Theoretical And Experimental Research On Lubrication Regime In Cold Strip Rolling

The flatness and surface topography of strip after rolling is directly influenced by rolling lubrication. Now as a key point in cold strip rolling production, rolling lubrication is attracting more and more interest of steel producers. The problems caused by rolling lubrication are always solved by trying different oils for their complexity, so this cost much. In order to intense the understanding of lubrication regimes, this paper constructed the numerical model for cold rolling lubrication, developed simulating program and conducted lab rolling experiments. Through these, a preliminary view of the variation of parameters in deformation zone is gotten, and the ways to value the performance of oils are also explored in this paper.Because of the need to control the rolling process stability and surface topography, mixed lubrication is the most important regime in practical rolling product. In the mixed lubrication regime, part of the interface load is carried by asperity contact and part by the pressurized lubricant in surface valleys. This paper put the emphasis on mixed lubrication and got such conclusions:(1) On the basis of learning and summarizing the theories early founded by experts around the world, this paper constructed the mixed lubrication model. The model includes the consideration of surface roughness and asperity flattening, divides the rolling zone into full film inlet zone, mixed film inlet zone and work zone three different zones. In each zone, different boundary conditions are applied, and the model also uses "high speed ","low speed " two different algorithms. The model can be used to a wide speed range.(2) On the basis of numerical model, a simulating program was developed using C++ program. The software is developed in a method of structed programming approach, so it's convenient to modify, develop and maintain. A runge-kutta method is used to calculate the differential equation, which is a method with high precision. The model can predict the lubricant pressure, rolling pressure, contact area and film thickness in the deformation zone. The variation of parameters can be plotted using Matlab engine.(3) This paper investigated the lubrication state variation caused by oil and rolling condition differences by cold rolling experiments. The experiments indicated that oil has a big influence to rolling process, and rolling speed directly influence the lubrication state. Rolling force, main current, roll gap are all the important aspects to value the oil's lubrication performance. The model calculating results agrees well with the experiment actual values, so the program developed in this paper can be used in the analysis of cold rolling lubrication. For the selection and use of the cold rolling oils, analyzing the problems happened in the real product, the program has a certain extent referencing meaning.