Austenite-to-ferrite phase transformation during continuous casting of steels

摘要

During the continuous casting process of carbon steels the solidified shell has to sustain thermal stresses as well as mechanical loading conditions (unbending) when transforming from austenite (γ) to ferrite (a) between the Ar{sub}3- and the Ar{sub}1-temperature. Micro-mechanical models have been developed in order to investigate the influence of different γ/α arrangements on the stress/strain situation in the particular composite. When thin ferritic films surround the inclusion-like austenitic grains a strain concentration has been observed that gives rise to inter-crystalline fracture. In order to consider microstructural variations, γ-αtransformation kinetics is investigated numerically. Carbon diffusion and interface migration, coupled by appropriate boundary conditions, determine the austenite to ferrite transformation. The results can be plotted in the form of TTT-diagrams. Additionally, a Finite Element model has been performed in order to investigate the influence of a uniaxially applied load on the transformation kinetics. This paper presents the results of two years' work on micro-mechanical modelling of the proeutectoid γ-α phase transformation.