The influence of prior austenite deformed at different temperature on the subsequent continuous cooling bainitic transformation has been investigated in an C-Ma-Cr-Ni-Mo plastic die steel. The results show that the pr...The influence of prior austenite deformed at different temperature on the subsequent continuous cooling bainitic transformation has been investigated in an C-Ma-Cr-Ni-Mo plastic die steel. The results show that the prior deformation in low temperature region of austenite retards significantly the bainitic transformation. For the same continuous cooling schedule, as austenite deformed at lower temperature, the quantity of the classical sheaf-like bainite becomes less. The present results show that severe deformation leads to mechanical stabilization of austenite and causes the difficulty of bainitic ferrite propagation into the austenite.展开更多
The ductility map of 304HC stainless was determined by using the Gleeble-1500 dynamic thermal-mechanical simulator. The effect of Cu on the hot ductility of 304HC stainless steel was analyzed and the mathematical mode...The ductility map of 304HC stainless was determined by using the Gleeble-1500 dynamic thermal-mechanical simulator. The effect of Cu on the hot ductility of 304HC stainless steel was analyzed and the mathematical model of resistance to deformation was established. The microstructure, inclusion and fracture surface were studied by using the method of micro structure analysis, scanning, energy spectrum and electron microscope. The results show that Cu has effect on the hot ductility, and the hot ductility of 304HC stainless steel decrease with the increase of content of Cu. The deformation temperature also has much effect on the hot ductility, the suitable deformation temperature are 1100-1200℃. The reason of it is that the Cu rich chemical compounds were precipitated from austenite phase during cooling. The Cu rich chemical compounds are brittle substance such as Cu2S, Cu2O and ε-Cu etc.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
A new multifunction thermo-mechanical simulator was successfully developed. The accuracy of measurement and control is very high through all digital control. More than twenty tests may be fulfilled including tension, ...A new multifunction thermo-mechanical simulator was successfully developed. The accuracy of measurement and control is very high through all digital control. More than twenty tests may be fulfilled including tension, compression, torsion, combination large deformation that meets the study of supersteel, etc. Its performance is introduced in the paper, such as designed ideas, machine structure, man-machine interface, control system, etc.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
An improved smoke-wire flow visualization technique using a large capacitor as the power source was proposed. Electric current discharged from capacitors was used to heat a fine metal wire suspended in the flow field....An improved smoke-wire flow visualization technique using a large capacitor as the power source was proposed. Electric current discharged from capacitors was used to heat a fine metal wire suspended in the flow field. The oil droplets attached to the wire were vaporized and smoke filaments followed the flow motions. A digital camera was used to record the images of the smoke filaments. The actions of discharging and camera shutter were triggered by signals from a microcontroller to ensure the accurate timing. Clear images of the streaklines were captured at a freestream velocity up to 12.9 m/s, much higher than the limits of the existing techniques.展开更多
On the basis of superelement model, Cahn’s transformation kinetics theory and Scheil’s additivity rule, the CCT diagrams and transformation kinetics in low carbon steel were predicted considering both undeformed and...On the basis of superelement model, Cahn’s transformation kinetics theory and Scheil’s additivity rule, the CCT diagrams and transformation kinetics in low carbon steel were predicted considering both undeformed and deformed conditions. The influence of deformation on phase equilibria and transformation incubation period was evaluated quantitatively. The recrystallization kinetics and the evolution of dislocation density were calculated during continuous cooling. The results show deformation considerably shortens transformation incubation period, accelerates transformation kinetics and makes CCT curve shift leftwards. The calculated CCT diagrams and the volume fraction of each phase are in good agreement with measurements.展开更多
文摘The influence of prior austenite deformed at different temperature on the subsequent continuous cooling bainitic transformation has been investigated in an C-Ma-Cr-Ni-Mo plastic die steel. The results show that the prior deformation in low temperature region of austenite retards significantly the bainitic transformation. For the same continuous cooling schedule, as austenite deformed at lower temperature, the quantity of the classical sheaf-like bainite becomes less. The present results show that severe deformation leads to mechanical stabilization of austenite and causes the difficulty of bainitic ferrite propagation into the austenite.
基金This study was financially supported by both the National Natural Science Founda- tion of China (Grant No.59995440)the Natural Science Foundation of Liaoning Province (Grant No.2001101021).
文摘The ductility map of 304HC stainless was determined by using the Gleeble-1500 dynamic thermal-mechanical simulator. The effect of Cu on the hot ductility of 304HC stainless steel was analyzed and the mathematical model of resistance to deformation was established. The microstructure, inclusion and fracture surface were studied by using the method of micro structure analysis, scanning, energy spectrum and electron microscope. The results show that Cu has effect on the hot ductility, and the hot ductility of 304HC stainless steel decrease with the increase of content of Cu. The deformation temperature also has much effect on the hot ductility, the suitable deformation temperature are 1100-1200℃. The reason of it is that the Cu rich chemical compounds were precipitated from austenite phase during cooling. The Cu rich chemical compounds are brittle substance such as Cu2S, Cu2O and ε-Cu etc.
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.50227401)
文摘A new multifunction thermo-mechanical simulator was successfully developed. The accuracy of measurement and control is very high through all digital control. More than twenty tests may be fulfilled including tension, compression, torsion, combination large deformation that meets the study of supersteel, etc. Its performance is introduced in the paper, such as designed ideas, machine structure, man-machine interface, control system, etc.
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.
基金supported by the National Natural Science Foundation of China (91752101 and 11572078)
文摘An improved smoke-wire flow visualization technique using a large capacitor as the power source was proposed. Electric current discharged from capacitors was used to heat a fine metal wire suspended in the flow field. The oil droplets attached to the wire were vaporized and smoke filaments followed the flow motions. A digital camera was used to record the images of the smoke filaments. The actions of discharging and camera shutter were triggered by signals from a microcontroller to ensure the accurate timing. Clear images of the streaklines were captured at a freestream velocity up to 12.9 m/s, much higher than the limits of the existing techniques.
基金National Key Basic Research and Development Programme of China(No.G199806150).
文摘On the basis of superelement model, Cahn’s transformation kinetics theory and Scheil’s additivity rule, the CCT diagrams and transformation kinetics in low carbon steel were predicted considering both undeformed and deformed conditions. The influence of deformation on phase equilibria and transformation incubation period was evaluated quantitatively. The recrystallization kinetics and the evolution of dislocation density were calculated during continuous cooling. The results show deformation considerably shortens transformation incubation period, accelerates transformation kinetics and makes CCT curve shift leftwards. The calculated CCT diagrams and the volume fraction of each phase are in good agreement with measurements.
