Development of 600 MPa High-strength Anti-seismic Rebars by Nitrogen-rich V-Cr Microalloyed Technology

In order to meet the needs of the upgrading development for construction steel,preparation of 600 MPa anti-seismic rebars by nitrogen-rich V-Cr microalloyed technology in domestic steel plant was carried out.The mechanical properties,fatigue performance,microstructure,precipitates and inclusions of the obtained rebars were tested and analyzed using tensile testing and material testing machines,metallographic microscopy,transmission electron microscopy and X-ray diffraction apparatus,respectively.The results show that the tested rebars feature favorable comprehensive properties with good strengthtoughness performance,anti-seismic properties,fatigue performance,high and low temperature tensile properties.The microstructure of the tested rebars are consisted of ferrite and pearlite(content 42%~48%),and the size of ferrite grains is greater than 10.5 grade with small and uniformly distributed particles.A large number of small and diffuse V(CN) precipitates sized 2~30 nm are formed and distributed on ferrite matrix,grain boundaries and dislocation lines,and the fraction of V(CN) precipitates is more than 70% to the total vanadium content.Meanwhile,there are a spot of small sized inclusions in the steel,which is helpful to improve the plasticity and toughness of the rebars.