(Chemical symbol: Si). A non-metallic element resembling graphite in appearance, used extensively in alloys. Silicon is not found free in nature but in combination with other elements and is probably more widely distributed in the solid matter of the earth than any other element except oxygen. Silicon is usually found in the oxide (silicate) form. Atomic weight, 28.06; melting point, 1410°C (2570°F); specific gravity, 2.42.

In a molten steel bath, silicon acts to promote fluidity by effecting a control over the oxygen content of the steel. High percentages of silicon are added to steel to reduce certain magnetic characteristics; of steel when it is used in electrical and magnetic applications. Adding silicon tends to improve oxidation resistance and increase the hardenability of steels carrying non-graphitizing elements. Silicon also contributes to the strength of low-alloy steels. It increases hardenability and performs a valuable function as a deoxidizer, eliminating occluded gas.

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