| Due to the high strength,good safety performance and low consumption,600 MPa high-strength rebar has been widely used in developed countries.Recently similar products have also started to be applied in some parts of China with the rapid development of China's infrastructure construction.Through analyses of the role of elements in steel,combined with the preparation process of rebar,the chemical composition and preparation process control scheme of microalloyed HRB600 E high-strength anti-seismic rebar were designed in this work.The trial-production for the rebar was conducted in small batches.According to the four schemes,the chemical compositions,the tensile and bending properties,the microstructures and inclusions,as well as the welding and fatigue properties of the trial steels were examined and analyzed.The trial rebars meet the technical requirements by China National Standards(GB1499.2-2018)for 600 MPa hot-rolled steel bar.The chemical composition and preparation process of the rebar were determined.On this basis,the application performances of HRB600 E high-strength anti-seismic reinforced concrete were tested and analyzed.The test results and contrastive analyses show that under the condition when LF furnace refining processes were adopted,the tensile,bending and aging properties of the HRB600 E rebar microalloyed by vanadium-niobium compositely can meet the technical requirements of anti-seismic rebar,the overall performances are stable,and the performance fluctuation is small.The pearlite content in the steel is 5 percent higher than that of the grade microalloyed by vanadium only.one more grade in grain size than that in vanadium microalloyed steel can be reached,and a higher average grain size can be gained.The non-metallic inclusions were found to be the types of A,C and D mainly and the grades of non-metallic inclusions are less than 2.0 on average.Under the two microalloying conditions,there was no significant difference in chemical composition,welding and fatigue performances.The preparation technology research shows that the final chemical compositions of HRB600 E high-strength anti-seismic rebar are as follows.As the chemical composition,the content of C in the steel is 0.25 percent to 0.28 percent,Si is 0.50 percent to 0.70 percent,Mn is 1.40 percent to 1.60 percent,V is 0.130 percent to0.160 percent,Nb is 0.010 percent to 0.040 percent,P is not more than 0.045 percent,S is not more than 0.045 percent and Ceq is 0.51 percent to 0.58 percent.The finalpreparation processes are as follows.Controlled by the LF furnace refining process.Various types of inclusions are not more than the level of 2.0 grade.After this preparation process,the strength indicators of HRB600 E high strength anti-seismic rebar have reached the national standard requirements of 600 MPa rebar and the anti-seismic performance is quite well.The flexural bearing capacity of beam,the anti-seismic performance of special-shaped columns and frame joints of HRB600 E high-strength reinforced concrete were tested and analyzed.The results indicate that this HRB600 E high-strength anti-seismic rebar has sufficient safety reserves,well flexural bearing capacity and good anti-seismic performance.It not only can successful explore for the HRB600 E steel bar preparation process,but also provide certain theoretical bases for the revision of high-strength steel building codes,and also can facilitate the promotion and application of HRB600E steel bar... |
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