Prediction of Precipitation Kinetics in Nb Added Steels

Abstract

In Nb, V and Ti added steels, carbo-nitrides are formed due to their strong interaction with C and N. The quantitative analysis of distribution of precipitates and the effect of precipitates are still far from satisfactory. In this study, the analysis of precipitates in austenite in was investigated using the fact that the formation of precipitates accelerates austenite/ferrite transformation. The formation of precipitates was controlled by adjusting holding temperature and time. Volume fraction transformed were measured by dilatometer. Iso-precipitation kinetics were determined by comparing 5% and 50% volume transformed at various conditions respectively. The thermodynamic and kinetic model for precipitation in austenite and ferrite as well as austenite/ferrite transformation was formulated. The thermodynamic and kinetic models were based on the sublattice model and on the nucleation and growth model. the results was compared with the calculated