Tungsten alloy is a kind of alloy based on tungsten (85% ~ 99% tungsten content), and a small amount of Ni. Cu, Fe. Co. Mo, Cr and other elements are added. Its density is as high as 16.5 ~ 18.75g/ cm³, commonly known as high specific gravity alloy, heavy alloy or high density tungsten alloy by the world. Tungsten alloys are widely used in the electronics and electric light source industries. They are also used to make rocket nozzles, die-casting molds, armor-piercing bullet cores, contacts, heating elements, and heat shields in aerospace, casting, weapons and other sectors.
| Name | Wolfram,Tungsten | Content | 90%~97% |
| Chemical formula | W-Ni-Fe, W-Ni-Cu, W-Ni-Cu-Fe | Hardness | 42HRC min |
| Element Symbol | W | Tensile Strength | 1400MPa min |
| Element Type | metal | Yield Strength | 1300MPa min |
| Melting point | 3410±20℃ | Elongation | 8% min |
| Moh’s Hardness | 7.5 | Atomic weight | 183.84 |
| Application | Rocket nozzles, die-casting molds, armor-piercing bullet cores used in electronics, electric light sources, aerospace, weapons | Belonging To Ethnic Group | Group VIB |
The Classification Of Tungsten Alloy
Molybdenum Tungsten Alloy
Alloys containing molybdenum and tungsten, which include molybdenum-based molybdenum-tungsten alloys and tungsten-based tungsten-molybdenum alloy series. This kind of alloy can be formed in any proportion and is a complete solid solution alloy at all temperatures.
Niobium Tungsten Alloy
A niobium alloy formed by adding a certain amount of tungsten and other elements based on niobium. Tungsten and niobium form an infinite solid solution. Tungsten is an effective strengthening element of niobium, but as the amount of tungsten increases, the plasticity-brittle transition temperature of the alloy will rise, and the grains will also grow significantly. Therefore, to obtain a high-strength niobium-tungsten alloy, the amount of tungsten added must be appropriately controlled, and at the same time, an appropriate amount of elements such as zirconium and hafnium that can refine grains and lower the plasticity-brittle transition temperature must be added. In 1961, the United States successfully developed the Nb-10W-2.5Zr alloy for the skin of the space shuttle, and later developed into the Nb-10W-1Zr-0.1C alloy. In the early 1970s, China also successfully developed NbWl0Zr2.5 and NbWl0Zr1C0.1 alloys.
Cemented carbide
Cemented carbide is the most common and main form of tungsten alloy. Different from the previous tungsten alloys, it is tungsten, carbon and cobalt, so it is often called tungsten-cobalt alloy. The most widely used tools in the industrial field are basically cemented carbide tools, so cemented carbide, a tungsten alloy, is also called “industrial teeth.”
Development History
In 1907, a tungsten alloy with low nickel content came out. It was prepared by mechanical processing, but its severe brittleness prevented its application. Until 1909, W.D. Coolidge of General Electric Company of the United States produced tungsten billets through powder metallurgy, and then used mechanical processing to produce tungsten wires that are ductile at room temperature, thus establishing the tungsten wire processing industry. The foundation also laid the foundation of powder metallurgy.
However, this “ductile” tungsten alloy exhibits obvious brittleness after the bulb is ignited. In 1913, Pintsch invented the thorium tungsten wire (ThO2 content is 1% to 2%), which greatly reduced the brittleness of the incandescent filament. At first, the sagging of the filament (see the anti-sagging performance of tungsten wire) was not a problem, because the filament at this time was a straight filament, but after 1913, Langmuir changed the straight filament to a spiral filament. When in use, the high working temperature and dead weight cause the filament to sag, so pure tungsten and thorium tungsten are difficult to meet the requirements of use.
