8 things you need to know about tungsten

The global tungsten resource reserves are relatively abundant. There are more than 20 kinds of tungsten minerals and tungsten-containing minerals that have been discovered, namely wolframite group: tungsten manganese ore, wolframite, wolframite; scheelite group: scheelite (calcium tungsten ore), molybdenum scheelite, copper scheelite; tungsten minerals: tungsten, hydrotungsten, high-rail tungsten, yttrium tungsten, copper tungsten, hydrotungsten; uncommon tungsten minerals: tungsten lead Ore, clinolite, tungsten zinc ore, molybdenum tungsten ore, tungsten bismuth ore, antimony tungsten pyrochlore, titanium yttrium thorium ore (containing tungsten), sulfur tungsten ore, etc. Although more than 20 kinds of tungsten minerals and tungsten-containing minerals have been discovered, only wolframite and scheelite are of economic value for mining.

Wolframite

Because it contains different proportions of iron tungstate and manganese tungstate, it is also called tungsten manganese ore, accounting for about 30% of the total global tungsten ore resources. If the iron content is high, it is called tungsten ore, and if the manganese content is high, it is called wolframite. The color of wolframite changes with changes in iron and manganese content. Common colors include dark gray, light reddish brown, light brown black, brown and iron brown. Wolframite has metallic or semi-metallic luster, is brittle, and has weak magnetism. Black tungsten ore is mainly produced in high-temperature hydrothermal quartz veins. Southern Jiangxi, eastern Hunan, and northern Guangdong in my country are all world-famous wolframite producing areas. In addition, Russia, Siberia, Myanmar, Thailand, Australia, Bolivia, etc. are also producers of wolframite ore. Main origin. Wolframite is mainly used to smelt tungsten and make tungstate.

Scheelite

Scheelite is a transparent to translucent mineral with a granular or massive appearance. The color changes with the change of molybdenum content. Common colors are white, gray, light yellow, light purple, light brown, light red, and green. etc., with grease luster or glass luster, accounting for about 70% of the world's total tungsten mineral resources. Scheelite is luminescent and emits light blue to yellow fluorescence under ultraviolet light irradiation.

Scheelite is mainly produced in contact metasomatic deposits, high-temperature hydrothermal veins and greystone. Yaogangxian, Hunan, my country is a world-famous source of scheelite. In addition, Dageng in Jiangxi, Dashunlong in Hunan, Wenshan in Yunnan, Shantang in southern Korea, Saxony in Germany, Cornwall in the UK, New South Wales in Australia, Northern Bolivia and Nevada in the United States are also the main producing areas of scheelite. Scheelite is mainly used to produce ferrotungsten and can also be used to make permanent magnets.

The melting point of tungsten is the highest among all metal elements, the density (19.3 g/cm³) is very high, close to gold, and the hardness of tungsten is also very high. For example, the hardness of tungsten carbide is close to diamond. In addition, tungsten also has good electrical and thermal conductivity, small expansion coefficient and other characteristics, so it is widely used in alloys, electronics, chemical industry and other fields. Among them, cemented carbide is the largest consumer field of tungsten.

Alloy field

Electronic field

Tungsten has strong plasticity, low evaporation rate, high melting point, and strong electron emission capability. Therefore, tungsten and its alloys are widely used in the electronics and power industry. For example, tungsten filament has high luminous rate and long service life, so it is widely used in manufacturing various light bulb filaments, such as incandescent lamps, iodine tungsten lamps, etc. Tungsten filament can also be used to make direct-heated cathodes and grids of electronic oscillation tubes. As well as thermal cathode heaters in various electronic instruments. The properties of tungsten also make it a good electrode material for TIG welding and other similar tasks.

Chemical industry

Tungsten compounds are often used as catalysts and inorganic colors. For example, tungsten disulfide is used as a lubricant and catalyst in the preparation of synthetic gasoline. Bronze-colored tungsten oxide is used in paintings. Calcium or magnesium tungsten is often used in phosphors.

