The invention provides tensile strength more than or equal to 780MPa grade hot-rolled
dual phase steel. The dual-phase steel comprises the following components in percentage by weight: 0.05-0.08 percent of C, not more than 0.5 percent of S, 0.6-1.2 percent of Mn, less than or equal to 0.015 percent of P, less than or equal to 0.005 percent of S, less than or equal to 0.006 percent of N, 0.01-0.1 percent of Als, 0.05-0.25 percent of Ti, less than or equal to 0.6 percent of Cr or less than or equal to 0.003 percent of B or mixture of Cr and B. The production method by using CSP comprises the following steps: melting and continuously
casting to form a slab; heating the continuous cast slab; rolling; carrying out
laminar cooling; reeling; and naturally cooling to
room temperature. The hot-rolled
dual phase steel has the tensile strength of more than or equal to 780MPa, elongation of more than or equal to 15 percent and
yield ratio of less than or equal to 0.70. An insulation cover additionally covers the intermediate insulation section, and the band steel
cooling speed is reduced, so that generation of
pearlite phase change can be effectively prevented. Production of hot-rolled
dual phase steel with thickness of 1.2-4.0mm can be realized, the product has the advantages of uniform structure, small molding resilience and no
cracking, existing equipment is utilized without adopting
ultra fast cooling and other equipment, the production efficiency is high, and the investment is small.