Surface Morphology Effect On The Lubrication Properties Of Cold Rolling And Experimental Research

Process lubrication is one of the main characteristics of the cold rolled strip production.It is the key technology in cold rolling process and plays a very important role in the rolling process.It can not only improve the surface quality of the products,control panel,reduce the rolling force parameters and prolong the service life of the rollers,but also be the key to achieve the high speed rolling and the production limit specification products.The surface morphology provides important surface information,and it has an important effect on the friction and lubrication characteristics of cold rolling.During the cold rolling process,with the slight change of the properties,temperature,geometric structure or surface appearance of lubricants and rolling pieces,there may be different lubrication states between the roll and the workpiece interface.These lubrication states are determined by the thickness of the interfacial oil film and the surface roughness of the interface.Therefore,this study is based on the domestic and foreign relevant theory of cold rolling through a combination of theory and practice.The effect of surface roughness and direction factor of lubrication were considered.Based on the mixed lubrication a new mathematical model was established with the average flow model and the asperity flattening theory.The main contents of this paper are as follows:(1)On the basis of the relevant theories of cold rolling and lubrication at home and abroad,a mathematical model of mixed lubrication was established,in which the effect of lubricant viscosity,temperature viscosity pressure and workpiece surface morphology are considered.The test of low carbon steel-Q235 was carried out at room temperature.The calculation accuracy of mixed lubrication model was improved with the modified deformation resistance model.(2)Based on the mean flow Reynolds equation of the three dimensional surface morphology of the interface,the inlet film thickness model and inlet length model considering rolling interface surface morphology and lubricant viscosity temperature effect are derived.The effect regulation of surface morphology(directional factor and roughness)and rolling parameters(reduction rate and rolling speed)on the oil film thickness and entry area length of the entry area were analyzed by the simulation.(3)The mixed lubrication model of the rolling deformation zone was established based on the analysis including the surface the morphology,the workpiece surface morphology calculation(direction factor,roughness)and the effect of the rolling parameters(pressure ratio,rolling speed,viscosity)on the deformation of mixed lubrication performance,such as the total pressure,the fluid pressure,the oil film thickness of the contact area,and the shear stress.In addition,we can get the average volume flow of the lubrieant in the deformation zone by calculating the integral constant C during the solving of this model,so as to provide evidence for the change of the contact state of the interface.(4)Rolling lubrication experiment was carried out in the laboratory.The variation rules of strip surface roughness,film thickness and rolling force with strip surface direction factor and lubrication conditions were explored.The relationship model between friction coefficient and film thickness was established.