500MPa Seismic Rebars Developed by Nitrogen-Rich and Vanadium-Microalloyed, Controlled Cooling Technology

摘要

500MPa high-strength seismic rebars was developed by nitrogen-rich & vanadium -microalloyed, controlled cooling technology in domestic steel plant of china, microalloy precipitates, microstructure, mechanical properties, welding performance and aging properties of rebars were researched by using metallographic microscopy, scanning electron microcopy, transmission electron microscopy, x-ray diffraction apparatus, flash-butt welding and mechanical properties testing. The results show that a large number of the dispersed V (C, N) precipitates are precipitated in the grain boundary, dislocation line and the ferrite matrix, precipitation size in the ferrite matrix is 10～20nm, V(C,N) precipitates amount accounts for 67.54% of the total amount of vanadium in steel, effect of precipitation strengthening is remarkable; when termination temperature after controlled cooling for rebars is controlled at 710°C～750°C, the core microstructure is polygonal ferrite and pearlite, ferrite grain grade is 11.0, outer layer microstructure is acicular ferrite, pearlite and a small amount of bainite, good effects on fine-grain strengthening and seismic performance are obtained; rebars have low strain aging and good welding performance; production cost is reduced by RMB 100 Yuan per ton steel compared with VN micro-alloyed and hot-rolling process, benefit is obvious.