In order to meet the severe requirements of market and reduce production costs of high quality steels,advanced run-out table cooling based on ultra fast cooling(UFC) and laminar cooling(LC) was proposed and applied to...In order to meet the severe requirements of market and reduce production costs of high quality steels,advanced run-out table cooling based on ultra fast cooling(UFC) and laminar cooling(LC) was proposed and applied to industrial production.Cooling mechanism of UFC and LC was introduced first,and then the control system and control models were described.By using UFC and LC,low-cost Q345B strips had been produced in a large scale,and industrial trials of producing low-cost dual phase strips were completed successfully.Application results show that the ultra fast cooling is uniform along the strip width and length,and does not affect the flatness of strips.The run-out table cooling system runs stably with a high precision,and makes it possible for the user to develop more high quality steels with low costs.展开更多
Mathematical models are been proposed to simulate the thermal and metallurgical behaviors of the strip occtLrring on the run-out table （ROT） in a hot strip mill. A variational method is utilized for the discretizati...Mathematical models are been proposed to simulate the thermal and metallurgical behaviors of the strip occtLrring on the run-out table （ROT） in a hot strip mill. A variational method is utilized for the discretization of the governing transient conduction-convection equation, with heat transfer coefficients adaptively determined by the actual mill data. To consider the thermal effect of phase transformation during cooling, a constitutive equation for describing austenite decomposition kinetics of steel in air and water cooling zones is coupled with the heat transfer model. As the basic required inputs in the numerical simulations, thermal material properties are experimentally measured for three carbon steels and the least squares method is used to statistically derive regression models for the properties, including specific heat and thermal conductivity. The numerical simulation and experimental results show that the setup accuracy of the temperature prediction system of ROT is effectively improved.展开更多
Non-uniformity of temperature distribution across strip width direction is the ultimate reason why the flatness defect occurs on the strip after cooling process although the strip is flat at the exit of finishing mill...Non-uniformity of temperature distribution across strip width direction is the ultimate reason why the flatness defect occurs on the strip after cooling process although the strip is flat at the exit of finishing mill.One thermal , microstructural and mechanical coupling analysis model for predicting flatness change of steel strip during the run-out table cooling process was established using ABAQUS finite element software.K Esaka phase transformation kinetics model was employed to calculate the phase transformation , and coupled with temperature calculation using the user subroutine program HETVAL.Elasto-plasticity constitutive equations of steel material , in which conventional elastic and plastic strains , thermal strain , phase transformation strain and transformation induced plastic strain were considered , were derived and programmed in the user subroutine program UMAT.The conclusion that flatness of steel strip will develop to edge wave defect under the functions of the differential thermal and microstructural behaviors across strip width during the run-out table cooling procedure was acquired through the analysis results of this model.Calculation results of this analysis model agree well with the actual measurements and observation.展开更多
Taking a published natural population life table of rice leaf roller, Cnaphalocrocis medinalis （Lepidoptera： Pyralidae）, as an example, we estimated the population trend index, I, via re-sampling methods （jackknif...Taking a published natural population life table of rice leaf roller, Cnaphalocrocis medinalis （Lepidoptera： Pyralidae）, as an example, we estimated the population trend index, I, via re-sampling methods （jackknife and bootstrap）, determined its statistical properties and illustrated the application of these methods in determining the control effectiveness of bio- agents and chemical insecticides. Depending on the simulation outputs, the smoothed distribution pattern of the estimates of I by delete-1 jackknife is visually distinguishable from the normal density, but the smoothed pattern produced by delete-d jackknife, and logarithm- transformed smoothed patterns produced by both empirical and parametric bootstraps, matched well the corresponding normal density. Thus, the estimates of I produced by delete-1 jackknife were not used to determine the suppressive effect of wasps and insecticides. The 95% percent confidence intervals or the narrowest 95 percentiles and Z-test criterion