How metallurgical silicon is made
Silicon smelters guard their carbon balance, because too much carbon fills the furnace hearth with silicon carbide.
- stations
- 8
- things upstream
- 5
- raw sources
- 3
- steps from the ground
- 2
The short version
Metallurgical silicon comes from smelting quartz with coke, coal, charcoal and wood chips in a submerged arc furnace, near 2000 °C at the electrode tip. Carbon strips the oxygen and leaves liquid silicon. It is tapped into a ladle, purged with an air-oxygen mix to drive calcium and aluminum into slag, then cast and crushed. Most of this grade goes into aluminum alloys.
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Size the quartz
Quartz or quartzite goes through crushers and is screened to lumps of a set size, since the furnace charge needs to stay porous.
Goes in -
Charge the furnace
Crushed quartz goes in with a blend of reductants: coke, coal, charcoal and wood chips. Charcoal reacts readily, coal can bring in iron that ends up in the metal, and fine petroleum coke can blow straight out with the furnace gas.
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Smelt in an arc
Electrodes run down into the charge. Near their tips the carbon pulls oxygen from the silica, through silicon monoxide gas and silicon carbide, and liquid silicon collects below. Operators keep silica in excess so silicon carbide does not pile up.
about 2000 °C near the electrode
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Tap into a ladle
Liquid metal runs from the furnace directly into a ladle. Refining often starts here, as the tap jet drags air into the melt.
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Blow the ladle
An air-oxygen mix is purged through the melt. Silica forms on the bubbles, reacts with calcium and aluminum impurities, and carries them off into a slag.
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Cast into molds
Refined silicon is poured into molds, then cooled until solid.
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Crush and size
The ingots are crushed, sized and packaged for buyers.
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Sort by purity grade
Output is sorted by purity. Grades of 95 to 99% count as metallurgical silicon, and a share goes on to be purified for semiconductors.
Worth repeating
- Most elemental silicon never leaves the steel industry as ferrosilicon, and only about 20% is refined to metallurgical-grade purity.
- About 55% of metallurgical-grade silicon goes into aluminum-silicon alloys, mainly for cast car parts.
- Only an estimated 15% of metallurgical-grade silicon is refined further to semiconductor purity.
Back to the ground
Follow every input upstream and metallurgical silicon starts as these 3 raw sources.
Where it goes next
Metallurgical silicon feeds 4 lines directly and reaches 191 things in total.
Further down the line
Keep walking
Sources
- Silicon
- Polysilicon
- Production of metallurgical-grade silicon from Egyptian quartz, Journal of the SAIMM
- Refining Kinetics of Selected Elements in the Industrial Silicon Process, Metallurgical and Materials Transactions B
- Silicon metal manufacturing process, KXG Alloy
Cite this page: "How metallurgical silicon is made." Assembly Line, 2026-11-03. https://assemblyline.org/make/silicon