Influence of niobium on metal properties

Among the various microalloying elements of steel, scrap niobium is the most effective microalloying element, and niobium's role is so great that an abundance of niobium atoms in the iron atom can be used to achieve an improvement in the properties of steel. In fact the addition of 0.001%-0.1% niobium to steel is sufficient to change the mechanical properties of steel. For example: when adding 0.1% of the alloying elements, to improve the yield strength of steel in the following order: niobium 118MPa; vanadium 71.5MPa; molybdenum 40MPa; manganese 17.6MPa; titanium is zero. In fact, steel only need to add 0.03% -0.05% Nb, steel yield strength can be increased by more than 30%. And the cost of steel per ton only increased by 1 U.S. dollars. For example: the yield strength of ordinary medium carbon steel is generally 250MPa, adding trace niobium can make the strength increase to 350-800MPa.

Niobium as a micro-alloying elements added to steel does not change the structure of iron, but with the steel of carbon # nitrogen # sulfur combination, change the microstructure of steel. The strengthening effect of niobium on steel is mainly fine grain strengthening and diffusion strengthening, niobium and carbon and nitrogen in steel to generate stable carbides and carbon-nitrides. It also disperses carbides and forms steel with fine crystallization.
Niobium also enables diffuse distribution of precipitates by inducing precipitation and controlling the cooling rate. The toughness level of the steel is adjusted over a wide range. Therefore, the addition of niobium not only increases the strength of steel, but also improves its toughness, resistance to high-temperature oxidation and corrosion resistance! Reduces the brittle transition temperature of steel, obtaining good welding properties and molding properties.