Manufacturing method for low-cost, high-toughness and thin-specification 9Ni steel plate

The invention discloses a manufacturing method for a low-cost, high-toughness and thin-specification 9Ni steel plate. Molten steel comprises 0.03%-0.06% of C, 0.1%-0.2% of Si, 0.5%-0.8% of Mn, 8.6%-9.1% of Ni, 0.02%-0.05% of Mo, 0.015%-0.035% of Als, smaller than or equal to 0.005% of S, smaller than or equal to 0.007% of P, smaller than or equal to 0.007% of N, and the balance Fe and impurities, wherein the impurities cannot be removed. A vacuum furnace with the vacuum degree smaller than or equal to 50 Pa is used for conducting smelting and alloying; the heating temperature ranges from 1,160 DEG C to 1,220 DEG C, the heat preservation time ranges from 90 min to 180 min, and the thickness of a blank ranges from 120 mm to 150 mm after cogging; two-stage controlled rolling is adopted, after rolling, the current temperature is kept for 10 s-15 s, then accelerated cooling is conducted to the temperature ranging from 440 DEG C to 550 DEG C with the cooling rate of 15-40 DEG C/s, and then air cooling is conducted to the room temperature; and the steel plate is heated to 575 DEG C-605 DEG C, and air cooling is conducted to the room temperature after tempering is conducted for 45 min-70 min. According to the manufacturing method, the characteristics of 9Ni steel materials and the thin-specification steel plate cooling characteristics are utilized, controlled rolling and controlled cooling are organically combined with a heat treatment technology, the material performance is improved, meanwhile, the technology process is shortened, the technology energy consumption is reduced, and the purpose of reducing the production cost of the high-toughness and thin-specification 9Ni steel plate is achieved.