—The work covers the effect of niobium, as well as both niobium and vanadium, on mechanical properties of high-strength chromium-nickel-molybdenum steel after thermal refining. The mechanical ...properties of steels were determined after applying various tempering temperatures (from 580 to 660°C) and durations of tempering (from 1 to 16 h), and also after quenching from rolling heat and furnace heat with subsequent tempering. It is shown that, after quenching and tempering in the temperature range of 580–660°C of the high-strength steel of the Cr–Ni–Cu–Mo composition alloyed with 0.02% Nb and 0.07% V, the yield strength is higher as compared with steel alloyed with niobium (0.05%), at only an insignificant decrease in the impact strength and ductility. Increase of the total composition of the basic alloying elements does not result in a significant change in the mechanical properties within the investigated tempering temperature interval. Quenching from rolling heat increases the strength while maintaining high toughness, and the increase in strength is most noticeable for steel microalloyed only with niobium.
On the basis of studying the effect of chemical composition, controlled rolling temperature and deformation parameters, and accelerated cooling parameters, technology is developed for manufacturing ...pipe steel of strength class K60, providing under Ural Steel mill 2800 conditions the required level of mechanical properties and cold resistance.
