Study on Microstructure and Properties of V-Ti-N Weathering Steel

The dynamic CCT diagrams, precipitated V, grain size and strength for V-Ti-N weathering steels containing 0%V, 0.05%V, 0.10%V and 0.15%V respectively have been examined.In the study, the equipments such as vacuum induction furnace, hot simulation test, ICP emission spectrometer, optical microscope, TEM and electronic tensile tester were used.The results show as follows:addition of 0.10%V into weathering steel has a limited effect on dynamic CCT diagrams and Bs temperature of bainite transformation for 0%V and 0.10%V steel is below 600℃;the grain size of V-Ti-N weathering steels is 6.2~7.8 μm and make a contribution of 101~175 MPa to precipitation strengthening.Yield strength increases with the increase of V×N product, but the strengthening efficiency decreases gradually;V-Ti-N micro-alloying is better fit for development of 400 MPa and 450 MPa high strength weathering steel for which V content should be less than 0.10%.