University of Oulu

Please cite this article as: V. Javaheri, S. Kolli, B. Grande, et al., Insight into the induction hardening behavior of a new 0.40% C microalloyed steel: Effects of initial microstructure and thermal cycles, Materials Characterization,

Insight into the induction hardening behavior of a new 0.40% C microalloyed steel : effects of initial microstructure and thermal cycles

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Author: Javaheri, Vahid1; Kolli, Satish1; Grand, Bjørnar2;
Organizations: 1Material engineering and production technology, University of Oulu, Oulu, Finland
2R&D, EFD Induction a.s., Skien, Norway
Format: article
Version: accepted version
Access: open
Online Access: PDF Full Text (PDF, 32.7 MB)
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Language: English
Published: Elsevier, 2019
Publish Date: 2021-01-25


The induction hardening behavior of a new, hot-rolled 0.4 wt% carbon steel with the two different starting microstructures of upper and lower bainite has been simulated using a Gleeble 3800. The effect of heating rate in the range 1–500 °C/s on austenite grain size distribution has been rationalized. Dilatometry together with Scanning Electron Microscopy combined with Electron Backscatter Diffraction analyses and thermodynamic simulations provide insight into the austenite formation mechanisms that operate at different heating rates. Two main mechanisms of austenite formation during re-austenitization were identified: diffusional and diffusionless (massive). At conventional (1–5 °C/s) and fast (10–50 °C/s) heating rates the austenite formation mechanism and kinetics are controlled by diffusion, whereas at ultrafast heating rates (100–500 °C/s) the formation of austenite starts by diffusion control, but is later overtaken by a massive transformation mechanism. Comprehensive thermodynamic descriptions of the influence of cementite on austenite formation are discussed. The finest austenite grain size and the highest final hardness are achieved with a lower bainite starting microstructure processed with a heating rate of 50 °C/s to an austenitization temperature of 850 °C followed by cooling at 60 °C/s.

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Series: Materials characterization
ISSN: 1044-5803
ISSN-E: 1873-4189
ISSN-L: 1044-5803
Volume: 149
Pages: 165 - 183
DOI: 10.1016/j.matchar.2019.01.029
Type of Publication: A1 Journal article – refereed
Field of Science: 216 Materials engineering
Funding: The authors are grateful for financial support from the European Commission under grant number 675715 – MIMESIS – H2020-MSCA-ITN-2015, which is a part of the Marie Sklodowska-Curie Innovative Training Networks European Industrial Doctorate programme.
EU Grant Number: (675715) MIMESIS - Mathematics and Materials Science for Steel Production and Manufacturing
Copyright information: © 2019. This manuscript version is made available under the CC-BY-NC-ND 4.0 license