Chair of Metal Forming, Ural State Federal University (Ekaterinburg, Russia):

Bogatov A. A., Dr. Eng., Prof., Head of the Chair
Pavlov D. A., Post-Graduate of the Chair, E-mail: pavlovda1989@mail.ru
Nukhov D. Sh., Post-Graduate of the Chair

Sinarsky Pipe Plant (Kamensk-Uralsky, Russia):

Ovchinnikov D. V., Cand. Eng., Chief Engineer
Lipnyagov S. V., Chief Rollerman

A three-high mill of screw rolling for reduction of the billets was installed at TPA-80 tube rolling unit of Sinarsky Pipe Plant (incorporated in TMK — Tube Metallurgical Company). This mill can use continuously cast billets in tube manufacturing process, for tubes of special usage; it is economically profitable, as well as provides improvement of steel structure quality and steel technological properties. While assimilating the new technological process, the problem of increase of defective products (in the form of tube buckles) has been identified. Formation of blinks on the back end of the billet and the subsequent formation of D-rings while piercing, as well as their break-away and getting into the deformation area were considered as the reasons for these defects. The article examines the reasons for formation of tube buckles in rolling, formulates and solves the problems of mathematical simulation in Deform-3D program of screw rolling and piercing processes. FEM and physical simulation of the method of shape forming for a billet end are described. It is concluded that the smallest values of blink length were received during reduction of the billet with cut cone and concave end having 70 mm length and 150 mm radius. The same form of the back billet end ensures the largest value of thickness of D-rings; it is confirmed by the results FEM simulation and industrial experiments. The results of full-scale industrial experiments directed on examination of this problem are evaluated. Practical recommendations for solving the manufacturing problem of defective products in the form of tube buckles are given.

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