University of Oulu

Kaikkonen, P.M.; Somani, M.C.; Karjalainen, L.P.; Kömi, J.I. Flow Stress Behaviour and Static Recrystallization Characteristics of Hot Deformed Austenite in Microalloyed Medium-Carbon Bainitic Steels. Metals 2021, 11, 138. https://doi.org/10.3390/met11010138

Flow stress behaviour and static recrystallization characteristics of hot deformed austenite in microalloyed medium-carbon bainitic steels

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Author: Kaikkonen, Pentti M.1; Somani, Mahesh C.1; Karjalainen, Leo Pentti1;
Organizations: 1Materials and Mechanical Engineering, Centre for Advanced Steels Research, University of Oulu, 90014 Oulun yliopisto, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 6.2 MB)
Persistent link: http://urn.fi/urn:nbn:fi-fe202103197883
Language: English
Published: Multidisciplinary Digital Publishing Institute, 2021
Publish Date: 2021-03-19
Description:

Abstract

In the past decade, efforts have been focused on developing very fine, medium-carbon bainitic steels via the low-temperature (typically 300–400 °C) ausforming process, which not only enables shorter isothermal holding times for bainitic transformation at low temperatures, but also offers significantly improved strength. This paper describes static recrystallization (SRX) characteristics of austenite in four medium-carbon 2%Mn-1.3%Si-0.7%Cr steels with and without microalloying intended for the development of these steels. The stress-relaxation method on a Gleeble simulator resulted in recrystallization times over a wide range of temperatures, strains and strain rates. Also, the occurrence of precipitation was revealed. Powers of strain (−1.7 to −2.7) and strain rate (−0.21 to −0.28) as well as the apparent activation energies (225–269 kJ/mol) were in the ranges reported in the literature for C-Mn and microalloyed steels with lower Mn and Si contents. The new regression equations established for estimating times for 50% SRX revealed the retardation effects of microalloying and Mo addition showing reasonable fits with the experimental data, whereas the previous model suggested for ordinary microalloyed steels tended to predict clearly shorter times on average than the experimental values for the present coarse-grained steels. The Boratto equation to estimate the non-recrystallization temperature was successfully modified to include the effect of Mo alloying and high silicon concentrations.

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Series: Metals
ISSN: 2075-4701
ISSN-E: 2075-4701
ISSN-L: 2075-4701
Volume: 11
Issue: 1
Article number: 138
DOI: 10.3390/met11010138
OADOI: https://oadoi.org/10.3390/met11010138
Type of Publication: A1 Journal article – refereed
Field of Science: 216 Materials engineering
Subjects:
Funding: This research was funded by European Research Fund for Coal and Steel under the contract RFCS-2015-709607 and the Academy of Finland under the “Genome of Steel” project #311934.
Academy of Finland Grant Number: 311934
Detailed Information: 311934 (Academy of Finland Funding decision)
Copyright information: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
  https://creativecommons.org/licenses/by/4.0/