Cr-Ni-Mo-V-Nb high-strength steel and preparation process thereof

The invention belongs to the technical field of heat treatment of metal materials, and relates to Cr-Ni-Mo-V-Nb high-strength steel and a preparation process thereof.The Cr-Ni-Mo-V-Nb high-strength steel is hot-rolled at the temperature of 1150 DEG C to obtain a plate, the plate is heated to 860 DEG C and then subjected to heat preservation for 2 h, then furnace cooling is conducted to 760 DEG C, heat preservation is continued for 2 h, the temperature is lowered to 400 DEG C and then air cooling is conducted to the room temperature, the plate is heated to 880 DEG C and subjected to heat preservation for 0.5 h, then water quenching is conducted to the room temperature, and the Cr-Ni-Mo-V-Nb high-strength steel is obtained. And the plate is tempered at the temperature of 200 DEG C for 4 h, and then air cooling is conducted to the room temperature. The structure of the Cr-Ni-Mo-V-Nb high-strength steel comprises lath martensite, twin crystals, retained austenite and carbides, the carbides comprise needle-shaped