| Customization: | Available |
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| Application: | Aviation, Electronics, Industrial, Medical, Chemical |
| Standard: | GB |
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Tungsten alloy is a kind of tungsten based (tungsten content of 85% ~99%), and add a small amount of Ni.Cu, Fe. Co. Mo, Cr and other elements of the alloy, its density is up to 16.5~ 18.75g/cm3, known as high specific gravity alloy, heavy alloy or high density tungsten alloy.
Tungsten alloy is widely used in electronics and electric light source industry, and is also used in aerospace, casting, weapons and other sectors to make rocket nozzle, die casting mold, armor piercing core, contacts, heating body and heat shield.
Molybdenum tungsten alloy
An alloy containing two elements, molybdenum and tungsten, including molybdenum based molybdenum tungsten alloy and tungsten based tungsten molybdenum alloy series. The alloy can be formed in any proportion and is a complete solid solution alloy at all temperatures.
Niobium tungsten alloy
A niobium alloy based on niobium formed by adding a certain amount of tungsten and other elements. Tungsten and niobium form infinite solid solutions. Tungsten is an effective strengthening element of niobium, but with the increase of tungsten addition, the plasticity and brittleness transition temperature of the alloy will rise, and the grain will grow significantly. Therefore, in order to obtain high strength niobium tungsten alloy, it is necessary to properly control the addition of tungsten, and at the same time, it is necessary to add appropriate amount of elements such as zirconium and hafnium to refine the grain and reduce the plastic-brittle transition temperature. In 1961, the United States successfully developed Nb-10W-2.5Zr alloy for the skin of the space shuttle, and later developed into Nb-10W-1Zr-0.1C alloy. In the early 1970s, China also successfully developed NbWl0Zr2.5 and NbWl0Zr1C0.1 alloys.
Hard metal alloy
Hard alloy is the most common and main form of tungsten alloy. Unlike 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 carbide tools, so carbide this tungsten alloy is also known as "industrial teeth".
Development history editor
In 1907, a tungsten alloy with low nickel content was introduced. It was prepared by mechanical processing, but severe brittleness prevented its application. It was not until 1909 that W. D. Coolidge of General Electric Company in the United States made tungsten billet by powder metallurgy and then mechanically processed it to produce tungsten wire with ducibility at room temperature, thus laying the foundation of tungsten wire processing industry as well as powder metallurgy.
However, this "ductile" tungsten alloy shows significant brittleness after the light bulb is lit. In 1913, Pintsch invented thorium tungsten filament (ThO2 content of 1% to 2%), which greatly reduced the brittleness of the incandescent filament. At first, the droop of the filament was not a problem, because the filament was straight at that time. However, after 1913, Langmuir changed the straight filament into spiral filament. In this way, when the bulb was used, the high working temperature and dead weight made the filament droop, so it was difficult for both pure tungsten and thorium tungsten to meet the application requirements.
In order to solve the problems of sagging tungsten wire and short life, in 1917, A. SPZ invented tungsten alloy with "no deformation" at high temperature. At first, he used a refractory crucible to roast WO3 when preparing pure tungsten. He accidentally found that the tungsten wire spiral made from the tungsten powder reduced by such WO3 mysteriously did not sag after recrystallization. Subsequently, after 218 times of repeated experimental verification, he finally found that in tungstic acid (WO3·H2O) adding potassium and sodium silicate, after reduction, pressing, sintering, processing and so on to make tungsten wire, recrystallization to form a very coarse grain structure, neither soft and anti sagging, this is the earliest non-sagging tungsten wire. Beth's discovery laid the foundation for the production of undrooped tungsten wire, which is still called "218 tungsten wire" in the United States, in honor of Beth's discovery.
The production process of doped tungsten alloy is lengthy, including tungsten smelting, powder metallurgy and plastic processing.
Ammonium paratungstate (APT) is usually used as raw material in the production of doped tungsten alloys. In addition to the traditional classical process, the extraction method and ion exchange method were studied internationally in the 1950s, and these processes were also adopted in China in the 1970s, thus simplifying the process flow and improving the recovery rate of tungsten. Since the 1960s, many countries have adopted blue tungsten oxide doping process to replace tungsten trioxide doping, so as to improve the doping effect. Pickling of tungsten powder began to be applied to production in the 1960s, its main purpose is to wash away the excess dopant, ultrafine powder and some harmful impurities in tungsten powder, so as to improve the machining performance and improve the high temperature performance of tungsten wire. Since the 1960s, the pass rolling method has been applied continuously. Pass rolling is to make billet in a pair of rotating roll through the hole, under the action of roll pressure to reduce the section and length extension.
