Metallurgical Silicon (Industrial Silicon)
title: "Metallurgical Silicon (Industrial Silicon)" description: "How metallurgical-grade silicon is smelted, the main purity grades (553/441/3303), and China's role as the world's dominant producer." section: "upstream"
Production Process
Metallurgical silicon — also called industrial silicon or metal silicon — is produced by carbothermal reduction of high-purity quartz in electric arc furnaces:
SiO₂ + 2C → Si + 2CO↑
The furnace runs at 1500–2000°C with submerged electrodes. Raw materials are silica ore (SiO₂ ≥99%), charcoal, coal, and wood chips as reductants. The molten silicon taps at the bottom, solidifies in moulds, then undergoes refining, crushing, and classification to achieve the target purity grade.
China accounts for roughly 75–80% of global metallurgical silicon production, concentrated in Sichuan, Yunnan, and Xinjiang where hydropower or coal keeps electricity costs low.
Grade Specifications
Metallurgical silicon grades are named by their three main impurity caps: iron (Fe), aluminium (Al), and calcium (Ca) in hundreds-of-ppm units.
| Grade | Fe max (%) | Al max (%) | Ca max (%) | Si min (%) | Typical use |
|---|---|---|---|---|---|
| 3303 | 0.30 | 0.30 | 0.03 | 99.0 | Silicone monomer, polysilicon feedstock |
| 441 | 0.40 | 0.40 | 0.10 | 99.0 | Aluminium alloy, chemical synthesis |
| 553 | 0.50 | 0.50 | 0.30 | 98.5 | Aluminium alloy (most common export grade) |
| 2202 | 0.20 | 0.20 | 0.02 | 99.5 | High-purity chemical-grade applications |
The chemical-silicone industry requires 3303 or 2202 grade to avoid catalyst poisoning during Rochow synthesis.
Downstream Pathways
Metallurgical silicon sits at the convergence of three major supply chains:
- Silicone route → chlorination to trichlorosilane or direct Rochow synthesis to methylchlorosilanes. See Silicone Monomers.
- Polysilicon route → further purification via Siemens or FBR process to semiconductor- or solar-grade silicon. See Polysilicon.
- Aluminium alloy route → alloying addition (4000-series Al-Si alloys, die-cast parts).