University of Oulu

Miettinen, J., Koskenniska, S., Somani, M. et al. Optimization of the CCT Curves for Steels Containing Al, Cu and B. Metall Mater Trans B 52, 1640–1663 (2021).

Optimization of the CCT curves for steels containing Al, Cu and B

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Author: Miettinen, Jyrki1; Koskenniska, Sami1; Somani, Mahesh1;
Organizations: 1Material and Mechanical Engineering, University of Oulu, P.O. Box 8000, 90014, Oulu, Finland
2Department of Materials Science and Engineering, Aalto University, Vuorimiehentie 2, 02150, Espoo, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 2.3 MB)
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Language: English
Published: Springer Nature, 2021
Publish Date: 2021-07-02


New continuous cooling transformation (CCT) equations have been optimized to calculate the start temperatures and critical cooling rates of phase formations during austenite decomposition in low-alloyed steels. Experimental CCT data from the literature were used for applying the recently developed method of calculating the grain boundary soluble compositions of the steels for optimization. These compositions, which are influenced by solute microsegregation and precipitation depending on the heating/cooling/holding process, are expected to control the start of the austenite decomposition, if initiated at the grain boundaries. The current optimization was carried out rigorously for an extended set of steels than used previously, besides including three new solute elements, Al, Cu and B, in the CCT-equations. The validity of the equations was, therefore, boosted not only due to the inclusion of new elements, but also due to the addition of more low-alloyed steels in the optimization. The final optimization was made with a mini-tab tool, which discarded statistically insignificant parameters from the equations and made them prudently safer to use. Using a thermodynamic-kinetic software, IDS, the new equations were further validated using new experimental CCT data measured in this study. The agreement is good both for the phase transformation start temperatures as well as the final phase fractions. In addition, IDS simulations were carried out to construct the CCT diagrams and the final phase fraction diagrams for 17 steels and two cast irons, in order to outline the influence of solute elements on the calculations and their relationship with literature recommendations.

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Series: Metallurgical and materials transactions. B, Process metallurgy and materials processing science
ISSN: 1073-5615
ISSN-E: 1543-1916
ISSN-L: 1073-5615
Volume: 52
Issue: 3
Pages: 1640 - 1663
DOI: 10.1007/s11663-021-02130-9
Type of Publication: A1 Journal article – refereed
Field of Science: 216 Materials engineering
Funding: This research was conducted within the framework of the Genome of Steel project funded by the Academy of Finland (Project #311934). Open access funding provided by University of Oulu including Oulu University Hospital.
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