The existing researches of hot ring rolling process are mainly based on forged billet. Compared with the existing process, the new ring casting-rolling compound forming process has significant advantages in saving mat...The existing researches of hot ring rolling process are mainly based on forged billet. Compared with the existing process, the new ring casting-rolling compound forming process has significant advantages in saving materials and energy, reducing emission and reducing the production cost. The microstructure evolution of the casting materials during hot deformation is the basis of the research of the new process. However, the researches on the casting materials are rare. The metadynamic recrystallization of the as-cast 42CrMo steel after normalizing and tempering during the hot compression is investigated. The tests are performed on the Gleeble-1500 thermal-mechanical simulator. The influence rule of the deformation parameters on the metadynamic recrystallization is obtained by analyzing the experimental data. The kinetic model of the rnetadynamic recrystallization is deduced. The analysis results show that the metadynamic recrystallization fraction increases with the increase of the deformation temperature and the strain rate. The metallographic experiments are used to investigate the influence rule of the deformation parameters on the grain size of the metadynamic recrystallization. The experimental results show that the grain of the metadynamic recrystallization could be refined with the increase of the strain rate and the decrease of the deformation temperature during hot compression. The occurrence of the metadynamic recrystallization during the hot deformation is more difficult in as-cast 42CrMo steel than in forged 42CrMo steel. The research can provide the foundation for the further research of the hot deformation behaviors of the as-cast structure and theoretical support for the new ring casting-rolling compound process.展开更多
The effect of undissolved ferrite amount in subcritically quenched 42CrMo steel on contact fatigue properties and failure mechanism were studied. The amount of undissolved ferrite in the steel were 0%,3%,10%,15% and 2...The effect of undissolved ferrite amount in subcritically quenched 42CrMo steel on contact fatigue properties and failure mechanism were studied. The amount of undissolved ferrite in the steel were 0%,3%,10%,15% and 20% in volume fraction, respectively. The experimental results show that the existence of undissolved ferrite can increase the contact fatigue life The contact fatigue life can be prolonged with increasing the amounts of undissolved ferrite The grain size can be fined by using subcritical quenching process and the area of phase boundaries can also be greatly increased. The stress relaxation and grain refinement due to occurring of plastic deformation are main reasons for improving the fatigue life. The existence of undissolved ferrite can increase the crack initiation period. Under the experiment conditions, when the amount of undissolved ferrite is 10%, the longest contact fatigue life can be the obtained.展开更多
Vacuum brazing of TiAl to 42CrMo steel was carried out at 8601000℃ for 5min using Ag-33Cu- 4.5Ti (mass fraction, %) filler metal. Formation phases and microstructures of the joints were investigated by SEM an...Vacuum brazing of TiAl to 42CrMo steel was carried out at 8601000℃ for 5min using Ag-33Cu- 4.5Ti (mass fraction, %) filler metal. Formation phases and microstructures of the joints were investigated by SEM and EPMA. The strength of the joints were evaluated by means of tensile tests. The results show that five interfacial formation phases occur in the brazing seam: AlCuTi and AlCu2Ti compounds, Ag solid solution, Ag-Cu eutectic phase and the reaction layer of TiC adjacent to the steel. The tensile strength of the brazed joints changes with the chang of brazing temperature. When the brazing temperature is 900℃, the tensile strength of the joint is 347MPa. TiAl turbine and 42CrMo steel shaft was brazed and the strength of TiAl/42CrMo turbine rotor was evaluated by means of tensile test, when the tensile load reached 100kN the joint of the rotor kept well.展开更多
The heat treatment properties of 42CrMo steel for bearing ring of varisized shield tunneling machine were investigated by optical microscope (OM), scanning electron microscope (SEM), transmission electron microsco...The heat treatment properties of 42CrMo steel for bearing ring of varisized shield tunneling machine were investigated by optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM), and impact tests. The addition of 0.03 wt% C into 42CrMo steel can increase the hardness. But it reduces the impact energy by 46 J because of the appearance of coarser carbides in the matrix and the carbides along the austenite grain boundary. The addition of 0.40 wt% Mn into 42CrMo steel can improve hardenability. However, the toughness of steel is also reduced by 26 J mainly because of the coarsening of carbides and the strengthening of matrix. Both hardenability and toughness of 42CrMo steel can be improved by adding 1.49 wt% Ni and reducing 0.32 wt% Cr. The depth of hardening layer can be raised to 45 mm, and the impact energy at -20 ℃ is 120 J. Thus, it is concluded that a good combination of hardness, hardenability, and toughness of 42CrMo steel can be achieved by alloying with adding some content of C and Ni. Detailed content of C and Ni should be on the requirements of heat treatment properties of steel for bearing ring of varisized shield tunneling machine.展开更多
