Alloying Elements
Alloying elements are added to steel to give particular properties in the final product, such as hardness, toughness, corrosion resistance, ability to be hardened and machinability. They are also used to assist in refining, eg. for deoxidation and desulphurisation.
They include:
· Carbon (C)
· Manganese (Mn)
· Silicon (Si)
· Chromium (Cr)
· Nickel (Ni)
· Aluminium (Al)
· Boron (B)
· Calcium (Ca)
· Cobalt (Co)
· Molybdenum (Mo)
· Titanium (Ti)
· Tungsten (W)
· Nitrogen (N) and
· Phosphorus (P).
Many are added as ferroalloys, of which high carbon ferromanganese (approximately 76% Mn and 7% C, remainder Fe) is the most common. Ferrosilicon, (typically 75% Si,<l %C), and silicochrome, ferronickel and nickel oxide (which is readily reduced to the metal during steelmaking) are other major alloys. Many are produced in electric smelting furnaces, often by quite complicated processes, to serve the steelmaking and foundries industries. Carbon may be added in the form of petroleum coke or as specially prepared high purity brown coal char.
Manganese is added as high, medium, or low carbon ferromanganese, electrolytic manganese or silicomanganese. They are produced in electric smelting furnaces from manganese ores and in manganese sinter plants for processing fines which are unsuitable for addition direct to the furnace.
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