Computer Simulation of Microstructural Evolution in Thermo mechanical Processing of Steel Plates

Abstract

The computer simulation model of microstructural evolution on the basis of chemical thermodynamics and classical nucleation and growth theory has been developed. The metallurgicai phenomenain thermomechanical treatment of steel, such as austenite grain growth, recrystallization and growth, carbonitride precipitation and austenite to ferrite phase transformation can be predicted by the model. The influences of steel chemistry and thermomechanical condition on the transformed microstructure of 0.10C-1. 5Mn-0.35Nbsteel (high C-high Mnsteel) and 0.06C-1. 25Mn-0.035Nbsteel (low C-Iow Mn steel) are evaluated by computer simulation. With the increase of Cand/or Mnconcentrations, the volume fraction of second phase increases and the ferrite grain size is refined C-high Mnsteel, the transformed microstructure consists of ferrite and pearlite phases at lower cooling rates and/or larger effective austenite interfacial area per unit volume. Sv, The volume fraction of second phase increases with the increase of cooling rate and/or the decrease of Sv value. The second phase of the steei at higher cooling rates is bainite. The transformed microstructure of low C-low Mnsteel consists of ferrite and bainite phases. The influences of the roiling condition and the cooling rate on the transformed microstructure are smaller in low C-low Mnsteel. However, the transformed microstructure is apparently influenced by the start temperature of accelerated cooling. © 1992, The Iron and Steel Institute of Japan. All rights reserved.