Resumen
The ferrite grain size of a 22MnVNb6 microalloyed steel can be estimated by developing a relationship between ferrite grain size, austenitising temperature and cooling rate from austenitising time, temperature. An extended Hall-Petch relationship was used to estimate the yield stress from the estimation ferrite grain size. Heat treatment as the annealing was used to improve the tensile and hardness properties of the steel. It was shown that the best combination of tensile and hardness properties were achieved when a higher austenitising temperature was used. Transmission electron and optical microscopy were used to study the morphology of ferrite and pearlite formed by the heat treatments. The microstructural studies showed that partition of grain by as-cast state was probably the reason for austenite and ferrite grain size improvement. Considering the experimental results, maximum errors of 14.5% and 7.5% were found in the estimation of ferrite grain size and tensile strength, respectively.