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Alloying Element: Any metallic element added during the making of steel for the purpose of increasing corrosion resistance, hardness or strength. The metals used most commonly as alloying elements in chrome steel include chromium, manganese and silicon.
Steel is a combination of iron and carbon. In its softened state, the base is a matrix composed of simple iron molecules (ferrite), in which are suspended molecules of iron carbide (cementite). When steel is heated to prescribed temperatures, then cooled at a specific rate, it undergoes physical internal changes which manifest themselves in the form of various micro-structures such as pearlite, bainite, and martensite. These micro-structures (and others) provide a wide range of mechanical properties, making steel an extremely versatile metal.
The presence of carbon in iron is necessary to make steel. Carbon is essential to the formation of cementite (as well as other carbides), and to the formation of pearlite, spheroidite, bainite, and iron-carbon martensite. The hardness of steel (or more accurately, the harden ability) is increased by the addition of more carbon, up to about 0.65 percent. Wear resistance can be increased in amounts up to about 1.5 percent. Beyond this amount, increases of carbon reduce toughness and increase brittleness.