In order to solve the problems of tungsten wire sagging and short life, in 1917, A. Pacz invented a tungsten alloy that was “undeformable” at high temperatures. At first, he used a refractory crucible to bake WO3 when preparing pure tungsten. He accidentally discovered that the tungsten wire spiral made from tungsten powder obtained by reduction of this WO3 was unusually mysterious and no longer sag after being recrystallized. Subsequently, after 218 repeated experiments and verifications, he finally found that the tungsten wire made by adding potassium and sodium silicate to tungstic acid (WO3·H2O) after reduction, pressing, sintering, and processing, recrystallized to form equivalent The coarse grain structure is neither soft nor sag resistant. This is the earliest tungsten wire that does not sag. Perth’s discovery laid the foundation for the production of non-sagging tungsten wires until the United States still called non-sagging tungsten wires “218 tungsten wires” to commemorate this major discovery of Perth.
The production process of doped tungsten alloy is lengthy, including the main stages of tungsten smelting, powder metallurgy billet making and plastic processing.
The production of doped tungsten alloys usually uses ammonium paratungstate (APT) as a raw material. In addition to the traditional classic processes for preparing ammonium paratungstate from tungsten concentrates, international studies on extraction and ion exchange were carried out in the 1950s. China also adopted these processes in the 1970s, thus simplifying the process and improving the tungsten The recovery rate. Since the 1960s, many countries have successively adopted the blue tungsten oxide doping process instead of tungsten trioxide doping, thereby improving the doping effect. The pickling of tungsten powder was used in production in the 1960s. Its main purpose is to wash away excess dopants, ultrafine powder and some harmful impurities in tungsten powder, thereby improving processing performance and improving the high-temperature performance of tungsten wire . Since the 1960s, the pass rolling method has been continuously applied. Pass rolling is to make the billet pass through the pass of a pair of rotating rolls, and under the pressure of the rolls, the section is reduced and the length is extended.
Although only a small part of tungsten ore is finally made into lamp tungsten wires and similar products, the most important scientific and technological significance of tungsten is the conversion of its research results to practical applications. The knowledge gained is of inestimable value in the new field of powder metallurgy, especially in the manufacture of cemented carbide.
The Use Of Tungsten Alloy
Filament industry
Tungsten was first used to make incandescent filaments. In 1909, American Coolidge (W.D. Coolidge) used tungsten powder pressing, remelting, swaging, and wire drawing processes to make tungsten wire. Since then, tungsten wire production has developed rapidly. In 1913, I. Langmuir and W. Rogers discovered that tungsten-thorium wire (also known as thorium-tungsten wire) had better electron emission performance than pure tungsten wire, and began to use tungsten-thorium wire, which is still widely used today. In 1922, a tungsten wire with excellent sagging resistance (called doped tungsten wire or non-sagging tungsten wire) was developed, which is a major progress in the research of tungsten wire. The non-sagging tungsten filament is an excellent filament and cathode material widely used. In the 1950s and 1960s, extensive exploration and research on tungsten-based alloys were carried out, hoping to develop tungsten alloys that could work at 1930-2760°C for the production of high-temperature parts for the aerospace industry. Among them, there are many studies on tungsten rhenium alloys. Research on tungsten smelting and processing and forming technology has also been carried out. Tungsten ingots are obtained by consumable arc and electron beam smelting, and some products are made by extrusion and plastic processing; however, the smelted ingots have coarse grains and poor plasticity , Processing is difficult, and the yield rate is low, so the smelting-plastic processing technology has not become the main production method. In addition to chemical vapor deposition (CVD method) and plasma spraying which can produce very few products, powder metallurgy is still the main method of manufacturing tungsten products.
Sheet Industry
China was able to produce tungsten wire in the 1950s. In the 1960s, research on tungsten smelting, powder metallurgy and processing technology was carried out, and now it can produce plates, sheets, foils, bars, pipes, wires and other special-shaped parts.
High temperature materials
The use temperature of tungsten materials is high, and the solid solution strengthening method alone has little effect on improving the high temperature strength of tungsten. However, dispersion (or precipitation) strengthening on the basis of solid solution strengthening can greatly improve the high temperature strength, and the strengthening effect of ThO2 and precipitated HfC dispersed particles is the best. Both W-Hf-C series and W-ThO2 series alloys have high high temperature strength and creep strength at around 1900°C. For the tungsten alloy used below the recrystallization temperature, the method of warm work hardening is adopted to produce strain strengthening, which is an effective strengthening method. For example, the fine tungsten wire has high tensile strength, the total processing deformation rate is 99.999%, the diameter of the fine tungsten wire is 0.015 mm, and the tensile strength can reach 438 kgf/mm at room temperature.
