Processing Technology of Tantalum Bar to Wire

The production of tantalum wire is usually carried out by powder metallurgy or other isostatic pressing, vacuum sintering to obtain a tantalum rod, followed by cold rolling and surface cleaning to obtain a tantalum strip, and then the wire is obtained by surface oxidation coating, stretching, pickling, water washing, and annealing. The processing process of the tantalum bar to wire includes the following steps.

Isostatic molding

The chemical composition of the tantalum powder raw material for preparing the tantalum should meet the specified requirements, and the particle size distribution should satisfy the requirement that 100% is less than 0.074 m, and the content of less than 0.038 m (400) is not less than 60%. The bar blank after press forming requires no defects on the surface, no cracks, and has a certain strength, reaching 70% of the theoretical density.

Isostatic-molding
Isostatic-molding

Vacuum sintering

Usually, the melt sintering is performed, the sintering vacuum should be less than 0.133Pa, and the highest sintering temperature should be controlled within 2600 °C. Generally, after two times of vertical melting and sintering, the relative density of the tantalum can reach about 98%, and the surface of the tantalum is required to be smooth, without cracks, melted tumor knots, and bubbling.

Cold rolling

The production of tantalum wire and the forging of tantalum bars are generally carried out by cold rolling. It can be used as a manufacturing process before die forging, or it can be directly rolled into an ingot. Roll forging is a process in which a tantalum rod is passed through a pair of rotating wrought rolls equipped with circular arc dies, and plastically deformed by means of a cavity to obtain the desired ingot.

Cold rolling
Cold rolling

Anodizing

The purpose of anodizing is to uniformly coat an oxide film on the surface of the tantalum ingot (wire). As a carrier of the lubricant, the oxide film can uniformly and firmly adhere the lubricant, which can reduce the tensile friction coefficient, ensure the surface quality of the silk, and cannot directly contact the metal and the mold, then prevent the bonding and improve the tensile performance.

The standard of the oxide film is that the adhesion is strong, the micro-tightness is firm, the color is not easy to fall off, the thickness is uniform, the insulation is good, the residual current is small, and the surface is less crystalline.

Stretching

Stretching is a major process in the production of tantalum wire. The choice of lubricant, drawing die, stretching pass and stretching speed will directly affect the quality of the wire. The stretching of tantalum is divided into the thick wire and fine wire. Solid wax is generally used as a lubricant for roughening the thick tantalum wire with an oxide film, an aqueous solution of grease soap is generally used as a lubricant when the tantalum wire with oxide film is finely drawn. The tensile die has cemented carbide and diamond, the latter is better but more expensive. The processing rate of the stretching pass depends mainly on the quality of the oxide film and the quality of the lubricant.

The surface of the wire after stretching is stuck with oil and residual oxide film, so it is necessary to clean the surface with acid and then with pure water. For the fine wire, the acidity of the pickling and the pickling time are strictly controlled. When the oxygen content and the surface brightness are good, the acidity and pickling time should be minimized.

Tantalum wire
Tantalum wire

Vacuum annealing

Annealing of the tantalum wire includes two parts, intermediate annealing and finished annealing. The purpose of intermediate annealing is to eliminate work hardening and improve the processing plasticity of the wire to continue stretching, while annealing is to achieve the desired properties of the finished product.

Tantalum has good plasticity at room temperature, and the work hardening tendency at room temperature is not large. The practice has shown that the billet produced by powder metallurgy can be processed until the total deformation rate is about 95%; the total deformation rate of the extruded billet by electron beam melting and consumable arc melting can reach more than 99%. After the recrystallization annealing, the plasticity of tantalum at room temperature is completely recovered.

Wire rewinding

In order to facilitate the material leaving the factory after the wire has been annealed, it is generally necessary to rewind on a certain winding machine. When rewinding, it is necessary to prevent the surface from being stained or scratched and to prevent twisting.

Stanford Advanced Materials supplies high-quality tantalum products to meet our customers’ R&D and production needs. Please visit https://www.samaterials.com/ for more information.

Super Performances of Tantalum in the Electronics & Aerospace Industries

Tantalum has a series of excellent properties, such as high melting point, low vapor pressure, good cold processing performance, high chemical stability, as well as strong resistance to liquid metal corrosion, etc., it has important applications in high and new technology fields such as electronics, metallurgy, superconducting technology, automobile electronics, aerospace, medical treatment, and scientific research. The following is a brief introduction to the super performances of tantalum in the electronics and aerospace industries.

Electronics industry

In the electronic industry, tantalum is mainly used as tantalum capacitors, which are usually used in the form of capacitor grade tantalum powder, tantalum wire, and tantalum foil. A tantalum capacitor is one of the indispensable electronic components of radar, aerospace aircraft and missile, and it is widely used for civil use, such as mobile communication, electronic equipment, and instruments.

Tantalum Capacitors
Tantalum Capacitors

As the specific surface area of tantalum powder is large, the dielectric constant of the thin film of the dielectric body is large, so the capacitance is large, then the small large-capacity capacitors can be made. The electrolytic capacitors made of tantalum have the advantages of small size, lightweight, good reliability, wide operating temperature range, and long service life.

Tantalum electrolytic capacitors can be classified into solid electrolytic capacitors and liquid electrolytic capacitors, and they are mainly divided into two anode types: foil anode and sintered anode. Tantalum wire is used as the anode lead for both capacitors.

With the development of electronic industry, the miniaturization and high reliability of tantalum capacitors are becoming increasingly strict. At present, the international commercial specific capacity of tantalum powder has reached more than 150,000 mu.F•V/g, and the laboratory has reached 30,000 mu.F•V/g.

Tantalum is also used as a material for electron tubes. Due to its high melting point, low real gas pressure, good processing performance, small linear expansion coefficient, and good inspiratory property, tantalum is a good material for launching tube and high-power electron tube parts.

Besides the above, tantalum target is an important material for magnetron sputtering coating of electronic chips due to its high chemical stability. You may check out more information at the specialized target website.

Tantalum Target
Tantalum Target

Aerospace industry

In addition to a large number of tantalum capacitors used in the aerospace industry, tantalum is also mainly used in high-temperature alloy and tantalum matrix heat resistant alloy in the aerospace industry, especially engine. High-performance alloys such as superalloy, corrosion-resistant alloy, and wear-resistant alloy can be made by adding tantalum to nickel base, cobalt base, and iron-base alloys.

Compared with niobium superalloy, tantalum superalloy has superior performance, higher heat resistance, and greater stress load. These alloys are mainly used as heat-resistant and high-strength structural materials for supersonic aircraft, solid propellant rockets, and missiles, as well as parts for control and adjustment devices. For example, the combustion chamber of the American Ajina Spacecraft is made of ta-10w alloy, and the flame temperature is very high (up to 2760℃) when its cover is small.

Superalloy
Superalloy

The aerospace industry is the second largest user of niobium and tantalum. Niobium and tantalum alloys, especially their superalloys and heat-resistant alloys based on them, are indispensable supporting materials for hot components of aircraft jet engines, rockets, spacecraft, and other vehicles.

Stanford Advanced Materials supplies high-quality tantalum products to meet our customers’ R&D and production needs. Please visit https://www.samaterials.com/ for more information.