Carbon occurs in nature in solid form as diamond or graphite. It can also be found chemically bound, in the form of oil, natural gas, coal or carbon dioxide. Carbon has been known to mankind since prehistoric times. The use of fire is the first chemical process that mankind made use of.
Carbon has enormous effects on the properties of iron and steel as an alloying element. If the carbon content is above 2%, it is cast iron and cannot be forged. If the carbon content is below 2%, the metal is forgeable and is called iron metal.
Influencing the carbon content is one of the most important processes in the production of steel. In steels with a low carbon content, the material can be enriched with carbon by carburising. If there is too much carbon, it can be removed from the alloy by refining.
In general, carbon has a direct influence on hardness and strength, depending on its concentration. With increasing content, the machinability, forgeability and weldability decrease. The carbon content must be adjusted during the manufacturing process to suit the later use.
Carbon can react with other alloying elements such as chromium, vanadium and tungsten to form carbides in the steel structure. The carbides increase the hardness and wear resistance of the steel.
The French chemist Lavoisier (1743-1794) inflamed a diamond with the help of burning glasses and was able to prove by burning that the mineral is crystalline carbon.
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