Large-thickness FH690 maritime work steel and preparation method thereof

The invention provides large-thickness FH690 maritime work steel and a preparation method thereof. The maritime work steel comprises the following chemical components in percentage by mass: 0.08-0.14% of C; 0.05%-0.25% of Si; 0.80% to 1.20% of Mn; p: less than or equal to 0.012%; s < = 0.002%; cu: less than or equal to 0.25%; 1.50% to 1.90% of Ni; 0.45% to 0.80% of Cr; 0.01% to 0.03% of Nb; 0.01% to 0.04% of V; 0.45% to 0.70% of Mo; b: 0.0007% to 0.002%; 0.05% to 0.08% of Als; o < = 0.001%; n is less than or equal to 0.005%, and the balance is Fe and inevitable impurities. The preparation method comprises the steps of smelting, continuous casting, casting blank slow cooling, a rolling process, a cooling process, a slow cooling process and a quenching and tempering heat treatment process. A large number of systematic experimental studies are carried out on the aspects of alloy element screening and proportioning, steel cleanliness control, a continuous casting process, a heating, controlled rolling and control