Although only a small fraction of tungsten ore is ultimately made into lamp tungsten wires and similar products, the most important scientific and technical significance of tungsten is the translation of research results into practical applications. The knowledge gained is of inestimable value in the new field of powder metallurgy, especially in the manufacture of cemented carbide.
Use editing broadcast
Filament industry
Tungsten was first used to make incandescent filament. In 1909, W.D.Coolidge in the United States made tungsten wire by tungsten powder pressing, remelting, rotary forging and wire drawing, and the production of tungsten wire developed rapidly. In 1913, I.Langmuir and W.Rogers found 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. The development of tungsten wires with excellent sagging resistance (called doped or non-sagging tungsten wires) in 1922 was a major advance in tungsten wire research. Non drooping tungsten wire is widely used as an excellent filament and cathode material. In the 1950s and 1960s, extensive research was carried out on tungsten based alloys, hoping to develop tungsten alloys that can work at 1930 ~ 2760ºC for the production of high temperature resistant parts for the aerospace industry. Among them, tungsten - rhenium alloys are more studied. The smelting and processing technology of tungsten are also studied. Tungsten ingots are obtained by consumable arc and electron beam smelting, and some products are made by extrusion and plastic processing. But the smelting ingot has coarse grain, poor plasticity, difficult processing and low yield, so the smelting and plastic processing technology has not become the main means of production. Except chemical vapor deposition (CVD) and plasma spraying can produce very few products, powder metallurgy is still the main means of producing tungsten products.
Sheet metal industry
China was able to produce tungsten wire in the 1950s. The study of smelting, powder metallurgy and processing of tungsten in the 1960s has led to the production of sheet, sheet, rod, tube, wire and other shaped parts.
High temperature material
Tungsten is used at a high temperature, so it is not effective to improve the high temperature strength of tungsten by solution strengthening alone. However, dispersion (or precipitation) strengthening on the basis of solid solution strengthening can greatly improve the high temperature strength, and ThO2 and precipitated HfC dispersion particles have the best strengthening effect.Both W-Hf-C and W-ThO2 alloys have high high temperature and creep strength at about 1900ºC. It is an effective way to strengthen tungsten alloys under recrystallization temperature by warm work hardening. For example, fine tungsten wire has very high tensile strength, the total processing deformation rate of 99.999%, diameter of 0.015 mm fine tungsten wire, tensile strength at room temperature can reach 438kg·N/mm2.
Among refractory metals, tungsten and tungsten alloys have the highest plastic-brittle transition temperature. The plastic-brittle transition temperature of sintered and melted polycrystalline tungsten is about 150 ~ 450ºC, which causes difficulties in processing and use, while the single-crystal tungsten is lower than room temperature. The interstitial impurities, microstructure, alloying elements, plastic processing and surface state have great influence on the plastic-brittle transition temperature of tungsten. Except rhenium, other alloying elements have little effect on reducing the plasticity - brittleness transition temperature of tungsten.
Tungsten has poor oxidation resistance, and its oxidation characteristics are similar to molybdenum. Tungsten trioxide volatilizes above 1000ºC, resulting in "disastrous" oxidation. Therefore, tungsten material must be protected under vacuum or inert atmosphere when used at high temperature. If used under high temperature oxidation atmosphere, protective coating must be added.
Military weapons industry
With the development and progress of science, tungsten alloy material has become the raw material for the production of military products, such as bullets, armor and shells, shrapnel heads, grenades, shotguns, bullet warheads, bulletproof vehicles, armored tanks, military aviation, artillery parts, guns and so on. The armor piercing bullet made by tungsten alloy is the main anti-tank weapon, which can penetrate the armor and composite armor with large dip Angle.
Processing, editing and broadcasting
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, extrusion, forging, rolling, spinning and drawing.
To prepare
Qualified billet is one of the key points of tungsten production, and qualified tungsten powder should be selected first to make billet. The characteristics of powder (mean particle size, particle size distribution, chemical composition), mixing, forming and sintering process have direct influence on the composition, density and microstructure of billet, and strongly affect the product processing and performance.
The silicon, aluminum and potassium added to the non-drooping tungsten wire are added in the form of oxides in tungsten trioxide or "blue tungsten" (a mixture of a variety of low cost tungsten oxide). The mixture is commonly washed with solution to remove impurities in the powder. Production of silk and small pieces of blank forming in the press, also can be used to form isostatic pressing.
The size of the billet is generally 12×12×400mm, and there are also large round, square or rectangular bars. The billet is first prefired in hydrogen atmosphere at 1200ºC for 1 hour to make it have certain strength and conductivity, and then it is electrified self-resistance sintering.
