Nickel-saving type steel plate for LNG (Liquefied Natural Gas) storage tank and manufacturing method thereof

The invention relates to a steel plate for a nickel-saving LNG (Liquefied Natural Gas) storage tank and a manufacturing method thereof, and belongs to the field of ferrous metallurgy, the steel plate comprises the following chemical components in percentage by mass: 0.02-0.05% of C, 0.05-0.20% of Si, 0.50-0.80% of Mn, 7.20-7.50% of Ni, less than or equal to 0.0070% of P, less than or equal to 0.0020% of S, 0.25-0.40% of Mo, 0.010-0.020% of Alt, 0.025-0.040% of Nb, 0.0005-0.0030% of Ca, less than or equal to 0.0010% of O, less than or equal to 0.004% of N, less than or equal to 0.00010% of H and the balance of Fe and inevitable impurity elements. The steel plate structure is uniform tempered sorbite, the yield strength is larger than or equal to 585 MPa, the tensile strength ranges from 690 MPa to 820 MPa, the yield ratio is smaller than or equal to 0.90, the ductility is larger than or equal to 20%, and the impact toughness at the temperature of minus 196 DEG C is larger than or equal to 200 J. The ultrasonic