The invention relates to 100 mm-120 mm Q460D extra-thick high-strength steel which comprises the following chemical components including, by
mass, 0.10% to 0.13% of C, 0.30% to 0.50% of Si, 1.40% to 1.60% of Mn, less than or equal to 0.0070% of P, less than or equal to 0.0020% of S, 0.020% to 0.050% of Nb, 0.008% to 0.020% of Ti, 0.020% to 0.040% of Al, 0.10% to 0.20% of Cu, 0.10% to 0.20% of Cr, 0.10% to 0.20% of Ni and the balance Fe and inevitable
impurity elements. The production process flow comprises the following steps of converter
smelting, LF refining, RH vacuum degassing, Ca treatment,
continuous casting,
casting blank
dehydrogenation treatment, heating, normalizing rolling,
air cooling, steel plate stacking and
slow cooling and unstacking. The yield strength of a steel plate ranges from 430 MPa to 470 MPa, the tensile strength ranges from 550 MPa to 570 MPa, the
ductility is larger than or equal to 20%, and the Charpy
impact energy at the 1 / 4 position and the 1 / 2 position of the thickness of -20 DEG C is larger than or equal to 200 J. The flaw detection result meets the ASTM A 578C level requirement, and the surface of the steel plate has no defect.