In order to study the high temperature flow behaviour of the V modified 2.25Cr-1Mo steel plate to guide the industrial rolling practice, the hot compression tests were carried out at the temperatures from 900 ℃ to 11...In order to study the high temperature flow behaviour of the V modified 2.25Cr-1Mo steel plate to guide the industrial rolling practice, the hot compression tests were carried out at the temperatures from 900 ℃ to 1150 ℃ and the strain rates from 0.01s^-1 to 1 s^-1 on Thermecmastor-Z equipment. Based on the experimental data of the hot compression tests, a kind of Arrhenius-type constitutive equation was developed.The equation can accurately show the relationship between the flow stress and the deformation temperature, the strain and the strain rate. The measured true stress-true strain curves exhibit two kinds of flow stress curves. Moreover, the forming mechanisms of these two types curves were explained by softening, wok hardening theory as well as metallographic and hardness experimental results. The accuracy of the developed Arrheniustype constitutive equation was identified by three kinds of statistic parameters and also by comparison of the measured and predicted data. The reasonable value of the three types of statistic parameters and the good agreement between the experimental and predicted data can confirm the validity of the developed Arrheniustype constitutive equation for V modified 2.25 Cr-1 Mo heat resistant steel plate.展开更多
The effects of hydrogen atoms on behaviour of low cycle fatigue of 2.25Cr-1Mo steel have been investigated in present work. The results indicate that the cyclic softening rate and low cycle fatigue life are respective...The effects of hydrogen atoms on behaviour of low cycle fatigue of 2.25Cr-1Mo steel have been investigated in present work. The results indicate that the cyclic softening rate and low cycle fatigue life are respectively increased and reduced remarkably by hydrogen atoms. In addition, hydrogen atoms make the original stress amplitude of low cycle fatigue increase, which is because of the drag effect of hydrogen atoms on the moving dislocations. Analyses using electron microscopy show that hydrogen atoms accelerate crack initiation of low cycle fatigue from inclusion and transfer the source of low cycle fatigue crack from the surface of specimen to the inclusion, which results in the marked decrease of low cycle fatigue life. The increase of cyclic softening rate for hydrogen charged specimen is due to hydrogen atoms accelerating the initiating and growing of microvoids from the secondary phase particles in the steel. The reducing of the drag effect of hydrogen atoms on moving dislocations is also helpful to the increase of the cyclic softening rate.展开更多
The quantitative determination of the mass fractions of precipitates in steels is very difficult using traditional materials characterization techniques. The Rietveld full-pattern fitting algorithm was introduced to s...The quantitative determination of the mass fractions of precipitates in steels is very difficult using traditional materials characterization techniques. The Rietveld full-pattern fitting algorithm was introduced to solve this problem. The precipitated multicomponents’ mass fraction of M3C, MC, M7C3 and M23C6 were evaluated precisely and relatively quickly. It is found evolution of carbides apparently occurs during tempering at high temperatures, and a two-step transformation mechanism is proposed for M7C3 during early tempering treatment. The method is an effective way on the investigation of precipitation kinetics, which may play a promising role in propertities’ enhancement and design of the heat-resistant steels.展开更多
Based on the theory of grain boundary segregation, a kinetics model of temper em-brittlement caused by long-term service for hot-wall hydrofining reactors was studied.The kinetics model was applied to phosphorus (P) s...Based on the theory of grain boundary segregation, a kinetics model of temper em-brittlement caused by long-term service for hot-wall hydrofining reactors was studied.The kinetics model was applied to phosphorus (P) segregation in 2.25Cr-1Mo steelused for a hot-wall hydrofining reactor, and the kinetics of grain boundary segrea-tion of impurity P in the steel exposed to the process environment of the hydrofiningreactor was calculated on the basis of the model. The Auger electron spectroscopytest was performed in order to determine the grain boundary concentration of P. Theexperimental result is agreement with the theoretical calculated data. The results showthat the kinetics equation is reasonable for predicting the levels of grain boundarysegregation of impurity P in 2.25Cr-1Mo steel used for hot-wall hydrofining reactors.展开更多
