1200 MPa-grade complex phase steel plate and preparation method thereof

The invention discloses a 1200 MPa grade complex phase steel plate and a preparation method thereof. The complex phase steel comprises the following chemical components in percentage by mass: 0.15 to 0.17 percent of C, 0.54 to 0.56 percent of Si, 1.55 to 1.75 percent of Mn, 0.27 to 0.31 percent of Cr, 0.58 to 0.62 percent of Mo, 0.05 to 0.10 percent of Al, 0.08 to 0.12 percent of Ti, 0.10 to 0.15 percent of V, 0.003 to 0.005 percent of B, 0.010 to 0.015 percent of N, less than or equal to 0.015 percent of P, less than or equal to 0.010 percent of S and the balance of Fe and inevitable impurities. The preparation method comprises the procedures of continuous casting, hot rolling and annealing. The yield strength of the multiphase steel plate is larger than or equal to 860 MPa, the tensile strength is larger than or equal to 1250 MPa, the yield ratio is smaller than or equal to 0.70, the hole expansion rate is larger than or equal to 20%, and the performance is excellent. 本发明公开一种1200MPa级复相钢板及其制备方法，复相钢的化学成分按质量百分