The valence electron structure (VES) in compound layer of steel plasma-nitrided at 560°C with rare earth (RE) addition was calculated based on the empirical electron theory (EET) of solids and molecules and BLD m...The valence electron structure (VES) in compound layer of steel plasma-nitrided at 560°C with rare earth (RE) addition was calculated based on the empirical electron theory (EET) of solids and molecules and BLD method. The results show that the presence of RE atoms diffused into surface layer leads to an increase of phase structure factor, which explains the catalyzing and micro-alloying effects of RE.展开更多
The dynamic recrystallization(DRX) simulation performance largely depends on simulated grain topological struc?tures. However, currently solutions used di erent models for describing two?dimensional(2 D) and three?dim...The dynamic recrystallization(DRX) simulation performance largely depends on simulated grain topological struc?tures. However, currently solutions used di erent models for describing two?dimensional(2 D) and three?dimensional(3 D) grain size distributions. Therefore, it is necessary to develop a more universal simulation technique. A cellular automaton(CA) model combined with an optimized topology deformation technology is proposed to simulate the microstructural evolution of 42 CrMo cast steel during DRX. In order to obtain values of material constants adopted in the CA model, hot deformation characteristics of 42 CrMo cast steel are investigated by hot compression metal?lographic testing. The proposed CA model deviates in two important aspects from the regular CA model. First, an optimized grain topology deformation technology is utilized for studying the hot compression e ect on the topology of grain deformation. Second, the overlapping grain topological structures are optimized by using an independent component analysis method, and the influence of various thermomechanical parameters on the nucleation process, grain growth kinetics, and mean grain sizes observed during DRX are explored. Experimental study shows that the average relative root mean square error(RRMSE) of the mean grain diameter obtained by the regular CA model is equal to 0.173, while the magnitude calculated using the proposed optimized CA model is only 0.11. This paper pro?poses a novel combined CA model for simulating the microstructural evolution of 42 CrMo cast steel, which notably uses a ICA?based grain topology deformation method to optimize the overlapping grain topological structures in simulation.展开更多
基金supported by Key Program of National Natural Science Foundation of China (Grant No. 51135007)National Natural Science Foundation of China (Grant No. 51075290)+1 种基金Shanxi Provincial Science and Technology Planning Project of China (Grant No. 20100321083)Shanxi Provincial Foundation for Returnees of China (Grant No.2011011025-1)
文摘The existing researches of hot ring rolling process are mainly based on forged billet. Compared with the existing process, the new ring casting-rolling compound forming process has significant advantages in saving materials and energy, reducing emission and reducing the production cost. The microstructure evolution of the casting materials during hot deformation is the basis of the research of the new process. However, the researches on the casting materials are rare. The metadynamic recrystallization of the as-cast 42CrMo steel after normalizing and tempering during the hot compression is investigated. The tests are performed on the Gleeble-1500 thermal-mechanical simulator. The influence rule of the deformation parameters on the metadynamic recrystallization is obtained by analyzing the experimental data. The kinetic model of the rnetadynamic recrystallization is deduced. The analysis results show that the metadynamic recrystallization fraction increases with the increase of the deformation temperature and the strain rate. The metallographic experiments are used to investigate the influence rule of the deformation parameters on the grain size of the metadynamic recrystallization. The experimental results show that the grain of the metadynamic recrystallization could be refined with the increase of the strain rate and the decrease of the deformation temperature during hot compression. The occurrence of the metadynamic recrystallization during the hot deformation is more difficult in as-cast 42CrMo steel than in forged 42CrMo steel. The research can provide the foundation for the further research of the hot deformation behaviors of the as-cast structure and theoretical support for the new ring casting-rolling compound process.
