“Bainitic Refinement” of Machine Steels Microalloyed with Vanadium and Nitrogen

Resumo

The effect of microalloying additions of N, V, Ti, Al, and Nb on structure formation and properties of medium-carbon steels alloyed mainly with chromium (30Kh2AF–40Kh2FABT type) is considered. Steel microalloying makes it possible to provide marked austenite structure refinement due to grain growth limitation by (Ti, V)N particles, retardation of austenite recrystallization and grain growth during stamping by Nb(C, N) particles (and Nb in solid solution), which leads to the formation of a fine final steel structure, as a result of which there is improvement of both strength properties and impact strength. Steel of the class in question may be produced by economic controlled stamping technology with cooling from rolling heating and subsequent tempering instead of heat treatment with quenching and separate heating and tempering. As a result, a unique set of properties is achieved: mechanical properties, brittle failure resistance, corrosion resistance, seismic resistance, fire resistance of long rolled product, building structure components, engineering components, oil recovery equipment, etc.