Dynamic Behavior Analysis And Dynamic Modeling Of Roll System And Strip Of Hot Tandem Mill

The real economy with manufacturing is the basis for national competitiveness and healthy economic development.Strip product is one of the main forms of the metal products.Taking iron and steel as the example,the strip production accounts for more than 50% of all the production.With the service time increasing of the rolling mill and the upgrading of the products,the dynamic instability inevitably limits the output and quality of the strip products.The rolling process of the strip is a complex nonlinear dynamic production process with the high speed,the heavy load,the high precision and the multi-dimensional coupling effects.The rolling mill system is composed of several subsystems,such as the vertical screwdown system of the rollins mill,the roll system motion system,the main drive system and the moving strip.Its dynamic characteristics are affected by the subsystems of the multi field,multi process,multi-scale and multi physical attributes.Based on the research on the dynamic instability of the first stand mill to the third stand mills(F1～F3)belonging to a hot strip mill in a steel plant,this paper further explores the stability influence mechanism of the mill structure and the dynamic of the moving strips between the stands,establishes the rolling process parameter model under the dynamic instability rolling interface,and then analyzes the complex dynamic influence mechanism of the coupled system consisted by the roll system,the driving system and the moving strip.Based on the analysis of the dynamic characteristics and the vibration instability mechanism of the hot strip mill,this paper studies the moving strip vibration features,the asymmetric vibration of roll system and the torsional vibration of the transmission system.Firstly,according to the vibration phenomena of the rolling mills with different structures in the test process,the causes of vibration instability and the formation mechanism of dynamic characteristics are explored through the test datas analysis.On this basis,the influencing factors of rolling mill dynamic instability are summarized.The rolling mill vibration instability is affected by the coupling dynamic characteristics of rolling mill structure and the moving strip,which can change the stability of the force and energy parameters in the rolling deformation zone.According to the analysis results,the further research is carried out based on the above results.The influence of the moving strip dynamic characteristics directly affects the stability of the strip tension.Therefore,the dynamic characteristics of the moving strip between the stands are necessary to be explored.In this study,the dynamic model of the moving strip between considering the looper supporting effect is established to study the modal values of the moving strip influenced by the strip speed,the looper support stiffness and the tension value on the strip stability.The position and dynamic characteristics of the looper support,the unstable rolling deformation process and the rolling parameters are considered to analyze the influence on the dynamic features of the moving strip.The results show that the change of the strip speed caused by dynamic instability of rolling mill affects the transverse vibration of the strip,which then should change the tension of the strip.According to the dynamic geometric relationship in the rolling deformation zone,the dynamic flow relationship of the rolled piece is analyzed considering the the roll system motion,the moving strip vibration and the driving system torsional vibration.The dynamic rolling process parameter models are established.According to the dynamic parameter modles,the multi-modal dynamic characteristics of the rolling mill system are analyzed,which indicate the instablity rolling process is caused by unsteady factors influencing the strip plastic deformation process.At the same time,through the method of Taylor expansion,the linearization models of the process parameters under the unstable rolling state are established,which are the preparation condition for the further study of the influence of dynamic characteristics of the rolling mill system.According to the test data and the simulation results of the dynamic vibration problems,the main manifestations of the the rolling mill system instability include the cross-swing and translation motion of the roll system,the torsional vibration of the transmission system and the transverse vibration of the moving strip.Considering the dynamic instability of the rolling mill under the dynamic rolling parameters,the multi degree of freedom motion coupling dynamic model of the roll system translation,swinging vibration and torsional vibration of the hot tandem rolling mill is established.The research results show that under the coupling effects of the rolling mill system and the strip motion in the strip rolling production process,the rolling mill system presents different dynamic coupling characteristics such as torsional vibration of the driving system,translation and cross-swing of the roll system and the moving strip vibration.Moreover,the asymmetric structural parameters and moving strip vibration of the rolling mill can aggravate the instability of the rolling process.The dynamic vibration characteristics of the rolling mill system is the premise of studying the active control of dynamic characteristics and the optimal design of process design matching.This study reveals the dynamic characteristics of equipment operation process and the synergy mechanism of the equipment process dynamic characteristics,which can provide a theoretical basis for equipment state judgment,fault analysis and prediction.The application of the unsteady rolling dynamic research is also the basis for the design and operation maintenance of the field equipment,which can promote the intellectualization of the strip production process.