Economical 700MPa-grade storage tank steel plate with excellent die welding performance and manufacturing method of economical 700MPa-grade storage tank steel plate

The economical 700MPa-grade storage tank steel plate comprises the following chemical components in percentage by mass: 0.10-0.20% of C, 0.30-0.50% of Si, 1.40-2.00% of Mn, less than or equal to 0.007% of P, less than or equal to 0.002% of S, 0.010-0.050% of Nb and Ti, 0-0.030% of Nb, 0-0.020% of Ti, 0.15-0.30% of Cr and the balance of Fe and inevitable impurity elements, and simultaneously meets the condition that the carbon equivalent CEV = C + Mn/6 + (Mo + V + Cr)/5 + (Ni + Cu)/15 is less than or equal to 0.47%, the element symbols in the formula represent the mass percentage content of the corresponding elements, and the element symbols in the formula represent the mass percentage content of the corresponding elements. Mo, V, Ni and Cu are residual elements, and w (Cr)/w (Nb + Ti) is more than or equal to 5 and less than or equal to 10. And the structure is tempered sorbite and tempered bainite, and the grain size reaches the level 8 or above. The transverse impact energy-70 DEG C KV2 at the 1/4 position