Tungsten

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Tungsten suppliers offer tungsten in four different forms: tungsten carbide, which is half carbon and twice as hard as any steel; alloyed tungsten, which is mixed with many different metals including copper and iron; pure tungsten, which is extremely electrically conductive and primarily used in electrical applications; and tungsten-based chemicals, which, although rare, are used to make organic dyes, pigment phosphors and x-ray screens. The metal is extracted and usually ground into tungsten powder, which is then sintered or molded to make tungsten bar, tungsten plate, tungsten wire, tungsten rod, tungsten foil or tungsten sheet. One of the most common industrial products made from tungsten is tungsten electrodes, which are used in electric arc welding. They transfer high amounts of electric current to two separate sheets of metal. The heat generated from the electricity causes the metal parts to melt together, thus forming a weld. Tungsten is used in many different industries, including the construction, engineering, consumer products, jewelry, welding, industrial machinery, mining, electric, lighting and medical industries. Additionally, tungsten is used in all light bulbs, x-ray screens and many other products and is sometimes coated onto tools to extend their lifespan by many years.Tungsten's coloring varies between a steel gray to a tin white and is also, at times, referred to as "wolfram". It has the atomic number of 74 on the periodic table, and occurs naturally in the earth. Tungsten has the highest melting point and lowest vapor pressure of all non-alloyed metals and has excellent resistance to corrosion. Despite these unique and useful properties, tungsten is very brittle in its raw state and can be hard to work with, especially under pressure. Most often, tungsten suppliers offer tungsten alloys and tungsten carbide for industrial and commercial applications. Tungsten has a wide range of uses, but is most often used as tungsten carbide in cemented carbides. Carbides are wear-resistant materials used in the metalworking, mining and construction industries. Tungsten alloys are used in armaments, heat sinks, turbine blades, parts, wear-resistant coatings and high-density items, like ballasts and weights.

Some of the most common tungsten products are alloyed with cobalt, which acts as a binder to form what is known as cemented carbide. This type of tungsten is used in cutting applications. The cobalt counteracts tungsten's tendency to become brittle under higher pressures, allowing it to be used in structural applications. Some alloys contain very little amounts of another substance. These are called tungsten heavy-metal alloys, and are at least 90% tungsten. Tungsten carbide is an extremely strong and wear resistant metal alloy that is half tungsten, half carbon alloy. It is an inorganic chemical compound that is twice as hard as any steel grade steel and much denser than titanium or steel. It is pressed and sintered to become all kinds of strong, durable metal products, parts and tools. There are over 20 different grades of tungsten carbide, which have differing grain size, hardness, tensile strength and melting point properties. Tungsten carbide is very useful in the metalworking, mining and construction industries. In fact, 60% of all tungsten carbide products are manufactured for applications within these industries, where it is quite useful for its tensile strength and hardness. Drilling equipment, tools, industrial machinery components, weapons and construction equipment are all sometimes fabricated from tungsten carbide. Most tungsten and tungsten alloys are initially fabricated into billets in the form of solid blocks by sintering or molding. They are then fabricated into bar, sheet, plate, rod or wire form by way of drawing, grounding, molding and die cutting, among others. Some products require further processing, and are solid in three different conditions: black, which maintains a coating of lubricant and oxide; cleaned, in which the coating has been removed with chemicals; or ground, in which the tungsten has been machined with diamond or silicon carbide tools to remove the coating and achieve a certain smoothness and diameter.

The metal's high melting point and hardness at high temperatures make it very useful in the aerospace industry, as well as in other various high-temperature applications, such as light bulb, cathode tube and vacuum tube filaments. Tungsten electrodes primarily serve as the current medium for arc welding, a process that uses high voltages of electric current to emit high temperatures and join two separate metal pieces. They are often used in electric discharge machining and gas tungsten arc welding, in which a heavy-metal tungsten alloy is typically used, which is composed of mostly tungsten and a small amount of thorium oxide (around 2%). Using ThO2 enhances the thermionic electron emission, which improves the starting characteristics of gas tungsten arc welding electrodes. In electronics, tungsten is used to connect materials on a circuit panel. Tungsten suppliers often provide pure tungsten to the electronics industry for this purpose, though also offers tungsten in bar, sheet, plate or wire forms. Because tungsten has such a wide range of purposes, it is in high demand for industry and commercial applications. About 45,000 tons of tungsten is mined each year, mostly in China and Russia. Tungsten is also recycled to be used again in other applications. Alternatively, the metal molybdenum may be used in place of tungsten in alloys.

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Tungsten Types

• Pure tungsten is a naturally occurring metal mined from the earth. In this raw form, pure tungsten can be very brittle.
  
• Tungsten alloys include any metal that is supplemented with tungsten. The addition of tungsten to other metals increases strength, melting point and hardness.
  
• Tungsten bar is one form of tungsten metal that is offered by  tungsten suppliers, usually as an alloy. Purchasing tungsten bar usually requires the buyer to specify bar size and composition of the alloy.
  
• Tungsten carbide is an extremely hard metal comprised of a carbon alloy and tungsten. Tungsten carbide is twice as hard as steel.
  
• Tungsten foil can be as thin as 0.001 inches and is cut-to-order by the supplier.
  
• Tungsten plate is tungsten alloy supplied in plate form.
  
• Tungsten sheet is supplied by distributors in a flat sheet form, which may either be rolled or coiled for easy transport and handling.
  
• Tungsten wire is often used in the electronics industry. The metal is supplied in wire form as an alloy.

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Tungsten Grades

Material	Tensile Strength at Break (MPa)	Tensile Strength, Yield (MPa)	Modulus of Elasticity (ksi)
Pure Tungsten	980	750	58000
All Tungsten Alloys	448 - 4900	310 - 1240	20000 - 62400
Tungsten, Soft Unalloyed	620	550	60200
WNiCu Class 1 Tungsten Alloy	755	605	40000
WNiFe Class 1 Tungsten Alloy	895	615	45000
WNiFe Class 2 Tungsten Alloy	786	579	47000
WNiCu Class 3 Tungsten Alloy	758	586	45000
WNiFe Class 3 Tungsten Alloy	827	621	50000
WNiCu Class 4 Tungsten Alloy	848	586	52900
W2Mo Tungsten Alloy	965	750	58000
W15Mo Tungsten Alloy	980	740	56600
CoCrWNi Alloy, ASTM F90	860	310	31900 - 33900

*These figures are guidelines based on industry research; they should not be presumed accurate under all circumstances and are not a substitute for certified measurements. The information is not to be interpreted as absolute material properties nor does it constitute a representation or warranty for which we assume legal liability. User shall determine suitability of the material for the intended use and assumes all risk and liability whatsoever in connection therewith.

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Tungsten Terms

Alloy - A solid solution or homogenous mixture of two or more metals or elements.

Brittle - Easily broken when stressed. Brittle substances show very little strain or deformity before fracturing.

Filament - A tiny metal wire, usually comprised of tungsten, which converts electricity to light within a light bulb.

Melting Point - The temperature at which a solid substance becomes a liquid.

Superalloy - An alloy which has excellent strength, hardness and resistance to corrosion. Usually has a metal base of nickel, cobalt or iron.

Tensile Strength - In engineering, the point at which a material fails under applied stress or pressure.

Wolfram - An alternative term for the metal tungsten. This term is derived from wolframite ore, the primary source of tungsten metal.

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