from the conferences organized by TANGER Ltd.
The results of studies of the influence of intercritical annealing parameters on the austenite formation and its stability in TRIP steel (0.41 % C, 1.52 % Mn and 1.22 % Si) were presented in the paper. Based on the results of a dilatometric analysis and metallographic investigation it was noted that the pearlite to austenite transformation does not occur at a constant temperature, which is referred to as Ac1, but rather within certain - possible to determine - temperature range which is enclosed within Ac1s and Ac1f values. It was shown, that in order to achieve austenite with a high carbon content, it is required to perform its annealing at a temperature slightly higher than the temperature at which the pearlite to austenite transformation begins (Ac1s). Dilatometric analyses of cooling curves confirmed these observations. It was noted that the austenite formed at a temperature of Ac1s+10 °C transforms into martensite at a much lower temperature (Ms) than austenite formed during annealing in two-phase (α+γ) temperature range, i.e. between Ac1f and Ac3 temperatures. It was also found that the formed austenite was the more stable the shorter annealing time was applied. Based on the obtained results the isothermal time-temperature-austenitisation (IHT) diagram was developed.
Keywords: TRIP steels, phase transformations, critical temperatures, IHT Diagram© This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.