420MPa normalizing super-thick steel plate, and preparation method thereof

The invention discloses a 420MPa normalizing super-thick steel plate, and a preparation method thereof. The 420MPa normalizing super-thick steel plate comprises following chemical components, by mass, 0.14 to 0.16% of C, 0.30 to 0.40% of Si, 1.0 to 1.60% of Mn, 0.015 to 0.025% of Als, 0.005 to 0.025% of Nb, 0.065 to 0.10% of V, 0.010 to 0.02% of Ti, 0.2 to 0.45% of Ni, 0.05 to 0.30% of Cu, P less than 0.01% , S less than 0.005%, and the balance Fe and unavoidable impurities. The preparation method comprises following steps: continuous casting steel slab, which contains the above chemical components and possesses a thickness of 400mm, is subjected to two stages of rolling without water cooling, is discharged rapidly, and is subjected to stacking slow-cooling for 72h or more; and after steel plate shot blasting, the steel plate is obtained by normalizing plus accelerated cooling heat treatment process. The normalizing 100-120mm steel plate prepared by the preparation method possesses excellent strength and toughness; yield strength is more than 420MPa; and the normalizing 100 -120mm steel plate can be used for preparation of key force support elements of buildings, bridges and tower structures with large span frameworks.