Ti-Zr composite microalloyed 700MPa-grade high-strength and high-toughness steel plate and preparation method thereof

The invention discloses a Ti-Zr composite microalloyed 700MPa-grade high-strength and high-toughness steel plate and a preparation method, and belongs to the technical field of high-strength and high-toughness steel plates. The steel plate comprises the following chemical components in percentage by mass: 0.02 to 0.05 weight percent of C, 0.20 to 0.30 weight percent of Si, 1.45 to 1.80 weight percent of Mn, less than or equal to 0.005 weight percent of P, less than or equal to 0.005 weight percent of S, 0.10 to 0.20 weight percent of Ti, 0.01 to 0.07 weight percent of Zr and the balance of Fe and inevitable impurities. Wherein the ratio of Ti to Zr is (10: 7)-(20: 1), and the ratio of Ti to Zr is 0.11-0.27 wt.%. Through design of alloy components, optimization of a controlled rolling and controlled cooling technology and control of phase composition of the steel plate, high strength, high toughness and low yield ratio are achieved, and the requirements for steel in the fields of engineering machinery, heavy-l