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At present, domestic building for low strength rebar are80percent of335Mpa level reinforced, namely20MnSi II grade steel, the application of highly strength rebar of400Mpa is less, it is a big miss distance compared with the developed countries.20MnSi II rebar the major disadvantage is low strength, and unsatisfactory bending performance, the strain rate decreased by20%-29%. Secondly, in construction of the dense reinforcement affect concrete pouring, and do not have the anti-seismic performance. And III reinforced high performance level, included high strength, excellent plasticity, good welding performance, the cold bending property, saving steel and the convenient construction, etc. For these purposes, our country enhanced the research and development of400Mpa rebar, lighted for reaching in the level of international as soon as possible, and speed up the upgrading of building steel, popularize application of400MPa level rebar.HRB400rebar is based on20MnSi rebar added micro alloying element niobium, titanium, vanadium, using of the precipitation strengthening function of its carbide and carbon compounds increased strength of steel, content the requirements of HRB400rebar. But in recent years, along with the rising price of vanadium, make the production cost increasing. In order to optimize the structure of products, reduce production cost of HRB400rebar, niobium micro alloying production of HRB400rebar were studied on by the factory.The test results show that, on the basic of the original process route of VN micro alloying, using of original production equipment, optimized the scheme of the Second-Cooling-Area water distribution of continuous casting, low multiple inspection qualified rate increased obviously; In the researching process of going through water cooling system in rolling, obtained a result that the best water pressure is about1.1MPa of the Nb micro alloying of HRB400rebar production.
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