The invention discloses a hot-rolled high-weather-resistance steel plate with extremely low
yield ratio and 850 MPa-grade tensile strength as well as a manufacturing method and application of the hot-rolled high-weather-resistance steel plate. The steel plate comprises chemical components in percentage by weight as follows: 0.06%-0.08% of C, 0.40%-0.60% of Si, 0.40%-0.60% of Mn, smaller than or equal to 0.015% of P, smaller than or equal to 0.005% of S, 2.50%-3.00% of Cr, 0.25%-0.30% of Cu, 0.13%-0.15% of Ti, 0.020%-0.040% of Alt, smaller than or equal to 0.0040% of N, smaller than or equal to 0.0030% of O and the balance of Fe and inevitable impurities. The high Cr + high Ti design is adopted, the tensile strength reaches 850 MPa, the
weather resistance index I value is larger than or equal to 8.0, addition of
precious metal Ni is omitted, the addition amount of the strong
hardenability element Cr in the steel exceeds 2.50%, a
fine grain ferrite and
bainite double-phase structure is obtained in combination with the controlled rolling and controlled cooling process, meanwhile, the
precipitation strengthening and
fine grain strengthening effects of Ti are fully exerted, control over high strength and the extremely-low
yield ratio smaller than 0.65 is achieved, and the high-strength and low-yield-ratio steel is obtained. The forming performance is excellent, the
corrosion rate is smaller than 40% relative to Q345B, and good
atmospheric corrosion resistance is achieved.