Ferrosilicon ExplainedProduction, FeSi Grades, Uses & Export Buying
Ferrosilicon (FeSi) is an iron-silicon ferroalloy, and it is one of the most heavily consumed additions in steel and cast iron production worldwide. In trade and procurement documents, you will also see it written as ferro silicon — both names describe the same alloy.
Steel mills use it to remove dissolved oxygen from liquid steel and to add silicon to specific grades. Foundries use it as the base of inoculants that control graphite in grey and ductile iron. Magnesium smelters use it as the reducing agent in the Pidgeon process.
Ferrosilicon is smelted in submerged arc furnaces by reducing quartz with carbon in the presence of iron. It is then sold by silicon content, with FeSi 75, FeSi 72, FeSi 65 and FeSi 45 being the most traded grades.
- 15–90%Silicon range
- 5Export grades
- HS 7202Customs heading
- UN 1408Transport class 4.3
Quick Answer
Ferrosilicon in 60 Seconds
- What it is: an alloy of iron and silicon, usually containing 15–90% Si, with small amounts of aluminum, calcium and carbon.
- Main job: deoxidizing liquid steel and adding silicon to steel and cast iron.
- How it's made: carbothermic reduction of quartz in a submerged arc furnace, at roughly 8,000–9,000 kWh per tonne of FeSi 75.
- Top grades: FeSi 75 and FeSi 72 for steel, FeSi 65 for cost-sensitive use, FeSi 45 for alloying, FeSi 15 powder for dense media separation.
- Trade codes: HS 7202.21 (above 55% Si) and 7202.29 (other); shipped as UN 1408, Class 4.3 when Si is 30% to below 90%.
- What drives price: electricity, quartz and reductant costs, and steel output — especially in China.
What Is Ferrosilicon?The Chemistry Behind the World's Workhorse Ferroalloy
Ferrosilicon — often abbreviated as FeSi and sometimes written as ferro silicon — is a master alloy that delivers silicon into molten iron and steel. Pure silicon is expensive to produce and dissolves slowly. By alloying it with iron, producers make silicon cheaper, denser and much easier for melt shops to add in controlled amounts. For an element-by-element breakdown, see our guide to ferrosilicon chemical composition.
Commercial grades contain between 15% and 90% silicon. The balance is iron, plus trace elements such as aluminum, calcium, carbon, phosphorus and sulfur. It is these minor elements — not just the silicon number — that separate a general-purpose lot from a premium one.
Physically, ferrosilicon is a brittle, silver-gray alloy. It is supplied as lumps, granules or powder. Its value comes from silicon's strong affinity for oxygen. Silicon is a stronger deoxidizer than manganese and weaker than aluminum, which is why many mills combine FeSi with manganese alloys or aluminum to fine-tune steel cleanliness. To see how FeSi compares with those alternatives, read our ferrosilicon vs. other ferro alloys comparison.
Why Steelmakers Depend on Ferrosilicon
When ferrosilicon dissolves in liquid steel, its silicon captures free oxygen and forms silica (SiO₂). The silica floats into the slag instead of staying trapped in the metal. The result is fewer oxide inclusions, fewer gas defects and more consistent mechanical properties in the finished steel.
Ferrosilicon at a Glance9 key specs · grades, HS code, sizes, packing and transport class
- Designation
- FeSi — iron-silicon ferroalloy (also "ferro silicon")
- Silicon Content
- 15–90% Si; main trade grades FeSi 45, 65, 72 and 75
- Production Route
- Carbothermic reduction of quartz in a submerged arc furnace
- Power Consumption
- About 8,000–9,000 kWh per tonne of FeSi 75
- Main Consumers
- Steelmaking first, then cast iron foundries and magnesium smelters
- HS Code
- 7202.21 (above 55% Si) · 7202.29 (other FeSi)
- Standard Sizes
- 10–50 mm and 10–100 mm lumps · 3–10 mm and 0–3 mm granules · powder
- Export Packing
- 1 MT jumbo bags; FOB or CIF by container or bulk
- Transport Class
- UN 1408, Class 4.3 (30% to below 90% Si)
Deoxidizer
Binds dissolved oxygen into silica slag, which reduces inclusions and improves the soundness of cast steel.
Alloying Agent
Adds silicon for strength, elasticity and electrical resistivity. Electrical steels typically carry around 3% Si.
Reducing Agent
Supplies the silicon that reduces magnesium oxide to metal in the Pidgeon process and in some ferroalloy routes.
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FOB and CIF delivery by container or bulk to major ports.
