400MPa-grade high-silicon weathering steel as well as preparation method and application thereof

The invention discloses 400MPa-grade high-silicon weathering steel as well as a preparation method and application thereof, and belongs to the technical field of iron and steel making. The invention provides the high-silicon weathering steel with brand new composition and good weathering effect, and the high-silicon weathering steel comprises less than or equal to 0.12% of C, 1.20% to 2.00% of Si,less than or equal to 1.50% of Mn, 0.005% to 0.030% of P, less than or equal to 0.015% of S, 0.20% to 0.80% of Cr, 0.10% to 0.40% of Ni, 0.20% to 0.60% of Cu, greater than or equal to 0.010% of Als and the balance of Fe and inevitable impurities. The atmospheric corrosion resistant index I of the high-silicon weathering steel is up to 8.05 to 9.16 and is significantly higher than 6.0, so that theexcellent atmospheric corrosion resistance of products is realized; and the high-silicon weathering steel can be exposed or light-coated in a dry areas and widely applied to the field of building, bridge construction or vehic