INCUBATION TIME OF ISOTHERMALLY TRANSFORMED ALLOTRIOMORPHIC FERRITE IN MEDIUM CARBON STEELS

摘要

A mathematical process to calculate the incubation time of allotriomorphic ferrite isothermally formed in three medium carbon steels has been described. Calculations are based on well known phase transformation theories in steels. The influence of the alloying elements on the nucleation of allotriomorphic ferrite has been taken under consideration in calculations via an evaluation of their effect in the diffusivity of carbon and in the volume free energy change estimations.Finally, experimental validation of calculations has been carried out using dilatometric and metallographic analysis. An excellent agreement (higher than 90 percent in R~2) between calculated and measured incubation time values for the isothermal formation of allotriomorphic ferrite has been found in the three medium carbon steels.