c1s and refines the original austenite grain size to 50%with more uniform cementite particle size.It is found that small deformation pretreatment accelerates the dissolution of carbides,but with the increase of deformation,the dissolution of carbides gradually decreases,resulting in the decrease of solid carbon content in the matrix and the increase of M_s temperature.For oil-quenched martensite treatment,pre-deformation treatment results in an increase in martensite content and a decrease in residual austenite content in the structure,thus reduce its impact toughness.For the treatment of bainite process,when the pre-deformation is large,the refinement of austenite grains and the reduction of carbon content in supercooled austenite can increase the bainite ferrite nucleation point and promote the transformation of bainite,which can significantly reduce the thickness of bainite ferrite slab.Finally,the impact toughness of the steel tested by isothermal 6 h process is increased from 44.9 J/cm² to 96.5 J/cm².The impact toughness of the isothermal 24 h process test steel increased from 64.9 J/cm² to 114.3 J/cm².After the pre-cooling deformation treatment,the hardness of the test steel is increased under the three quenching processes.The yield strength is increased but the plasticity is reduced by oil quenching martensite process.Tensile properties of two isothermal bainite process test steels have little change.Under isothermal bainite process,the 40%test steel with pre-cooling deformation has the best wear resistance and the undeformed steel has the worst wear resistance due to the reduction of the number of coarse cementite in the deformed structure and the substantial increase of toughness.Under the same amount of deformation,the wear resistance of isothermal 24 h process test steel is the best,the oil quenched martensite process is the second,and the isothermal 6 h process is the lowest.