Inhomogeneity of deformation during lengthwise rolling of tubes

The formation of the pipes wall thickness variation occurs in the process of lengthwise rolling on a stub mandrel as a result of inhomogeneity of metal deformation in the roll pass. This problem leads to a decrease in the accuracy of the production. The paper presents the results of a study of the dependence of pipes wall thickness variation and the inhomogeneity of metal deformation on the frequency of rotation of the rolls during lengthwise rolling on a stub mandrel. The study was performed using computer simulation. We used a dimensionless parameter equal to the ratio of the pipe wall thickness in the outlet of the gauge to the wall thickness at the top of the gauge to evaluate the difference in the pipes. During the simulation, the rotation frequency of the rolls varied from 95 to 135 rpm. It was noted that with an increase of the rotation frequency of the rolls during lengthwise rolling, an increase in the temperature of the pipe on the contact surface occurred, which led to an increase in the intensity of the softening process. It should also be noted that along with the process of softening the metal of the pipe, the process of high-speed hardening also proceeded. The difference between the pipes when changing the rotation frequency of the rolls changed nonlinearly due to the occurrence of these two competing processes. The critical value of the rotation frequency of the rolls is found. The wall thickness variation of the pipe is observed at this frequency. It was found that during lengthwise rolling on a stub mandrel, it is possible to reduce the wall thickness variation of the pipe by selecting rational speed modes of deformation. Practical recommendations for choosing speed modes for lengthwise rolling, which increase the accuracy of pipes and reduce the level of defects are formulated based on the studies.