Regarding development of the dedicated slag for electroslag remelting,crystallization characteristics of the slag exert a strong influence on the initial solidification of liquid metal in mold and surface quality of a...Regarding development of the dedicated slag for electroslag remelting,crystallization characteristics of the slag exert a strong influence on the initial solidification of liquid metal in mold and surface quality of as-cast ingot.The crystallization behavior of CaF_(2)-CaO-Al_(2)O_(3)-based slag with varying SiO_(2)and B_(2)O_(3)contents and their correlation with the slag structure were investigated.Increasing SiO_(2)(0.24-8.95 mass%)and B_(2)O_(3)(0-3.20 mass%)contents lowers the crystallization temperature and suppresses the crystallization of the slag melts,as well as decreases the sizes of the crystalline phases.The crystalline phases precipitated during continuous cooling of the slag melts are faceted 11CaO·7Al_(2)O_(3)·CaF_(2),faceted or spherical CaF_(2),and non-faceted MgO·Al_(2)O_(3)(or MgO)in sequence irrespective of the SiO_(2)and B_(2)O_(3)contents of the slag.The polymerization degree of slag melts increases with increasing either SiO_(2)or B_(2)O_(3)contents.The crystallization of the slag melts is increasingly retarded with increasing the SiO_(2)and B_(2)O_(3)contents of the slag caused by increased component diffusion resistance originating from increased polymerization degree of the slag melts.展开更多
Isothermal hot compression tests of as-cast high-Cr ultra-super-critical（USC） rotor steel with columnar grains perpendicular to the compression direction were carried out in the temperature range from 950 to 1250...Isothermal hot compression tests of as-cast high-Cr ultra-super-critical（USC） rotor steel with columnar grains perpendicular to the compression direction were carried out in the temperature range from 950 to 1250°C at strain rates ranging from 0.001 to 1 s^（-1）. The softening mechanism was dynamic recovery（DRV） at 950°C and the strain rate of 1 s^（-1）, whereas it was dynamic recrystallization（DRX） under the other conditions. A modified constitutive equation based on the Arrhenius model with strain compensation reasonably predicted the flow stress under various deformation conditions, and the activation energy was calculated to be 643.92 kJ ×mol^（-1）. The critical stresses of dynamic recrystallization under different conditions were determined from the work-hardening rate（θ）–flow stress（σ） and-θ/σ–σ curves. The optimum processing parameters via analysis of the processing map and the softening mechanism were determined to be a deformation temperature range from 1100 to 1200°C and a strain-rate range from 0.001 to 0.08 s^（-1）, with a power dissipation efficiency η greater than 31%.展开更多
Low fatigue samples were obtained from the outer edges of rotor steel (30CrlMolV) which had operated under different temperatures conditions. Based on this data, the effects of temperature on fatigue crack growth rate...Low fatigue samples were obtained from the outer edges of rotor steel (30CrlMolV) which had operated under different temperatures conditions. Based on this data, the effects of temperature on fatigue crack growth rates were investigated. This paper presents a derivation of the superposition expression of two natural logarithms governing crack growth rates and also discusses the relationship between a material’s constants and temperature. These results can provide experimental and theoretical references for fatigue life design of rotor steel in steam turbines.展开更多
The layout features of unit shafting and their effects on vibration, as well as evaluation criteria, were introduced for a 1000-MW ultra-supercritical turbine-generator unit with Simens technology. Based on vibration ...The layout features of unit shafting and their effects on vibration, as well as evaluation criteria, were introduced for a 1000-MW ultra-supercritical turbine-generator unit with Simens technology. Based on vibration diagnosis and treatment for more than 10 units, some typical vibration faults were summarized, such as the vibration fluctuation of the high pressure (HP) rotor, abnormal vibration increases of the No.3 bearing pedestal and large vibration of the exciter rotor during its critical speed range. The vibration characteristics and the causes of faults and countermeasures were analyzed. Three applications for further illustration were given. The vibration fault identification method, control measures, and applications can provide a reference for vibration diagnoses and treatment of same type units.展开更多
基金The financial support by the National Natural Science Foundation of China(Grant No.52074027)the Fundamental Research Funds for the Central Universities(Grant No.FRF-AT-20-13)is greatly acknowledgedThe authors are also grateful to the financial support from the State Key Laboratory of Advanced Metallurgy(Grant No.41621024).