were employed to compare the effectiveness of Trichogrammajaponicum Ashmead and insecticides （powder, 1.5% mevinphos ＋ 3% alpha-hexachloro cyclohexane） against the rice leaf roller based on the estimates of I produced by delete-d jackknife and bootstrap techniques. At a = 0.05 level, there were statistical differences between wasp treatment and control, and between wasp and insecticide treatments, if the normality is ensured, or by the narrowest 95 percentiles. However, there is still no difference between insecticide treatment and control. By Z-test criterion, wasp treatment is better than control and insecticide treatment with P-value 〈 0.01. Insecticide treatment is similar to control with P-value 〉 0.2 indicating that 95% confidence intervals procedure is more conservative. Although similar conclusions may be drawn by re-sampling techniques, such as the delta method, about the suppressive effect of trichogramma and insecticides, the normality of the estimates can be checked and guaranteed, and the correlation among sequential life stages of rice leaf roller is also considered in the estimation. Judged by the P-values from Z-test, the delta method is more conservative.展开更多
Solution heat treatment combined with a rapid quenching operation,which can effectively suppress the decomposition of the supersaturated solid solution in the matrix,is a vital process step for producing large precipi...Solution heat treatment combined with a rapid quenching operation,which can effectively suppress the decomposition of the supersaturated solid solution in the matrix,is a vital process step for producing large precipitation-hardenable aluminum alloy thick plates with desired properties.However,large thermal gradients that result from the non-uniform cooling rates during quenching usually give rise to severely heterogeneous distributions of residual stress in thick plates.The presence of roller-hearth furnaces makes it possible to achieve continuous and integral solution-quenching treatment for large aluminum alloy thick plates.The conveyor velocity of the roller table in the roller-hearth furnace is a key parameter but its influence is less addressed in literature.Thus,in the present work,finite element thermal-mechanical simulations taking into account different conveyor velocities of the roller table were employed to predict the temperature variations and residual stress distributions in large aluminum alloy thick plates during quenching process.Four different velocities were utilized in the simulations.The modeling results showed that the temperature evolutions as well as the distributions of the induced internal stresses in those large thick plates during quenching treatments were indeed affected by the conveyor velocities.Slower velocities were demonstrated to be favorable for gaining thick plates being with relatively homogeneous residual stress distributions in the plates.展开更多
基金Project(50634030) supported by the National Natural Science Foundation of China
文摘In order to meet the severe requirements of market and reduce production costs of high quality steels,advanced run-out table cooling based on ultra fast cooling(UFC) and laminar cooling(LC) was proposed and applied to industrial production.Cooling mechanism of UFC and LC was introduced first,and then the control system and control models were described.By using UFC and LC,low-cost Q345B strips had been produced in a large scale,and industrial trials of producing low-cost dual phase strips were completed successfully.Application results show that the ultra fast cooling is uniform along the strip width and length,and does not affect the flatness of strips.The run-out table cooling system runs stably with a high precision,and makes it possible for the user to develop more high quality steels with low costs.
基金the National Basic Research Program (973) of China (No. 2006CB705400)the National Natural Science Foundation of China (No. 50575200)
文摘Mathematical models are been proposed to simulate the thermal and metallurgical behaviors of the strip occtLrring on the run-out table （ROT） in a hot strip mill. A variational method is utilized for the discretization of the governing transient conduction-convection equation, with heat transfer coefficients adaptively determined by the actual mill data. To consider the thermal effect of phase transformation during cooling, a constitutive equation for describing austenite decomposition kinetics of steel in air and water cooling zones is coupled with the heat transfer model. As the basic required inputs in the numerical simulations, thermal material properties are experimentally measured for three carbon steels and the least squares method is used to statistically derive regression models for the properties, including specific heat and thermal conductivity. The numerical simulation and experimental results show that the setup accuracy of the temperature prediction system of ROT is effectively improved.
