Effect of Self-Tempering Temperature on Precipitation of Secondary Phase in V–Ti–N High-Strength Seismic Bars

Abstract

The effect of self-tempering temperature on precipitation of secondary phase is studied by using a V–Ti–N hot-rolled anti-seismic reinforced bar (HRB500E) at 800–900 °C. The results show that the secondary phase precipitated in steel is mainly square titanium nitride and elliptical vanadium carbonitride, and the size of TiN is above 50 nm, while that of V(C, N) is below 20 nm. As the self-tempering temperature decreases, the size of V(C, N) decreases, but the amount of precipitates at 850 °C is close to 900 °C, and the size is slightly less than that at 800 °C. With the decrease in self-tempering temperature, ferrite grains are gradually refined, yield strength increases, and strength ratio and elongation decrease. By controlling self-tempering temperature at 850 °C, the excellent comprehensive performance can be acquired with matched strength and toughness simultaneously.