Other areas

Because the thermal expansion of tungsten is similar to that of borosilicate glass, it is used to make glass or metal seals. Tungsten has low sensitivity and is therefore used to make high-purity tungsten jewelry. In addition, tungsten is also used in radioactive medicine, and some musical instruments also use tungsten wire.

A brief history of the discovery of tungsten

The history of tungsten dates back to the 17th century. At that time, miners in the Erzgebirge Mountains of Saxony, Germany noticed that some ores would interfere with the reduction of cassiterite and produce slag. The miners gave these ores some German nicknames: "wolfert" and "wolfrahm".

Scheler In 1758, the Swedish chemist and mineralogist Kronstedt discovered a mineral, which he called "tungsten", which means "heavy stone" in Swedish. He was convinced that the mineral contained an element that had not yet been discovered.

In 1781, Swedish chemist Carl Wilhelm Scheele discovered scheelite and extracted tungstic acid from it. He believed that a new metal might be obtained by reducing tungstic acid.

In 1783, brothers José de Luyard and Faustou Deluyar also extracted tungstic acid from wolframite ore. In the same year, they used carbon to reduce tungsten trioxide and obtained tungsten powder for the first time.

Later, Jöns Jacob Berzelius and Friedrich Wöhler gave this metal a new name: wolfram, but this term is more recognized in Germany and Scandinavia, while the United Kingdom, the United States and other countries prefer to use Kronstadt The name given to this metal is "tungsten".

Development of tungsten industry

In 1841, chemist Robert Oxland obtained a British patent for the production method of sodium tungstate, tungstic acid and tungsten metal. This was a major advancement in the history of modern tungsten chemistry and opened the way for the industrial production of tungsten.

In the 1750s, chemists noticed that adding tungsten to steel would affect the properties of steel. However, it was not until the late 19th century and early 20th century that tungsten steel began to be mass-produced and widely used. High-speed steel containing 20% ​​tungsten was first exhibited at the Paris World's Fair in 1900. The emergence of this steel marked a major technological progress in the field of metal cutting and processing.

In 1900, Russian inventor А.Н.Ладыгин first proposed the application of tungsten in lighting bulbs. In 1903, Coolidge in the United States used tungsten powder pressing, remelting, forging, and drawing processes to make tungsten wire. The emergence of tungsten wire promoted the development of the lighting industry. This method is also considered the beginning of modern metal powder production. In 1909, Кулидж created the powder metallurgy method, which used a pressure processing process to make it possible for tungsten to be widely used in electric vacuum technology.

In 1925, Schrutter obtained a U.S. patent for the invention of tungsten carbide cobalt carbide. This patented method was first used in industrial production in Europe in 1926. This is the basis of modern tungsten industrial production processes. In 1927-1928, cemented carbide with tungsten carbide as the main component was developed. This was an important stage in the history of tungsten's industrial development. These cemented carbides are widely used in modern technology due to their good properties.

GB/T 10116-2007 Ammonium paratungstate National Quality Supervision, Inspection and Quarantine

GB/T 4295-2008 Tungsten carbide powder National Quality Supervision, Inspection and Quarantine

GB/T 2967-2008 Casting tungsten carbide powder National Quality Supervision, Inspection and Quarantine

GB/T 23272-2009 Tungsten wire for lighting and electronic equipment National Quality Supervision, Inspection and Quarantine

GB/T 26055-2010 Regenerated tungsten carbide powder National Quality Supervision, Inspection and Quarantine

GB/T 26496-2011 Tungsten and tungsten alloy scrap National Quality Supervision, Inspection and Quarantine

GB/T 26725-2011 Ultrafine tungsten carbide powder National Quality Supervision, Inspection and Quarantine

GB/T 26726-2011 Ultrafine tungsten powder National Quality Supervision, Inspection and Quarantine