文摘Non-uniformity of temperature distribution across strip width direction is the ultimate reason why the flatness defect occurs on the strip after cooling process although the strip is flat at the exit of finishing mill.One thermal , microstructural and mechanical coupling analysis model for predicting flatness change of steel strip during the run-out table cooling process was established using ABAQUS finite element software.K Esaka phase transformation kinetics model was employed to calculate the phase transformation , and coupled with temperature calculation using the user subroutine program HETVAL.Elasto-plasticity constitutive equations of steel material , in which conventional elastic and plastic strains , thermal strain , phase transformation strain and transformation induced plastic strain were considered , were derived and programmed in the user subroutine program UMAT.The conclusion that flatness of steel strip will develop to edge wave defect under the functions of the differential thermal and microstructural behaviors across strip width during the run-out table cooling procedure was acquired through the analysis results of this model.Calculation results of this analysis model agree well with the actual measurements and observation.
文摘Taking a published natural population life table of rice leaf roller, Cnaphalocrocis medinalis （Lepidoptera： Pyralidae）, as an example, we estimated the population trend index, I, via re-sampling methods （jackknife and bootstrap）, determined its statistical properties and illustrated the application of these methods in determining the control effectiveness of bio- agents and chemical insecticides. Depending on the simulation outputs, the smoothed distribution pattern of the estimates of I by delete-1 jackknife is visually distinguishable from the normal density, but the smoothed pattern produced by delete-d jackknife, and logarithm- transformed smoothed patterns produced by both empirical and parametric bootstraps, matched well the corresponding normal density. Thus, the estimates of I produced by delete-1 jackknife were not used to determine the suppressive effect of wasps and insecticides. The 95% percent confidence intervals or the narrowest 95 percentiles and Z-test criterion were employed to compare the effectiveness of Trichogrammajaponicum Ashmead and insecticides （powder, 1.5% mevinphos ＋ 3% alpha-hexachloro cyclohexane） against the rice leaf roller based on the estimates of I produced by delete-d jackknife and bootstrap techniques. At a = 0.05 level, there were statistical differences between wasp treatment and control, and between wasp and insecticide treatments, if the normality is ensured, or by the narrowest 95 percentiles. However, there is still no difference between insecticide treatment and control. By Z-test criterion, wasp treatment is better than control and insecticide treatment with P-value 〈 0.01. Insecticide treatment is similar to control with P-value 〉 0.2 indicating that 95% confidence intervals procedure is more conservative. Although similar conclusions may be drawn by re-sampling techniques, such as the delta method, about the suppressive effect of trichogramma and insecticides, the normality of the estimates can be checked and guaranteed, and the correlation among sequential life stages of rice leaf roller is also considered in the estimation. Judged by the P-values from Z-test, the delta method is more conservative.
基金National Program on Key Research and Development Project of China(No.2020YFF0218202)Innovation Fund Project of GRINM Group Co.,Ltd。
文摘Solution heat treatment combined with a rapid quenching operation,which can effectively suppress the decomposition of the supersaturated solid solution in the matrix,is a vital process step for producing large precipitation-hardenable aluminum alloy thick plates with desired properties.However,large thermal gradients that result from the non-uniform cooling rates during quenching usually give rise to severely heterogeneous distributions of residual stress in thick plates.The presence of roller-hearth furnaces makes it possible to achieve continuous and integral solution-quenching treatment for large aluminum alloy thick plates.The conveyor velocity of the roller table in the roller-hearth furnace is a key parameter but its influence is less addressed in literature.Thus,in the present work,finite element thermal-mechanical simulations taking into account different conveyor velocities of the roller table were employed to predict the temperature variations and residual stress distributions in large aluminum alloy thick plates during quenching process.Four different velocities were utilized in the simulations.The modeling results showed that the temperature evolutions as well as the distributions of the induced internal stresses in those large thick plates during quenching treatments were indeed affected by the conveyor velocities.Slower velocities were demonstrated to be favorable for gaining thick plates being with relatively homogeneous residual stress distributions in the plates.
