Method for manufacturing thin strip continuously cast 700mpa-grade high strength weather-resistant steel

Abstract

A method for manufacturing thin strip continuously cast 700 Mpa grade high strength weather-resistant steel, the method comprising the following steps: 1) casting a 1-5 mm thick cast strip in a double roller continuous casting machine, the cast strip comprising the following chemical compositions by weight percent: C 0.03-0.1%, Si≤0.4%, Mn 0.75-2.0%, P 0.07-0.22%, S≤0.01%, N≤0.012%, and Cu 0.25-0.8%, further comprising more than one of Nb, V, Ti and Mo: Nb 0.01-0.1%, V 0.01-0.1%, Ti 0.01-0.1%, and Mo 0.1-0.5%, and the balance being Fe and unavoidable impurities; 2) cooling the cast strip at a rate greater than 20° C./s; 3) hot rolling the cast strip under a temperature of 1050-1250° C. at a reduction rate of 20-50% and a deformation rate greater than 20 s−1; then conducting austenite online recrystallization, the thickness of the hot rolled strip being 0.5-3.0 mm; 4) cooling at a rate of 10-80° C./s; and 5) rolling up under a temperature of 500-650° C. The obtained steel strip microstructure mainly consists of uniformly distributed bainites and needle-shaped ferrites.