The invention provides low-yield-ratio super-thick maritime work steel with excellent core low-temperature
toughness and a manufacturing method of the low-yield-ratio super-thick maritime work steel, and belongs to the field of steel and iron material preparation. The low-yield-ratio super-thick marine steel with the excellent core low-temperature
toughness comprises the following chemical components in percentage by
mass: 0.10%-0.15% of C, 0.35%-0.45% of Si, 1.20%-1.50% of Mn, 3.00%-3.50% of Ni, 0.30%-0.50% of Mo, 0.15%-0.3% of Cr, 0.01%-0.02% of Ti, 0.030%-0.040% of V, 0.050%-0.060% of Nb, 0.0016%-0.0020% of B, 0.15%-0.25% of Cu, 0.060%-0.070% of Al, less than or equal to 0.010% of P, less than or equal to 0.004% of S, less than or equal to 0.39% of CET and the balance of Fe and inevitable impurities. According to the invention, a component design thought of a low-C, Ni-Nb-Mo-Al-B
system is adopted, and a three-section rolling and
quenching and
tempering heat treatment process is combined. Through strict control of
smelting continuous casting, controlled rolling and controlled cooling processes and
quenching and
tempering heat
treatment parameters, the super-thick marine steel with excellent comprehensive mechanical properties is successfully prepared. The steel shows good low-temperature
toughness in the core part, and meanwhile, the steel has a relatively low
yield ratio. According to the low-yield-ratio super-thick maritime work steel with the excellent core low-temperature toughness, the thickness range is 80-150 mm, the yield strength is larger than or equal to 690 MPa, the tensile strength is larger than or equal to 920 MPa, the percentage elongation after fracture is larger than or equal to 20%, the
yield ratio is smaller than or equal to 0.77, and the
impact energy KV2 at the temperature of-60 DEG C is larger than or equal to 80 J.