Research On Dynamic Characteristics Of Unsteady Rolling Lubrication Interfaces

Proper lubrication was used during the metal cold rolling process which not only reducing the friction, the wear and the energy consumption but also improving the surface quality of the strip. The demand of rolling strip and its quality which comes from every trade was increased as the industrial technology continuously developed. Unsteady lubticating problem was standing out because of the high efficiency and high-accuracy production requirement. This unsteady phenomenon could not only affect the accuracy of thickness and surface quality of the strip but also lead to strip breakage and equipment damnification which could cause economic losses.Lubrication is brought by the rolls and the strip to flow past the roll gage when the strip has plastic deformation during the rolling process. Rolling process is a transient and unsteady process, even tiny disturbance may turn the lubrication system into an unsteady state especially under the condition of high speed rolling process. The macroscopical representation of this unsteady problem is the mill vibration. High speed rolling will be a tendency because of the improvement of the productivity and this is the reason why we study the lubrication characteristics of the unsteady rolling interfaces. Based on the theory of rolling, hydrodynamics and vibration, this paper has theoretical study and numerical analysis on the steady rolling interfaces and unsteady rolling interfaces of cold rolling process. The main contents are as follows:1) The steady rolling interface models of fluid lubrication and mixed film lubrication were built up according to the actual situation of rolling lubrication and the numerical calculation and simulation of these models at different working condition was also conducted.2) The unsteady rolling interface lubrication models of fluid lubrication and mixed film lubrication were built up which concerns surface topography. New disturbance factors were proposed by theoretical derivation and the corresponding numerical calculation and simulation was also done. Based on the steady rolling interface lubrication models the evaluation system of unsteady rolling interface was proposed which was used to analyze and evaluate the characteristic parameters such as rolling pressure and film thickness under the unsteady condition. 3) The rolling lubrication experiment of aluminum alloy strip was carried out on a two-roll mill. The test results obtained by the laboratory work were compared with the theoretical results, and the comparison shows that the trends of theoretical results and experimental results were same, meanwhile, the deviation of the two results were relatively small which validates the correctness of theoretical analysis.4) Based on the microscopic stress distribution of steady rolling interface the vertical vibration and torsional vibration models of the mill were built up which can be used to analyze and simulate the macroscopic vibration of the mill under different disturbance factors and different working conditions.