National University of Science and Technology “MISiS” (Moscow, Russia):

Samusev S. V., Dr. Eng., Prof., Metal Forming Chair, e-mail: samusev@misis.ru
Zhigulev G. P., Cand. Eng., Associate Prof., Metal Forming Chair, e-mail: zhigulev@misis.ru
Skripalenko M. M., Cand. Eng., Associate Prof., Metal Forming Chair
Fadeev V. A., Assistant, Metal Forming Chair

The paper considers the production of welded longitudinal pipes for trunk pipelines in modern technological lines, including tube electric pipe welded line TESA 1420. Stepwise forming operation, which is based on elastic-plastic bending of the billet is studied. The model with double bending radius of strip billet in the free deformation area is presented for the contact interaction between billet and tool and for the step of billet separation from the punch. Diagrams of the moments and stresses across billet are thickness determined for specific sections of the deformation area. The results of research of shape settings for tube billet during forming in a dedicated bending machine for two stages of bending process are determined. The experiments have shown that billets have complicated curvature shape in the area of working tool retardation; this curvature was approximated by a polynomial and the process data for specific deformation conditions were obtained. The curve of billet shape has been received taking into account variation of curvature of billet separation from the punch. The phenomenon of billet separation has been used in calculation of billet width geometry and deformation work for specific sections in the deformation area for two forming stages.

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