With the sixth large-scale railway speed-up,the quality of the axles is essential to the safety of the locomotive.According to the high-speed axle technical standard for the control of alloy elements in axle steel,opt...With the sixth large-scale railway speed-up,the quality of the axles is essential to the safety of the locomotive.According to the high-speed axle technical standard for the control of alloy elements in axle steel,optimization experiments of 25CrMo steel composition were performed by vacuum inductive melting.In order to study the hardenability of high-speed rail axles,an improved end-quench test was put forward.The advantage is that it enables the heat to transfer along the axial direction,thus avoiding edge effects.The hardenability of 25CrMo axle steels with Mn content of 0.60wt.% and 0.80wt.% was investigated mainly by means of optical microscopy and hardness tests.The experimental results indicate that the Mn has a pronounced effect on the hardenability of the steel.With an increase in Mn content from 0.60wt.% and 0.80wt.%,the hardenability of 25CrMo axle steel increases and the hard microstructure is maintained at an increasing distance from the quenched end.From the surface of the water quenched end to the center of the sample,the microstructure is martensite,martensite with bainite,and bainite.展开更多
The dynamic recrystallization behavior of 25CrMo4 steel was systematically investigated by compression deformation at different temperatures and strain rates on a Gleeble 1500 thermal mechanical simulation tester. The...The dynamic recrystallization behavior of 25CrMo4 steel was systematically investigated by compression deformation at different temperatures and strain rates on a Gleeble 1500 thermal mechanical simulation tester. The flow curves under different deformation conditions were obtained, and the effects of deformation temperature and strain rate on the appearance of the flow curves were discussed. Based on the experimental flow curves, the activation energy determined by regression analysis was Q = 337 kJ/mol, and the constitutive model was constructed. All the characteristic points of the flow curves were identified from the work hardening rate curves （θ= dσ/dε vs σ）, which were derived from the flow curves. Then, the kinetics model of dynamic recrystallization was determined by combining the Avrami equation with the stress loss resulted from the dynamic recrystallization. With the aid of the kinetics model, the effect of strain on the efficiency of power dissipation was discussed. Furthermore, the optimum parameters for the forging process were determined based on the processing maps.展开更多
基金financially supported by the National Ministry of Science and Technology:The reliability of materials and components for high-speed railway CRH3axle materials,No.2009BAG12A07-C02-1
文摘With the sixth large-scale railway speed-up,the quality of the axles is essential to the safety of the locomotive.According to the high-speed axle technical standard for the control of alloy elements in axle steel,optimization experiments of 25CrMo steel composition were performed by vacuum inductive melting.In order to study the hardenability of high-speed rail axles,an improved end-quench test was put forward.The advantage is that it enables the heat to transfer along the axial direction,thus avoiding edge effects.The hardenability of 25CrMo axle steels with Mn content of 0.60wt.% and 0.80wt.% was investigated mainly by means of optical microscopy and hardness tests.The experimental results indicate that the Mn has a pronounced effect on the hardenability of the steel.With an increase in Mn content from 0.60wt.% and 0.80wt.%,the hardenability of 25CrMo axle steel increases and the hard microstructure is maintained at an increasing distance from the quenched end.From the surface of the water quenched end to the center of the sample,the microstructure is martensite,martensite with bainite,and bainite.
基金financially supported by the National Basic Research Program of China(No.2011CB012903)
文摘The dynamic recrystallization behavior of 25CrMo4 steel was systematically investigated by compression deformation at different temperatures and strain rates on a Gleeble 1500 thermal mechanical simulation tester. The flow curves under different deformation conditions were obtained, and the effects of deformation temperature and strain rate on the appearance of the flow curves were discussed. Based on the experimental flow curves, the activation energy determined by regression analysis was Q = 337 kJ/mol, and the constitutive model was constructed. All the characteristic points of the flow curves were identified from the work hardening rate curves （θ= dσ/dε vs σ）, which were derived from the flow curves. Then, the kinetics model of dynamic recrystallization was determined by combining the Avrami equation with the stress loss resulted from the dynamic recrystallization. With the aid of the kinetics model, the effect of strain on the efficiency of power dissipation was discussed. Furthermore, the optimum parameters for the forging process were determined based on the processing maps.