GB/T 29521-2013 Safety production specifications for underground mining of tungsten mines National Quality Supervision, Inspection and Inspection

GB/T 29822-2013 Tungsten-rhenium thermocouple wire and indexing table National Quality Supervision, Inspection and Quarantine

GB 30039-2013 Safety Production Regulations for Tungsten Carbide Powder National Quality Supervision, Inspection and Quarantine

GB/T 26496-2011 Tungsten and tungsten alloy scrap National Quality Supervision, Inspection and Quarantine

Distribution of tungsten resources and reserves

The world's tungsten mineral resources are relatively abundant. The content of tungsten in the earth's crust is 0.001%. There are more than 20 kinds of tungsten minerals and tungsten-containing minerals that have been discovered, namely the wolframite mineral family: wolframite, wolframite, wolframite; scheelite Mineral family: scheelite (scheelite), molybdenum scheelite, copper scheelite; tungsten minerals: tungsten, hydrotungsten, high-iron tungsten, yttrium tungsten, copper tungsten, hydrotungsten ; Uncommon tungsten minerals: tungstenite, tungstenite, molybdenite, tungstenite, tungsten bismuthite, antimony tungsten pyrochlore, titanium yttrium thoriumite (containing tungsten), tungstenite, etc. Although more than 20 kinds of tungsten minerals and tungsten-containing minerals have been discovered, only wolframite and scheelite have economic value in mining. Wolframite accounts for about 30% of the total global tungsten mineral resources, and scheelite is about 30%. Accounting for 70%.

Local distribution

The world's tungsten mineral resources are mainly concentrated in the Alps-Himalayas and the Pacific Rim geological belt. China is located in these two geological zones, so it has abundant tungsten reserves, ranking first in the world. China's tungsten mines are mainly distributed along the eastern coast of Guangdong on both sides of China's Nanling Mountains. The reserves in southern Jiangxi are the largest, accounting for more than half of the world's reserves.

Russia's tungsten ore resources are mainly concentrated in the middle section of the Sikhote-Alin Mountains in the North Caucasus, Eastern Siberia and the Far East. The larger mines include Verkhne-Kayrakty.

Tungsten ore resources in the United States are mainly concentrated in California and Colorado.

Canadian tungsten ores are mainly concentrated in the Selwyn tungsten belt, and the most commercially valuable deposits are located from the Cassiar batholith in British Columbia to MacMillan on the border of Yukon and Northwest Territories. ) mineral deposit extension zone.

Country distribution

According to data released by the United States Geological Survey in 2015, global tungsten resource reserves are approximately 3.3 million tons. China has the largest tungsten resource reserves at 1.9 million tons, accounting for approximately 58% of the global total. This is followed by Canada (290,000 tons), Russia (250,000 tons) and the United States (140,000 tons). Other countries with rich tungsten reserves in the world include Bolivia (53,000 tons), Australia (10,000 tons) and Portugal (4,200 tons).

Global tungsten production

According to data released by the United States Geological Survey in 2015, global tungsten production in 2014 was approximately 82,400 tons, a slight increase of 1% from 81,400 tons in 2013. China is the main producer of tungsten. In 2014, its tungsten ore output was 68,000 tons, accounting for approximately 84% of the global total. This was followed by Russia (3,600 tons) and Canada (2,200 tons). Other countries with large tungsten ore production include Vietnam (2000), Bolivia (1300 tons), Austria (850 tons), Congo (800 tons), Portugal (700 tons), Rwanda (700 tons) and Australia (600 tons) ).

China's tungsten production and mining indicators from 2002 to 2013

Tungsten health effects

As the production scale of tungsten and its products continues to expand, the scope of use of tungsten is becoming wider and wider, and the potential threat of tungsten element pollution to the environment is also rising. As a substance that can affect chemical changes in organisms and disrupt biochemical exchange channels, people should also start to pay attention to the impact of tungsten on human health.

