100 mm-120 mm Q460D extra-thick high-strength steel and preparation method thereof

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 DE