Speaker
Description
The microstructure of austenite developed during plate rolling is significant for the final microstructure and therefore for the mechanical properties of heavy plates. Accurate prediction of the grain size, including its homogeneity and distribution, at each pass is essential for optimizing the rolling schedule. Especially in the production of heavy plates rolled from very thick slabs or plates with large widths, rolling passes with very low deformations cannot be avoided. In those passes, the microstructure can only partially recrystallize, which may result in an inhomogeneous grain size distribution.
The recrystallization kinetics of different alloying systems, with and without microalloying elements, were investigated in detail by performing uniaxial compression tests on a Gleeble 3800. In these tests, a wide range of deformation parameters, such as strain, interpass time, and temperature, were systematically varied. In particular, understanding the evolution of the microstructure during the recrystallization is important. For this purpose, samples deformed to different strain levels were quenched at various times during the recrystallization process, and the austenitic microstructure was revealed by etching.
These results were used to optimize the recrystallization model, which is implemented in the rolling simulation tools, to reliably simulate recrystallization and the evolution of austenite grains at the pass level. Special attention was given to ensure that the model can predict the inhomogeneous grain size distribution evolving from partial recrystallization and not only the correct average grain size. To validate the model, various rolling schedules were simulated, and the predicted final microstructures were compared with those of the rolled plates.