Resumen
The problem about parametrical fluctuations of system «sleeve (pipe) ? mandrel ? core» of an automatic mill of the pipe-rolling unit is considered. The differential equation of movement of a core mandrel of an automatic mill of the pipe-rolling unit is worked out. Dynamic processes are presented by the differential equations system in the form of Matier-Hill equations. The stability areas of functioning the mechanism of keeping the automatic mill mandrel are determined.