Calculation Theory And Simulation Analysis On Flatness Control Of Four-High Cold Rolling Mill Based On Dynamic Friction Of Roll Gap

In recent years,The rolled strip products have been widely used in the automotive industry,military products,aerospace and other modern industries,and the demand for the surface quality of rolled strip products is also getting higher and higher.This paper takes a certain type of four-high reversible strip cold rolling mill as the research object,In view of the flatness quality problems in the process of cold rolling of plate and strip,The friction coefficient model based on the dynamic friction of the roll and the mathematical model of the elastic deformation of the roll system are established,The influence of the dynamic friction of roll gap on the flatness and the change of the plate convexity is studied and analyzed,and the cold rolling process of strip is simulated and analyzed by the finite element software,Finally,the accuracy and reliability of the proposed mathematical model and the finite element model are verified by the measured data of the rolling process of the Four-high cold rolling mill.The main contents of this thesis include:(1)The calculation of flatness control based on the research of basic control theory of plate shape,this paper systematically analyzes the common form of plate defect and the main cause of plate shape defect in plate and strip rolling process,It also analyzes the influence between the convexity and flatness of the relationship,the essence of shape control is to realize the control of the crown of plate and strip,The calculation method of the elastic deformation of the roll system and the calculation method of the shape control based on the dynamic friction of the roll gap are emphasized.(2)The rolling process of the strip strip considering the roll gap friction and the method of determining the friction state of the roll gap in the rolling process are introduced,Then,the mathematical model of the roll gap friction coefficient and the elastic deformation of the roll system are established.The effects of strip width and roll bending force on the elastic deformation of roll system under different friction conditions in strip rolling process are analyzed.In the process of solving the mathematical model of the elastic deformation of the roll system,in order to facilitate the calculation,it is assumed that the rolling process of the roll system does not cause additional deflection.On this basis,the plate shape control model is solved and analyzed,and the analysis results are expressed in the form of charts.(3)Based on the mathematical model established in the third chapter,a finite element model of strip shape control considering roll gap friction is established.UsingLS-DYNA module in ANSYS to establish the finite element model.The stress and strain of work roll and back-up roll under different frictional conditions were simulated and analyzed.Then the influence of roll system elastic deformation on plate shape under different friction conditions is further analyzed,The stress distribution and strain distribution of different friction condition in shape,but also to analyze other factors that influence the quality of different shaped plate.(4)Taking four-high reversing cold rolling mill in a domestic enterprise as the test object,the mathematical model and the finite element model established in this paper are compared with the actual test data and the simulation data to verify the established model,The influence of roll friction coefficient,strip width and rolling force on the crown of plate and strip was studied by obtaining the measured data of crown profile.Measured data and finite element simulation results were compared and analyzed.It is concluded that the law of variation is basically consistent,and the feasibility and accuracy of the established model are further verified,which has a certain guiding significance for the actual production of rolling.