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Views: 291 Author: Site Editor Publish Time: 2022-03-24 Origin: Site
Tungsten is a non-ferrous metal and an important strategic metal. Tungsten ore was called heavy stone in ancient times. In 1781, the Swedish chemist Karl discovered scheelite and extracted a new element acid-tungstic acid. Two years later, it was also discovered by the Spanish Depuria. In the same year, Tungsten powder was obtained for the first time by reducing tungsten trioxide with carbon. Now the content of tungsten in the earth's crust is 0.001%. At present, there are 20 kinds of tungsten-containing minerals that have been discovered. Tungsten deposits are generally formed with the activity of granitic magma. After smelting, tungsten is a silver-white shiny metal with extremely high melting point and high hardness.
As the materials of contacts parts, there are many advantages for tungsten. The key is that its price is low comparing with other metals or alloy materials, so the price of tungsten contacts is relatively low comparing with other electrical contacts. High-quality tungsten contacts are widely used in various fields such as industry, agriculture, science and technology, and national defense. And it is widely use for the metal contacts stamped parts of electronic devices and electrical appliances such as AC contactors, automobiles, motorcycles, electric horns, magneto and other electrical products.
Processing requirements
With the continuous development of the manufacturing industry, the requirements for tungsten contact materials have increased rapidly. The user's requirements for tungsten contact include smooth surface with no cracks and scratches, small and uniform cross-section grains, short fibers, good straightness, concentricity and roundness, high hardness, good impact toughness, vapor pressure Low, low evaporation rate, low thermal expansion coefficient, good and stable arc resistance. The physical and mechanical properties of tungsten contact parts have greatly improved in order to meet the requirements. And a lot of works are done to avoid the splitting, brittle fracture, and uneven cross-sectional grain size produced in the production process of tungsten metal contact material. The problems that the O degree and flatness cannot meet the requirements have been comprehensively analyzed, and a series of measures have been taken.
About the quality problems encountered in the process of producing tungsten contact materials, and rod diameter concentricity and flatness which cannot meet the requirements, the tungsten raw materials are classified according to the crystal type based on the analysis of the reasons. And the corresponding processing temperature is determined, and the 1-2 rotary forging processes before the finished product are controlled by the processing sheet, and the ellipticity and sizing of the forging die are controlled. A series of improvement measures such as controlling the length of the zone have taken to improve the product quality and yield rate to a certain extent.
For example, silver and tungsten are not mutually soluble in liquid or solid state. The preparation of silver-tungsten alloy can only be made by powder metallurgy to make sintered materials. Of course, extrusion can also be used. And alloys with more than 60% tungsten are mostly produced by the soaking method. If tungsten contacts parts are manufactured by powder metallurgy, the material is characterized by high hardness, resistance to arc erosion, adhesion and fusion welding.