Among refractory metals, tungsten and tungsten alloys have the highest plastic-brittle transition temperature. The plasticity-brittle transition temperature of sintered and smelted polycrystalline tungsten material is between 150 and 450°C, which causes difficulties in processing and use, while single crystal tungsten is lower than room temperature. The interstitial impurities, microstructure and alloying elements in tungsten materials, as well as plastic processing and surface conditions, have a great influence on the plasticity-brittle transition temperature of tungsten materials. Except for rhenium, which can significantly reduce the plasticity-brittle transition temperature of tungsten materials, other alloying elements have little effect on reducing the plasticity-brittle transition temperature (see metal strengthening).
Tungsten has poor oxidation resistance, and its oxidation characteristics are similar to those of molybdenum. Tungsten trioxide volatilizes above 1000°C, resulting in “catastrophic” oxidation. Therefore, tungsten materials must be protected by vacuum or inert atmosphere when used at high temperature. If used in high temperature oxidizing atmosphere, protective coating must be added.
Military weapon industry
With scientific development and progress, tungsten alloy materials have become the raw materials for making military products today: such as bullets, armor and shells, shrapnel heads, grenades, shotguns, bullet bullets, bulletproof vehicles, armored tanks, military aviation, artillery parts, guns, etc. The armor-piercing projectiles made of tungsten alloy can penetrate large-angle armor and composite armor, and are the main anti-tank weapons.
Processing
Tungsten has a high melting point, is hard and brittle, and is difficult to process. However, as long as there is a reasonable process, tungsten can be processed into materials by powder metallurgy billeting, extrusion, forging, rolling, spinning and drawing. As the degree of plastic working of tungsten increases, its structure, tensile strength and plastic-brittle transition temperature are greatly improved.
Ready
Qualified blanks are one of the keys to tungsten production. To make a good blank, you must first select qualified tungsten powder. The characteristics of the powder (average particle size, particle size distribution, chemical composition), mixing, forming and sintering processes have a direct impact on the composition, density and microstructure of the blank, and strongly affect the processing and use performance of the product.
The silicon, aluminum, and potassium added to the non-sagging tungsten wire are added in the form of oxides in tungsten trioxide or “blue tungsten” (a mixture of a variety of low-order tungsten oxides). The mixture is usually containing hydrofluoric acid The solution is washed to remove impurities in the powder. The blanks for the production of filaments and small sheets are mostly formed on a press, and can also be formed by isostatic pressing.
The size of the powder blank is generally 12×12×400 mm, and there are also larger round rods, square rods or rectangular rods. The powder body is first sintered in a hydrogen atmosphere at 1200°C for 1 hour to make it have a certain strength and conductivity, and then conduct energization and self-resistance sintering.
Electrified self-resistance sintering, commonly known as “vertical melting”, is a method developed in tungsten processing. The principle is to pass the current directly through the sintered billet, which generates Joule heat due to the electrical resistance of the billet itself, and uses this heat to sinter the billet. The sintering current is usually 90% of the fusing current. The resulting blank is a self-resisting sintered bar (also called a vertical melting bar). The general standard for vertical frit bars that can be processed into wire is to control the number of cross-sectional crystal grains to be about 10,000 to 20,000 per square millimeter, and to have a density of 17.8 to 18.6 g/cm3. For pipes, sheets or other large-size products, isostatic pressing (pressure above 2500 kgf/mm2) is often used for forming, and sintered under vacuum or hydrogen protection at a high temperature of 2300-2700℃.
