Thermal treatment method for improving mechanical performances of normalized steel plate

The invention discloses a heat treatment method for improving mechanical property of a normalized steel plate, which belongs to the medium and thick steel plate manufacturing technical field. A rolled microalloying steel plate containing niobium is placed into a quenching furnace for conventional normalizing treatment, and is taken out of the furnace after 3 to 40 minutes of heat insulation, the quenching furnace is adopted to perform weak water-cooling treatment to the steel plate, the ratio of water supply and drain at a water outlet of a quenching machine is controlled to between 1 and 1.8, the roll speed is maintained to between 10 and 40m/min, and the measured surface temperature of the steel plate after the weak water-cooling treatment is between 600 and 800 DEG C. The method greatly improves the comprehensive performance of the steel plate compared with the conventional normalizing treatment: the yield strength is improved by between 50 and 80MPa, the tensile strength is improved by between 20 and 30MPa, the low-temperature toughness and the strain aging performance of the steel plate are both improved, the uniformity of the performance in the thickness direction of the steel plate is improved, and the plate shape and the surface quality of the steel plate are good.