1. Nonferrous metals
Tungsten is a nonferrous metal. Usually people divide metals into two categories according to their color and properties: ferrous metals and non-ferrous metals. Ferrous metals mainly refer to iron, manganese, chromium and their alloys, such as steel, pig iron, ferroalloy, cast iron, etc. Metals other than ferrous metals are called nonferrous metals. Tungsten belongs to the category of non-ferrous metals. The strength and hardness of non-ferrous alloys are generally higher than that of pure metals. The resistance of non-ferrous alloys is larger than that of pure metals, and the temperature coefficient of resistance is smaller. It has good comprehensive mechanical properties. Therefore, as a non-ferrous metal, tungsten has very high strength and hardness. Because of this characteristic, tungsten carbide with high hardness and wear resistance has been widely used in cutting tools and mining tools.
2. Refractory Metals
Tungsten is the refractory metal with the highest melting point. Generally, metals with a melting point higher than 1650 C and a certain amount of reserves and metals with a melting point higher than zirconium melting point (1852 C) are called refractory metals. Typical refractory metals are tungsten, tantalum, molybdenum, niobium, hafnium, chromium, vanadium, zirconium and titanium. As a refractory metal, tungsten has the most important advantages of good high temperature strength, good corrosion resistance to molten alkali metals and vapors. Only when tungsten is above 1000 C, can oxides volatilize and liquid oxides occur. However, it also has the disadvantage of high plastic-brittle transition temperature and difficult plastic processing at room temperature. Refractory metals represented by tungsten have been widely used in metallurgy, chemical industry, electronics, light source, machinery industry and other sectors.
3. Rare metals
Tungsten is a rare metal. Rare metals usually refer to those with less content or scattered distribution in nature. Tungsten is a widely distributed element, which can be found in almost all kinds of rocks, but its content is low. The content of tungsten in the crust is 0.001%, and the average content in granite is 1.5 *10-6. This characteristic makes it very difficult to extract tungsten. Usually, it can only be separated and extracted by organic solvent extraction and ion exchange method. With the development of science and technology
With the development of metallurgical technology, equipment and analytical testing technology, as well as the expansion of production scale of rare metals, the purity of tungsten is continuously improved, its performance is continuously improved, and its variety is continuously increased, thus expanding the application field of tungsten. China is rich in tungsten resources, and the output and export of tungsten account for the first place in the world.
4. Strategic Metals
Tungsten is a strategic metal. As we all know, rare metals are an important strategic resource of our country, and tungsten is a typical rare metal with extremely important uses. It is an important part of modern high-tech new materials. A series of electronic optical materials, special alloys, new functional materials and organic metal compounds all need tungsten with unique properties. Although the dosage is not large, it is very important, but it can not be lacked. Therefore, it is widely used in modern communication technology, electronic computer, space development, medical and health, photosensitive materials, photoelectric materials, energy materials and catalyst materials.