Rotary forging
Rotary forging is a common plastic processing method for the production of tungsten wire blanks and thin rods. Rods of different sizes are heated to 1400-1600°C in a hydrogen atmosphere and forged on different types of rotary forging machines. The deformation of the initial pass should not be too large, and then the deformation can be appropriately increased. Graphite lubrication is used between the workpiece and the die during the swaging deformation process. The density of the processed tungsten rod can reach 18.8～19.2 g/cm3. Since the billet is forged into a round billet, the deformation of each part is different, which makes the structure uneven. At this time, recrystallization annealing should be carried out. The final diameter of the swaging bar is about 3 mm.
Drawing
The wire drawing billet can be produced by rotary forging or rolling; the billet produced by the rolling method has large pass deformation and relatively uniform structure, which is conducive to subsequent processing. The tungsten wire is drawn from the tungsten wire blank using the “warm wire drawing” method. First, it is pulled to a diameter of 1.3 mm on a chain stretching machine, and then the diameters are 0.2, 0.06, and less than 0.06 mm by rough drawing, middle drawing and fine drawing respectively. As the diameter decreases, the heating temperature should be reduced and the drawing speed should be increased. The deformation of the pass is generally between 10 and 20%.
The wire drawing adopts gas-air mixing heating, and the temperature is 900～400℃. The thick wire uses a cemented carbide die, and the thin wire uses a diamond die. The mold material, hole shape, and grinding technology have a great influence on the quality of the wire. The quality, particle size, ratio, and coating method of the graphite lubricant also affect the quality of the wire.
The non-uniformity of the wire diameter is one of the most important reasons for wire breakage during use. A deviation of 0.2 to 0.4 microns will greatly reduce the life of the tungsten wire in the vacuum tube. The diameter of the filament can be measured by the gravimetric method or the vacuum standard current method. In the process of drawing, as the diameter decreases, the deformation resistance increases (for example, the breaking strength of a tungsten wire with a diameter of 0.1 to 0.3 mm can be as high as 350 kgf/mm2), and its plasticity also decreases accordingly. In order to improve the reprocessing performance, it is generally necessary to perform stress relief intermediate annealing. In addition, electrolytic corrosion can be used to process the wire into a thin wire with a diameter of less than 0.01 mm.
Grade Standard
AMS-T-21014
|
AMS-T-21014
|
Class 1
|
Class 1
|
Class 2
|
Class 2
|
|
Ratio
|
90W7Ni3Fe
|
91W6Ni3Fe
|
92W5Ni3Fe
|
93W4Ni3Fe
|
|
Density (g/cm3)
|
17.1±0.15
|
17.25±0.15
|
17.50±0.15
|
17.60±0.15
|
|
Heat treatment
|
sintering
|
sintering
|
sintering
|
sintering
|
|
Tensile strength (MPa)
|
900-1000
|
900-1000
|
900-1100
|
900-1100
|
|
Elongation (%)
|
18-29
|
17-27
|
16-26
|
16-24
|
|
Hardness (HRC)
|
24-28
|
25-29
|
25-29
|
26-30
|
|
AMS-T-21014
|
Class 3
|
Class 3
|
