(a) the nature of tantalum
Refractory metal tantalum is the world's third, its melting point than tungsten, molybdenum, as high as 2980 ℃, pure tantalum with blue color, good plasticity, in the cold state without intermediate annealing can be rolled into thin plate is less than 0.01 mm (thickness.
Tantalum emission electron ability is weak, because of tantalum escape electronic power is lower than tungsten molybdenum and other refractory metal, has been widely used in electric vacuum technology.
Tantalum with a strong ability to resist corrosion, comparable with glass, under the environment of middle temperature (150 ℃), only the fluorine, hydrofluoric acid, sulfur trioxide (including fuming sulfuric acid), alkali, and some molten salt affect tantalum. Stable performance when metal tantalum in room temperature, but when heated to a temperature higher than 500 ℃ will generate Ta205 accelerated oxidation.
(b) of tantalum purposes
Tantalum metallurgical products for tantalum powder and tantalum alloy.
1. The capacitor tantalum powder and its application
Tantalum anode can be used as a capacitor, generated directly by anodic oxidation of dielectric oxide film. Tantalum capacitor is superior than other capacitors,, because of tantalum oxide dielectric film with high permittivity and breakdown voltage. The higher the purity of tantalum powder, tantalum capacitor anode membrane of the higher breakdown voltage, because of the high specific surface area of tantalum powder, even after pressing and sintering due to its special remains high specific surface area, pore structure makes the tantalum capacitor with high volume. We usually say the high volume of tantalum powder is suitable for the working voltage of less than 25 v tantalum capacitor, the main thermal reduction with sodium fluoride potassium tantalum acid preparation; Medium voltage (35 ~ 40 v) and pressure (50 ~ 63 v) for working voltage tantalum powder is used in more than 25 v tantalum capacitor, higher requirements for its purity and physical properties of the powder, such as control of the C, O and granularity, must use electron beam melting into ingot, then through hydrogenation burst to tantalum powder.
The capacitor tantalum powder is moving toward the direction of high volume, high purity, abroad tantalum powder volume has reached 40000 ~ 50000 micro method, v/g; Micro method, v / 70000 grams of tantalum powder has started trial, individual manufacturer to manufacture the direction of the micro method, v / 100000 g.
Tantalum capacitor is the annual output reaches 25 billion, 2000 years to tantalum powder 800 tons, tantalum nearly 150 tons. Since the tantalum capacitor in - 55 ~ 125 ℃ temperature range wide capacitance stability, high reliability and with compact, efficient and on time is long, etc, make it in computer, communications systems, aircraft, missiles, ships and weapons systems with the application of the instrument and control system of enduring, become the most important application of tantalum. In addition, in addition to the tantalum powder, tantalum foil for the foil type capacitors, tantalum used as capacitor anode lead.
2. Tantalum and its alloy and application
Tantalum alloy matrix elements is extremely popular, because tantalum has the tolerance clearance element tolerance and reasonable elastic modulus. Tantalum with high corrosion resistance and easy to implement an inert gas tungsten arc welding (GTA), therefore is suitable for manufacturing various chemical equipment, such as manufacturing all kinds of heat exchangers, coil, tube for condenser, cooling pipe and plug-in heater, etc. For example, the Cabot corporation manufacture standard specification is 1.2 m * 3.7 m * 3.7 mm of tantalum sheet has can be connected by explosion process to produce steel, copper and aluminum liner, use the tantalum lining material can produce chemical equipment of large, relatively cheap. Explosive welding is a kind of using explosives in a very short period of time the release of high-energy metal connection or processing method, which can realize large area between substrate and the cladding layer (cover) welding or compound, is a base material costs are relatively low, cladding, contact resistance, high temperature resistant special functions such as the effective method. In addition, tantalum crucible is suitable for the vacuum under high temperature and chemical reaction and special glass melting. Tantalum can also be some liquid metal corrosion resistance, such as can come in contact with the liquid sodium of 1375 ℃.
All product of tantalum and tantalum alloy with electron beam furnace smelting processing, according to the purpose, in order to obtain uniform composition of ingot casting, tantalum after electron beam furnace smelting purification, also for vacuum arc remelting (VAR).
Tantalum alloy lowest ductile-brittle transition temperature (196 ℃), good plasticity, small work hardening coefficient at low temperature, excellent high temperature strength, is 1600-1800 ℃ under the work of ideal structural material. At present has formed - Nb and Ta Ta - W two alloy materials, used in the manufacture of aviation navigation industry and space nuclear power system components.
3. The other application and application of tantalum allocation proportion
At present, the largest tantalum and outlook is also the most optimistic is the application field of electronic industry, estimates of total consumption (the global metal tantalum annual consumption of about 900 tons) of 66%; The second is the cutting tool industry, accounting for 22% of the total consumption; The third is the tantalum as super alloy high temperature strengthening additives, accounting for 6% of the total consumption. Is the fourth in the chemical engineering department, such as valves, heat exchangers and insert the heater in chemical equipment, accounting for 3% of the total consumption. The fifth is used for military purposes, accounted for 2% of the total consumption; 6 is used in medical field, accounting for 1% of the total consumption.
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