Ultra-high strength steel plate and production method thereof

The invention discloses an ultra-high strength steel plate and a production method thereof and belongs to the technical field of engineering machinery. The steel plate comprises the following chemical components in percent by weight: 0.14-0.2 percent of C, 0.2-0.5 percent of Si, 0.6-1.0 percent of Mn, less than or equal to 0.010 percent of P, less than or equal to 0.006 percent of S, 0.02-0.05 percent of Al, 0.3-0.8 percent of Cr, 0.3-0.6 percent of Mo, 0.3-1.0 percent of Ni, 0.01-0.05 percent of Nb, 0.01-0.05 percent of Ti and the balance of Fe and inevitable impurities, wherein the carbon equivalent is 0.59 to 0.64. The production method comprises the following steps: smelting by adopting a 500kg vacuum furnace, and forging cast ingots; and heating a forging billet, controlling rolling, controlling cooling, quenching and performing tempering and heat treatment to obtain low-temperature tempering martensite. According to the method, the ultra-high strength steel plate with the yield strength of 1200-1300 Mpa can be successfully and stably produced.