JSC Seversky Tube Works, Polevskoy, Russia:
O. A. Panasenko, Head of the Pipe-Rolling Laboratory of the Research Center, e-mail: PanasenkoOA@stw.ru

Ural Federal University named after the first President of Russia B. N. Yeltsin, Ekaterinburg, Russia:
D. Sh. Nukhov, Cand. Eng., Associate Prof., Dept. of Metal Forming, e-mail: d.s.nukhov@urfu.ru
A. O. Khalezov, Postgraduate Student, Dept. of Metal Forming, e-mail: alekssanja633@mail.ru

Over the past decades, high-performance units have become widespread in the technology of production of hot-worked tubes, existing pipe mills are being actively modernized, the range of products has been significantly expanded, and the requirements for its quality have been increased. The tasks of theoretical research and practical implementation of new technical solutions in improving the technology of seamless tube rolling, in which a special place is occupied by the process of screw piercing of a continuously cast billet, become topical. The main difficulty of the theoretical study of the screw piercing process in cross-rolling mills lies in the exact determination of the geometric parameters of the deformation zone, which have a significant effect on the deformation-speed and energy-power parameters of the process. The use of analytical solutions developed on the basis of numerical models allows to more quickly obtain the desired solutions as a result of engineering calculations. Previously, under the guidance of professor A. A. Bogatov, a technique for studying the shape change of the billet was developed, which takes into account the complexity of metal movement in the longitudinal and transverse directions of the deformation zone. The application of this technique made it possible to obtain the distributions of the relative billet reduction (Δr/r0), ovalization coefficient (ξ), and the ratio of the billet radius to the width of the contact surface (r0/b) for each helix line pitch number. It has been established that with an increase in the feed angle β, the number of helix pitches before meeting with the plug decreases, and the value of partial reduction increases. It was revealed that screw piercing with a reduced rolls rotation frequency contributes to reduction of the uneven outflow of the peripheral and central layers of the billet, reduction of the process cyclicity in the final stage, which reduces the annular delamination of the metal and the probability of defects formation.

The study was carried out within the framework of the design part of the state task No. 075-03-2023-006 dated 01/16/2023.

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