| Customization: | Available |
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| Shape: | Powder |
| Purification Method: | Electromigration |
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The metal tungsten in powder form is the raw material for the preparation of tungsten processing materials, tungsten alloys and tungsten products.
Gray-black metal with metallic luster (body centered cubic crystal). Melting point 3400ºC. Boiling point 5555ºC. The hardness of tungsten is the hardest of the metals, the hardness of the sintered tungsten strip is 200 to 250, and the hardness of the rotary hammer rod is 350 to 400. Mixed acid soluble in nitric acid and hydrofluoric acid. Fused 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. Type a is a stable body-centered cubic structure at standard temperature and atmospheric pressure. Type B tungsten occurs only in the presence of oxygen. It is stable below 630ºC, and converts to tungsten a above 630ºC, and this process is irreversible.
Writing method editor
Tungsten trioxide or ammonium paratungstate was prepared by hydrogen reduction. The process of producing tungsten powder by hydrogen reduction is generally divided into two stages: in the first stage, tungsten trioxide is reduced to tungsten dioxide at the temperature of 500-700 ºC; In the second stage, tungsten dioxide is reduced to tungsten powder at 700 ~ 900ºC. Reduction reactions are usually carried out in tubular or rotary furnaces.
The properties of reduced tungsten powder (such as purity, particle size, particle size composition, etc.) mainly depend on the reduction process. In the process of reducing tungsten powder in tubular furnace, the main process parameters affecting the reduction speed are reduction temperature, tungsten oxide loading in the boat, moving speed of the boat, hydrogen flow rate and water content in hydrogen. With the increase of reduction temperature, the particle size of tungsten powder becomes coarser.
In addition to hydrogen reduction method, tungsten oxide carbon reduction method was also used in the early preparation of tungsten powder. The reduction temperature was higher than 1050ºC. The purity of tungsten powder obtained by this method is low. In addition, the process of reducing tungsten oxide with aluminum, calcium, zinc and other metals is also in progress. For the tungsten powder with high purity and ultra-fine particle size required for special application, the tungsten chloride hydrogen reduction method was developed, and the particle size of the obtained tungsten powder can be less than 0.05μm.
It can be produced by reducing tungsten trioxide with hydrogen in industrial production. Or ammonium paratungstate with acid treatment, and then mature decomposition to get tungsten trioxide, with hydrogen reduction to produce.
Hydrogen reduction of tungsten trioxide method: Reduction with hydrogen can be divided into two stages, the first stage of the tungsten trioxide heating to 550 ~ 800ºC, with hydrogen reduction, the second stage of reduction at 650 ~ 850ºC, to produce tungsten powder finished products.
Ammonium paratungstate can also be first reduced to blue tungsten oxide (blue tungsten) with or without hydrogen, and then reduced to tungsten powder with hydrogen. The particle size and composition of tungsten powder are important quality indexes. Reduction is carried out in tubular or rotary electric furnace. [1] [2]
Performance and Standards editorial broadcast
In addition to the requirement of impurity content, oxygen content of tungsten powder should be controlled within a certain range. The average size of tungsten powder is 2 ~ 10μm. Tungsten powder is a polygonal particle shape. In addition, the specific surface, loose density and solid density of tungsten powder also vary within a certain range. The properties of tungsten powder have direct influence on the production of tungsten material and the quality of tungsten powder metallurgy products, especially the purity and particle size. Tungsten powder is classified according to purity and particle size and different uses.
The earliest production of tungsten powder was divided into three levels according to chemical purity. Japan has formulated the "tungsten powder and tungsten carbide powder" industry standard (JISH2116-1979); The United Kingdom, France and the former Soviet Union have unified national standards for tungsten powder. In 1982, Technical Conditions for Hydrogen Reduction of Tungsten Powder (GB3458-82) was formulated for industrial production of Tungsten Powder in China. The standard specifies the properties and classification of tungsten powder. And the inspection methods, acceptance rules, packaging, transportation and storage items have made clear provisions. For special use and military special tungsten powder, manufacturers can according to user requirements trial production. [3]
Use editing broadcast
Tungsten is mostly used in the production of cemented carbides and tungsten iron. Tungsten, chromium, molybdenum and cobalt constitute heat-resistant and wear-resistant alloy for the production of cutting tools, metal surface hardening materials, gas turbine blades and combustion tubes. Tungsten and tantalum, niobium, molybdenum and other forms of refractory alloys. Tungsten-copper and tungsten-silver alloys are used as electrical contact materials. A high density tungsten-nickel-copper alloy is used as a shield against radiation. Tungsten wire, rod, sheet and so on are used to make electric bulbs, electronic tube parts and arc welding electrodes. Tungsten powder can be fired into a filter of various porosity. FW-1 is used for large slab, tungsten - rhenium electric couple raw materials. FW-2 is used for contact alloy and high specific gravity shielding material. FWP-1 is used for plasma spray materials.
