Vn Microalloying 77b Of 82b Steel Microstructure And Properties Of Study

Prestressed wires are used in high-span Bridges, highway, railway, high-rises buildings, television tower, nuclear power plant water conservancy project and other modern important projects due to its high strength and low relaxation. At present, domestic general high strength steel strands are 1860Mpa level.With the improvement of prestressed steels standards and intensity index of construction industry,the demand of high strength steel strand and galvanized steel wires above2000MPa is increasing gradually,the more high strength and toughness prestressed steels are required.There are a lot of research about V in low carbon steels now and the technical application is quite skilled,but it is very few in high-carbon steels.In this paper, the influences of V-N micro-alloying on microstructure and properties of 77B and 82B rods were researched,the strengthen-toughening mechanism was discussed to provides the basic theory for the actual production.In this research, the 77B and 82B steels which from non-vacuum smelting induction furnace were used as raw material, and the effect of V-N microalloying on the microstructure and properties of 77B and 82B were investigated by Gleeble thermal simulator simulating control rolling and control cooling processing technique of high carbon wire and salt bath isothermal test. In the end, the strengthen-toughening mechanism of V-N microalloyed hard steel wire were discussed. By analysis the conclusion is as follow:1. Before phase transition,V-N micro-alloyed 77B steels have higher comprehensive mechanical properties while cooling rate of 12℃/s-15℃/s.Eutectoid ferrite precipitates are effectively controlled with the increaseing the phase-change cooling rate; During phase transition,V-N micro-alloyed 77B steels have higher comprehensive mechanical properties while cooling rate of 2℃/s-3℃/s.Eutectoid ferrite precipitates are effectively controlled with the increaseing the phase-change cooling rate. 2. In the V micro-alloyed 77B and 82B steels,sorbite clusters are refined and the sorbite interlaminar spacing get thin. In the V-N complex micro-alloyed 77B and 82B steels,Sorbite clusters get more finer but the sorbite interlaminar spacing increase.3. N promote the precipitation of V,which take full advantage of the precipitation strengthening effect of V.These types of precipitates mainly are V(CN),the size is only a few nm.Most of them precipitate at the interface of ferrite.4. Compared with Vanadium micro-alloyed 77B and 82B steels,V-N micro-alloyed 77B and 82B steels has a higher tensile strength and cross-section shrinkage rate.