Class 4
|
|
Ratio
|
95W3Ni2Fe
|
96W3Ni1Fe
|
97W2Ni1Fe
|
|
Density (g/cm3)
|
18.10±0.15
|
18.30±0.15
|
18.50±0.15
|
|
Heat treatment
|
sintering
|
sintering
|
sintering
|
|
Tensile strength (MPa)
|
920-1100
|
920-1100
|
920-1100
|
|
Elongation (%)
|
10-22
|
8-20
|
6-13
|
|
Hardness (HRC)
|
27-32
|
28-34
|
28-36
|
Anviloy
|
Product
|
Normal Ratio
|
Density (g/cm3)
|
Ultimate tensile strength (N/mm2)
|
Hardness (HRC)
|
Application
|
|
Anviloy 1150
|
90%W4Mo4Ni2Fe
|
17.25
|
965
|
34
|
|
|
Anviloy 4200
|
93%WNiFeMo
|
17.8
|
885
|
30
|
Die Casting
|
|
Anviloy 4000
|
90%WNiFeMo
|
17.3
|
960
|
32
|
Die casting tools
|
|
Anviloy 4100
|
86%WNiFeMo
|
16.7
|
1075
|
36
|
Die casting tools
|
Mil-T-21014
|
GRADE
|
Mil-T-21014
|
|||||
|
Class1
|
Class 1
|
Class 2
|
Class 3
|
Class 3
|
Class 4
|
|
|
Ratio
|
90%W,
6%Ni4%Cu
|
90%W,
7%Ni3%Fe
|
92.5%W,
5.25%Ni
2.25%Fe
|
95%W,
3.5%Ni
1.5% Cu
|
95%W,
3.5%Ni
1.5%Fe
|
97%W,
2.1%Ni
0.9%Fe
|
|
Density (gm/cc;lbs/in3)
|
17;0.614
|
17;0.614
|
17.5;0.632
|
18;0.65
|
18;0.65
|
18.5;0.668
|
|
Hardness (RC)
|
24
|
25
|
26
|
27
|
27
|
28
|
|
Ultimate tensile strength (PSI)
|
110,000
|
120,000
|
114,000
|
110,000
|
120,000
|
123,000
|
|
Yield strength, .2% Offset (PSI)
|
80,000
|
88,000
|
84,000
|
85,000
|
90,000
|
85,000
|
|
Elongation (% in 1″)
|
6
|
10
|
7
|
7
|
7
|
5
|
|
Proportional Elasticity Limit (PSI)
|
45,000
|
52,000
|
46,000
|
45,000
|
44,000
|
45,000
|
|
Magnetic
|
Nil
|
Slightly
Magnetic
|
Slightly
Magnetic
|
Nil
|
Slightly
Magnetic
|
Slightly
Magnetic
|
|
ASTM-B-459-67
|
Grade1
Type Ⅱ && Ⅲ
|
Grade1
Type Ⅱ && Ⅲ
|
Grade2
Type Ⅱ && Ⅲ
|
Grade3
Type Ⅱ && Ⅲ
|
Grade3
Type Ⅱ && Ⅲ
|
Grade4
Type Ⅱ && Ⅲ
|
NAVY MIL-T-21014: Tungsten-based parts, high specific heavy metals (sintered or hot pressed), plating, chromium plating.
ASTM B 777-99
|
Class
|
1
|
2
|
3
|
4
|
|
|
Tungsten ratio%
|
90
|
92.5
|
95
|
97
|
|
|
Density (g/cc)
|
16.85-17.25
|
17.15-17.85
|
17.75-18.35
|
18.25-18.85
|
|
|
Hardness (HRC) Max
|
32
|
33
|
34
|
35
|
|
|
Ultimate tensile strength
|
ksi
|
110
|
110
|
105
|
100
|
|
Mpa
|
758
|
758
|
724
|
689
|
|
|
Yield strength at 0.2% off-set
|
ksi
|
75
|
75
|
75
|
75
|
|
Mpa
|
517
|
517
|
517
|
517
|
|
|
Elongation,%
|
5
|
5
|
3
|
2
|
|
Other Processing
The tungsten tube can be directly extruded with a sintered blank, and the extruded tube or the sintered tube can be processed by spinning. Spinning can also produce special-shaped products of tungsten. Large diameter bars are mostly produced by extrusion or rolling processes.
Cutting
Tungsten is hard and sensitive to notches, and cutting is difficult, requiring the use of cemented carbide tools. In order to prevent cutting cracks, the workpiece is often heated above the plasticity-brittle transition temperature for cutting, and the cutting operation procedures must be strictly controlled. The grinding of tungsten needs to be lightly ground with a specific type of grinding wheel, and it needs to be cooled, otherwise cracks will occur. Tungsten sheets with a thickness of more than 0.2 mm must be pre-heated before punching and cutting. Sheets with a thickness exceeding a certain thickness cannot be cut and often need to be cut with a grinding wheel.
