The invention discloses high
nickel steel for an ultralow-temperature
pressure vessel and a manufacturing method thereof. The high
nickel steel comprises the following chemical components, by weight, 0.01-0.08% of C, Si being less than or equal to 0.05%, 0.90-1.20% of Mn, 7.00-7.50% of Ni, 0.05-0.10% of Mo, 0.30-0.60% of Cr, 0.01-0.03% of Ti, S being less than or equal to 0.005%, P being less than or equal to 0.008% and the balance Fe and impurities. Two-stage controlled rolling is adopted. First-stage rolling temperature is greater than or equal to 1050 DEG C, secondary-stage rolling temperature is greater than or equal to 850 DEG C, finish rolling temperature is 750+ / -20 DEG C, and
air cooling is carried out after rolling;
thermal insulation is carried out for 2min / mm at 800-850 DEG C and
quenching is carried out,
thermal insulation is carried out for 2min / mm at 630-700 DEG C and
quenching is carried out,
thermal insulation is carried out for 4min / mm at 550-600 DEG C and
tempering is carried out, and
air cooling is finally carried out. The high
nickel steel for an ultralow-temperature
pressure vessel can replace 9% Ni steel. Thus, manufacturing cost of steel for an
LNG storage tank is reduced, and direct economic benefit can be created.