Numerical Simulation Study Of Microstructure And Residual Stress In Air Cooling On Bainite Steel Rail

Bainite steel rail has the advantages of high rigidity, good abrasion resistance, longservice life.However, the microstructure transformation of bainite steel rail after rollingand heat treatment processis is not uniform,and the bending deformation is too large, andthe residual stress is the outstanding problem, so that the heat treatment strengthening ofthe bainite steel rail after rolling becomes a research hotspot in recent years.In this paper, the stress-strain curves of bainite rail at different temperatures are measuredby experiments,So the thermal physical parameters of bainite rail such as Young’s modulus andthermal expansion coefficient are obtained.;The TTT curves and CCT curves of bainite railwere obtained by experiments.;Through air cooling experiment of rail,The heat transfercoefficient of the rail60kg/m bainite rail and the60AT rail in the air cooling process after therolling was measured.In this paper,The finite element method is used,so that the evolution law of temperaturefield, microstructure field, longitudinal stress field and bending deformation of60kg/m bainiterail and60AT rail rail were simulated. The evolution law provides a very important theoreticalbasis about. Some key issues how to guarantee the uniform of the rail organization,to reduce theamount of bending deformation,to reduce the residual stress after rolling in air cooling of60kg/mbainiterailand60AT switchrailinfuture.The simulation results of temperature field, microstructure field and longitudinal stressfield in the air cooling process after rail rolling are showed：In the process of cooling afterrolling on the rail, the high temperature zone runs through rail head, resulting thatmicrostructure transformation is uneven;The longitudinal stress field has a close relationshipwith the transformation of the organization, and the relationship of the temperature is second;Atthe end of the cold, the60kg/m bainite rail belongs to the geometry of the shaft, and themaximum tensile stress of its section is150MPa, and the maximum compressive stress is-110MPa, the60AT switch rail belongs to the geometry of the asymmetric axis, the maximum tensile stress is250MPa and the maximum compressive stress is-150MPa.Bending deformationis influenced by microstructure transformation,At the end of the cold,60kg/m bainiterailbelongs to the geometry of the axis，The rail only has a bending deformation in thedirection of Z (frontal bending), and the bending deflection of the rail in the Z direction is0.255mm.However, the60AT switch rail belongs to the geometry of the asymmetric axis, andhas a bending deformation in the Y direction (lateral bending) and the Z direction.,the bendingdeflection of the Y direction is0.075mm,and the ultimate direction is the short edge of therail.Thebendingdeflection oftheZ direction is0.255mm,and theultimatedirectionis raidhead.