Iron and steel are two of the oldest metals known to man. In the modern world these metals have become indispensable. Nearly 200 years they form the backbone of the industrial progress.
Steel is essentially an alloy of iron and carbon. Because pig iron already has a substantial carbon content, steel is made by removing most of the carbon from the iron. The amount of carbon in the steel, which is rarely more than 1%, the metal that is produced is changing, and whole. Steel ranges from a relatively soft quality low carbon to high carbon steel, which is so strong that made cutting tools to be able are from razor blades to saw for other metals.
Much development is focused on the search for super steel with a tensile strength of so ?? s 35,000 kg per square cm ?? twice as much as the strongest of steel which is now commonly used.
The manufacture is expensive, but the alloy can be processed particularly easy and provides the valuable combination of great strength and low weight. Such steels are further developed and are already widely used for undercarriages of aircrafts, special vessels for liquid and gas under high pressure and for gears and drive shafts, which have to be particularly strong.
Before the discovery of the new steels aluminum was the only metal that was both strong already light weight. The process of this metal on a large scale from its ore, bauxite, to release, was developed in 1886. Since then it has an increasingly important role in the technical industries. Except that it is light, weathers aluminum is not, because it protected by a sturdy layer of aluminum oxide. It is also a good conductor of electricity. Aluminum is widely used instead of copper. Especially if something should not be too heavy. Probably aluminum be used mostly in the aircraft industry. Although there are new alloys come forward, it remains a valuable material because the light, cheap and strong.
See also: Heavy metals: effects on health
The development of iron and steel