Dr. Rood
ENV 250
9 October 2014
Metals: Tungsten
Figure 1
Tungsten is a rare metal and is one of the transition metals in the periodic table. According to various sources, the name is reputed to come from the words meaning "heavy" and "stone" in Swedish. It is also identified by its German name, wolfram, from whence is derived the "W" symbol by which it is indicated on the periodic table. It has an atomic number of 74 and is a silvery-white, lustrous metal. It is an extremely dense, brittle metal and is not particularly ductile except under certain conditions. It is distinguished by having the highest melting point (3410 degrees Celsius) of any metal element and retains its strength at very high temperatures, which makes it extremely useful in industry, which will be addressed later (Andrews 7).
Figure 2
It was discovered in t1783 by two Spanish scientist/chemist brothers named Elhuyar, and was considered rare until refinement process were developed using acids (such as tungstic acid) to separate it from its mineral form. It is most commonly found in minerals known as wolframite and scheelite and a tin-based mineral called cassiterite. The wolframite minerals usually contain a mixture of tungsten with either manganese or iron, and the scheelite mineral contains a combination of calcium and tungsten. The majority of tungsten-containing mineral deposits are found in China (2/3 according to Lenntech), and the rest can be found in Russia, parts of Europe and the central part of South America. Lenntech also claims that world production equals approximately 40,000 tonnes, and that reserves equal approximately 5 million tonnes.
Figure 3
The metal was used extensively for the first time in the early 1900s, with the discovery of its usefulness as filament in electric lights due to its exceptionally high melting point and high resistance. Difficulty was encountered in the process of drawing the metal into a wire, leading to the development of the extrusion and amalgam processes (tungsten.com). These, and other early processes involved mixing the metal powder with a binding agent to give the metal "plasticity," and then the agent would be removed through "chemical or thermal treatment" (tungsten.com). According to the Midwest Tungsten Service, the modern refinement process of tungsten starts with mineral ore extraction, crushing of the ore, chemical extraction of the tungsten, and hydrogen furnace processing, which leads to pure tungsten powder. It is then mixed with additives and binders and subjected to another hydrogen furnace, after which it is milled into a finished product.
Figure 4
According to Andrews, tungsten alloy steels are used as tools in high-speed working environments in which friction build-up from rapid use raises the temperature of the tools. Adding tungsten as an allow allows the tools to be used faster and at higher temperatures because it will retain its shape, strength, and properties at very high temperatures. Additionally, it is used in drill bits and armor-piercing weapons. It was named a "strategic metal" during the first World War, made even more necessary because of its discovery as a useful armor-piercing material in World War II (Andrews 10). Tungsten also finds use in many electronic components for its resistance and temperature qualities.
Figure 5
The metal is not known to cause any chronic medical conditions, as opposed to certain heavy metals. The dust can be an irritant, however, and its mineral dusts can be hazardous. According to an MSDS provided by the Midwest Tungsten Service, the dust can be flammable or explosive under certain conditions and concentrations.
In terms of its life cycle, tungsten can be recycled, and according to Lenntech, recycled Tungsten meets 30% of overall demand for the element.
https://www.youtube.com/watch?v=0z31POXO6U0
Citations:
Figure 1
http://www.tungsten.com/mtstung.html
Figures 2 and 4
http://imgarcade.com/1/tungsten-uses/
http://vitalmetals.com.au/markets/tungsten/mining-and-processing/
Figure 5
http://www.alibaba.com/product-detail/Tungsten-Carbide-Burr_318800325/showimage.html
MSDS for Pure Tungsten
http://www.tungsten.com/MSDStung.pdf
General information
http://www.tungsten.com/mtstung.html
http://www.tungsten.com/tipscost.pdf
http://www.lenntech.com/periodic/elements/w.htm
http://www.chemicalelements.com/elements/w.html
Online Book Source
Andrews, Mildred Gwen. Tungsten: The Story of an Indispensable Metal. Washington D.C.: The Tungsten Institute, 1955. Web.
