Modeling of Dynamic Recrystallization and Flow Stress of NbBearing Steels

• Published in: Multidiscipline modeling in materials and structures Vol. 3; no. 1; pp. 27 - 41
• Main Authors: Ma, L.Q., Yuan, X.Q., Jiao, S.H., Liu, Z.Y., Wu, D., Wang, G.D.
• Format: Journal Article
• Language: English
• Published: Emerald Group Publishing Limited 01.01.2007
• Subjects: Deformation activation energy; Dynamic precipitation; Dynamic recrystallization; Flow stress model; Nbbearing steels
• ISSN: 1573-6105; 1573-6113
• DOI: 10.1163/157361107781360103

The dynamic recrystallization DRX and flow stress of Nbbearing steels were investigated by means of isothermal single compression testing at temperatures of 850105 and at constant strain rate from 0.1 to 20s1 using a Gleeble 3800 thermomechanical simulator in order to model the DRX processes and predict the flow stress during plate rolling. On the basis of the measured flow stress, a new model of DRX kinetics was proposed to calculate the volume fraction of dynamically recrystallized grains, which was a function of processing parameters such as deformation temperature, strain, strain rate, the initial austenite grain size and Nb content. The effect of deformation conditions was quantified by the ZenerHollomon parameter, in which the activation energy of deformation was expressed as a power function of Nb content. The critical strain was determined by using the method proposed by Jonas and coworkers. It is shown that the ratio of the critical strain to the peak strain decreases with increasing Nb content, from which an empirical equation was developed. In addition, the influence of Nb content and deformation conditions on the steady state grain size was determined by fitting the experimental results to a linear relationship. Finally, the flow stress of Nb bearing steels was accurately predicted using a oneinternalvariable evolution equation by taking Nb content as a parameter and including the influence of DRX. The comparison between the experimental and theoretical results confirmed that the modeling had a good accuracy to predict flow stresses during hot deformation.