Niobium wire, as an important refractory metal material, has similarities in production and application with tantalum wire, but it also has its own unique features. Niobium is renowned for its superconductivity, corrosion resistance and excellent processing performance.
The production of niobium wire also involves a precise processing procedure from powder to fine wire, with the core lying in the cycle of plastic processing and intermediate annealing. The overall process is similar to that of tantalum wire. The starting point of the process is high-purity niobium raw material, usually obtained from niobium rods through electron beam melting (EBM) or vacuum arc melting (VAR) to obtain high-purity niobium ingots, which are then forged and billet opened. This is the main method for producing high-performance niobium wire. Niobium powder is prepared by powder metallurgy, pressed into rods and then sintered. Hot working involves forging, extruding or rolling niobium ingots or sintered billets at high temperatures (typically above 1000°C but below their melting point of 2468°C) to process them into bars with smaller diameters (such as a few millimeters to tens of millimeters in diameter). This step aims to break the as-cast structure and enhance the material's density and plasticity. Cold working and intermediate annealing (core cycle) This is a key step in drawing niobium rods into wires, and it is a repeated cycle process.
In addition, niobium wire drawing is carried out at room temperature through a series of gradually shrinking molds to draw niobium rods/wires, reducing their diameter and increasing their length. Work hardening niobium also hardens rapidly and its plasticity decreases during cold working. Intermediate annealing must be carried out when the deformation reaches a certain extent and the material becomes too hard to continue drawing. Annealing is carried out in a high vacuum furnace to completely avoid oxidation and nitriding. Annealing temperatures typically range from 1000°C to 1400°C, depending on the desired grain size and mechanical properties. This step causes the material to recrystallize, completely eliminating work hardening and restoring plasticity. After each annealing, an oxide layer forms on the surface of the niobium wire, which needs to be removed by electrolytic polishing, acid washing or grinding to ensure a smooth surface, facilitating subsequent drawing and preventing mold wear.
The wide application of niobium wire is mainly based on its four major characteristics: superconductivity, high melting point, biocompatibility and corrosion resistance in certain media. This is the most renowned and technologically advanced application of niobium wire in the field of superconductivity (the most important and top-notch application).
Electronics and vacuum technology
Vacuum electronic devices: Due to the low venting rate and high melting point of niobium, niobium wire is used as the gate, support and getter material in vacuum tubes, traveling wave tubes and other devices. Neutralizers used in aerospace for space propulsion systems such as ion thrusters. Although capacitors are not as common as tantalum capacitors, niobium capacitors do exist, taking advantage of the niobium oxide dielectric film formed on their surfaces. Niobium wire can be used as an anode lead.
Niobium wire is one of the indispensable key materials in modern high-tech industries, especially in cutting-edge physical research, high-end medical care and vacuum industry.
