Study of the kinetics of recrystallization and precipitation in low carbon content steels; Estudio de la cinetica de recristalizacion y de precipitacion en aceros de bajo contenido en carbono

The kinetics of precipitation and recrystallization in low carbon steels was studied, from the point of view of the interaction between both phenomena, in a series of experiments involving interrupted annealing. Two kinds of steel with very different nitrogen content were used, and an aluminum nitrate dissolution treatment at a temperature of 1220{sup o}C was carried out during three hours, after which the steel was air cooled, when AIN precipitation was not attained. An aluminum nitrate precipitation treatment was also carried out at 800{sup o}C for eight hours, after which, the air was cooled. A treatment of interrupted conventional annealing was performed, measuring the recrystallized fraction based on measurements of hardness. The activation energy for the recrystallization was determined in each case, with the AIN precipitation producing a delay in the recrystallization, shown by the greater activation energies for the corresponding recrystallization in those samples where the nitrogen was free at the start of the annealing treatment (522 kJ/mol against 469 kJ/mol). The steels that contained all the precipitated nitrogen had lower activation energies, which suggests that the aluminum nitride precipitation during recrystallization produces a delay, probably due to the decreased mobility of the grain edges from the effect of the precipitates (CW)