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The results of a complex analysis of the stressed-strain state of the rolls of the working stand of cold-pilger reducing mills (CRM) equipped with grooves in the form of half-discs and ring dies using information technologies and the finite element method are presented. A comparative analysis of the stressed-strain state of the working stand rolls of domestic CRMs is performed. It has been established that when rolling pipes of improved quality from hard-to-deformed steels and alloys, in view of the optimal stressstrain state and a significant increase in the rigidity of the roll-groove system, it is advisable to use rolls with ring dies in combination with a working stand of rational design on all types of CRMs of all sizes. [ABSTRACT FROM AUTHOR]

The solution of a task on unsteady oscillations of system "pipe –mandrel - core" of piercing mill of pipe-rolling plant is specified. Differential equation of forced longitudinal oscillations of a mandrel with a core, taking into account unsteady influence of deformation zone and variability in time of pipe mass is worked out. Exact solution of the task concerning non-steady longitudinal oscillations of the system "pipe –mandrel - core" of piercing mill in Bessel's and Neumann's fundamental function is given. Analysis of dynamics of the system "pipe –mandrel - core" is represented by dynamic factor. Some peculiarities of functioning of the mechanism of mandrel holdup taking into account variability of mass of mill exit end and non-stationary influence from the side of deformation zone are established [ABSTRACT FROM AUTHOR]