Microstructure–property relationship of a high strength–toughness Cr–Mo–V steel

• Quenching at 800°C leads to untransformed ferrite and large undissolved carbides, severely degrading tensile strength and impact toughness. • Optimal precipitation strengthening is achieved with smaller carbides via low-temperature tempering (600°C), balancing strength and toughness. • Higher quenching temperatures enlarge prior austenite grains and sub-boundaries, reducing grain refinement and dislocation strengthening, thus lowering toughness. • The developed Cr–Mo–V steel achieves a tensile strength range of 971–1226 MPa and impact toughness of 65–236 J, offering a promising balance for ultra-deep well applications.