Superhigh-strength high-toughness steel plate for ocean engineering and production method thereof

The invention discloses a superhigh-strength high-toughness steel plate for ocean engineering and a manufacturing method thereof. The superhigh-strength high-toughness steel plate comprises the following chemical components in percentage by weight: 0.06-0.10% of C, 0.20-0.40% of Si, 1.10-1.65% of Mn, at most 0.010% of P, at most 0.0020% of S, 0.030-0.050% of Nb, 0.020-0.060% of V, 0.006-0.015% of Ti, 0.60-1.30% of Ni, 0.30-0.60% of Cr, 0.20-0.60% of Cu, 0.40-0.60% of Mo, 0.020-0.040% of Alt, and the balance of Fe and inevitable impurities. The production method comprises the following steps: smelting in a converter, rolling on a Steckel reversing mill, and finally carrying out hardening and tempering heat treatment by a TMCP (thermomechanical rolling process) technique. The steel plate has favorable properties: the tensile strength is 770-840 MPa, the yield strength is 710-800 MPa, the elongation percentage is 16-19%, the -40 DEG C low-temperature lateral impact and low-temperature ageing impact properties are greater than or equal to 90J, and the cold bending resistance is qualified; and thus, the steel plate has the advantages of ultrahigh strength, excellent low-temperature impact and low-temperature ageing impact properties, and stable production technique.