The invention discloses an ultralow-temperature high-
toughness 7Ni steel plate based on composite microalloying and a short-process preparation method, and relates to the technical field of steel production. The steel plate comprises the following chemical components in percentage by
mass: 0.03 to 0.06 percent of C, 0.15 to 0.30 percent of Si, 0.80 to 1.20 percent of Mn, 6.80 to 7.20 percent of Ni, 0.3 to 0.6 percent of Cr, 0.10 to 0.20 percent of Mo, 0.010 to 0.020 percent of Nb, 0.008 to 0.015 percent of Ti, less than or equal to 0.004 percent of P, less than or equal to 0.002 percent of S, less than or equal to 0.0015 percent of O and the balance of Fe and inevitable impurities. The preparation method sequentially comprises the steps of KR molten iron pretreatment,
oxygen converter
smelting, LF / RH refining,
continuous casting (
casting blank
slow cooling for 48 h), heating to 1180-1280 DEG C in the steel rolling stage, two-stage controlled rolling and gradient controlled cooling, and heat treatment is not needed. The transverse and longitudinal Rm of the steel plate is 690-825 MPa, the
Rel is larger than or equal to 600 MPa, the A is larger than or equal to 20%, the
impact absorption energy AKV at-196 DEG C is larger than or equal to 120 J, the Ni cost and
energy consumption are greatly reduced, and the stability and
batch manufacturing advantages of the steel plate are improved.