Research On Contact Dynamic Response Of The Process Of Tandem Rolling Mill Based On Mechanism Of The Thermo-mechanical Coupling Friction

With the development and progress of metallurgical industry technology and industry,the requirements and manufacturing standards of seamless steel tubes are becoming more and more severe.However,in the process of hot tandem rolling of seamless steel tubes,vibration is inevitable in the tandem rolling mill,and the vibration of the tandem rolling mill will lead to a serious decrease in the surface quality and dimensional accuracy of seamless steel tubes.In order to produce seamless steel tubes with high precision and high quality,it is necessary to analyze and control the dynamic characteristics and vibration response of tandem rolling mill.This paper takes the five-stand tandem rolling mill of a steel pipe company as the research object and mainly analyzes the influence factors of rolling force and its influence on the dynamic response of the tandem rolling mill.Therefore,it is necessary to establish a precise rolling force calculation model to study the dynamic change of rolling force in the whole rolling process,and then analyze the influence of rolling force on dynamic characteristics and vibration response of tandem rolling mill.Secondly,the friction and contact stiffness between the roll and the tube in the rolling contact region have a direct impact on the mechanical properties and dynamic characteristics of the tandem rolling mill.It is also necessary to study the stiffness of the tandem rolling mill and the friction characteristics of the rolling region.In this paper,the shortcomings of the commonly used nonlinear polynomial friction coefficient model in estimating the friction coefficient of rolling contact region are firstly discussed.On this basis,the relationship between friction coefficient and surface roughness of the roll,surface roughness of the tube,rolling temperature,rotation speed of the roll and movement speed of the tube are analyzed,and a new calculation model of friction coefficient is put forward.Then the parameters in the calculation model are optimized according to the actual rolling process data and the results show that the calculated results of the optimized model are closer to the actual measurement results and meet the requirements of actual production.The mechanical model of rolling process is established and the distribution and calculation method of contact stiffness in rolling contact region are studied.The finite element method is used to calculate the rolling force under different rolling reduction and friction coefficient,and the relation of contact stiffness with rolling force and friction coefficient is discussed.The results show that the contact stiffness increases with the increase of rolling force and friction coefficient.The oil film stiffness of sliding bearing of the tandem rolling mill is studied by theoretical analysis and analytical method and analyze the variation of oil film stiffness with the oil film clearance ratio by a concrete example.The results show that the stiffness values in the three directions ofK_{x x}?K_{y x}andK_yyy decrease with the increase of the oil film clearance ratio.Therein K_yx andK_yy decrease quickly when the clearance ratio is small and the decreasing speed becomes slower with the increase of the clearance ratio;The decrease speed of K_{x x}is more gentle;K_xy increases with the increase of the oil film clearance ratio,and its overall change is more gentle who is negative when the clearance ratio is small.Based on the shortcomings of the existing rolling force calculation and considering the crushing strength of the tube in the reduced-diameter region,the calculation method and model of the rolling force based on the dimension and rolling parameters of the tube are proposed and calculate the rolling force at different roll speeds with a concrete example.And the nonlinear finite element software ABAQUS is used to simulate the rolling process when the rotational speed of the roll is 2.501 rad/s,and the dynamic changing process of rolling force was obtained.The results show that the rolling force is a fluctuating force,and the rolling force increases rapidly with the tube being pulled into the gap;the range of variation of the rolling force is small after entering the stable rolling;and the rolling force rapidly drops to zero with the end of the rolling process.Taking the simulated rolling force as the input load,the vertical vibration response of the roll who is the key parts of the tandem rolling mill is analyzed by using the dynamic method based on the finite element model of the roll of the PQF?premium quality finishing?tandem rolling mill.The dynamic response curve of roll under rolling condition is obtained,and the influence of rolling force on the vertical vibration of the roll and the tandem rolling mill is studied.The results show that the larger the fluctuation range of rolling force is,the greater the dynamic response of tandem rolling mill is.Thus,it provides technical support for rolling schedule formulation.Finally,the rolling force of the rolling process is tested and obtain the rolling force test data in the actual production process,and compare it with the theoretical calculation results and the simulation results.The results show that the relative error between the theoretical calculation value and the measured mean value of rolling force is less than 10%,and the rolling force curve which is simulated is the same as the actual rolling force curve and the maximum error is less than 15%,which is a reasonable error range.Therefore,the practicability of the calculation model and the reliability of the numerical simulation results are verified,which provides a reliable basis for the design,manufacture and use of the tandem rolling mill.