Ferro Niobium Properties and Uses

Niobium is a high melting point metal, steel gray, atomic weight 92.9064, outer electronic structure 4d5s, melting point 2467 ° C, boiling point 4740 ° C, density (20 ° C) is 8.6 g/cm3. Figure 1 shows the equilibrium phase diagram of the ferro-niobium binary system. There are two eutectic points and a MgZn2-type Raschmannian phase εNbFe2. The two eutectic points are located in Nb11.6%, 1360 ℃ and Nb about 55%, 1560 ℃. The melting temperature of industrially produced ferro-niobium (FeNb60) ranges from 1520 to 1600°C, with a density of about 8.0 g/cm3.

Ferro Niobium is mainly used in the smelting of high temperature (heat resistant) alloys, stainless steel and high strength low alloy steel. Niobium in stainless steel and heat-resistant steel, and the carbon in the steel to produce stable niobium carbide. Uniformly distributed in the grain boundaries of steel, preventing the grain growth of steel at high temperatures, the organization of the steel to play a role in refining, can improve the strength, toughness and creep properties of steel. The chemical affinity between niobium and carbon is much greater than that between chromium and carbon, therefore, when niobium is present in stainless steel, it can prevent chromium carbide from precipitating at the grain boundaries of steel, thus improving the corrosion resistance of steel. Niobium and nitrogen in steel to generate stable niobium nitride, improving the corrosion resistance of the steel surface. Niobium and oxygen in steel to generate stable niobium oxide, so that the surface of the steel to form a niobium oxide film, which can prevent the diffusion of oxygen to the internal antioxidant effect. Carbon steel add Nb0.015% ~ 0.05%, can play a role in refining the organization, so that the steel has good formability and welding performance. Niobium on the steel austenite recrystallization has a strong preventive effect, so that the steel at higher temperatures, effective control of rolling, and control of rolling toughening effect is very significant. So niobium as a microalloying element in carbon steel in the amount of greatly increased. The United States in microalloying with niobium, in 1959 only 1.9% of the total consumption of niobium, while in 1988 rose to 68%.
Niobium in high-temperature alloys play a solid solution strengthening and carbide precipitation strengthening role, improve the yield strength and surface stability of high-temperature alloys. The weight of niobium is one of the lighter of the refractory metals and is one of the factors for the large number of high temperature alloys used. Niobium-nickel alloys are used as additives to nickel-based high-temperature alloys, mainly to produce 718 alloy. The addition of niobium to permanent magnet alloys improves the coercivity properties of the alloy.
The addition of niobium to cast iron contributes to the formation of spheroidal and pearlitic organizations. It acts as a pregnant and refined casting organization. Niobium improves the strength, toughness, hardness and service life of castings at high temperatures. Electrodes use ferro-niobium as a solder component to improve the quality of the weld.