Research On Surface Topography And Its Evolution Of Textured Work Roll During Cold Rolling

The textured work roll is an important part during cold rolling,which plays a decisive role on the surface quality and surface performance of cold rolled strip.With the continuous improvement of surface quality requirements for high quality automobile sheet and home appliance plate,the evolution for surface topography of textured working roll has never been valued than ever before.However,the research methods are mainly based on industrial test and mathematical statistics.The semi-theoretical and semi-empirical model is not supported by basic theory.The wear and attenuation of the surface topography of textured work roll is only forecasted empirically based on the rolling process parameters,and the evolution process is difficult to predict effectively.In this paper,the evolution of surface topography of textured work roll during cold rolling under the action of complex micromechanical behavior was studied by the methods of industrial test,theoretical analysis,experiment and numerical simulation.Considering the measurement and characterization of surface topography of work roll,the complex micromechanical coupling behavior of the rolling interface is studied,and a deterministic mathematic model for mixed lubrication in point contacts,which takes into account of friction,wear and lubrication,was built to obtain the oil film thickness and the distribution of contact pressure.Furthermore,a dynamic simulation model based on the cellular automation method was established,which showed the wear process of microscopic topography on the surface of work roll.Finally,the prediction system for surface topography of work roll during cold rolling has been constructed based on the simulation theory,by which the evolution for surface topography of textured work roll was studied,and revealed the attenuation law of textured work roll surface topography under the combined effects of friction,wear and lubrication,which could be a good theoretical foundation for the wear-resistant design and process control of roll surface topography during cold rolling,and supply the basic scientific theoretical system of the strip surface topography control.The main research work and results are reflected in the following aspect:(1)The surface topography of electrical-discharge textured work roll was measured and characterized in industrial production.The evolution for surface topography of work rolls during cold rolling is preliminarily analyzed.The sample piece of wok roll and steel strip was imitated based on the initial surface characteristics,and the surface topography of the sample was measured by the white light interferometer,which laid a foundation to analyze the mixed lubrication and dynamic evolution characteristics of rolling interface.In order to avoid the edge effect of Gaussian filtering in the process of determining the mean line or mean surface of work roll and strip surface,a similar profile extension method was proposed,which can effectively eliminate the edge effect and improve the reliability of edge data for convolution algorithm and fast Fourier transform algorithm.(2)Taking the surface topography of textured work roll as the initial condition,the lubrication state of rolling interface during cold rolling was studied by considering the material characteristics and the rolling process parameters in the actual production.The deterministic mathematic model for mixed lubrication in point contacts was built by finite element method(FEM)based on the mixed lubrication theory.The oil film thickness and the distribution of contact pressure is calculated,which provided the rolling pressure information for dynamic wear model.(3)The dynamic simulation model of the wear process of the surface micro topography was established by means of cellular automation method,combined with the field measurement results and physical mechanism of the surface topography wear of the work roll during cold rolling.Taking the the materials of rolled steel(9Cr2Mo)and Q345 rolling strip as the typical research materials,the effectiveness of the model was verified by using the MRH-3 high speed ring block wear tester.Finally,the evolution for surface topography and characterization parameters of the work roll are analyzed,which can lay the foundation for the prediction of the surface topography of the work roll.(4)The prediction system for surface topography of work roll during cold rolling has been constructed based on wear theory,by which the evolution process for surface topography of textured work roll in the rolling process was predicted effectively.The evolution for surface topography of textured work roll during the service period was analyzed,which provides the basis for controlling the surface topography of work roll and strip in the production process.