The hardness, tensile strength and
impact toughness of one quenched and tempered
steel with nominal composition of Fe-0.25C-3.0Cr-3.0Mo-0.6Ni-0.1Nb (mass fraction) both at room temperature and at elevated temperatures were investigated in order to develop high-strength steel for long-life gun barrel use. It is found that the steel has lower decrease rate of tensile strength at elevated temperature in comparison with the commonly used G4335V high-strength gun steel, which contains higher Ni and lower Cr and Mo contents. The high
elevated-temperature strength of the steel is attributed to the strong secondary hardening effect and high tempering softening resistance caused by the tempering precipitation of fine Mo-rich M2C carbides in the aaaaaaaaaaaaaaaa-Fe matrix. The experimental steel is not susceptible to secondary hardening embrittlement, meanwhile, its room-
temperature impact energy is much higher than the normal requirement of impact
Toughness for high strength gun steels. Therefore, the steel is suitable for production of long-life high-strength gun barrels with the combination of superior
elevated-temperature strength and good
Impact toughness.
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