本发明公开了一种785MPa级别海洋平台用特厚调质齿条钢板及制备方法，所述钢板化学组成按重量百分比为：C：0.08～0.15％，Mn：0.60～1.5％，Si：0.10～0.50％，S：0.002～0.005％，P：0.005～0.015％，Ni：2.7～4.％，Cr：0.40～1.00％，Mo：0.30～0.70％，Cu：0.10～0.40％，Nb：0～0.080％，V：0～0.10％，Ti：0～0.08％，Al：0.02～0.08％，B：0.0008～0.0015％，余量为Fe和其他不可避免的杂质。采用低C、高Ni‑Cr‑Mo合金化及Nb、V、Ti微合金化成分体系，屈服强度≥795MPa，抗拉强度≥865MPa，‑60℃夏比V型缺口冲击功≥140J，Z≥35％，最大厚度为100mm，可用于制造海洋平台用齿条。本发明所述的785MPa级别高淬透性高强韧海洋平台用特厚调质齿条钢板还具有低屈强比的特点，应用范围更广，结构安全性更高，适用于极低温度海域的工作环境。

The invention discloses an extremely thick quenched and tempered rack steel plate for a 785 MPa level ocean platform and a preparation method. The steel plate comprises the chemical components in percent by weight: 0.08-0.15% of C, 0.60-1.55 of Mn, 0.10-0.50% of Si, 0.002-0.005% of S, 0.005-0.015% of P, 2.7-4.0% of Ni, 0.40-1.00% of Cr, 0.30-0.70% of Mo, 0.10-0.40% of Cu, 0-0.080% of Nb, 0-0.10% of V, 0-0.08% of Ti, 0.02-0.08% of Al, 0.0008-0.0015% of B and the balance Fe and other inevitable impurities. By adopting a low C and high Ni-Cr-Mo alloyed and Nb, V and Ti microalloyed component system, the yield strength is greater than or equal to 795 MPa, the tensile strength is greater than or equal to 865 MPa, the -60 ℃ Charpy V-shaped notch impact energy is greater than or equal to 140J, Z is greater than or equal to 35%, and the maximum thickness is 100 mm, and the extremely thick quenched and tempered rack steel plate can be used for manufacturing a rack for the ocean platform. The extremely thick quenched and tempered rack steel plate for the 785 MPa level ocean platform with high hardenability and high toughness further has a characteristic of low yield ratio, and is widerin application range, higher in structural safety and suitable for a working environment in an extremely low-temperature sea area.