Most of the tungsten that enters the body can be excreted from the body through the digestive system and excretion system in a short period of time. A small amount of tungsten that enters the blood may stay in bones, nails or hair for a period of time before being excreted. However, tungsten compounds, such as carbonized Long-term excessive exposure to tungsten dust, sodium tungstate, tungsten oxide, tungsten carbide, etc. may irritate the skin and eyes, cause inflammation of the skin and eyes, cause respiratory diseases such as asthma, and cause gastrointestinal disorders. In addition, researchers at the University of Exeter in the UK found a link between people with high levels of tungsten in their urine and high rates of stroke, and this phenomenon was particularly evident among women and those under 50 years old. Even after taking into account other risk factors such as age, socioeconomic status, smoking status, body mass index, occupation and alcohol consumption, people exposed to tungsten metal have a higher risk of stroke than others. The researchers also said that while other metal elements commonly used with tungsten, such as nickel and copper, may also be linked to stroke rates, the pathology of a large number of stroke cases shows that tungsten is the most important factor.

Tungsten pollution prevention measures

In order to avoid the adverse effects on human health caused by exposure to large amounts of tungsten, the following are recommended:

Physical examination Personnel working in a tungsten production or processing environment should go to the hospital regularly to check whether the tungsten content in the body exceeds the standard through medical monitoring.

Environmental workers in the tungsten industry should take measures such as wearing gas masks, gloves, eyes, and dustproof clothing.

Enterprises should post safety and health tips in tungsten-related workplaces. In addition, enterprises should take measures to prevent dust leakage, conduct workshop cleaning and industrial waste disposal in a timely manner to prevent secondary pollution.

Other personnel should try to avoid using water and food contaminated with tungsten. Residential areas should be as far away from tungsten pollution or processing companies as possible.

Tungsten beneficiation process

Tungsten Ore Processing At present, the development and utilization of tungsten ore in my country is mainly wolframite ore, followed by scheelite ore. Although scheelite reserves are large, there are few rich ores, lower grades, and more refractory ores, so the mining volume only accounts for about 10% of tungsten ore production. Although the reserves of wolframite ore are smaller than those of scheelite, there are more rich ores and they are easy to mine and screen. Therefore, the total mining volume accounts for more than 90% of the tungsten ore production. The main methods of beneficiation of tungsten are as follows:

Gravity separation: A method of selecting ores based on mineral density differences in a certain medium or medium flow (mainly water). The advantages of this method are simple equipment structure, convenient operation and low production cost. Common gravity separation processes include heavy medium selection, jig selection, shaker selection, chute selection, centrifugal selection, etc.

Flotation: It is the most widely used mineral processing method. It is a method to separate useful minerals from ores based on the different physical and chemical properties of the mineral particle surfaces. Flotation is suitable for fine and micro-grained materials, as well as fine mineral particles smaller than 10 μm that are difficult to recover by other mineral processing methods. Union Carbide Corporation of the United States has developed the "lime method" for flotation of scheelite, and shear flocculation flotation has also been used in the flotation of scheelite by some factories.

Magnetic separation: It is a method that uses magnetism to remove magnetic metal impurities in oil. The application of magnetic separation is to use the magnetic differences of various ores or materials to perform the separation process under the action of magnetic force and other forces.

Elutriation: A method of separating minerals based on their density. Place the sand sample in a sand pan filled with water and repeatedly shake, stir and wash it. The heavy minerals will remain at the bottom of the pan, and the light minerals will float out with the water, thereby separating the light and heavy minerals.

The beneficiation of wolframite in my country mainly uses gravity separation, with a recovery rate of 92-93%. In some cases, flotation and magnetic separation are also used. The beneficiation of scheelite is based on the dissipation characteristics of the ore, using a combination of gravity separation and flotation, or a single flotation method, or an elutriation method. In some cases, it is also pre-enriched, and is first selected from the raw ore using an ultraviolet fluorescent sorting machine. Half of the waste rock is then processed for mineral processing, and the recovery rate of scheelite reaches 90-96%.

