Small dispersoid particles inhibit recrystallisation and are thus 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 sery 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 Nucleate 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. When comparing the predictions of the model with results of experimental investigation on V(C,N) precipitating in austenite, they have good coincidence. The nose temperature is around 850℃obtained by experiment which is 30℃ difference with the model, and nitrogen has more effect on the shape of “C” curve of PTT diagram then carbon that made “C” curve leftward significantly.

Small dispersoid particles inhibit recrystallisation and are thus 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 sery 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 Nucleate 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. When comparing the predictions of the model with results of experimental investigation on V(C,N) precipitating in austenite, they have good coincidence. The nose temperature is around 850℃obtained by experiment which is 30℃ difference with the model, and nitrogen has more effect on the shape of “C” curve of PTT diagram then carbon that made “C” curve leftward significantly.