A Model for Precipitation Kinetics in Vanadium Microalloyed Steel

Small dispersoid particles inhibit recrystallization which is critical in controlling the grain structure of many high strength low alloy steels. A general kinetic model has been developed to predict precipitation of V(C, N) in vanadium microalloyed steels with a series of carbon and nitrogen contents. The solubility product and driving force of carbonitrides precipitated in austenite as well as the interfacial energy and other parameters can be evaluated to predict Nucleation rates-Temperature (NrT) and Precipitation-Time-Temperature (PTT) diagram. By using stress relaxation tests and fitting with Avrami equation, it is possible to draw PTT diagrams. The predictions of the model coincide with results of experimental investigation on V(C, N) precipitation in austenite. The nose temperature is around 850 degrees C obtained by experiment which is different from the prediction of the model and the difference is 30 degrees C and nitrogen has more effect on the shape of "C" curve of PTT diagram than carbon that makes "C" curve move leftward significantly.