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What is Magnesium?
Magnesium is the lightest of all commonly used structural materials with a density of 1.7g/cm3 (106.13lb/ft3) approximately 1/3 lighter than aluminum. It is the 8th most abundant element in the earth’s crust however, it is rarely found in its pure form due to the fact that it bonds with other elements easily. It was first produced in 1808 in small quantities by Sir Humphrey Davy and industrial production first began in 1886 in Germany. Magnesium was first found in an area of Thessaly/Greece called Magnesia. The ore got its name from this location and can still be found in great quantities there.
Where is Magnesium Found?
Most magnesium produced globally comes from natural minerals such as dolomite and magnesite in the form of magnesium carbonate. It can also be found in seawater which contains 0.13 percent of the element in the form of magnesium chloride, and in salt lakes brines or underground mineral salt deposits. Magnesium can be produced through several different methods including the electrolytic process or thermal-reduction as practiced in the most commonly used Pidgeon process.
The electrolytic process involves the electrolysis of molten magnesium chloride between 655°C and 720°C which produces molten magnesium and chlorine. The magnesium chloride comes either from salty brines after solar evaporation and chemical treatments or solid carnallite (KCl.MgCl2.6H20) dehydrated. The metal is cast into ingots for further processing as needed and the chlorine by product may be sold for use in the production of polymers (e.g. PVC).
In the thermal-reduction method calcined magnesium containing ores (magnesite and dolomite) are broken down into fine powder and mixed with reducing agents and catalyst agent. The mixture is heated up to 1200°C in a vacuum chamber producing magnesium vapors which later condense into crystals. The crystals are then melted, refined and poured into ingots for further processing.
The Pidgeon process, using ferrosilicon as the reductant and CaF2 as catalyst, is most commonly used for production of magnesium due to the fact that its operation is relatively easy, versatile and has low capital cost. The traditional process using horizontal retorts is high in energy consumption and has low productivity; however more modern vertical designs are more efficient. In the horizontal process, magnesium is generally collected from a condenser on the outside of a furnace. High purity magnesium can be obtained from the condenser since the vapor pressure of impurities that may be in the magnesium are low under the conditions in the retort.
The largest producers of magnesium are China, USA, Israel, Brazil, Russia, Kazakhstan and Turkey. New plants have been built in Malaysia, South Korea and Iran, and pilot plants for future operations have been constructed in Australia and Canada.
Advantages of Magnesium Use
There are many advantages to using magnesium and its alloys. With the lowest density of all commercial casting alloys, magnesium is 33 percent lighter than aluminum and 75 percent lighter than steel. Despite the lower density, magnesium alloys have a comparable strength to weight ratio to aluminum. Magnesium and its alloys also have a high vibration damping capacity making them an ideal material choice for many high speed applications. Electromagnetic interference reduction is another desirable quality that magnesium can offer as a material. In an increasingly environmentally conscious world, the full recyclability and ample availability of the metal also make it a suitable choice.