Method for improving low-temperature impact toughness of high strength thick steel plate

The invention discloses a production method for improving the low-temperature impact toughness of a high strength thick steel plate, and belongs to the technical field of medium and thick steel plate production. The steel comprises the following chemical compositions: 0.05 to 0.15 percent of C, 0.15 to 0.40 percent of Si, 0.90 to 1.60 percent of Mn, less than 0.01 percent of P, less than 0.01 percent of S, 0.10 to 0.80 percent of Ni, 0.1 to 0.5 percent of Mo, 0.0008 to 0.0015 percent of B, 0.01 to 0.06 percent of microalloy element Nb, 0.01 to 0.07 percent of V, 0.01 to 0.03 percent of Ti and the balance of Fe; the thick steel plate is produced by soft reduction technology in a continuous casting process under the condition that a compression ratio is less than 4.0; and by a heat treatment process which comprises the steps of quenching, quenching and tempering, the texture of the steel plate after double quenching is controlled to be a hybrid texture with a hard phase and a soft phase, and the requirements on steel plate strength and low-temperature toughness are met at the same time. Under a small compression ratio, the thick steel plate has the performance equivalent to that of a thin steel plate by the combination of the heat treatment process and texture control; and compared with the methods such as die casting, forging and the like, the method is simple and feasible, and has high yield and low production cost.