By using newly developed CuNi5~25Ti16~28 B rapldly solidifled brazing filler the joining of Si3 N4/1.25Cr-0.5Mo steel has been carried out with interlayer method. If employing the interlayer structure of steel (0.2 mm...By using newly developed CuNi5~25Ti16~28 B rapldly solidifled brazing filler the joining of Si3 N4/1.25Cr-0.5Mo steel has been carried out with interlayer method. If employing the interlayer structure of steel (0.2 mm)/W (2.0 mm)/Ni(0.2 mm), the joint strength can be increased greatly compared with employing that of Ni/W/Ni, and the three point bend strength of the Joint shows the value of 261 MPa. The metallurgical behaviour at the interface between Si3N4 and the interlayer has been studied. It is found that Fe participated in the interfacial reactions between Si3N4 and the brazing filler at the Si3N4/steel (0.2 mm) interface and the compound Fe5Si3 was produced. However, since the reactions of Fe with the active Ti are weaker than those of Ni with Ti, the normal inter facial reactions were still assured at the interface of Si3N4/steel (0.2 mm) instead of Si3N4/Ni (0.2 mm), resulting in the improvement of the joint strength. The mechanism of the formation of Fe5Si3 is also discussed. Finally, some ideas to further ameliorate and simplify the interlayer structure are put forward.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 cyclic oxidation behavior of Fe-9Cr-1Mo steel (9Cr-1Mo) in 10%H2O+90%Ar (volume fraction) atmosphere at 600, 650 and 700 ℃ for various time was studied. The oxidation mechanism of 9Cr-1Mo steel in 10%H2O+90%Ar at...The cyclic oxidation behavior of Fe-9Cr-1Mo steel (9Cr-1Mo) in 10%H2O+90%Ar (volume fraction) atmosphere at 600, 650 and 700 ℃ for various time was studied. The oxidation mechanism of 9Cr-1Mo steel in 10%H2O+90%Ar atmosphere was discussed. The thermal stress was evaluated in two oxide layers to illustrate the spallation of the oxide layer. The experimental results indicate that there exists a duplex oxide scale with an outer layer of Fe2O3 and an inner layer of mixed (Fe, Cr)3O4 formed on 9Cr-1Mo steel during cyclic oxidation. Some cracks generated in both inner and outer oxide layers. Parts of oxide scales spalled from substrate during the cyclic oxidation. A higher tensile stress in the oxide layer is formed at the early oxidation stage than at the later oxidation stage during heating. This tensile stress results in the formation of cracks in the oxide layer.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
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 cyclic plastic straining electrode technique has been used to investigate the transient electrochemical behaviour of Fe-26Cr1Mo stainless steel in 1M H2SO4 solution at a passive potential.The influence of plastic ...The cyclic plastic straining electrode technique has been used to investigate the transient electrochemical behaviour of Fe-26Cr1Mo stainless steel in 1M H2SO4 solution at a passive potential.The influence of plastic strain amplitude and plastic strain rate on the dissolution current response was analysed. The experimental results showed that the transient current was dependent on the competitive process of the surface film rupture and repassivation of the new surface. The high plastic strain amplitude and the high plastic strain rate caused a change of electrochemical activity of specimen surface. In the condition of low strain amplitude and strain rate, the characteristics of current response was mainly relative tp the process of new surface repassivation.The competition kinetics has been analysed through the comparison of plastic strain rate and repassivating rate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
文摘By using newly developed CuNi5~25Ti16~28 B rapldly solidifled brazing filler the joining of Si3 N4/1.25Cr-0.5Mo steel has been carried out with interlayer method. If employing the interlayer structure of steel (0.2 mm)/W (2.0 mm)/Ni(0.2 mm), the joint strength can be increased greatly compared with employing that of Ni/W/Ni, and the three point bend strength of the Joint shows the value of 261 MPa. The metallurgical behaviour at the interface between Si3N4 and the interlayer has been studied. It is found that Fe participated in the interfacial reactions between Si3N4 and the brazing filler at the Si3N4/steel (0.2 mm) interface and the compound Fe5Si3 was produced. However, since the reactions of Fe with the active Ti are weaker than those of Ni with Ti, the normal inter facial reactions were still assured at the interface of Si3N4/steel (0.2 mm) instead of Si3N4/Ni (0.2 mm), resulting in the improvement of the joint strength. The mechanism of the formation of Fe5Si3 is also discussed. Finally, some ideas to further ameliorate and simplify the interlayer structure are put forward.
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Project(2006-8) supported by the Huadian International Corporation Limited
文摘The cyclic oxidation behavior of Fe-9Cr-1Mo steel (9Cr-1Mo) in 10%H2O+90%Ar (volume fraction) atmosphere at 600, 650 and 700 ℃ for various time was studied. The oxidation mechanism of 9Cr-1Mo steel in 10%H2O+90%Ar atmosphere was discussed. The thermal stress was evaluated in two oxide layers to illustrate the spallation of the oxide layer. The experimental results indicate that there exists a duplex oxide scale with an outer layer of Fe2O3 and an inner layer of mixed (Fe, Cr)3O4 formed on 9Cr-1Mo steel during cyclic oxidation. Some cracks generated in both inner and outer oxide layers. Parts of oxide scales spalled from substrate during the cyclic oxidation. A higher tensile stress in the oxide layer is formed at the early oxidation stage than at the later oxidation stage during heating. This tensile stress results in the formation of cracks in the oxide layer.
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 cyclic plastic straining electrode technique has been used to investigate the transient electrochemical behaviour of Fe-26Cr1Mo stainless steel in 1M H2SO4 solution at a passive potential.The influence of plastic strain amplitude and plastic strain rate on the dissolution current response was analysed. The experimental results showed that the transient current was dependent on the competitive process of the surface film rupture and repassivation of the new surface. The high plastic strain amplitude and the high plastic strain rate caused a change of electrochemical activity of specimen surface. In the condition of low strain amplitude and strain rate, the characteristics of current response was mainly relative tp the process of new surface repassivation.The competition kinetics has been analysed through the comparison of plastic strain rate and repassivating rate
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.
