ENERGY DISSIPATION AND INSTABILITY PARAMETER AT HIGH TEMPERATURE FORMING OF MIDDLE CARBON STEEL

1 KLIBER Jiří
Co-authors:
1 SCHINDLER Ivo 1 KAWULOK Petr 2 SEDLÁČEK René
Institutions:
1 VSB - Technical University of Ostrava, Faculty of Metallurgy and Materials Engineering, 17 listopadu 15, 708 33 Ostrava - Poruba, Czech Republic, EU, jiri.kliber@vsb.cz, ivo.schindler@vsb.cz, petr.kawulok@vsb.cz
2 OSTROJ a.s., Těšínská 1586/66, 746 41 Opava-Předměstí, Czech Republic, EU, sedlacek@ostroj.cz
Conference:
26th International Conference on Metallurgy and Materials, Hotel Voronez I, Brno, Czech Republic, EU, May 24th - 26th 2017
Proceedings:
Proceedings 26th International Conference on Metallurgy and Materials
Pages:
370-374
ISBN:
978-80-87294-79-6
ISSN:
2694-9296
Published:
9th January 2018
Proceedings of the conference were published in Web of Science and Scopus.
Metrics:
25 views / 10 downloads
Abstract

Deformation characteristics of carbon steel are studied in the temperature range 900 - 1200 °C and strain rates 0.1 - 100 s-1 on the plastometr Gleeble using compression tests on cylindrical samples. Processed a single dissipation maps in the field of forming are developed on the basis of changes in the effectiveness of dissipation, depending on temperature and deformation resistance, taking into account the strain rate. Strass-strain curves under different deformation conditions were used. Map of absorption of energy reveals that peak efficiency of strain rate sensitivity parameter is achieved of m values of 0.21 and from that the energy dissipation efficiency η is calculated with purpose to find the optimal forming conditions. At the same time to the contour dissipation map, the map of an instability criterion ξ has been added. The instability forming mode is recorded lower values of ξ, in the present case, however, it is not a dramatic slump, only a warning on the possibility of defects. Behavior analysis indicated that there were a dynamic recrystallization at higher temperatures and in all conditions forming since the value 0.2 deformation (deformation at lower strain rates there) and always above 0.2 to 0.4 even at high strain rates.

Keywords: steel, forming, energy dissipation, instability parameter
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