Study of austenite grain size of microalloyed steel by simulating initial solidification during continuous casting

Abstract

The austenite grain growth behaviour of microalloyed steel during continuous casting was simulated by confocal laser scanning microscope, and the effect of the cooling rate during the solidification, T γ (the starting temperature for austenite grain growth) and steel composition on the behaviour of austenite grain growth were analysed. Next, the model for predicting the austenite grain size, which is put forward by the Bernhard model, was revised. The results show that by the lab simulation of continuous casting initial solidification process at the cooling rate between 1·5 and 2·5°C s−1, the austenite grain size lying within the size range on the slab surface was obtained; T γ was calculated using equivalent carbon content CP and showed the exponential function relation to the latter; the revision factor K, describing the effect of microalloyed elements on austenite grain sizes, showed exponential function relation with PTi (precipitation amount of titanium); both T γ and K were used to revise the Bernhard model, and the calculated value by the revision model closely corresponds to the measured values.