Improvement of roll installation mechanisms of two-stand mill 250 of SPE “Metchiv” LLC

The article presents the results of the reconstruction of the two-stand rolling mill 250 of the Scientific and Production Enterprise (SPE) “Metchiv” intended for the production of a wide range of simple and shaped sections from special steels and alloys. The mill was developed in 1966. South Ural Machine-Building Plant (SUMP, Orsk), now SUMP LLC. The mechanisms of radial installation of rolling rolls were reconstructed with the replacement of the hydraulic balancing mechanism with spring balancing. This made it possible to eliminate operational difficulties of the hydraulic balancing system, which prevented its use for many years. The absence of a balancing mechanism for the upper rolling rolls led to well-known shortcomings in the operation of rolling stands: discrepancies in the distance between the working surfaces of the rolling rolls during setup and during rolling due to the selection of the specified gaps in the nut-screws-cushions-rolls system, the action of dynamic loads in the specified system of mechanisms. Several possible options for the placement of helical cylindrical compression springs and disc springs were worked out: in the rod cavities of the balancing hydraulic cylinders; between the chocks of the lower and upper rolling rolls; on the outer side surfaces of the rolling stand frames; on the cross-beams connecting the beds of the rolling stands. The best option in terms of compactness of placement and the ability to perform the required functions was chosen with the option of placing helical cylindrical springs in the rod cavities of the balancing hydraulic cylinders. The springs were calculated using a well-known method and selected according to GOST 13773–86. The reconstruction was carried out without complex design changes in the parts of the rolling stands with minimal changes in the “filling” of the hydraulic cylinders while maintaining the required balancing force in the design range of change in the gap between the rolling rolls. The reconstructed mechanisms were manufactured, assembled and are in constant operation, demonstrating high efficiency.