Tungsten smelting process

The smelting process of tungsten includes the steps of concentrate decomposition, tungsten compound purification, tungsten powder and dense tungsten production.

Tungsten concentrate decomposition methods: fire method and wet method.

① The sodium carbonate sintering method is commonly used for fire decomposition. This method is to place wolframite concentrate and sodium carbonate together in a rotary kiln and sinter them at 800 to 900°C. When processing scheelite concentrate, quartz sand needs to be added in order to obtain calcium orthosilicate with low solubility. The sintering temperature is about 1000°C. After about two hours of sintering, the decomposition rate of the concentrate can reach 98-99.5%. The sintered material is leached with water at 80-90°C and filtered to obtain sodium tungstate solution and insoluble residue.

② The wet method is divided into alkali decomposition method and acid decomposition method. When decomposing wolframite concentrate, use sodium hydroxide solution to leach at a temperature of 110 to 130°C or higher. The scheelite concentrate is leached with sodium carbonate solution in an autoclave at 200-230°C, or decomposed with hydrochloric acid at 90°C to obtain solid crude tungsten acid. The decomposition rate of wet-processed tungsten concentrate can reach 98-99%.

Tungsten compound purification

Impurities such as silicon, phosphorus and arsenic contained in sodium tungstate solution are in the form of sodium silicate, sodium hydrogen phosphate and sodium hydrogen arsenate respectively in the solution. Boil the solution and neutralize it with dilute hydrochloric acid. When the pH of the solution is 8 to 9, sodium silicate is hydrolyzed into silicic acid and condenses and precipitates. Magnesium chloride and ammonium chloride solutions are added to make phosphorus and arsenic generate ammonium magnesium phosphate and arsenic acid with very low solubility. Ammonium and magnesium are precipitated and removed.

Add sodium sulfide to the sodium tungstate solution, molybdenum forms sodium thiomolybdate before tungsten, neutralize it with hydrochloric acid, and when the pH of the solution is 2.5 to 3.0, the molybdenum precipitates into insoluble molybdenum trisulfide and is removed. Calcium chloride solution is added to the purified sodium tungstate solution to obtain calcium tungstate (CaWO) precipitation. The calcium tungstate precipitate is decomposed with hydrochloric acid to obtain industrial tungstic acid. The tungstic acid is calcined at 700-800°C to obtain industrial pure trioxide. Tungsten oxide

To prepare chemically pure tungsten trioxide, industrial tungstic acid can be dissolved in ammonia water to obtain an ammonium tungstate solution, leaving impurities such as silicon in the slag. The solution was evaporated and crystallized to obtain flaky ammonium paratungstate [5(NH) O 12WO 5H O] crystals. Since the solubility of ammonium paramolybdate is greater than that of ammonium paratungstate, the molybdenum content of ammonium paratungstate crystals decreases after crystallization. After drying ammonium paratungstate, it is calcined at 500-800°C to obtain chemically pure tungsten trioxide. In the 1970s, the tertiary amine (RN) method or method was used to convert sodium tungstate solution into ammonium tungstate solution, which simplified the process and increased the recovery rate of tungsten.

Tungsten powder production

Methods for producing tungsten powder include hydrogen reduction, carbon reduction and metal thermal reduction. The most common method in modern industry is the hydrogen reduction method of primary or secondary hydrogen reduction of tungsten trioxide or blue tungsten oxide. This method can accurately control the particle shape, particle size and particle size composition of tungsten powder. Generally, the blue tungsten oxide doping process is better. The primary reduction method saves electricity, hydrogen and cooling water than the secondary reduction method. The cost of tungsten powder is low, but the production is difficult.

Preparation of dense tungsten

Tungsten powder is formed, sintered, melted and other processes to obtain dense tungsten. Industrially, the powder metallurgy method is used, that is, using tungsten powder or tungsten powder containing additives, molding - pre-sintering - vertical melting sintering and isostatic pressing - indirect sintering into strips (doped strips, alloy strips) There are two processes. The former process is often used for mass production of small strips, while high-purity tungsten products are generally electron beam melted.

