Modelling of isothermal austenite grain growth in a Si-Mn TRIP steel - experimental and calculation

Using the theory described in the preliminary publication, the isothermal g rain growth of a low carbon. silicon-manganese bearing TRIP-steel has been studied. The austenitic grain size was established through the measurement of the mean linear intercept distance, which has been transformed into the real mean austenite grain size. A general model of the form d(n)=d(0)(n)+K( l)t exp(K-2/T) was used and the coefficients n, K-1 and K-2 have been stati stically determined. It has been demonstrated that for low annealing temper atures the value of n is situated around 6, whereas at high temperatures n rapidly drops and adopts a value of 2. This behaviour was related to the di ssolution of the precipitates present in the austenitic matrix during the s oaking treatments. The model delivers very good predictions for soaking temperatures up to 120 0 degreesC. For higher temperatures, the deviations between the predicted g rain size and the really measured one are higher.