Hydrogen induced cracking resistant pressure vessel steel plate with thickness of more than 200-250mm and manufacturing method of hydrogen induced cracking resistant pressure vessel steel plate

The invention relates to a hydrogen induced cracking resistant pressure vessel steel plate with the thickness larger than 200-250 mm. The steel plate comprises the following chemical components: 0.10%-0.20% of C, 0.15%-0.40% of Si, 0.95%-1.35% of Mn, less than or equal to 0.005% of P, less than or equal to 0.0008% of S, 0.10%-0.30% of Cr, 0.25%-0.40% of Ni, 0.08%-0.12% of Mo, 0.02%-0.05% of Alt, 0.01%-0.02% of Nb, 0.01%-0.03% of V, 0.01%-0.02% of Ti, less than or equal to 0.0005% of B and the balance of Fe and inevitable impurity elements. Meanwhile, the chemical components meet the requirements that the carbon equivalent Ceq is smaller than or equal to 0.45%, and Ceq = C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15. By strictly controlling the purity of molten steel and the metallurgical quality of a continuous casting base blank and adopting high-temperature diffusion heating, high-permeability rolling and normalizing, water accelerated cooling and tempering heat treatment processes, the optimal matching of the