Next, let’s introduce the overall information of tungsten.
Tungsten powder is the main raw material for processing powder metallurgy tungsten products and tungsten alloys. It can be made into processed materials and shaped products, such as wires, rods, pipes and plates. can be mixed with other metal powder to make various tungsten alloys, such as tungsten-molybdenum alloy, tungsten-alloy, copper alloy and high-density tungsten alloy.Another important application of it is the manufacture of tungsten carbide. Powder, and then prepare carbide tools, such as turning tools, milling cutters, drill bits and molds.
It is grayish black metal with metallic luster (body-centered cubic crystal). Melting point 3400 ℃. Boiling point 5555 ℃. The hardness of tungsten is the hardest among metals. The hardness of sintered tungsten bars is 200-250, and that of tungsten rods after rotary hammer is 350-400. Mixed acid dissolved in nitric acid and hydrofluoric acid. Melt with a mixture of sodium hydroxide and sodium carbonate. Slightly soluble in nitric acid, sulfuric acid, aqua regia; insoluble in water, hydrofluoric acid, potassium hydroxide. There are two variants of tungsten, a and B. At standard temperature and normal pressure, type a is a stable body-centered cubic structure. B-type tungsten can only appear in the presence of oxygen. It is stable below 630 ℃, it is converted to a tungsten above 630 ℃, and this process is irreversible.
Performance and standards:
In addition to certain requirements for the impurity content of it , the oxygen content should be controlled within a certain range. The particle size of commonly used tungsten powder is generally Fischer’s average particle size 2 ～ 10μm. The it is in the shape of polygonal particles. In addition, the specific surface, bulk density, and tap density of it also vary within a certain range. The performance of tungsten powder has a direct impact on the production of tungsten materials and the quality of tungsten powder metallurgy products, especially the effect of purity and particle size is more obvious. It is classified according to purity and particle size and different uses.
The earliest production of tungsten powder is to divide hydrogen-reduced tungsten powder into three grades according to chemical purity; Japan has formulated the industrial standard of “tungsten powder and tungsten carbide powder” (JISH2116-1979); the United Kingdom, France and the former Soviet Union have Unified national standard for tungsten powder. The tungsten powder produced by China’s industry formulated the “Technical Conditions for Hydrogen Reduction Tungsten Powder” in 1982 (GB3458-82). The standard specifies the performance and classification of tungsten powder. It also makes clear provisions on inspection methods, acceptance rules, packaging, transportation and storage. For special purpose and military-specific tungsten powder, the production plant can be trial-produced according to user requirements.
|Tungsten / tungsten powder|
|Chemistry / Level||FW-1||FW-2||FWP-1|
|Less than (Max.)||Fe||0.005 (particle size ≤ 10um)||0.03||0.03|
|0.01 (particle size >10um)|
Most of tungsten is used to produce cemented carbide and ferro-tungsten. Tungsten, chromium, molybdenum, and cobalt are heat-resistant and wear-resistant alloys used to make tools, hardened materials for metal surface, gas turbine blades and combustion tubes. Tungsten and tantalum, niobium, molybdenum and other refractory alloys. Tungsten copper and tungsten silver alloys are used as electrical contact materials. High-density tungsten-nickel-copper alloy is used as a shield against radiation. Metal tungsten wires, rods, sheets, etc. are used to make parts for light bulbs, electron tubes and electrodes for arc welding. Tungsten powder can be sintered into various porosity filters. FW-1 is used as raw material for large slab and tungsten rhenium couplers. FW-2 is used for contact alloy and high specific gravity shielding raw materials. FWP-1 is used for plasma spraying materials.
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