PLASTIC PROPERTIES OF STEEL AISI 4140 INFLUENCED BY STRAIN RATE AND TEMPERATURE

1 Kotásek Ondřej
Co-authors:
1 RUSZ Stanislav 1 Schindler Ivo 1 KAWULOK Petr 1 Opěla Petr
Institution:
1 VSB – Technical University of Ostrava, Faculty of Metallurgy and Materials Engineering, 17. listopadu 15, 708 33 Ostrava, Czech Republic, EU, ondrej.kotasek.st@vsb.cz, stanislav.rusz2@vsb.cz, ivo.schindler@vsb.cz, petr.kawulok@vsb.cz, petr.opela@vsb.cz
Conference:
27th International Conference on Metallurgy and Materials, Hotel Voronez I, Brno, Czech Republic, EU, May 23rd - 25th 2018
Proceedings:
Proceedings 27th International Conference on Metallurgy and Materials
Pages:
401-406
ISBN:
978-80-87294-84-0
ISSN:
2694-9296
Published:
24th October 2018
Proceedings of the conference were published in Web of Science and Scopus.
Metrics:
108 views / 33 downloads
Abstract

Deformation behavior of continuously cast steel with 0.43 % C, 1.01 % Cr and 0.19 % Mo was studied in the austenite region. Its solidus temperature was calculated as 1435 °C and the nil strength temperature at heating was determined as 1402 °C using a special testing method. Hot ductility was measured by means of the uniaxial tensile tests in wide range of mean strain rate (0.00074 – 63 s-1) and temperature (800 – 1375 °C). At medium strain rate of 0.65 s-1, formability steadily increased to a temperature of approx. 1335 °C and then sharply dropped as a result of overheating and burning of the steel. The nil ductility temperature was determined as 1365 °C in this case. Influence of strain rate on formability was evaluated at two temperature values corresponding to relatively poor and/or good plastic properties. At a temperature of 900 °C, ductility increased rather moderately with the increasing strain rate. At a temperature of 1280 °C, the growth of ductility at increasing strain rate was sharper and both dependencies intersected at a strain rate of approx. 0.008 s-1. Formability was improved by higher temperature at high strain rates and deteriorated at very low strain rates, which is a quite unique result. It was not possible to determine the value of the strain rate corresponding to the local maximum of ductility, even if applying the strain rate range of 6 orders. SEM analysis of the broken samples confirmed the expected influence of microstructure development on hot formability.

Keywords: Uniaxial tensile test, mean strain rate, ductility

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