Finite Element Simulation And Experimental Verification Of Roll System Stability Of Four-high Mill

Steel is still the most widely used material of the 21st century.Rolling is the main method of production of iron and steel materials and Non-ferrous metal in China.Rolling mill equipment is an indispensable and important equipment in China's iron and steel industry.It represents the overall progress and development level of a large country's iron and steel industry.Four-high mill is the basic structure of all kinds of modern plate and strip mills,and it is also the most common mill.Modern rolling mill equipment is marching towards large heavy load,precision,high speed and short flow.Since modern times,a large number of modern rolling mills have been introduced or made in China,and the equipment level of rolling mills has been improved significantly.However,a large number of short life and burning loss of thrust bearings or tapered roller bearings also occurred in the actual industrial production process,restricting the large reduction and high-speed production,the annual loss of up to one billion yuan.The offset is generally set to ensure the parallel positioning between rolls and the stability of the four-high mill rolls to prevent the cross between rolls,which has become the main method for the parallel positioning of four-high mill rolls.The roll system of the four-high mill which appeared one after another in modern times set offset,but the mechanism of offset could not be ensured,and the dynamic cross behavior between rolls occurred frequently,causing excessive axial force to damage thrust bearings or tapered roller bearings or to create a rolling branch reaction bias destroys flatness control stability.This paper discusses the accuracy of the Rolling Friction Coefficient and the radius of the friction circle in the calculation formula of the critical offset of the roller in the design theory of the rolling mill.The influence of the roll bending force,the friction of the roll system and the transmission system on the stability of the roll system are analyzed.First of all,on the basis of previous studies,the force state of roll system is analyzed,the theory of offset design of rolling mill is expounded,and the variables in the formula of offset calculation are analyzed: The factors affecting the rolling friction coefficient,the rationality of the value of the friction circle radius,the influence of the roll bending force,the reduction system and the transmission system on the stability of the roll system.The results show that,in the actual rolling process,due to the friction between the screwdown system and the back-up roll,and the friction between the hydraulic bending roll system and the working roll housing,when the roll is installed,the back-up Roll Chock with high quality and high friction can be pressed against the frame in advance,and a suitable gap is left between the back-up Roll Chock and the frame so that the offset set can realize the stability of the roll system.But setting offset in no-load state can not realize the stability of roll system by its own weight.In addition,rolling process with different rolling force and different roll diameter was simulated by finite element software ABAQUS.Rolling Friction Coefficient and friction circle radius were calculated and compared with theoretical results.The results show that the value of rolling friction coefficient m is concentrated between 0.1 and 0.3,which is consistent with the value of rolling friction coefficient m=0.1 to 0.3 given by the calculation formula of offset.It is found that the value of rolling friction coefficient m increases with the increase of rolling force,it decreases with the increase of roll diameter.By analyzing the horizontal force between the work roll and the bearing seat on the operating side and the transmission side,it is shown that the influence of the transmission system on the stability of the roll system can be neglected because of the small angle of the two axes of the universal joint in the finishing rolling of 1580 four-high mill.But when the mill is used for rough rolling,the horizontal force between the working roll and the bearing seat on the operating side and the driving side is not equal due to the large angle of the two axes of the universal joint,so the influence of the driving system on the stability of the roll system can not be ignored.