The invention relates to ultrafine grained
hot rolled dual-phase steel with tensile strength of above 750MPa and a manufacturing method of a plate thereof, belonging to the technical field of steel rolling, and the dual-phase steel comprises the following chemical components by weight percentage: 0.06-0.16% of C, 0.10-0.50% of Si, 1.00-2.00% of Mn, 0.02-0.06% of Al, 0.01-0.08% of Nb, 0-0.03% of Ti, not more than 0.1 of P, not more than 0.05 of S and the balance of Fe. The manufacturing method of the dual-phase steel comprises the following steps: 1) heating, heating a plate blank with the thickness of not less than 60mm to 1100-1250 DEG C, and keeping the temperature for 1-4h; 2) rolling and adopting the two-stage controlled rolling, wherein the
reduction rate in a recrystallization zone is larger than 60%, the
reduction rate in a non-recrystallization zone is larger than 70%, the initial rolling temperature of the recrystallization zone is 1100-1150 DEG C, the initial rolling temperature of the non-recrystallization zone is 880-940 DEG C, and the final rolling temperature is 770-860 DEG C; and 3) cooling, and adopting the continuous cooling after final rolling, wherein the
cooling rate is 30-40 DEG C / s, the coiling temperature is lower than 350 DEG C, and the thickness of a finished product is 2-10mm. The manufacturing method can obtain the high-performance steel plate with high strength, low yield-strength ratio and good extension property, and the steel plate can be suitable for forming
processing of high-strength automobiles, other industrial mechanical parts and the like.