The invention discloses a method for improving the performance of 700 MPa grade V-N microalloyed high strength
weathering steel. The method is specific to the characteristics of the sheet billet
continuous casting and tandem rolling technology and
metallurgy component, and adopts an electric furnace or a revolving furnace to smelt, refine, continuously cast sheet billet which directly enters into a roller
hearth to heat after a
casting blank concretes, or soaking furnace, hot rolling, laminar flow cooling and wind-up process flow. The
chemical composition of
molten steel is :C occupies less than or equal to 0.08Wt. percent, Si occupies from 0.25 to 0.75Wt. percent, Mn occupies from 0.2 to 2.0Wt.percent, P occupies less than or equal to 0.025Wt. percent, S occupies less than or equal to 0.040Wt. percent, Cu occupies from 0.25 to 0.60Wt. percent, Cr occupies from 0.30 to 1.25 Wt.percent, Ni occupies less than or equal to 0.65Wt. percent, V occupies from 0.02 to 0.20Wt. percent and N occupies from 0.015 to 0.030 Wt. percent. The invention takes full advantages of the characteristics of the sheet billet
continuous casting and tandem rolling short flow process and adopts the V-N microalloyed technique to produce 700 MPa grade high strength
weathering steel under the
thinning function of VN and V (C, N) nanometer scale precipitate on
crystal grain in
casting blank of the sheet billet
continuous casting and tandem rolling flow and the theory of
precipitation strength. By the optimization design of the
metallurgy component of V-N microalloyed 700MPa grade high strength
weathering steel, the invention increases the low temperature
impact ductility of coil of strip and improves the shaping property.