Tungsten powder is the main raw material for processing powder metallurgy tungsten products and tungsten alloys. Pure tungsten powder can be made into wire, rod, tube, plate and other processing materials and certain shape products. Tungsten powder mixed with other metal powders can be made into various tungsten alloys, such as tungsten molybdenum alloy, tungsten rhenium alloy, tungsten copper alloy and high density tungsten alloy. Another important application of tungsten powder is in the preparation of tungsten carbide powder for carbide tools such as turning cutters, milling cutters, drills and dies. [3]
Grade editing broadcast
According to different particle size, tungsten powder can be divided into 14 grades:
level
Particle size (µm)
Oxygen content (%,Max.)
W-0
0.40 ~ 0.69
0.3
W-1
0.70 ~ 0.99
0.3
W-2
1.00 ~ 1.49
0.25
W-3
1.50 ~ 1.99
0.2
W-4
2.00 ~ 2.49
0.15
W-5
2.50 ~ 2.99
0.15
W-6
3.00 ~ 3.49
0.1
W-7
3.50 ~ 3.99
0.1
W-8
4.00 ~ 4.49
0.07
W-9
4.50 ~ 4.99
0.07
W-10
5.00 ~ 6.99
0.05
W-11
7.00 ~ 8.99
0.05
W-12
8.99 ~ 14.99
0.05
W-13
15.00 ~ 25.00
0.05
Granular editing broadcast
Tungsten powder particles refer to the tungsten powder sintered into bars and other tungsten blocks, and then broken into tungsten particles. Tungsten powder particles are distinguished by mesh number. Tungsten particle is used as catalyst of alloy powder, etc.
Physical performance analysis
category
describe
Head number analysis
mesh
Weight ratio %
GW-1220
- 12 / + 20
+12 to -20
0 ~ 10
GW-2060
- 20 / + 60
Plus 20 to minus 60
0 ~ 10
GW-6000
60 / + 200
+60 to 200
0 ~ 10
Chemical composition analysis
Metal Element content Table (WT %)
The element
Maximum value
The element
Maximum value
Al
0.01
Fe
0.10
Cr
0.02
Mo
0.10
Cu
0.02
Ni
0.05
Non-metallic element content Table (WT %)
C
< 0.10
O
< 0.10
Tungsten (WT %) > 99.5
Graded editing broadcast
The quality of tungsten powder directly determines the quality and alloy properties of WC. The classification of tungsten powder can effectively change the performance of WC powder, solve the problem of the thickness and fineness of powder clip, reduce the difference between the minimum particle size, maximum particle size and average particle size, and produce coarser and more uniform WC powder. Because the characteristics of tungsten decide that it is not easy to break, moderate crushing is carried out before classification to separate the agglomeration particles in the powder, which can more effectively separate the powder and improve the uniformity. The operation parameters of the system must be regulated strictly and precisely. The best operation process must be found according to the characteristics of the original powder.
Security
For toxicity of tungsten powder, see tungsten trioxide. The product is loaded into a clean polyethylene plastic bottle, the bottle cap should be tightened, the plastic bottle is placed in a wooden case with soft material around, or the product is loaded into an iron bucket lined with polyethylene plastic bag, the net weight of each box (bucket) is 30kg. Products should be stored in dry, ventilated and acid - and alkali - free atmosphere in the warehouse, strictly prevent oxidation. The product transportation process to prevent rain and moisture, not violent collision. The storage period of FW-1 and FW-2 should not exceed half a year, and the storage period of FWP-1 should not exceed half a year
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