Improvement of tool calibration in cold pilligrim rolling mill

Abstract

In the manufacture of cold rolled tubes, the process performance of the rolling mill and the deformed metal is determined by tool calibration. The method of calibration calculation, the method and equipment of its reproduction significantly affect the deformability and quality of pipes, the cost of rolling tools, productivity, and in general the efficiency of cold (warm) rolling of pipes. Tool calibration is the distribution of individual compressions along the length of the working stroke of the rolls, determined by the shape and size of the grooves and the mandrel. The need to improve the calibration of rolling tools is determined by the ever-increasing requirements for pipe production products. In this article, it is proposed to set the function of relative reductions as a product of elementary functions. In the course of the work, the coefficients of the proposed function were determined from the condition of the minimum load on the gauge at the pre-calibration section to ensure the minimum longitudinal difference in the thickness of the pipes. Calibration and forces during rolling of stainless thin-walled pipes of size 95×2 mm by the improved method have been calculated using MS Excel. The force parameters of rolling, calculated using the improved method, are compared with the forces calculated using other well-known calibration calculation methods. It is shown that the proposed technique provides lower values of force on most of the crimping section, which allows reducing longitudinal variation of pipes and increasing durability of calibers. To assess the accuracy of rolled pipes, the calculation of the elastic deformation of the stand was carried out depending on the force in the pre-calibrating section. The calculated value shows that the proposed improved method of tool calibration allows rolling pipes of increased accuracy. The developed procedure involves the use of size 95×2 mm pipes made of 12X18H10T steel for rolling in order to produce from a two-pass scheme to a single-pass scheme while ensuring the required high cost of pipes.