Editing Silicon (section)

===Alloys===
Elemental silicon is added to molten [[cast iron]] as [[ferrosilicon]] or silicocalcium alloys to improve performance in casting thin sections and to prevent the formation of [[cementite]] where exposed to outside air. The presence of elemental silicon in molten iron acts as a sink for oxygen, so that the steel carbon content, which must be kept within narrow limits for each type of steel, can be more closely controlled. Ferrosilicon production and use is a monitor of the steel industry, and although this form of elemental silicon is grossly impure, it accounts for 80% of the world's use of free silicon. Silicon is an important constituent of [[transformer steel]], modifying its [[resistivity]] and [[ferromagnetic]] properties.

The properties of silicon may be used to modify alloys with metals other than iron. "Metallurgical grade" silicon is silicon of 95–99% purity. About 55% of the world consumption of metallurgical purity silicon goes for production of aluminium-silicon alloys ([[silumin]] alloys) for aluminium part [[Casting|casts]], mainly for use in the [[automotive industry]]. Silicon's importance in aluminium casting is that a significantly high amount (12%) of silicon in aluminium forms a [[eutectic mixture]] which solidifies with very little thermal contraction. This greatly reduces tearing and cracks formed from stress as casting alloys cool to solidity. Silicon also significantly improves the hardness and thus wear-resistance of aluminium.<ref name="diecasting">{{cite web|last=Apelian |first=D.|date=2009 |url=http://www.diecasting.org/research/wwr/WWR_AluminumCastAlloys.pdf |title=Aluminum Cast Alloys: Enabling Tools for Improved Performance |publisher=North American Die Casting Association |location=Wheeling, Illinois|archive-url=https://web.archive.org/web/20120106013105/http://www.diecasting.org/research/wwr/WWR_AluminumCastAlloys.pdf|archive-date=2012-01-06}}</ref><ref name="USGS" /> Metallurgical grade silicon is made by melting quartz or quartzite in a large arc furnace, in a carbothermal reduction process with carbon-containing material such as coal, coke or charcoal and woodchips for gas circulation. This production technique without iron is often used for [[polysilicon]] production for photovoltaics and also semiconductors.<ref>Troszak T.A. (2021) The hidden costs of solar photovoltaic power, NATO ENSEC COE Energy highlights Vol 16, pp 22. Copyright 2021 NATO Energy Security Center of Excellence</ref><ref>https://hackaday.com/2021/11/15/mining-and-refining-pure-silicon-and-the-incredible-effort-it-takes-to-get-there/</ref><ref>https://magazine.elkem.com/material-science-insights/from-quartz-to-silicon-to-silicones/#:~:text=Metallurgical%2Dgrade%20silicon%20is%20produced,a%20submerged%20electric%20arc%20furnace.</ref><ref>https://www.mdpi.com/1996-1073/12/8/1495</ref>