High-temperature creep rupture behavior of modified 9Cr-lMo steel used for steam cooler was investigated at temperature of 838 and 923 K and stress ranging from 100 to 250 MPa.Based on the analysis of creep rate-time ...High-temperature creep rupture behavior of modified 9Cr-lMo steel used for steam cooler was investigated at temperature of 838 and 923 K and stress ranging from 100 to 250 MPa.Based on the analysis of creep rate-time curves,it is found that the creep rupture life decreases with the increase in the applied stress and temperature.The creep damage tolerance factor has been identified as a value of 8.In the normalized and tempered condition,the studied steel shows typical martensitic microstructure with Cr-rich M23C6 and Nb-or V-rich MX precipitates.Moreover,the Laves phase has been found along the grain boundaries.The fracture morphology characterized by field emission scanning electron microscope is adopted to reveal the creep failure mechanisms.The investigated results indicate the occurrence of the transgranular fracture under all the creep test conditions.展开更多
To verify the microalloying function and segregation behavior of trace Mg at grain boundary in steel,the 2.25Cr–1Mo steel doped with 0.056%P containing different Mg contents was refined with a vacuum-induction furnac...To verify the microalloying function and segregation behavior of trace Mg at grain boundary in steel,the 2.25Cr–1Mo steel doped with 0.056%P containing different Mg contents was refined with a vacuum-induction furnace.The effects of trace Mg addition on the temper embrittlement susceptibility of 2.25Cr–1Mo steel were studied by step-cooling test and the segregation behavior of Mg at grain boundary was explored by Auger electron spectroscopy.It is shown that P-induced temper embrittlement susceptibility can be reduced after subjecting to step-cooling treatment with trace Mg addition,mainly benefited from the segregation of Mg at grain boundary.This segregation can decrease the segregation amounts of P and S,especially for P,and increase the grain boundary cohesion,reducing the adverse effect on temper embrittlement caused by P and S.展开更多
The carbide precipitation was analyzed during aging of 2.25Cr–1Mo steel at 550℃.The as-received steel was aged in two different manners:the first treatment was an isothermal aging at 550℃ for time up to 1000 h,and ...The carbide precipitation was analyzed during aging of 2.25Cr–1Mo steel at 550℃.The as-received steel was aged in two different manners:the first treatment was an isothermal aging at 550℃ for time up to 1000 h,and the second one was carried out by a cyclical aging,which consisted of aging at 550℃ for 1 h,water quenching at room temperature and then newly heating at 550℃.This procedure was repeated up to 300 times.The M_(23)C_(6) and M6C carbide precipitation took place intragranularly and intergranularly for both aging treatments.The carbide coarsening was detected to occur with the increasing aging time.Nevertheless,the growth kinetics of precipitation occurred more rapidly in the case of cyclical aging.The specimen hardness decreased with the aging time in both cases;however,it occurred in shorter aging time for the cyclical aging.Nanoindentation testing indicated the increase in ductility with the aging time,and the cyclically aged specimens showed larger ductility than the isothermally aged specimens.展开更多
基金Funded by the New Product Research Program(No.X18ECQ0A00)of Baoshan Iron&Steel Co.Ltd.
文摘In order to study the high temperature flow behaviour of the V modified 2.25Cr-1Mo steel plate to guide the industrial rolling practice, the hot compression tests were carried out at the temperatures from 900 ℃ to 1150 ℃ and the strain rates from 0.01s^-1 to 1 s^-1 on Thermecmastor-Z equipment. Based on the experimental data of the hot compression tests, a kind of Arrhenius-type constitutive equation was developed.The equation can accurately show the relationship between the flow stress and the deformation temperature, the strain and the strain rate. The measured true stress-true strain curves exhibit two kinds of flow stress curves. Moreover, the forming mechanisms of these two types curves were explained by softening, wok hardening theory as well as metallographic and hardness experimental results. The accuracy of the developed Arrheniustype constitutive equation was identified by three kinds of statistic parameters and also by comparison of the measured and predicted data. The reasonable value of the three types of statistic parameters and the good agreement between the experimental and predicted data can confirm the validity of the developed Arrheniustype constitutive equation for V modified 2.25 Cr-1 Mo heat resistant steel plate.
文摘The effects of hydrogen atoms on behaviour of low cycle fatigue of 2.25Cr-1Mo steel have been investigated in present work. The results indicate that the cyclic softening rate and low cycle fatigue life are respectively increased and reduced remarkably by hydrogen atoms. In addition, hydrogen atoms make the original stress amplitude of low cycle fatigue increase, which is because of the drag effect of hydrogen atoms on the moving dislocations. Analyses using electron microscopy show that hydrogen atoms accelerate crack initiation of low cycle fatigue from inclusion and transfer the source of low cycle fatigue crack from the surface of specimen to the inclusion, which results in the marked decrease of low cycle fatigue life. The increase of cyclic softening rate for hydrogen charged specimen is due to hydrogen atoms accelerating the initiating and growing of microvoids from the secondary phase particles in the steel. The reducing of the drag effect of hydrogen atoms on moving dislocations is also helpful to the increase of the cyclic softening rate.
