1180MPa-grade martensitic steel and preparation method thereof

The invention relates to the technical field of martensitic steel preparation, in particular to 1180MPa-grade martensitic steel and a preparation method thereof, and the martensitic steel comprises the following chemical components: 0.18-0.22 wt% of C, 2.30-2.90 wt% of Mn, 1.30-1.80 wt% of Si, 0.015-0.03 wt% of Nb, less than or equal to 0.01 wt% of P, less than or equal to 0.01 wt% of S, less than or equal to 0.004 wt% of N and Fe; the technical problems that in the prior art, high-strength steel is prone to cracking in the forming process, and the yield is low are solved, and according to the technical scheme adopted by the invention, a reasonable high-Si and high-Mn content alloy component system is designed; compared with traditional dual-phase steel, the martensite steel has the advantages that the yield strength of the martensite steel is 1000-1150 MPa, the tensile strength of the martensite steel is 1200-1300 MPa, the elongation of the martensite steel is 10-14%, and the hole expansion rate of the marte