Dynamics of mandrel holding mechanism of pipe-rolling line automatic mill

Abstract

The different walled parameter of shells is one of the essential indices, determining quality of hot-rolled seamless pipes, produced at pipe-rolling line (PRL). Thickness variation of shell walls makes a considerable share of the longitudinal and cross-section different walled parameter of finished pipes. The phenomena is stipulated mainly by the rod dynamics with the mandrel in the mill deformation hearth. Based on a study of dynamic model of the mandrel holding mechanism rod, the character of dynamic processes progress at the exit part of PRL automatic mill determined, accounting the shell rolling parameters. A system of differential equations composed for the mandrel holding mechanism rod dynamics, accounting technological parameters and inertia parameters of the rolled shell. The solution of the differential equations system with variable coefficients until the forth approximation realized digitally by application of Runge-Kutt method for correspondent forms of the mandrel rod oscillation. The solution obtained taking the example of calculation of the PRL 350 automatic mill. The picture of dynamic processes of the mandrel holding mechanism rod system at realization of the whole technological process of seamless pipes production at the PRL 350 automatic mill specified. At that, the variable impact of the deformation hearth and change of the rolled shell mass were taken into account. A wide range of mathematic experiment accomplished, that enabled to select necessary technological and dynamic system parameters, determine the stable pipe rolling regimes. Analytical solution of the task obtained, that considerably differs from the earlier known mathematic models. The obtained solution reflects much better the dynamic processes in the mandrel holding mechanism rod system of the PRL 350 automatic mill and specifies the peculiarities of pipe longitudinal different-walled phenomena formation mechanism.