||A mixture lubrication model suitable for emulsions has been developed in the partial lubrication analysis of cold rolling. The rolling section is divided into the inlet, work and outlet zones, where the elastic deformations of the rolls and the strip are considered. At the high rolling speed, the two adsorbed layers on the surfaces of the rolls and strip are separated by the emulsion layer, but they merge to form a continuous oil film at the low rolling speed. In this study, the modified Reynolds and Von Karman equations are simultaneously derived and solved by the Newton-Raphson method for the smooth surfaces of the rolls and the strip. Results show that roller and the strip come into contact with each other at the outlet zone for the roll speed lower than 0.3 m/s using pure oil and 10 m/s using emulsion with 5% oil concentration. In general, the critical speed to cause this contact increases along with reduction ratio).|
Considering the asperity and the dent on the strip surface at work zone, the pressure (pf) generated by hydrodynamic film is different from that (ps) on the surface of strip. The pressure (pf) significantly increases with the height of asperity, but ps increases slightly. If the strip has dents, the pressure (pf) decreases quickly, but ps changes a little.
The film thickness of the emulsion increases along with the pressure-viscosity coefficient and the roll speed, but the contact length decreases because the film thickness increases. With increasing reduction ratio or decreasing front tension, the contact length increases. Considering the elastic recovery on the contact zone, the contact pressure significantly increases along with the height of asperity, so that the plastic deformation may occur, but it cannot generate the contact pressure in the dent area.