Method for reducing ductile-brittle transition temperature of martensitic high strength steel

The present invention relates to a method of high strength martensitic steel DBTT decreases, belonging to the technical field plate production. The range of the chemical composition of steel: C: 0.14 ~ 0.15%, Si: 0.20 ~ 0.25%, Mn: 1.0 ~ 1.1%, P≤0.02%, S≤0.005%, Cr: 0.30 ~ 0.80%, Ni: 0.30 ~ 0.80 %, Mo: 0.30 ~ 0.35%, Nb: 0.035 ~ 0.040%, Ti: 0.011 ~ 0.015%, B: 0.0010 ~ 0.0020%, the balance being Fe and unavoidable impurities. The present invention uses a zero heat hardening process, incubation times as compared with conventional quenching process the obtained steel sheet, the steel sheet of this process resulting in strength, impact toughness, have a certain level of hardness increase, in particular reduced DBTT 20 ℃ above. This production process is simple, short cycle, low degree of oxidation of the steel sheet, low energy consumption, high production efficiency.