Sheet rolling
Tungsten plate rolling can be divided into hot rolling, warm rolling and cold rolling. Due to the large deformation resistance of tungsten, ordinary rolls cannot fully meet the requirements of tungsten sheet rolling. Rolls made of special materials should be used. During rolling, the rolls should be preheated. According to different rolling conditions, the preheating temperature is 100-350°C. The blank can be processed only when its relative density (the ratio of actual density to theoretical density) is greater than 90%, and the processing performance is good when the blank density is 92-94%. The blooming temperature of hot rolling is between 1350 and 1500 ℃, and the deformation process parameters of the blooming are not properly selected, and the billet will be stratified. For a hot-rolled sheet with a starting temperature of 1200°C and a thickness of 8 mm, the warm rolling can reach 0.5 mm. Due to the large deformation resistance of the tungsten plate, the roll body bends and deforms during rolling, which makes the thickness of the plate uneven in the width direction. When changing rolls or mills, the plate may crack due to uneven deformation of various parts. The plasticity-brittle transition temperature of the 0.5 mm thick sheet is still room temperature or above, and the sheet is brittle. The sheet should be rolled to 0.2 mm at 200-500°C. In the later stage of rolling, the tungsten sheet is thin and long. In order to ensure the uniform heating of the sheet, graphite or molybdenum disulfide is often coated, which not only facilitates the heating of the sheet, but also has a lu.
The Design Of Tungsten Alloy
When designing tungsten alloys
- (1) in order to improve the plasticity of tungsten alloys, the content of oxygen and carbon must be reduced;
- (2) grain refinement and hot working are also effective methods to reduce the %BTT of tungsten alloys:
- (3) considering For the comprehensive properties of tungsten alloys, Re and Mo are the most effective solid solution strengthening elements, but when used in nuclear radiation environments, except for Re elements;
- (4) Refractory metal carbides are the most effective second-phase strengthening particles.
- (5) In order to realize the industrial production of tungsten-based composite materials, it is necessary to reduce its preparation and processing costs, so in-situ reaction and reactive infiltration methods are ideal methods for preparing tungsten-based composite materials
Tungsten Alloy Plating
The “corrosion” and “wear” of oilfield equipment are called two world-class problems. Approximately 29,200 oil wells across the country have different degrees of corrosion and wear. With the growth of my country’s oil and gas field development years and equipment service life, the situation is getting worse. In addition, the import volume of high-sulfur crude oil has increased significantly, and the problem of corrosion of refining equipment has also become increasingly prominent. Even more frightening is that the adverse effects of corrosion and wear on the safe and stable operation of equipment will become more and more prominent.
Among several main electroplating processes, the chromium electroplating process is wear-resistant and has low cost, but the environmental pollution is serious, and it is not resistant to chloride ion corrosion; the chemical nickel-phosphorus plating process is corrosion-resistant but not wear-resistant, and the cost is high; various thermal spraying processes The technical indicators are good, but the production cost is high and it is difficult to promote it on a large scale.
According to a well-known young chemical expert in my country, a postdoctoral fellow at the University of California, Professor Fengjiao He, a PhD supervisor at Hunan University, pointed out: “Research on the failure of parts caused by wear and corrosion shows that most of these failures occur on the surface of the material. Surface engineering is used to treat the surface of the material. Improve the surface properties of materials and effectively extend the service life of parts. Therefore, surface engineering has an important position in the petroleum and petrochemical industry.”
“Only tungsten alloy electroplating technology performance has been greatly improved, its hardness is equivalent to wear resistance and electroplating chromium, but acid and alkali resistance, low production cost, and the electroplating solution can be configured according to the specific operating conditions of the oil well, and the corresponding electroplating process can be implemented to meet The operating requirements. Under the same environment, the service life of equipment using tungsten alloy electroplating is several times longer.” Professor He Fengjiao explained, “The reason why tungsten alloy electroplating has such superior performance is that the coating obtained after tungsten alloy electroplating is new The alloy material has an amorphous structure in the plating state. After different heat treatment processes, it can be transformed into an amorphous inclusion nanocrystalline or nanocrystalline structure. The national authority has tested that the alloy has good wear resistance, good acid resistance, Alkali resistance, salt spray resistance, and excellent resistance to high temperature oxidation, and have a good bond with the base material.”
