| abstract |
Provided is an ultra high strength and toughness steel plate having a low yield ratio, with the chemical elements therein having the following mass percent contents: C:0.18-0.34%, Si: 0.10—0.40%, Mn: 0.50-1.40%, Cr: 0.20—0.70%, Mo: 0.30—0.90%, Nb: 0—0.06%, Ni: 0.50-2.40%, V: 0—0.06%, Ti: 0.002-0.04%, Al: 0.01-0.08%, B: 0.0006-0.0020%, N≤0.0060%, O≤0.0040%, Ca: 0-0.0045%, and the balance being Fe and other inevitable impurities. Also provided is a method for manufacturing the steel plate, comprising: a heating temperature of 1080-1250°C, a quenching temperature of 860-940°C, and a tempering temperature of 150-350°C. |