Niobium and columbium often coexist with tantalum, and their functions in steel are similar. Niobium and tantalum are partially dissolved into the solid solution and play a solid solution strengthening role. Significantly improves the hardenability of steel when dissolved into austenite. However, when present in the form of carbide and oxide particles, it refines the grains and reduces the hardenability of steel. It can increase the tempering stability of steel and has a secondary hardening effect. Trace amounts of niobium can increase the strength of steel without affecting its plasticity or toughness.
Due to the effect of refining grains, it can improve the impact toughness of steel and reduce its brittle transition temperature. When the content is greater than 8 times of carbon, almost all the carbon in the steel can be fixed, giving the steel good hydrogen resistance. In austenitic steel, intergranular corrosion of steel by oxidizing media can be prevented. Due to the effects of fixed carbon and precipitation hardening, it can improve the high-temperature properties of heat-strength steel, such as creep strength.
Niobium can improve the yield strength and impact toughness of ordinary low-alloy steels used in construction, and reduce the brittle transition temperature, which is beneficial to the welding performance. In carburizing and quenched and tempered alloy structural steel, it can increase the hardenability. Improve the toughness and low temperature properties of steel. It can reduce the air hardening of low carbon martensitic heat-resistant stainless steel, avoid hardening and tempering brittleness, and improve creep strength.
Zirconium is a strong carbide forming element and its role in steel is similar to that of niobium, tantalum and vanadium. Adding a small amount of zirconium can degas, purify and refine grains, which is beneficial to the low-temperature performance of steel and improves stamping performance. It is often used in the manufacture of ultra-high-strength steel and nickel-based high-temperature alloys used in gas engines and ballistic missile structures.
