The Exploitation And Development Of Aseismic Reinforcement HRB400E

The quick development of build structure has a much higher requirement for build-steels. High strength and high capability aseismic reinforcement steel is becoming a hot point home and aboard, especially after Wen Chuan earthquake. According to the high strain and low periodic fatigue stress during earthquake, aseismic reinforcement steel's strength level must be as same as the distinctive normal steel bar. Besides, the ratio of test tensile strength to yield strength shouldn't be smaller than 1.25 and yield strength to its eigenvalue shouldn't be bigger than 1.30, while the total elongation should be equal to 9% or even bigger.Refined grain strength can elevate the metal material's mechanism performances with refining the grains. Based the Hall-Petch formula, it's the only way to get high strength and good plasticity. Nowadays, micro alloying and control rolling is adopted to obtain good colligate capabilities in producing steel bar. As a result, we use V-N micro alloying to adjust the chemistry composition based on the HRB400, and control the last pass temperature to get fine ferrite and pearlite structure.The main content are as follows: convertor melting (V-N micro alloying)-Heat billet- Rough rolling-Mill rolling-Final rolling-Cold. For avoiding appearing the fibre structure and get mass deformed strip austenite non-recrystallization grain in order to get fine ferrite after phase transition, the final rolling temperature is controlled at about Ar3,that is 910℃nearby. The element Nitrogen can promote Vanadium to separate out. By electrolysis phase, proportion of vanadium precipitates is about 31.82%。On the one hand, vanadium precipitate provide more non-uniform nucleation sites which is propitious to separate out proeutectoid ferrite in austenite. Meanwhile, water cold and air cold after rolling makes steel bar's recrystallization occur at the temperature range of shred ferrite and pearlite transformation. It can increase pearlite to a certain extent and improve the structure's uniformity. On the other hand, vanadium precipitate has deposition pinning effect on the austenite grain boundary to refine grain.Steel bar's average grain size is about 11 levels with the average line length method. The final structure is proeutectoid ferrite+pearlite. The faster cold rate at edge makes pearlite nucleation rate increase, so pearlite content is much more than that at center. As the rough rolling temperature is 890~910℃, it may cause austenite component be uneven when initial rolling temperature is 1150℃, which result in reticulation proeutectoid ferrite during air cold.The main chemistry composition of productive steel bar with XRF is: (wt%):C=0.24,Mn=1.31,V=0.036,N=0.008,Ceq=0.47.Through the room temperature tensile experiment, the yield strength, tensile strength and elongation ratio of master material are approximately 475MPa, 632MPa and 26% respectively. The ratio of test tensile strength to yield strength is 1.33 and yield strength to its eigenvalue is 1.19. The average yield strength (Rel) and tensile strength (Rm) of weldment are 473MPa and 610MPa respectively. Steel bar own good bending capability, surface quality and size precision. All conditions are accord with the nation standard of aseismic reinforcement. Accordingly, this paper's produce method that is V-N micro alloying + control rolling can obtain HRB400E successfully. It has some guiding significance for industry manufacture.