Multi Modal Coupling Vibration Analysis Of Hot Strip Mill Considering Clearance

The vibration of the rolling mill not only affect the quality of the plate,but also cause serious damage to the equipment,for which scholars at home and abroad have done a lot of work.The gap between the work roll bearing base and the stand is one of the main causes of the horizontal vibration of the rolling mill,which will not only aggravate the horizontal vibration of the work roll,but also cause the vertical vibration of the rolling mill.Therefore,it is necessary to establish a vertical-horizontal vibration coupling model to study the influence of clearance on rolling mill vibration.In this paper,1580 hot continuous rolling in a factory was taken as the research object,and the gap between the work roll bearing base and the frame was considered.With the help of finite element software,a simplified mass-spring model of hot rolling mill was established.Through dynamic analysis,the influence of clearance on rolling mill vibration was explored,which provided theoretical support for restraining rolling mill vibration.Firstly,taking F2 rolling mill as the research object,the frame was separated on the basis of the simplified mass-spring model of hot rolling mill,the frame profile was built by beam element,and the simplified mass-spring model of single stand rolling mill was established.The influence of clearance on the dynamic characteristics of rolling mill system was studied by modal analysis.The results showed that the clearance leads to the increase of low-order frequency and vibration of the rolling mill system.The measured dominant frequencies of 32 Hz,42hz and 79 hz are found in modal analysis.Especially in 79 Hz,the work roll seriously deviated,resulting in roll gap fluctuation.This directly affected the quality of the strip and caused the roll body to produce vibration marks,which belongs to the key mode.Secondly,taking F1 and F2 rolling mills as the research object,on the basis of the mass-spring simplified model of hot rolling mill,the rolling piece and tension roll model are added,and a simplified model of two-stand hot continuous rolling considering clearance was established to simulate the dynamic rolling process of hot rolling mill.The results showed that the clearance has a great influence on the vibration of the rolling mill and is the main factor causing the horizontal vibration of the work roll.At the same time,the simulation results showed that when the clearance is reduced,the horizontal acceleration of the work roll decreases obviously,the attenuation speed increases,and the vibration energy decreases,so reducing the clearance can restrain the horizontal vibration of the rolling mill.Finally,based on the simplified model of two-stand hot strip mill,F3 mill was added to establish a simplified model of multi-stand hot strip mill with variable gap,which was used to explore the vibration law of hot strip mill under the action of tension.The results show that the work roll is inclined to the inlet side under tension,which restricts the horizontal displacement.Therefore,changing the clearance has little influence on the vibration of the stable rolling stage,while the influence of changing the clearance on the horizontal vibration is mainly reflected in the steel biting stage of the hot strip mill.