文摘The effect of undissolved ferrite amount in subcritically quenched 42CrMo steel on contact fatigue properties and failure mechanism were studied. The amount of undissolved ferrite in the steel were 0%,3%,10%,15% and 20% in volume fraction, respectively. The experimental results show that the existence of undissolved ferrite can increase the contact fatigue life The contact fatigue life can be prolonged with increasing the amounts of undissolved ferrite The grain size can be fined by using subcritical quenching process and the area of phase boundaries can also be greatly increased. The stress relaxation and grain refinement due to occurring of plastic deformation are main reasons for improving the fatigue life. The existence of undissolved ferrite can increase the crack initiation period. Under the experiment conditions, when the amount of undissolved ferrite is 10%, the longest contact fatigue life can be the obtained.
文摘Vacuum brazing of TiAl to 42CrMo steel was carried out at 8601000℃ for 5min using Ag-33Cu- 4.5Ti (mass fraction, %) filler metal. Formation phases and microstructures of the joints were investigated by SEM and EPMA. The strength of the joints were evaluated by means of tensile tests. The results show that five interfacial formation phases occur in the brazing seam: AlCuTi and AlCu2Ti compounds, Ag solid solution, Ag-Cu eutectic phase and the reaction layer of TiC adjacent to the steel. The tensile strength of the brazed joints changes with the chang of brazing temperature. When the brazing temperature is 900℃, the tensile strength of the joint is 347MPa. TiAl turbine and 42CrMo steel shaft was brazed and the strength of TiAl/42CrMo turbine rotor was evaluated by means of tensile test, when the tensile load reached 100kN the joint of the rotor kept well.
基金supported by the National High Technology Research and Development Program of China (No. 2012AA03A503)
文摘The heat treatment properties of 42CrMo steel for bearing ring of varisized shield tunneling machine were investigated by optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM), and impact tests. The addition of 0.03 wt% C into 42CrMo steel can increase the hardness. But it reduces the impact energy by 46 J because of the appearance of coarser carbides in the matrix and the carbides along the austenite grain boundary. The addition of 0.40 wt% Mn into 42CrMo steel can improve hardenability. However, the toughness of steel is also reduced by 26 J mainly because of the coarsening of carbides and the strengthening of matrix. Both hardenability and toughness of 42CrMo steel can be improved by adding 1.49 wt% Ni and reducing 0.32 wt% Cr. The depth of hardening layer can be raised to 45 mm, and the impact energy at -20 ℃ is 120 J. Thus, it is concluded that a good combination of hardness, hardenability, and toughness of 42CrMo steel can be achieved by alloying with adding some content of C and Ni. Detailed content of C and Ni should be on the requirements of heat treatment properties of steel for bearing ring of varisized shield tunneling machine.
基金support from the key laboratory foundation of precision hot forming for national defense science and technology.
文摘The valence electron structure (VES) in compound layer of steel plasma-nitrided at 560°C with rare earth (RE) addition was calculated based on the empirical electron theory (EET) of solids and molecules and BLD method. The results show that the presence of RE atoms diffused into surface layer leads to an increase of phase structure factor, which explains the catalyzing and micro-alloying effects of RE.
基金Supported by Key Program of National Natural Science Foundation of China(Grant No.51135007)National Natural Science Foundation of China(Grant Nos.51575371,61301250)Program for the Outstanding Innovative Teams of Higher Learning Institutions of Shanxi Province of China(Grant No.[2015]3)
文摘The dynamic recrystallization(DRX) simulation performance largely depends on simulated grain topological struc?tures. However, currently solutions used di erent models for describing two?dimensional(2 D) and three?dimensional(3 D) grain size distributions. Therefore, it is necessary to develop a more universal simulation technique. A cellular automaton(CA) model combined with an optimized topology deformation technology is proposed to simulate the microstructural evolution of 42 CrMo cast steel during DRX. In order to obtain values of material constants adopted in the CA model, hot deformation characteristics of 42 CrMo cast steel are investigated by hot compression metal?lographic testing. The proposed CA model deviates in two important aspects from the regular CA model. First, an optimized grain topology deformation technology is utilized for studying the hot compression e ect on the topology of grain deformation. Second, the overlapping grain topological structures are optimized by using an independent component analysis method, and the influence of various thermomechanical parameters on the nucleation process, grain growth kinetics, and mean grain sizes observed during DRX are explored. Experimental study shows that the average relative root mean square error(RRMSE) of the mean grain diameter obtained by the regular CA model is equal to 0.173, while the magnitude calculated using the proposed optimized CA model is only 0.11. This paper pro?poses a novel combined CA model for simulating the microstructural evolution of 42 CrMo cast steel, which notably uses a ICA?based grain topology deformation method to optimize the overlapping grain topological structures in simulation.