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Optimization of the CCT Curves for Steels Containing Al, Cu and B
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A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
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en
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24
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Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science, Volume 52, issue 3, pp. 1640–1663
Abstract
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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Funding Information: This research was conducted within the framework of the Genome of Steel project funded by the Academy of Finland (Project #311934). Publisher Copyright: © 2021, The Author(s). Copyright: Copyright 2021 Elsevier B.V., All rights reserved.
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Miettinen, J, Koskenniska, S, Somani, M, Louhenkilpi, S, Pohjonen, A, Larkiola, J & Kömi, J 2021, 'Optimization of the CCT Curves for Steels Containing Al, Cu and B', Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science, vol. 52, no. 3, pp. 1640–1663. https://doi.org/10.1007/s11663-021-02130-9