Electrocurrent self - resistance sintering, commonly known as "vertical melting", is a method developed in tungsten processing. The principle is to direct the current through the sintered billet, due to the resistance of the billet itself to produce Joule heat, using this heat to sintering billet, sintering current is usually 90% of the fuse current. The resulting blank is self - resistance sintered strip (also known as vertical melt strip). The general standard of vertical melt strips that can be processed into wire is to control the number of grain sections of about 10000 ~ 20000 per square millimeter, and the density of 17.8 ~ 18.6g/cm3. For pipe, sheet or other large size products, usually adopt isostatic pressing (pressure above 2500kg·N/mm2) forming, sintering at high temperature of 2300 ~ 2700ºC in vacuum or hydrogen protection.
Rotary swaging
Rotary forging is a common plastic machining method for producing tungsten billets and fine rods. Rods of different sizes are heated to 1400 ~ 1600ºC in a hydrogen atmosphere and are spun on different types of rotary forging machines. The first pass deformation should not be too large, and then the deformation can be appropriately increased. The workpiece and die are lubricated with graphite during the deformation of rotary forging. The density of tungsten rod after processing can reach 18.8 ~ 19.2g/cm3. Because the billet is forged into a round billet, the deformation of each part is different, so that the structure is not uniform, recrystallization annealing should be carried out at this time. The final diameter of the rotary forging bar is about 3 mm.
Drawing blank can be produced by rotary forging or rolling. The billet produced by rolling method has large pass deformation and uniform structure, which is conducive to the future processing. The drawing method of tungsten wire blank is "warm drawing". First on the chain stretching machine to the diameter of 1.3 mm, and then coarse, medium and fine drawing respectively to the diameter of 0.2, 0.06 and less than 0.06 mm. As the diameter decreases, the heating temperature should be reduced and the drawing speed increased. The pass deformation is generally between 10 ~ 20%.
Drawing using gas - air mixed heating, the temperature is 900 ~ 400ºC. Hard alloy die is used for drawing coarse wire, and diamond die is used for drawing fine wire. The mold material, pass type and grinding technology have great influence on the quality of the wire. The quality, particle size, ratio and coating method of graphite lubricant also affect the quality of the wire.
The non-uniformity of wire diameter is one of the main reasons for wire breakage. A deviation of 0.2 ~ 0.4 micron will greatly reduce the life of tungsten wire in vacuum tube. The diameter of the filament can be determined by gravimetric method or vacuum standard current method. In the process of wire drawing, the deformation resistance increases with the decrease of the diameter (for example, the fracture strength of tungsten wire with a diameter of 0.1-0.3mm can be up to 350kg·N/mm2), and its plasticity decreases accordingly. In order to improve the reprocessing performance, stress relief intermediate annealing is generally needed. In addition, electrolytic etching can be used to process the wire into a diameter of less than 0.01 mm.
Tungsten tube can be directly extruded by sintering billet, extruded tube billet or powder extrusion sintered tube billet is also processed by spinning. Spinning can also produce tungsten - shaped products. Large diameter bars are usually produced by extrusion or rolling process.
Cutting and machining
Tungsten is hard and sensitive to notch, difficult to cut, require the use of carbide tool. In order to prevent cutting cracks, the workpiece is often heated to the plastic-brittle transition temperature above for cutting, and the cutting operation procedure must be strictly controlled. Tungsten grinding requires light grinding with a specific type of grinding wheel and cooling, otherwise it will crack. The tungsten sheet with a thickness of more than 0.2mm should be pre-heated before being pressed and cut. The sheet with a thickness of more than 0.2mm cannot be cut and often needs to be cut with grinding wheel.
Sheet metal rolling
Tungsten plate rolling can be divided into hot rolling, warm rolling and cold rolling. Due to the large deformation resistance of tungsten, the ordinary roll can not meet the requirements of tungsten sheet rolling, so the special roller should be used. Rolling, roll to preheat, according to different rolling conditions, preheat temperature is 100 ~ 350ºC. Only when the relative density of billet (the ratio of actual density to theoretical density) is greater than 90% can it be processed, and when the billet density is between 92 and 94%, the processing performance is good. The billet temperature of hot rolling is between 1350 ~ 1500ºC, and the deformation parameters of billet are not selected properly. A hot rolled plate with a thickness of 8mm and a starting temperature of 1200ºC can reach 0.5mm after warm rolling. Due to the large deformation resistance of the tungsten plate, the roll body is bent and deformed during rolling, resulting in uneven thickness of the plate along the width direction. During roll change or mill change, the plate may crack due to uneven deformation of all parts. The plastic-brittle transition temperature of 0.5 mm thickness sheet is still at or above room temperature, the sheet is brittle, and the sheet should be rolled to 0.2 mm at 200 ~ 500ºC. At the later stage of rolling, the tungsten sheet is thin and long. In order to ensure uniform heating of the sheet, graphite or molybdenum disulfide is often coated, which is not only conducive to heating of the sheet, but also has lubrication effect during processing.
