Continuously cast 140-mm thick plate Q345E and production method thereof

The invention discloses a continuously cast 140-mm thick plate Q345E and a production method thereof. The continuously cast 140-mm thick plate Q345E comprises the following chemical components in percentage by weight: 0.10%-0.15% of C, 0.15%-0.35% of Si, 1.2%-1.45% of Mn, less than or equal to 0.010 of P, less than or equal to 0.003 of S, 0.020%-0.050% of Als, 0.020%-0.040% of Nb, 0.010%-0.020% of Ti and the balance of Fe and residual elements. According to the production method, by virtue of processes of KR hot metal pretreatment, converter smelting, argon blowing treatment, LF refining and VD refining, harmful elements, such as P and S which are adverse to the toughness of materials, of types of steel are strictly controlled, so that the purity of molten steel can be guaranteed, and the internal quality of the steel is improved; by utilizing relatively low heating temperature, the excessive growth of austenite crystals in the heating process can be avoided; in a stack cooling process of steel plates, the internal stress generated in controlled rolling and controlled cooling processes can be relieved, and hydrogen is substantially expanded, so that the internal quality of the steel plates is effectively improved; in a thermal treatment link, the temperature increase speed and the holding temperature as well as the cooling speed of the steel plates after the steel plates are discharged from a furnace are strictly controlled, crystal grains of the steel plates are uniformly refined, and the differences of grain structures in the thickness direction are reduced, so that the excellent comprehensive mechanical properties of the steel plates are guaranteed.