LAUSR

The influence of Nb in the transformation behavior of ultra‐high‐strength pearlitic steels is studied. The phase transition temperature is measured by thermal simulation device, and the continuous cooling transformation curve is established. Results show that with addition of Nb, the equilibrium transformation temperature of the test steel increases, and both size of the original austenite, pearlite colonies and pearlite lamellar spacing are refined. Pearlitic transformation mechanism has changed by the addition of Nb through the interaction of solid solution and precipitation. Nb microalloy delays the beginning and ending point of pearlite transformation when the cooling rate is greater than 1.00 and 0.10 °C s−1, respectively. In contrast, the transformation point is advanced when the cooling rate is less than 0.50 and 0.05 °C s−1. This variation is mainly due to the morphology and distribution of Nb‐containing precipitates at different cooling rates.