基金Funded by the New Products Development Research Projects of Shang-hai Baoshan Iron & Steel Research Institute(X08ECEJ160)
文摘The quantitative determination of the mass fractions of precipitates in steels is very difficult using traditional materials characterization techniques. The Rietveld full-pattern fitting algorithm was introduced to solve this problem. The precipitated multicomponents’ mass fraction of M3C, MC, M7C3 and M23C6 were evaluated precisely and relatively quickly. It is found evolution of carbides apparently occurs during tempering at high temperatures, and a two-step transformation mechanism is proposed for M7C3 during early tempering treatment. The method is an effective way on the investigation of precipitation kinetics, which may play a promising role in propertities’ enhancement and design of the heat-resistant steels.
文摘Based on the theory of grain boundary segregation, a kinetics model of temper em-brittlement caused by long-term service for hot-wall hydrofining reactors was studied.The kinetics model was applied to phosphorus (P) segregation in 2.25Cr-1Mo steelused for a hot-wall hydrofining reactor, and the kinetics of grain boundary segrea-tion of impurity P in the steel exposed to the process environment of the hydrofiningreactor was calculated on the basis of the model. The Auger electron spectroscopytest was performed in order to determine the grain boundary concentration of P. Theexperimental result is agreement with the theoretical calculated data. The results showthat the kinetics equation is reasonable for predicting the levels of grain boundarysegregation of impurity P in 2.25Cr-1Mo steel used for hot-wall hydrofining reactors.
基金National Natural Science Foundation of China (Grant No.51705316)Shanghai Municipal Bureau of Quality and Technical Supervision (No.2016-40).
文摘High-temperature creep rupture behavior of modified 9Cr-lMo steel used for steam cooler was investigated at temperature of 838 and 923 K and stress ranging from 100 to 250 MPa.Based on the analysis of creep rate-time curves,it is found that the creep rupture life decreases with the increase in the applied stress and temperature.The creep damage tolerance factor has been identified as a value of 8.In the normalized and tempered condition,the studied steel shows typical martensitic microstructure with Cr-rich M23C6 and Nb-or V-rich MX precipitates.Moreover,the Laves phase has been found along the grain boundaries.The fracture morphology characterized by field emission scanning electron microscope is adopted to reveal the creep failure mechanisms.The investigated results indicate the occurrence of the transgranular fracture under all the creep test conditions.
基金The authors thank the National Natural Science Foundation of China for their financial support under contract No.51801210.
文摘To verify the microalloying function and segregation behavior of trace Mg at grain boundary in steel,the 2.25Cr–1Mo steel doped with 0.056%P containing different Mg contents was refined with a vacuum-induction furnace.The effects of trace Mg addition on the temper embrittlement susceptibility of 2.25Cr–1Mo steel were studied by step-cooling test and the segregation behavior of Mg at grain boundary was explored by Auger electron spectroscopy.It is shown that P-induced temper embrittlement susceptibility can be reduced after subjecting to step-cooling treatment with trace Mg addition,mainly benefited from the segregation of Mg at grain boundary.This segregation can decrease the segregation amounts of P and S,especially for P,and increase the grain boundary cohesion,reducing the adverse effect on temper embrittlement caused by P and S.
文摘The carbide precipitation was analyzed during aging of 2.25Cr–1Mo steel at 550℃.The as-received steel was aged in two different manners:the first treatment was an isothermal aging at 550℃ for time up to 1000 h,and the second one was carried out by a cyclical aging,which consisted of aging at 550℃ for 1 h,water quenching at room temperature and then newly heating at 550℃.This procedure was repeated up to 300 times.The M_(23)C_(6) and M6C carbide precipitation took place intragranularly and intergranularly for both aging treatments.The carbide coarsening was detected to occur with the increasing aging time.Nevertheless,the growth kinetics of precipitation occurred more rapidly in the case of cyclical aging.The specimen hardness decreased with the aging time in both cases;however,it occurred in shorter aging time for the cyclical aging.Nanoindentation testing indicated the increase in ductility with the aging time,and the cyclically aged specimens showed larger ductility than the isothermally aged specimens.