Making tungsten strips from tungsten powder mainly goes through two processes: forming and sintering:

① Forming. There are two methods: molding (mechanical forming method) and isostatic pressing. The former is generally only used to press billets with small size and unit weight. It is easier to operate and can more accurately control the size and appearance quality of the billet, but the compact density is small and uneven. The isostatic pressing method can press billets with larger unit weight and size (shapes include round, rectangular and rectangular), tube blanks and complex parts, and the compact density is high and uniform. However, the size and appearance quality of the compact are worse than those of the molding method, and machining and shaping are generally required before sintering.

②Sintering. There are vertical sintering (direct sintering method) and indirect sintering method. Before sintering, the compact must be pre-sintered to remove the forming agent. Vertical fusion sintering is only used for sintering small billets. The indirect sintering method is divided into hydrogen protection sintering and vacuum sintering processes, which can sinter large-size tungsten billets or tungsten parts that need to be machined.

Current status of tungsten recycling

With the continuous development of the tungsten industry, the consumption of tungsten metal raw materials is increasing, and the recoverable resources are becoming less and less. Therefore, the recycling and utilization of tungsten has attracted the attention of governments around the world. Countries such as the United States and Russia have even established tungsten strategies. To reserve, Japan established a special Tungsten Recycling Committee (WR Committee) in 1775. In addition, in today's tungsten industry, an important indicator of a tungsten company's technology, scale and comprehensive competitiveness is whether the company can recycle secondary tungsten resources in an environmentally friendly manner. In addition, compared with tungsten concentrate, the tungsten content of waste tungsten It is high and easy to recycle, so the recycling and reuse of tungsten has become a focus of the tungsten industry.

At present, the global supply of tungsten mainly consists of two parts. One part is the supply of newly produced tungsten concentrate, which accounts for about 76% of the total tungsten supply, 66% of which enters the final tungsten product, and 10% becomes waste in the production process. Re-production. The other part comes from the recycling of secondary resources from tungsten, that is, the recycling of solid waste residues in the tungsten production process and end consumer product waste, such as waste cemented carbide, tungsten materials, alloy steel, and tungsten contact materials As well as chemical catalysts, etc., this part accounts for approximately 24%.

Tungsten recycling methods

With the continuous improvement of the recycling rate of tungsten secondary resources in various countries, the technologies for recycling tungsten resources are also increasing. Common ones include mechanical crushing method, saltpeter method, zinc melting method, electrolysis method, leaching method, reduction method, and roasting method. - Ammonia leaching method, etc. Some recycling methods have been gradually eliminated due to large environmental pollution and low recovery rate, such as the production of APT by soda sintering method. Some new recycling methods have also emerged, such as tungsten in the liquid after tungsten smelting and exchange. The recovery method; the method invented by J. Arvidson to prepare iron- and tungsten-containing materials starting from cemented carbide powder, pure WC or crane ore, etc.

Development status of China's recycled tungsten industry

China's recycled tungsten industry started late, and the recycling and utilization of scrap tungsten is relatively low, only 10% of the tungsten supply, while the scrap tungsten utilization rate in advanced foreign countries is generally above 30%. The recycling area of ​​tungsten secondary resources in my country is also relatively narrow, mainly concentrated in cemented carbide and chemical catalysts. The recycling field is mainly concentrated in the fields of alloys and sodium tungstate. Moreover, some recycling methods cause serious secondary environmental pollution. Therefore, from the perspective of protecting the environment and efficiently utilizing resources, our country should pay attention to the recycling of tungsten resources, strengthen research on low-cost, high-quality, high-grade and high-purity tungsten recycling technology, and improve the comprehensive recovery rate of tungsten and valuable metal elements. , turning resource advantages into technological advantages.

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