The ductile-to-brittle transition temperature(DBTT)of high strength steels can be optimized by tailoring microstructure and crystallographic orientation characteristics,where the start cooling temperature plays a key ...The ductile-to-brittle transition temperature(DBTT)of high strength steels can be optimized by tailoring microstructure and crystallographic orientation characteristics,where the start cooling temperature plays a key role.In this work,X70 steels with different start cooling temperatures were prepared through thermo-mechanical control process.The quasi-polygonal ferrite(QF),granular bainite(GB),bainitic ferrite(BF)and martensite-austenite constituents were formed at the start cooling temperatures of 780℃(C1),740℃(C2)and 700℃(C3).As start cooling temperature decreased,the amount of GB decreased,the microstructure of QF and BF increased.Microstructure characteristics of the three samples,such as high-angle grain boundaries(HAGBs),MA constituents and crystallographic orientation,also varied with the start cooling temperatures.C2 sample had the lowest DBTT value(−86℃)for its highest fraction of HAGBs,highest content of<110>oriented grains and lowest content of<001>oriented grains parallel to TD.The high density of{332}<113>and low density of rotated cube{001}<110>textures also contributed to the best impact toughness of C2 sample.In addition,a modified model was used in this paper to quantitatively predict the approximate DBTT value of steels.展开更多
A semi-parametric single-index model based approach was proposed for prediction of mechanical properties of hot rolled strip. Based on industrial production data, a semi-parametric single-index model was developed by ...A semi-parametric single-index model based approach was proposed for prediction of mechanical properties of hot rolled strip. Based on industrial production data, a semi-parametric single-index model was developed by choo-sing the appropriate kernel function and window width to predict the yield strength, tensile strength and elongation. When data samples are limited, compared with regression method and neural network method, the prediction results show that the semi-parametric single-index model based method is more adaptive and the prediction performance is superior to those by both regression and neural network methods.展开更多
Hot deformation behavior of GCr15（ASTM 52100） steel was investigated using single-hit compression tests on Gleeble-1500 simulator at the temperature range of 850-1 100 ℃ and strain rate range of 0.1-10 s-1.The flow...Hot deformation behavior of GCr15（ASTM 52100） steel was investigated using single-hit compression tests on Gleeble-1500 simulator at the temperature range of 850-1 100 ℃ and strain rate range of 0.1-10 s-1.The flow stress constitutive equation of GCr15 steel during hot deformation was determined by stress-strain curves analysis on the basis of the hyperbolic sine equation.And the models of dynamic recrystallization fraction and dynamic recrystallization grain size of GCr15 steel were established by the measured curves and microstructure observation in different experimental conditions.The mean activation energy and the time exponent of dynamic recrystallization kinetics equation in the range of experimental conditions were determined to be 356.2 kJ/mol and 2.12,respectively.Meanwhile,the flow stress model was also established by the method of allocating flow stress curve with three main stress values,the saturation stress,the steady state stress and the stress when strain is 0.1.The flow stress curves predicted by the developed models under different deformation conditions are in good agreements with the measured ones.展开更多
基金Project(2018XK2301) supported by the Change-Zhu-Tan National Independent Innavation Demonstration Zone Special Program,China。
文摘The ductile-to-brittle transition temperature(DBTT)of high strength steels can be optimized by tailoring microstructure and crystallographic orientation characteristics,where the start cooling temperature plays a key role.In this work,X70 steels with different start cooling temperatures were prepared through thermo-mechanical control process.The quasi-polygonal ferrite(QF),granular bainite(GB),bainitic ferrite(BF)and martensite-austenite constituents were formed at the start cooling temperatures of 780℃(C1),740℃(C2)and 700℃(C3).As start cooling temperature decreased,the amount of GB decreased,the microstructure of QF and BF increased.Microstructure characteristics of the three samples,such as high-angle grain boundaries(HAGBs),MA constituents and crystallographic orientation,also varied with the start cooling temperatures.C2 sample had the lowest DBTT value(−86℃)for its highest fraction of HAGBs,highest content of<110>oriented grains and lowest content of<001>oriented grains parallel to TD.The high density of{332}<113>and low density of rotated cube{001}<110>textures also contributed to the best impact toughness of C2 sample.In addition,a modified model was used in this paper to quantitatively predict the approximate DBTT value of steels.
基金Item Sponsored by National Key Technology Research and Development Program of China (2006BAE03A09)National Natural Science Foundation of China ( 61203219 )
文摘A semi-parametric single-index model based approach was proposed for prediction of mechanical properties of hot rolled strip. Based on industrial production data, a semi-parametric single-index model was developed by choo-sing the appropriate kernel function and window width to predict the yield strength, tensile strength and elongation. When data samples are limited, compared with regression method and neural network method, the prediction results show that the semi-parametric single-index model based method is more adaptive and the prediction performance is superior to those by both regression and neural network methods.
基金Item Sponsored by National Project of Scientific and Technical Supporting Program in 11th Five-Year Plan of China(2006BAE03A08,2006BAE03A04)
文摘Hot deformation behavior of GCr15（ASTM 52100） steel was investigated using single-hit compression tests on Gleeble-1500 simulator at the temperature range of 850-1 100 ℃ and strain rate range of 0.1-10 s-1.The flow stress constitutive equation of GCr15 steel during hot deformation was determined by stress-strain curves analysis on the basis of the hyperbolic sine equation.And the models of dynamic recrystallization fraction and dynamic recrystallization grain size of GCr15 steel were established by the measured curves and microstructure observation in different experimental conditions.The mean activation energy and the time exponent of dynamic recrystallization kinetics equation in the range of experimental conditions were determined to be 356.2 kJ/mol and 2.12,respectively.Meanwhile,the flow stress model was also established by the method of allocating flow stress curve with three main stress values,the saturation stress,the steady state stress and the stress when strain is 0.1.The flow stress curves predicted by the developed models under different deformation conditions are in good agreements with the measured ones.
