Thermodynamic analysis of γ→α during hot deformation of X80 pipeline steel based on dislocation density

Deformation resistance of X80 pipeline steel was researched by experiment with the Gleeble-3500. Establishing the model of dislocation density of X80 pipeline steel through the corresponding relationship between dislocation density and deformation resistance, then combining with the thermodynamic model of X80 pipeline steel which is based on the KRC thermodynamics model in order to analysis the effect of different deformed temperature, strain rate and deformation on the transformation kinetics and phase equilibrium temperature. Through the experiment we can see that the calculation and the measured date of phase equilibrium temperature have good agreement and the relative error is 5.43%, which shows that the model has an important role in predicting the γ → α transformation, ferrite grain size, microstructure and property of X80 pipeline steel.