Without considering the effects of alloying interaction on the Jominy end-quench curves, the prediction resuits obtained by YU Bai-hai＇s nonlinear equation method for multi-alloying steels were different from those e...Without considering the effects of alloying interaction on the Jominy end-quench curves, the prediction resuits obtained by YU Bai-hai＇s nonlinear equation method for multi-alloying steels were different from those experimental ones reported in literature. Some alloying elements have marked influence on Jominy end-quench curves of steels. An improved mathematical model for simulating the Jominy end-quench curves is proposed by introducing a parameter named alloying interactions equivalent （Le）. With the improved model, the Jominy end-quench curves of steels so obtained agree very well with the experimental ones.展开更多
The microstructure of an alloy is affected intensively by the cooling process.To figure out the inherent relation between the cooling rate and microstructure of an advanced nickel-based superalloy,experimental and num...The microstructure of an alloy is affected intensively by the cooling process.To figure out the inherent relation between the cooling rate and microstructure of an advanced nickel-based superalloy,experimental and numerical studies on the cooling process were conducted.Specifically,the measurement was performed concerning both the temperature of the specimen during the end-quench test and the size of the secondaryγ′phase of the specimen after that.The heat transfer coefficient of the quenched surface was determined by the inverse heat transfer method for simulation.The results show that the cooling rate of the quenched surface exceeds 1574 K/min.Based on the averaged cooling rate obtained from the simulation and the measured size of the secondaryγ′phase,an empirical correlation in a double logarithmic relationship between them is proposed.The relationship is verified by the experiment with specified cooling rates.展开更多
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
In this paper, a method of optimizing the number of hidden layer neurons has been put forward. This optimizing method is suitable for three layers B-p network. The purpose of this optimizing method is to reduce the pr...In this paper, a method of optimizing the number of hidden layer neurons has been put forward. This optimizing method is suitable for three layers B-p network. The purpose of this optimizing method is to reduce the predicting errors when the model is used as predicting model. As an example of application, a predicting model of steel end-quench curves has been designed by using this optimizing method. The result shows that the optimization of ANN hidden layer architecture has an effect on reducing predicting errors.展开更多
To obtain the phase transformation latent heat corresponding to different cooling rates with low test workload and cost,the Newton thermal analysis method and the improved Newtonian thermal analysis method were discus...To obtain the phase transformation latent heat corresponding to different cooling rates with low test workload and cost,the Newton thermal analysis method and the improved Newtonian thermal analysis method were discussed based on the cooling curve obtained in the end-quench test.The validity of two methods was given by the latent heat calculation of 45^(#) steel.The results show that the relative error of latent heat is 5.20%through the improved Newtonian thermal analysis method,which is more accurate than the Newtonian thermal analysis method.Furthermore,the latent heat release of phase transformation of the self-designed CSU-A1 powder metallurgy nickel-based superalloy increases from 4.3 to 12.29 J/g when the cooling rate decreases from 50.15 to 33.40℃/min,because there is more sufficient time for the alloy microstructure to complete the phase transformation process when the cooling rate is smaller.展开更多
基金Item Sponsored by National Natural Science Foundation of China(50271009)
文摘Without considering the effects of alloying interaction on the Jominy end-quench curves, the prediction resuits obtained by YU Bai-hai＇s nonlinear equation method for multi-alloying steels were different from those experimental ones reported in literature. Some alloying elements have marked influence on Jominy end-quench curves of steels. An improved mathematical model for simulating the Jominy end-quench curves is proposed by introducing a parameter named alloying interactions equivalent （Le）. With the improved model, the Jominy end-quench curves of steels so obtained agree very well with the experimental ones.
基金Project(2016YFB0700300) supported by the National Key Research and Development Program of ChinaProject(2019zzts262) supported by the Postgraduate Independent Exploration and Innovation Program of Central South University,China
文摘The microstructure of an alloy is affected intensively by the cooling process.To figure out the inherent relation between the cooling rate and microstructure of an advanced nickel-based superalloy,experimental and numerical studies on the cooling process were conducted.Specifically,the measurement was performed concerning both the temperature of the specimen during the end-quench test and the size of the secondaryγ′phase of the specimen after that.The heat transfer coefficient of the quenched surface was determined by the inverse heat transfer method for simulation.The results show that the cooling rate of the quenched surface exceeds 1574 K/min.Based on the averaged cooling rate obtained from the simulation and the measured size of the secondaryγ′phase,an empirical correlation in a double logarithmic relationship between them is proposed.The relationship is verified by the experiment with specified cooling rates.
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.
文摘In this paper, a method of optimizing the number of hidden layer neurons has been put forward. This optimizing method is suitable for three layers B-p network. The purpose of this optimizing method is to reduce the predicting errors when the model is used as predicting model. As an example of application, a predicting model of steel end-quench curves has been designed by using this optimizing method. The result shows that the optimization of ANN hidden layer architecture has an effect on reducing predicting errors.
基金the financial supports from the National Key Research and Development Program of China(No.2016YFB0700300)the Postgraduate Independent Exploration and Innovation Project of Central South University,China(No.2019zzts262)。
文摘To obtain the phase transformation latent heat corresponding to different cooling rates with low test workload and cost,the Newton thermal analysis method and the improved Newtonian thermal analysis method were discussed based on the cooling curve obtained in the end-quench test.The validity of two methods was given by the latent heat calculation of 45^(#) steel.The results show that the relative error of latent heat is 5.20%through the improved Newtonian thermal analysis method,which is more accurate than the Newtonian thermal analysis method.Furthermore,the latent heat release of phase transformation of the self-designed CSU-A1 powder metallurgy nickel-based superalloy increases from 4.3 to 12.29 J/g when the cooling rate decreases from 50.15 to 33.40℃/min,because there is more sufficient time for the alloy microstructure to complete the phase transformation process when the cooling rate is smaller.
