National University of Science and Technology "MISIS" (NUST "MISIS"), Moscow, Russia

A. S. Aleshchenko, Cand. Eng., Associate Prof., Head of the Dept. of Metal Forming, e-mail: aleschenko.as@misis.ru
V. A. Lakiza, Postgraduate Student, Dept. of Metal Forming, e-mail: lvladislavl@mail.ru
B. A. Romantsev, Dr. Eng., Prof., Dept. of Metal Forming, e-mail: boralr@yandex.ru

Vyksa branch of NUST MISIS, Vyksa, Russia
A. V. Korol, Cand. Eng., Associate Prof., Dept. of Technology and Equipment for Metal Forming, e-mail: korol_av@omk.ru

One of the key steps in the production of hot-rolled pipes is the helical piercing process, as this process establishes the initial geometry and quality of the resulting pipe. Wear of the working tool surface is one of the factors that lead to deterioration of pipe quality and decrease of equipment productivity. Particular attention is paid to mandrels because it is their condition that influences the quality of inner surface of the produced tubing and the accuracy of geometrical dimensions. Increased wear of piercing mandrels also leads to loss of productivity of industrial units due to necessity of their frequent replacement. The wear of mandrels during piercing of billets of corrosion-resistant steel 20Cr13 into sleeves on an experimental screw-rolling mill MISIS-130D is investigated in the present paper. Experimental piercing of billets of 20Cr13 steel 60 mm in diameter and 400 mm in length was carried out using piercing mandrels of different steel grades to determine the material subjected to less wear. We used mandrels from steel grades 20Cr2Ni4А, 4Cr5MoVSi, 3Cr3W8V, 3Cr3Mo3V, 4Cr4WMoVSi, 5Cr3W3MoVSi. To reproduce the operating conditions of mandrels close to the production, we varied the frequency of rolls rotation, the length of pierced workpieces and the angle of rolls in order to compare the wear resistance of mandrels under different rolling modes. On the basis of the obtained data the conclusion about the durability of the mandrel material when piercing steel 20Cr13 was formed, as well as the effect of several factors of the rolling process on the wear rate of the mandrel was estimated.
The work was carried out as part of a comprehensive project on the topic “Development and implementation of integrated technologies for production of seamless pipes from new generation steels with controlled corrosion resistance under difficult operating conditions for the fuel and energy complex of the Russian Federation” within the framework of Agreement No. 075-11-2023-011 dated 10.02. 2023 according to Decree of the Government of the Russian Federation No. 218 of 04.09.2010.

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