Tungsten alloy electroplating process solves the two major problems of corrosion and wear in one fell swoop. According to statistics, my country’s annual oil well pipes are more than 3 million tons, and high-tech, high value-added high-end oil well pipes, such as anti-H2S, Cl-corrosion-resistant oil pipes, etc. Import: 600,000 tons of oil pipes are imported each year, worth more than 30 billion yuan. The achievement has obtained 8 patent licenses, won the first prize of the National Machinery Industry Science and Technology Award, and won the National Key New Product Certificate. What made Professor He even more pleased was that the State Environmental Protection Administration listed the technology as a national key environmental protection practical technology (Class A), as a resource-saving and comprehensive utilization and environmental protection technology encouraged by the country to develop.
The application of tungsten alloy electroplating process in the petroleum machinery industry can not only solve the pollution problem caused by electroplating of chromium, but more importantly, it can improve the performance of various key parts and products of China’s petroleum machinery manufacturing industry, which will give the entire petroleum machinery manufacturing industry a boost. Changes have come and have promoted the overall upgrade of the industrial chain. Especially the anti-corrosion and sulfur-resistant oil well arms and sulfur-resistant drill pipes can be used in extreme corrosive environments with H2S content greater than or equal to 150,000 PPM and CL- content of 150 g/L. It has reached an internationally leading level in this industry, and solved the current situation of my country’s high-end drilling equipment relying on imported equipment.
The Related Information Of Tungsten
According to different uses, tungsten alloys are divided into hard alloys, high specific gravity alloys, metal sweating materials, contact materials, electronic and electric light source materials.
Doped tungsten wire is the addition of about 1% silicon, aluminum and potassium oxides to tungsten powder. During the vertical melting (self-resistance sintering) process, the additive potassium oxide volatilizes, forming pores inside the material, and the pores are processed along the edge. Axial elongation; after annealing, the elongated pores form a diffuse row of bubbles parallel to the silk axis. This diffused bubble is commonly known as potassium bubble. Potassium bubbles hinder the lateral growth of tungsten grains, improve the high-temperature sag resistance of tungsten, and can also improve the room temperature plasticity after recrystallization, which is beneficial to winding, transportation and storage. According to the high temperature creep value of China’s doped tungsten wire, there are three grades of WAl1, WAl2, and WAl3.
In the W-ThO2 series alloy, due to the addition of an appropriate amount of dispersed ThO2 particles with good thermal stability, not only can the electron work function be reduced, but also the growth of tungsten grains can be inhibited, so that the material has a high recrystallization temperature and is excellent High temperature strength and creep resistance. Tungsten-thorium alloy is not only a widely used thermionic emission material, but also an excellent electrode material.
In the tungsten rhenium alloy, the addition of rhenium can not only increase the strength of the material, and increase the recrystallization temperature of the alloy by about 200-400℃, so that the plasticity after secondary recrystallization is good, the grain growth is slow, and the plasticity-brittle transition can be significantly reduced. temperature. If the added rhenium exceeds 30%, the processing performance of the alloy will be impaired. Tungsten-rhenium alloy also has a high thermoelectric potential. At 2200℃, its thermoelectric potential has a linear relationship with temperature. The measurement temperature of tungsten rhenium thermocouple can be as high as 3000℃, which is an excellent high temperature thermocouple material.
The main problems existing in my country’s cemented carbide industry:
- First, the scale of enterprises is small, and the industrial concentration is not high.
- Second, the investment in science and technology is small, the lack of high-end technical talents, and the weak technological research and development capabilities. my country’s cemented carbide industry invests less than 3% of sales revenue in science and technology, the level of scientific and technological research and development is not high, and the original core technological achievements are few.
- The third is the low level of product quality, and the product structure needs to be adjusted. my country’s cemented carbide production accounts for more than 40% of the world’s total output, but cemented carbide sales revenue is less than 20% of the world’s total, mainly due to high-performance ultra-fine alloys, high-precision and high-performance abrasive coated blades, super-hard tool materials, and complex Due to the low output of high value-added products such as large-scale products and precision carbide CNC tools, insufficient deep-processing supporting facilities and incomplete varieties.
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