The Influence Of Oxide Film Peeling Of High-speed Steel Roll On Vertical Vibration Of Rolling Mill

In the hot rolling process,a layer of oxide film is formed on the surface of high-speed steel roll,which can reduce roll wear and reduce the impact between roll and strip,and has a very positive effect on the rolling process.In the actual production process,the oxide film peeling causes product quality decline and equipment operation instability,which seriously restricts the application level of high-speed steel roll in strip hot rolling process.Therefore,this paper conducts an in-depth study on the influence of oxide film peeling of high-speed steel roll on vertical vibration of rolling mill.Firstly,the vertical vibration of F2 mill in 1780 mm finishing mill is monitored.The engineering test data is analyzed,and the oxide film peeling state during the use of highspeed steel rolls and the characteristics of vertical vibration of rolling mill system under different oxide film peeling states are summarized.The influence of rolling interface friction on vertical vibration of rolling mill is analyzed emphatically.It is concluded that two kinds of oxide film spalling states which limit the application of high-speed steel roll are periodic spalling and complete spalling.Secondly,in view of the periodic spalling and complete spalling of the oxide film on the roll,the surface roughness of the roll is recorded on the spot,and the friction coefficient model of the rolling interface under two kinds of oxide film spalling states is established.The effect of two kinds of oxide film spalling states on the friction coefficient of rolling interface is simulated.The results show that the friction coefficient of the rolling interface is in a harmonic wave along the circumferential direction of the roll under the periodic spalling of the roll oxide film.When the oxide film is completely peeled off,the friction coefficient of the rolling interface does not change significantly along the circumferential direction of the roll.Thirdly,the dynamic rolling force model is established based on the Aklund rolling force model,considering the influence of oxide film peeling and roll vibration displacement.The dynamic rolling force is expanded by the third-order Taylor formula with the friction coefficient of the rolling interface and the vibration displacement of the roll as variables,and the nonlinear stiffness and nonlinear excitation are obtained.The nonlinear excitation characteristics of two kinds of oxide film spalling styles is simulated and analyzed.The results show that the nonlinear excitation is in a simple harmonic wave state when the oxide film is periodically exfoliated.When the oxide film is completely exfoliated,there is no nonlinear excitation in the dynamic rolling force.At this time,the roller vertical dynamic system generates forced vibration under external load.Finally,according to the actual structural parameters of F2 rolling mill,the dynamic equation of vertical vibration of rolling mill is established,and the equation is solved by multi-scale method to obtain the amplitude-frequency characteristic equation of the system.MATLAB simulation is used to analyze the vertical vibration characteristics of rolling mill under two kinds of oxide film spalling states.The results show that under the periodic exfoliation state of oxide film,with the variation of exfoliation degree,the vertical vibration of rolling mill exhibits multiple motion forms such as single-cycle,multi-cycle and chaotic motion.Compared with the good condition of roll oxide film,the vibration of rolling mill is relatively stable under the condition of oxide film completely peeling.