STRUCTURAL FEATURES OF STRUCTURAL STEELS MICROALLOYED WITH NITROGEN AND VANADIUM

Results are presented for a study of medium-carbon structural steels for the effect of microalloying with nitrogen, vanadium, and other nitride-forming elements on the microstructure and processes of nitride formation after hardening with tempering and rolling. The level of mechanical properties is compared after different treatment. It is shown that a lower bainite structure forms with high dislocation density after rolling and cooling steel to 550 degrees C. Within ferrite plates there is precipitation of finely dispersed densely located vanadium carbonitride. Strengthening as a result of good dispersion of the fine lower bainite structure, high dislocation density, and dispersion strengthening with precipitation of nanosize carbonitride phase provides a high level of mechanical properties after rolling and cooling to 550 degrees C, comparable with the level of properties after hardening and tempering.