Design editor broadcast
1, in order to improve the plasticity of tungsten alloy, it is necessary to reduce the content of oxygen and carbon elements;
2. Grain refinement and hot working are also effective methods to reduce %BTT of tungsten alloy;
3. Considering the comprehensive properties of tungsten alloy, Re and Mo are the most effective solution strengthening elements, except for Re when applied in nuclear radiation environment;
4. Refractory metal carbides are the most effective second phase strengthening particles.
5. In order to realize the industrial production of tungsten-based composites, the preparation and processing costs must be reduced, so in-situ reaction and reactive infiltration are ideal methods for preparing tungsten-based composites [2].
Tungsten alloy electroplating editor broadcast
The "corrosion" and "wear" of oilfield equipment are known as the two major world problems. About 29,200 oil Wells in China all have different degrees of corrosion and wear. With the increase of the development life of oil and gas fields and the service life of equipment, it is getting worse and worse. In addition, the import of high-sulfur crude oil has increased significantly, so has the corrosion problem of refining equipment. What's more, the adverse impact of corrosion and wear on the safe and stable operation of equipment will become more and more prominent.
Among several main electroplating processes, chromium electroplating process is wear-resistant and low-cost, but it has serious environmental pollution and is not resistant to chloride ion corrosion. Electroless nickel phosphorus plating is corrosion-resistant but not wear-resistant and has high cost. The technical indicators of thermal spraying process are good, but the production cost is high, it is difficult to popularize in a large scale.
Tungsten alloy electroplating process solves the two major problems of corrosion and wear in one stroke. According to statistics, China's oil well pipe is more than 3 million tons every year, and the high-end oil well pipe with high technology content and high added value, such as anti-H2S and Cl-anti-corrosion pipe, almost relies on imports. The imported oil pipe is 600,000 tons every 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 obtained the National Key new product certificate. What makes him even happier is that the State Environmental Protection Administration has listed the technology as A national key environmental protection practical technology (Class A), as well as a resource conservation and comprehensive utilization and environmental protection technology encouraged by the state.
The application of tungsten alloy electroplating process in petroleum machinery industry can not only solve the pollution problem caused by chromium electroplating, but more importantly, improve the performance of various key parts and components in China petroleum machinery manufacturing industry, bring changes to the whole petroleum machinery manufacturing industry and promote the overall upgrade of the industry chain. In particular, the antiseptic and sulfur-resistant oil well arm and sulfur-resistant drill pipe can be applied to the extreme corrosive environment with H2S content greater than or equal to 150,000 PPM and Cl- content up to 150g/L, which makes China reach the international leading level in this industry and solves the current situation that China's high-end drilling equipment depends on foreign imports.
According to different uses, tungsten alloy is divided into hard alloy, high specific gravity alloy, metal sweating material, contact material, electronic and electric light source material.
Doped tungsten wire is to add about 1% of the oxides of silicon, aluminum and potassium in tungsten powder. In the process of vertical melting (self-resistance sintering), the additive potassium oxide is volatile, forming pores in the material, and the pores are elongated along the axial axis after processing; After annealing, the pores are elongated to form dispersed rows of bubbles parallel to the wire axis, which are commonly known as potassium bubbles. The K bubble can inhibit the transverse growth of tungsten grains, improve the high temperature sag resistance, and improve the room temperature plasticity after recrystallization, which is conducive to wire winding, transportation and storage. There are three kinds of high temperature creep values of Chinese doped tungsten wire: WAl1, WAl2 and WAl3.
In W-ThO2 alloys, the addition of appropriate ThO2 particles with good thermal stability can not only reduce the electron escape work, but also inhibit the growth of tungsten grains, so that the material has high recrystallization temperature, excellent high temperature strength and creep resistance. Tungsten-thorium alloy is not only a widely used thermoelectron emission material, but also an excellent electrode material.
In tungsten-rhenium alloys, the addition of rhenium can not only improve the material strength, increase the recrystallization temperature of the alloy about 200 ~ 400ºC, resulting in good plasticity and slow grain growth after secondary recrystallization, but also significantly reduce the plastic-brittle transition temperature. If more than 30% rhenium is added, the machining properties of the alloy will be damaged. Tungsten-rhenium alloys also have a high thermoelectric potential, at 2200ºC, the thermoelectric potential and temperature in a linear relationship. Tungsten-rhenium thermocouple measuring temperature can be up to 3000ºC, is an excellent high temperature thermocouple material.
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