In this work, a parametric approach is presented and utilized to determine the creep properties of weldments; then the model of creep strain for cross weld specimen is given. On the basis of the experimental results, ...In this work, a parametric approach is presented and utilized to determine the creep properties of weldments; then the model of creep strain for cross weld specimen is given. On the basis of the experimental results, attempt has been made to establish equations of the isochronous stress-strain for weld joint that can predict the function of loading and service time in use of the creep data of base metal and weld metal.展开更多
The influence of hot deformation conditions on continuous cooling bainitic transformation has been investigated for a low carbon microalloyed steel. The CCT diagrams show that deformation in unrecrpstallized austcnite...The influence of hot deformation conditions on continuous cooling bainitic transformation has been investigated for a low carbon microalloyed steel. The CCT diagrams show that deformation in unrecrpstallized austcnite ation can accelerate transformation process. Bainitic transformation in intermediate transformation temperature region is prominent, and the proeutectoid polygonal ferrite transformation at evelated high temperature is suppressed. According to optical and TEM analyses, low carbon bainitic ferrite is characterized by granular and lathlike ferrite, based on the cooling rate and deformation conditions. For nondeformation, groaps of coarse parallel ferrite lath form from the prior austenite grain boundaries with the same crystallographic orientation. For heavy deformaton, cell structure within the austenite grains due to the high dislocation density formed, which provides more nucleation sites for bainite ferrite. So deformation can discontinue the growth of ferrite laths and decrease the length of ferrite laths.展开更多
10CrMo910 and 316 stainless steel are widely adopted in high temperature structures of power generations, chemical processing plants and petroleum refineries. In this work, a total of 10000 hour tensile creep test on ...10CrMo910 and 316 stainless steel are widely adopted in high temperature structures of power generations, chemical processing plants and petroleum refineries. In this work, a total of 10000 hour tensile creep test on 16 specimens of such two materials was conducted at 550℃. On the basis of the experimental results, the isochronous stress-strain curves and time-dependent failure assessment curves of the two materials were given. Finally, the formulae of time dependent failure assessment curve for 10CrMo910 and 316 stainless steel corresponding to long-term creep cases, which could be utilized in the high temperature defects assessment, were established. The procedure for defining the time-dependent failure assessment curves was also presented.展开更多
On the thermodynamics basis of regular solution sub-lattice model and soperelement model, kinetics basis of Cahn's transformation kinetics theory, and according to Scheil's additivity rule and eoperimental res...On the thermodynamics basis of regular solution sub-lattice model and soperelement model, kinetics basis of Cahn's transformation kinetics theory, and according to Scheil's additivity rule and eoperimental results obtained by thermal dilation method,a prediction model of transformations from hot-deformed austenite to ferrite, pearlite and bainite in low alloy steels, which could be applied to continuoas cooling process, is developed. The calculated transformed junctions of each phase based on laboratory controlled rolling and controlled cooling conditions in a low alloy steel are in reasonable agreement with the measured ones.展开更多
Localized creep damage in a notched round specimen has been investigated in this paper based on the creep damage mechanics and the DCPD technique. Expressions of creep damage equivalent stress under multi-axial state ...Localized creep damage in a notched round specimen has been investigated in this paper based on the creep damage mechanics and the DCPD technique. Expressions of creep damage equivalent stress under multi-axial state are given to describe the validity for localized damage in ductile materials. A DCPD method is introduced into the measurement of local creep damage near the tip of V-type notch of round bar. The technique with instrument configuration, selection of probe position and measuring calibration is also presented in the paper. Some results of creep damage estimation are shown on 2.25Cr-1Mo at 550℃.展开更多
基金supports provided by Natural Science Foundation of Shanghai(contract No.03ZR14022)the“Tenth Five”National Key Technological Research and Development Program(contract No.2001BA803B03)National Natural Science Foundation of China(contract No.50225517)are gratefully acknowledged.
文摘In this work, a parametric approach is presented and utilized to determine the creep properties of weldments; then the model of creep strain for cross weld specimen is given. On the basis of the experimental results, attempt has been made to establish equations of the isochronous stress-strain for weld joint that can predict the function of loading and service time in use of the creep data of base metal and weld metal.
文摘The influence of hot deformation conditions on continuous cooling bainitic transformation has been investigated for a low carbon microalloyed steel. The CCT diagrams show that deformation in unrecrpstallized austcnite ation can accelerate transformation process. Bainitic transformation in intermediate transformation temperature region is prominent, and the proeutectoid polygonal ferrite transformation at evelated high temperature is suppressed. According to optical and TEM analyses, low carbon bainitic ferrite is characterized by granular and lathlike ferrite, based on the cooling rate and deformation conditions. For nondeformation, groaps of coarse parallel ferrite lath form from the prior austenite grain boundaries with the same crystallographic orientation. For heavy deformaton, cell structure within the austenite grains due to the high dislocation density formed, which provides more nucleation sites for bainite ferrite. So deformation can discontinue the growth of ferrite laths and decrease the length of ferrite laths.
基金supported by the National Natural Science Foundation of China(No.50225517)the Natural Science Foundation of Shanghai(No.03ZR14022)
文摘10CrMo910 and 316 stainless steel are widely adopted in high temperature structures of power generations, chemical processing plants and petroleum refineries. In this work, a total of 10000 hour tensile creep test on 16 specimens of such two materials was conducted at 550℃. On the basis of the experimental results, the isochronous stress-strain curves and time-dependent failure assessment curves of the two materials were given. Finally, the formulae of time dependent failure assessment curve for 10CrMo910 and 316 stainless steel corresponding to long-term creep cases, which could be utilized in the high temperature defects assessment, were established. The procedure for defining the time-dependent failure assessment curves was also presented.
文摘On the thermodynamics basis of regular solution sub-lattice model and soperelement model, kinetics basis of Cahn's transformation kinetics theory, and according to Scheil's additivity rule and eoperimental results obtained by thermal dilation method,a prediction model of transformations from hot-deformed austenite to ferrite, pearlite and bainite in low alloy steels, which could be applied to continuoas cooling process, is developed. The calculated transformed junctions of each phase based on laboratory controlled rolling and controlled cooling conditions in a low alloy steel are in reasonable agreement with the measured ones.
文摘Localized creep damage in a notched round specimen has been investigated in this paper based on the creep damage mechanics and the DCPD technique. Expressions of creep damage equivalent stress under multi-axial state are given to describe the validity for localized damage in ductile materials. A DCPD method is introduced into the measurement of local creep damage near the tip of V-type notch of round bar. The technique with instrument configuration, selection of probe position and measuring calibration is also presented in the paper. Some results of creep damage estimation are shown on 2.25Cr-1Mo at 550℃.
