University of Oulu

Aarne Pohjonen, Pentti Kaikkonen, Oskari Seppälä, Joonas Ilmola, Vahid Javaheri, Timo Manninen, Mahesh Somani, Numerical and experimental study on thermo-mechanical processing of medium carbon steels at low temperatures for achieving ultrafine-structured bainite, Materialia, Volume 18, 2021, 101150, ISSN 2589-1529,

Numerical and experimental study on thermo-mechanical processing of medium-carbon steels at low temperatures for achieving ultrafine-structured bainite

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Author: Pohjonen, Aarne1; Kaikkonen, Pentti1; Seppälä, Oskari1;
Organizations: 1Materials and Mechanical Engineering, Centre for Advanced Steels Research, University of Oulu, yliopisto, Oulun 90014, Finland
2Outokumpu Stainless Oy, Tornio 95400, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 7.7 MB)
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Language: English
Published: Elsevier, 2021
Publish Date: 2021-10-21


A combination of experimental and numerical approaches was applied for constructing a dynamic model for thermomechanical processing, which was used for simulating laboratory rolling and cooling, and for designing a cooling path to enable phase transformation from austenite to ultrafine (~ 50–100 nm) bainitic laths. Physical thermomechanical simulation experiments were used for calibrating the numerical models. Hot rolling and water cooling experiments were conducted and they were numerically simulated. The calibrated numerical models were used for simulating the main processing stages affecting the final microstructure evolution during a laboratory scale processing, i.e. the low temperature (500 °C) ausforming and subsequent cooling schedules leading to the decomposition of austenite into bainite and martensite. The fitted model parameters and simulation results are presented for the laboratory rolling and two different cooling paths: (i) air cooling to 350 °C temperature with subsequent holding for 1–1.5 h, and (ii) water cooling close to martensite start temperature, and furnace holding for 1–1.5 h. Microstructural analysis was carried out using scanning electron microscopy combined with electron backscatter diffraction as well as X-ray diffraction and the structures were corroborated with mechanical properties evaluated in respect of hardness, tensile and impact toughness properties. The achieved mechanical properties and microstructures were further interpreted with the numerical simulation results. The results show that the calibrated numerical simulations provide an effective tool for designing suitable thermomechanical processing paths leading to desired microstructure.

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Series: Materialia
ISSN: 2589-1529
ISSN-E: 2589-1529
ISSN-L: 2589-1529
Volume: 18
Article number: 101150
DOI: 10.1016/j.mtla.2021.101150
Type of Publication: A1 Journal article – refereed
Field of Science: 216 Materials engineering
Funding: European commission funded this study under RFCS contract RFCS-2015-709607. A part of the funding of this research activity under the auspices of Genome of Steel (Profi3) project through grant #311934 by the Academy of Finland is gratefully acknowledged.
Copyright information: © 2021 The Author(s). Published by Elsevier B.V. on behalf of Acta Materialia Inc. This is an open access article under the CC BY license (