Researches into the Deformation of Metals by Cold Rolling

Abstract

A large number of experiments have been carried out on an experimental cold rolling mill installed at Sheffield University by the Steel Industry, and this paper summarizes the results obtained. The experimental technique is described, and details are given of the mechanical tests made on the strip materials used. In connexion with various theories of rolling, the yield stress characteristic of the strip is required. Two methods of determining the yield stress—one depending on a tensile test, the other on a compression test—are put forward. The principal theories of rolling are examined in relation to the experimental results. Using the theory of Orowan as criterion, it is found that the theories of von-Karman and Ekelund yield satisfactory accuracy for practical calculation of the roll force over the normal range of cold rolling conditions. These theories do not allow the torque to be directly calculated, but it is shown that the “lever arm” method can be modified to allow for roll flattening, and can then be used, in combination with the simple methods for roll force, to determine the torque. It was considered that a method of calculation was required, simpler than Orowan's exact method, yet applicable when rolling with strip tension. A new theory was evolved which fulfils these requirements, and is examined in relation to the experimental results. The method allows of further simplification, so that calculation is reduced to a minimum, most of the information being obtained from graphs, with very little loss of accuracy. It is shown that there is an approximate relationship between the roll force and the corresponding energy of deformation. This relationship is used in the “energy method” for rapid calculation of rolling schedules.