National University of Science and Technology “MISiS”, Moscow, Russia:
N. M. Vavilkin, Dr. Eng., Professor, Dept. of Metal Forming, e-mail: moose2@yandex.ru

Abstract: A technique has been developed for the quantitative assessment of piercing (P) based on the use of the values of the relative elongation δ at a temperature of 1200 °C and the deformation rate corresponding to the conditions of piercing 1 s^-1 and correction factors taking into account the state of the original workpiece, the composition of the deformation zone and the combined effect of the factors of the deformation area — the angle flow β and ovalization ratio ξ definitely. Based on the experimental results processed in the EXCEL program, the presence of four characteristic zone combinations of β and ξ has been established, which have the most significant effect on the critical compression ucr. The statistically significant values of the corresponding coefficients K1 and K2 have been established. An experimental assessment of the correction factor K3, which determines the combined effect of the factors of the deformation zone, has been carried out. The adequacy of the developed technique was checked using real conditions of piercing on TPA-140 with an automatic mill of JSC “PNTZ”, the correct use of the applied structure of the deformation area. The established criterion is P = 50 %, below which axial destruction occurs during piercing.

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