文摘Regarding development of the dedicated slag for electroslag remelting,crystallization characteristics of the slag exert a strong influence on the initial solidification of liquid metal in mold and surface quality of as-cast ingot.The crystallization behavior of CaF_(2)-CaO-Al_(2)O_(3)-based slag with varying SiO_(2)and B_(2)O_(3)contents and their correlation with the slag structure were investigated.Increasing SiO_(2)(0.24-8.95 mass%)and B_(2)O_(3)(0-3.20 mass%)contents lowers the crystallization temperature and suppresses the crystallization of the slag melts,as well as decreases the sizes of the crystalline phases.The crystalline phases precipitated during continuous cooling of the slag melts are faceted 11CaO·7Al_(2)O_(3)·CaF_(2),faceted or spherical CaF_(2),and non-faceted MgO·Al_(2)O_(3)(or MgO)in sequence irrespective of the SiO_(2)and B_(2)O_(3)contents of the slag.The polymerization degree of slag melts increases with increasing either SiO_(2)or B_(2)O_(3)contents.The crystallization of the slag melts is increasingly retarded with increasing the SiO_(2)and B_(2)O_(3)contents of the slag caused by increased component diffusion resistance originating from increased polymerization degree of the slag melts.
基金supported by the Major State Basic Research Development Program of China (No.2011CB012900)the National Natural Science Foundation of China (No.51374144)the Shanghai Rising-Star Program (No.14QA1402300)
文摘Isothermal hot compression tests of as-cast high-Cr ultra-super-critical（USC） rotor steel with columnar grains perpendicular to the compression direction were carried out in the temperature range from 950 to 1250°C at strain rates ranging from 0.001 to 1 s^（-1）. The softening mechanism was dynamic recovery（DRV） at 950°C and the strain rate of 1 s^（-1）, whereas it was dynamic recrystallization（DRX） under the other conditions. A modified constitutive equation based on the Arrhenius model with strain compensation reasonably predicted the flow stress under various deformation conditions, and the activation energy was calculated to be 643.92 kJ ×mol^（-1）. The critical stresses of dynamic recrystallization under different conditions were determined from the work-hardening rate（θ）–flow stress（σ） and-θ/σ–σ curves. The optimum processing parameters via analysis of the processing map and the softening mechanism were determined to be a deformation temperature range from 1100 to 1200°C and a strain-rate range from 0.001 to 0.08 s^（-1）, with a power dissipation efficiency η greater than 31%.
基金the Heilongjiang Province Natural Science Foundation under Grant No. A009the Foundation of Harbin Engineering University under Grant No. HEUF04005.
文摘Low fatigue samples were obtained from the outer edges of rotor steel (30CrlMolV) which had operated under different temperatures conditions. Based on this data, the effects of temperature on fatigue crack growth rates were investigated. This paper presents a derivation of the superposition expression of two natural logarithms governing crack growth rates and also discusses the relationship between a material’s constants and temperature. These results can provide experimental and theoretical references for fatigue life design of rotor steel in steam turbines.
文摘The layout features of unit shafting and their effects on vibration, as well as evaluation criteria, were introduced for a 1000-MW ultra-supercritical turbine-generator unit with Simens technology. Based on vibration diagnosis and treatment for more than 10 units, some typical vibration faults were summarized, such as the vibration fluctuation of the high pressure (HP) rotor, abnormal vibration increases of the No.3 bearing pedestal and large vibration of the exciter rotor during its critical speed range. The vibration characteristics and the causes of faults and countermeasures were analyzed. Three applications for further illustration were given. The vibration fault identification method, control measures, and applications can provide a reference for vibration diagnoses and treatment of same type units.
