National University of Science and Technology MISiS, Moscow, Russia:

A. N. Koshmin, Postgraduate Student of the Department of Metal Forming, e-mail: koshmin.an@misis.ru
A. V. Zinoviev, Professor of the Department of Metal Forming, Doctor of Technical Sciences

“Svelen” Ltd., St. Petersburg, Russia:
A. Y. Chasnikov, Advisor to General Director, Doctor of Technical Sciences
G. N. Grachev, General Director

The influence of temperature and pressing rate parameters on the continuous extrusion process conditions of rectangular busbars with size 1060 mm and made of M1 copper are investigated. With using software for finite element modeling (Q-Form) data on changes in temperature and stresses in the deformation zone at different pressing rates were obtained. The increase of pressing rate from 4 to 6 m/min leads to a slight increase in the average temperature of the extrusion process by 10–20 ^оC, what can significantly reduce the level of stress triaxiality in the deformation zone. The maximum of stress values are observed in the zone of contact between a metal and a abutment, where the direction of its flow changes. In the same zone, the release of more heat in a metal due to deformation was recorded. For metallographic investigation samples of rods cast at drawing rates of 300 and 500 mm/min and rectangular busbars extruded at workpiece feed rates of 4 and 6 m/min were produced on technological equipment. In result of the study macro- and microstructure images were obtained, indicating a weak effect of casting and pressing rates on the formation of structure in the ranges considered in this work. The macrographs of cast rods indicate an influence of drawing rate on a formation and size of the material structure, however, further deformation processing leads to a complete restructuring of the cast structure. The average grain size of the extruded samples is 15–30 μm. The results of measuring hardness and electrical conductivity also indicate a low effect on influence of the pressing rates in the considered range on the formation of these characteristics. All investigated bus samples show a tendency to increase hardness at edges, which is caused by more intensive cooling of a metal in these zones at an exit from the deformation zone. The average hardness of the tested busbars samples is ~ 66 HV1.
The reported study was funded by RFBR, project number 19-38-90104.

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