700MPa grade cold-resistant high-strength structural steel plate and manufacturing method thereof

The invention belongs to the technical field of smelting, and in particular relates to a 700MPa grade cold-resistant high-strength structural steel plate and a manufacturing method thereof. The 700MPa grade cold-resistant high-strength structural steel plate is characterized by comprising the following main components: 0.12-0.22% of carbon, 0.10-0.55% of Si, 0.80-1.80% of manganese, no more than 0.55% of copper, no more than 0.020% of phosphor, no more than 0.005% of sulfur, 0.0005- 0.0030% of boron, 0.08-0.50% of molybdenum and the balance of Fe and unavoidable impurities. The high-strength steel produced by the invention for various 25-80 ton heavy-duty truck beam frame structure in rigid regions achieves excellent strength and toughness coupling, ductile-brittle transition temperature below -40 DEG C, and flatness of 0.9-2.5mm / m. The steel plate has yield strength of 610-750 MPa, and tensile strength in the range of 730-950 MPa; through reasonable quenching and tempering process, the steel plate gains strength of 700MPa, has tissue stress eliminated, and shows high impact toughness below -40 DEG C, improved plastic toughness index, and elongation reaching 16-26%. Therefore, compared with the Q345 prior art, the present invention makes obvious substantive progress and the enforcement effect is substantial.