Steel it not a fixed material that exists in one form. Rather, it is a chemical mixture of a number a different elements. These mixtures produce wide variations in the properties of steel, and a small addition of one element or the omission of another can change its properties, making it either harder or brittle.
Iron and Carbon
Steel requires two mandatory ingredients; iron and carbon. Iron is an elemental metal that makes up more than 90% of any steel. Without carbon, however, iron remains prone to corrosion and limited to its innate properties. Adding just 1% carbon creates steel, which can then accept further refinements and additives for specific properties and applications.
Adding up to 15% chromium to steel creates an alloy frequently called "stainless steel," which is very resistant to rusting. The corrosion resistance varies depending on the chromium content; however, the chromium content also affects the strength and durability of steel.
In addition to the basic requirements of steel, alloy steels can have small amounts of vanadium, manganese, molybdenum and other elements. Adding these elements increases certain properties of steel and decreases other properties. For instance, the addition of vanadium produces a tougher and more wear-resistant steel, but that steel alloy is more difficult to harden.
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