ISIJ International
Online ISSN : 1347-5460
Print ISSN : 0915-1559
ISSN-L : 0915-1559
Regular Article
Modelling Simultaneous Formation of Bainitic Ferrite and Carbide in TRIP Steels
Fateh FazeliMatthias Militzer
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2012 Volume 52 Issue 4 Pages 650-658

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Abstract

The addition of 1.5–2 wt% Si is a commonly used alloying approach for TRIP steels. Si delays cementite precipitation during bainite transformation thereby enabling that an adequate amount of austenite can be retained at room temperature due to sufficient carbon enrichment. However, the degree of cementite prevention and thus the fraction of retained austenite depend on the employed processing parameters and steel chemistry. The present work proposes a modelling framework to quantify the delayed carbide precipitation during bainite formation. A nucleation-growth based model describes the simultaneous formation of bainitic ferrite and cementite precipitation for various continuous cooling scenarios. The retarding effect of Si on cementite precipitation is explicitly accounted for. The fraction of bainite and the carbon content of the remaining austenite, which determines the Ms temperature of remaining austenite, can be tracked along non-isothermal processing paths. The proposed model is evaluated using continuous cooling transformation data for a 0.19C–1.5Mn–1.6Si–0.2Mo (wt%) steel.

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© 2012 by The Iron and Steel Institute of Japan
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