Cold-rolled DH steel and preparation method thereof

The invention relates to the technical field of cold-rolled high-strength steel, in particular to cold-rolled DH steel and a preparation method thereof. The method comprises the steps that continuous annealing is conducted on a cold-rolled coil with set chemical components, and the atmosphere components and the dew point temperature of continuous annealing are controlled in a staged mode; and the annealed cold-rolled coil is flattened, the flattening elongation is controlled, and the cold-rolled DH steel is obtained. The grain size of a surface phosphating film of the DH steel prepared through the method is 5 microns or below, the coverage rate is 100%, and the P ratio is 88% or above. In addition, the yield strength of the DH steel ranges from 780 MPa to 920 MPa, and the tensile strength of the DH steel ranges from 1180 MPa to 1200 MPa. According to the method, the technical problem that the surface phosphorization performance of existing cold-rolled DH steel is poor is solved. 本申请涉及冷轧高强钢技术领域，尤其涉及一种冷轧DH钢及其制备