Research on Single-Side Long Edge of Hot Rolled Strip Caused by Asymmetrical Stiffness of Mill Stand

To analyze and solve the problem of single-side long edge of hot rolled strip in certain domestic factory, the asymmetrical deformation of rolls and strip in asymmetrical stiffness mill stand based on slit beam model, the strip profile and rolling force distribution at the exit of asymmetric stiffness stand mill were calculated using influence function method. Considering the character of in-site equipment and technology, a scheme of adjusting load distribution in finishing mill was made and the experiment was applied. Comparison of strip profile between new load distribution and the old one shows that the method can solve single-side long edge problem well.

Application of distributed model predictive control based on neighborhood optimization in gauge-looper integrated system of tandem hot rolling

To solve the coupling relationship between the strip automatic gauge control and the looper control in traditional control strategy of tandem hot rolling,a distributed model predictive control(DMPC)strategy for the tandem hot rolling was explored,and a series of simulation experiments were carried out.Firstly,based on the state space analysis method,the multivariable dynamic transition process of hot strip rolling was studied,and the state space model of a gauge-looper integrated system in tandem hot rolling was established.Secondly,DMPC strategy based on neighborhood optimization was proposed,which fully considered the coupling relationship in this integrated system.Finally,a series of experiments simulating disturbances and emergency situations were completed with actual rolling data.The experimental results showed that the proposed DMPC control strategy had better performance compared with the traditional proportional-integral control and centralized model predictive control,which is applicable for the gauge-looper integrated system.

Optimization of Temperature and Force Adaptation Algorithm in Hot Strip Mill

In the hot strip rolling control system,the temperature distribution and deformation resistance are the main parameters affecting prediction of rolling force.In order to improve the model prediction precision,an optimization algorithm based on objective function was put forward,in which the penalty function index was adopted.During the adaptation process,the temperature distribution and deformation resistance were taken as the optimized parameters,and the Nelder-Mead simplex algorithm was used to search the optimal solution of the objective function.Furthermore,the temperature adaptation and force adaptation were solved simultaneously.Application results show that the method can improve the accuracy of the rolling force model obviously,and it can meet the demand of the industrial production and has a good application prospect.

Modeling and Analysis of Interstand Tension Control in 6-high Tandem Cold Rolling Mill

The interstand tension control is one of the most important ways to meet tight tolerances for strip product quality during tandem cold rolling process.Using coordinate analysis and parabolic approximation for the mass flow balance principle,the strip velocities eliminating the use of forward slips and backward slips were calculated.In order to reduce the effect of roll eccentricity on the tension measurement,a filter based on bilinear transformation was designed.Applying a first-order Taylor series approximation,the transfer function matrix model of interstand tension stress was derived.The actual measurements on-site and the final calculation results showed that the established model had high calculation accuracy and was beneficial for interstand tension control of tandem cold rolling process.

Data-based flatness prediction and optimization in tandem cold rolling

In cold rolling process,the flatness actuator efficiency is the basis of the flatness control system.The precision of flatness is determined by the setpoints of flatness actuators.In the presence of modeling uncertainties and unmodeled nonlinearities in rolling process,it is difficult to obtain efficiency factors and setpoints of flatness actuators accurately.Based on the production data,a method to obtain the flatness actuator efficiency by using partial least square(PLS)combined with orthogonal signal correction(OSC)was adopted.Compared with the experiential method and principal component analysis method,the OSC-PLS method shows superior performance in obtaining the flatness actuator efficiency factors at the last stand.Furthermore,kernel partial least square combined with artificial neural network(KPLS-ANN)was proposed to predict the flatness values and optimize the setpoints of flatness actuators.Compared with KPLS or ANN,KPLS-ANN shows the best predictive ability.The root mean square error,mean absolute error and mean absolute percentage error are 0.51 IU,0.34 IU and 0.09,respectively.After the setpoints of flatness actuators are optimized,KPLS-ANN shows better optimization ability.The result in an average flatness standard deviation is 2.22 IU,while the unoptimized value is 4.10 IU.

Analysis of Hot Tandem Rolling Force with Logarithmic Velocity Field and EA Yield Criterion

In order to analyze the hot tandem rolling force,a new logarithmic velocity field is proposed.Using the field and linear EA(equal area)yield criterion,the plastic deformation power for plate rolling is analyzed,and the friction power is obtained based on the co-line vector inner product method.Then analytical solution of plate rolling power functional is obtained.Finally,by minimizing the power functional,the rolling force and torque are received.Compared with those measured ones in hot tandem rolling on-line,the calculated rolling forces are in good agreement with the actual measured ones since the maximum error is less than 12%.Moreover,the effects of various rolling conditions such as thickness reduction,friction factor and shape factor,upon separating force,location of neutral angle,and stress state coefficient are discussed systematically.

Microstructure and Mechanical Properties of Semi-continuous Equal-channel Angular Extruded Interstitial-free Steel

An innovative method called semi-continuous equal-channel angular extrusion(SC-ECAE)has been developed to produce ultrafine grained steel by inducing severe plastic deformation.In contrast to the external forces that are exerted on specimens in traditional ECAE,the driving forces are applied on the dies in the novel SC-EACE process.Commercial interstitial-free steel sheets with width of 160 mm and thickness of 2 mm were processed repeatedly to various passes at room temperature using this method.The microstructural evolution was characterized using high-resolution electron backscatter diffraction(EBSD),and the mechanical properties were investigated by tensile testing.The EBSD images indicated that the fraction of high-angle boundaries(HABs)began to increase gradually after four passes;after six passes,elongated HAB structures with nearly submicron-scale average spacings were formed.The tensile testing results showed that strengthening was accompanied by a decrease in tensile ductility,but no significant anisotropy was observed.After 10 passes,a final HAB fraction of about 90% and an overall grain size of 0.55μm,yield strength of 638.7 MPa,an ultimate tensile strength(UTS)of 710.3 MPa,and a total elongation of 12.0% were obtained.

Simplified Weighted Velocity Field for Prediction of Hot Strip Rolling Force by Taking into Account Flattening of Rolls

The weighted velocity field was simplified for analysis of hot strip rolling.Using the field and GM(geometric midline)yield criterion,the deformation power,friction power and shear power were obtained respectively.Summing the partial power contributions,the total deformation power for strip rolling was presented.Then,by minimizing the power function,the rolling force was obtained;meanwhile,considering the effect of roll elastic flattening,iterative calculation of the roll radius was carried out until the radius was convergent.On-line data were compared with the calculated results to verify the model accuracy.It was indicated that the calculated rolling forces were basically in agreement with the measured ones since the maximum error was less than 10.0%.Moreover,the effects of various rolling conditions such as thickness reduction,friction factor and shape factor,upon separating force,location of neutral angle,and stress state coefficient were discussed systematically.