MEASUREMENTS OF FRICTION IN COLD METAL ROLLING

Measurements of friction in rolling of aluminium sti ip on an experime ntal mill are described. Friction depended most strongly on the ratio Lambda of the smooth film thickness to the combined roughness of the r oll and strip, and on the reduction in strip thickness. Whether the gr eater roughness was on the roll or on the strip was found to be unimpo rtant. Varying the oil temperature from 40 to 60 degrees C was also So und to be of secondary importance. Profilometry, results suggested tha t friction was determined by the mean film thickness between the surfa ces. At the slowest speeds and smallest films, friction was close to t he value of 0.09 found in separate measurements in a disk machine of t he boundary additive properties. At the highest speed the friction val ues, which were less than 0.01, could be explained by hydrodynamic lub rication. The transition between. these two extremes occurred when the film thickness was of the order of the additive molecule length of 3 nm.