Tantalum alloy is an alloy composed of tantalum and other elements. The anodic oxide film of tantalum is stable, corrosion-resistant and has excellent dielectric properties, which is suitable for manufacturing electrolytic capacitors. Tantalum has strong chemical corrosion resistance, in addition to hydrogen fluoride, sulfur trioxide, hydrofluoric acid, hot concentrated sulfuric acid and alkali, can resist the corrosion of all organic and inorganic acids, so it can be used as a corrosion resistant material in chemical industry and medicine. Tantalum carbide is an important additive in the manufacture of cemented carbide. Tantalum is also used in some electronic tubes. In 1958, Ta-10W alloy was put into production. In the 1960s, tantalum alloy was used in the aerospace industry as a high-temperature structural material. Tantalum and tantalum alloy products include sheet, strip, foil, bar, wire, shaped parts and sintered products.
The plasticity of pure tantalum is good, the deformation resistance is small, the work hardening rate is small, all kinds of profiles and shaped parts can be obtained by plastic processing method. Pure tantalum can be rolled into sheet, strip, foil, tube and bar at room temperature, and the processing rate can reach more than 90%. In order to reduce oxidation, plastic processing of pure tantalum is often carried out at room temperature or below 500℃. Tantalum alloy due to high strength and poor plasticity of the ingot, must first be opened above 1200℃, after the processing technology is the same as pure tantalum. The extrusion ratio of the blank should be greater than 4, and the forging ratio should be greater than 2. When the billet is heated, it is necessary to prevent gas pollution and reduce the plasticity of the material. In order to ensure that the product has good stamping and spinning properties, it is necessary to use cross rolling. The processing rate before cross rolling should be maintained at about 80%. Tantalum sheet can be made into cups, caps, tubes, cones, nozzles and other parts with different shapes by spinning and deep drawing. The diameter of the rotary forging rod for wire drawing is generally 2.5 mm. Because the tantalum is soft and easy to bond with the mold and scratch the surface, the wire drawing surface is often anodized to form an oxide film and lubricated with beeswax.
Tantalum and its alloy billets can be produced by powder metallurgy process or melting process. The powder metallurgy process is mostly used to produce small tantalum products and billets for processing. The powder tantalum raw material obtained by thermal reduction or electrolysis is pressed and then sintered under vacuum. The sintering process depends on the requirements for the use of the product. Primary sintering (1600 ~ 2200℃) is used to produce electrodes and porous anodes for smelting. Secondary sintering is used to produce billets for plastic processing such as forging, rolling and drawing. Forging or rolling is often carried out between two sintering, and the processing rate is about 50%. The secondary sintering temperature is 2000 ~ 2700℃.
