|Si||Melting point 1410 °C||Silicon|
Si is contained in all steel in the same way as manganese, as iron ores incorporate a quantity of it according to their composition. In steel production itself, silicon is absorbed into the melt from the refractory furnace linings. But only those steels are called silicon steels which have an Si content of > 0.40%. Si is not a metal, but a metalloid as are also, for example, phosphorus and sulphur. Si deoxidizes. It promotes graphite precipitation and restricts the γ-phase significantly, increases strength and wear resistance (Si-Mn heat treatable steels); significant increase in the elastic limit, thus useful alloying element in spring steels. It significantly increases scale resistance, so that heat resisting steels are alloyed with it. The possible content is limited however on account of its impairing hot and cold formability. With 12% Si, acid resistance is achieved to a large extent, but such grades can only be produced as very hard, brittle steel castings which can be machined only by grinding. On account of significant reduction of electrical conductivity, coercive field intensity and low wattage loss, Si is used in steels for electrical quality sheet.