Views:5 Author:Tungsten China Publish Time: 2015-07-02 Origin:TungstenChina
Tungsten is a metallic chemical element classified among the transition metals of the periodic table of elements. It is well known for its strength and durability, which make it extremely useful in a wide range of industrial applications. Some consumers also own products which contain tungsten or were produced with tungsten. The world's major sources of this element are Russia, Austria, China, and Portugal, where it is extracted from minerals such as scheelite and wolframite
This element is not found in a pure form in nature. When it is isolated, tungsten in a very hard, brittle, gray to white metal which is extremely corrosion resistant. It has the highest melting point and tensile strength of any metal, and it also has the lowest vapor pressure point. The metal is identified with the symbol W on the periodic table of elements, a reference to its alternate name, wolfram. Tungsten's atomic number is 74.
People have known about the existence of tungsten since at least the early 1700s, when observers noted that the metal interacted with tin. In 1784, the de Elhuyar brothers managed to isolate tungsten in Spain, using tungstic acid extracted from wolframite. Tungsten has classically been a very valuable metal, since its durability and strength make it extremely useful for military and industrial uses. The name of the element comes from the Swedish tung, or “heavy,” and sten, for “stone.”
One of the most famous uses of tungsten is as a filament in light bulbs. The metal is also used in an assortment of alloys to increase their hardness and tensile strength. Many structural metal alloys incorporate tungsten since the metal has an extremely high melting point, and the element is also used to make wear-resistant tools. While tungsten tools can be expensive, many workers like them because of their durability and long lifetimes.
Tungsten does have some safety precautions. Dust from the metal can be flammable or explosive, and it also irritates mucus membranes such as the inside of the nose and mouth. In some regions, tungsten has been linked with serious infections of the lungs in people who work with the element on a regular basis without adequate protections. Tungsten exposure has also been correlated with increased rates of cancer, although hard evidence to turn the correlation into causation has not been uncovered.
Tungsten is a metal with a wide range of uses. Tungsten Alloy has the highest melting point, lowest vapor pressure and highest tensile strength at temperatures above 1650 degrees Celsius of all metals. It can only be attacked slightly by most mineral acids. It's coefficient of thermal expansion makes it a common choice for glass to metal sealing applications. Tungsten also has low emmisivity.
Atomic weight 183.85
Density 19.3 g/cc
Melting Point 3695 k 3410°C, 6191°F
Boiling Point 5828K, 5900°C, 10031°F
Some Common Applications for Tungsten are:
elevision and light bulb filament
Glass to metal sealing
Tungsten is extremely difficult to work with. It is difficult to turn and mill. Forming must be done at extremely high temperatures. Welding and riveting are not recommended. E.D.M. is the most practical way to machine Tungsten.