Controlled Chemistry
Tight Si, Al and C windows, verified on every lot.
Standards-Based
Specs aligned with ISO 5445, ASTM A100 and GB/T 2272.
Direct Pricing
Producer-direct offers with flexible payment and trade terms.
How Ferrosilicon Is ProducedFrom Quartz and Scrap to Sized FeSi Lumps
Every tonne of ferrosilicon starts in a submerged arc furnace (SAF). Three large carbon electrodes are buried in a burden of quartz, carbon reductants and iron units. Current passing through the charge creates a reaction zone well above 1,800 °C. At that temperature, carbon strips oxygen from silica and the released silicon dissolves into molten iron.
The chemistry is simple on paper but demanding in practice. The reduction passes through intermediate species silicon monoxide gas and silicon carbide and any SiO that escapes the charge is lost as fume. That is why furnace operators watch charge porosity, electrode depth and the carbon balance closely. A well-run ferro silicon furnace recovers roughly 85–90% of the silicon it charges.
Electricity is the dominant cost. Producing one tonne of FeSi 75 typically takes 8,000–9,000 kWh, so plants cluster where power is cheap. Learn how leading ferro silicon manufacturers control quality at scale, or compare milled vs. atomized ferrosilicon powder if you buy fine material.
Raw MaterialsWhat Goes Into One Tonne of FeSi 75
Silica Source
Lump quartz or quartzite (SiO₂), usually 97–99% silica. Low Al₂O₃ and Fe₂O₃ in the quartz keep aluminum and other impurities out of the alloy.
≈ 1.7–1.9 t per tonne
Carbon Reductants
A blend of coke, low-ash coal, charcoal and wood chips. The mix sets reactivity, electrical resistance and gas permeability of the charge.
≈ 0.8–0.9 t per tonne
Iron Units
Steel scrap, turnings, mill scale or iron ore pellets. The ratio of iron to quartz decides whether the furnace makes FeSi 45, 65 or 75.
≈ 0.2–0.25 t per tonneIndicative consumption for FeSi 75; actual figures vary with raw material quality and furnace practice.
Smelting & RefiningInside the Submerged Arc Furnace
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Charging
Weighed batches of quartz, reductants and iron units are fed continuously from bins above the furnace. The charge stays loose enough to let reaction gases escape evenly.
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Electric Smelting
Self-baking carbon electrodes carry tens of megawatts into the burden. The hottest zone under the electrode tips runs at around 2,000 °C (3,632 °F).
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Carbothermic Reduction
Silica reacts with carbon to release silicon and carbon monoxide. The silicon dissolves in the iron bath and forms the alloy.
SiO₂ + 2C → Si + 2CO↑ -
Tapping
Molten ferrosilicon is tapped at intervals into refractory-lined ladles. Silicon fume leaving the furnace is captured in bag filters and sold as microsilica for high-performance concrete.
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Ladle Refining
When low-aluminum or low-calcium ferrosilicon is ordered, the ladle is treated with oxygen or air and slag formers. This oxidizes Al and Ca into the slag and brings the alloy into specification.
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Casting & Cooling
The alloy is cast in shallow layers so it cools quickly. Fast, even solidification limits segregation and gives a more uniform chemistry across the lot.
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Crushing, Screening & Sampling
Cooled cakes are crushed and screened into lumps, granules or powder. Each lot is sampled and analyzed before a certificate of analysis is issued.
Comparing Ferrosilicon Producers?
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Ferrosilicon Grades and SpecificationsFeSi Chemistry, Impurity Limits and Sizes
Ferrosilicon grades are named after their nominal silicon content. FeSi 75, for example, contains about 75% silicon. The grade number tells a buyer how much silicon each tonne delivers. The impurity limits tell them how that silicon will behave in the melt.
FeSi 75, FeSi 72, FeSi 65 and FeSi 45 cover most steel, foundry and alloying needs. Low-silicon FeSi 15 is a separate product, sold as powder for dense media separation. For deeper element limits, see our full ferrosilicon composition guide.
| Grade | Silicon (Si) | Al max | C max | P max | S max | Typical Application |
|---|---|---|---|---|---|---|
| FeSi 75Most traded | 75 – 80% | 1.5% | 0.10% | 0.035% | 0.02% | Steel deoxidation, electrical and spring steel, Pidgeon magnesium, inoculant base |
| FeSi 72 | 72 – 75% | 1.5% | 0.20% | 0.04% | 0.02% | General steelmaking deoxidation and alloying |
| FeSi 65 | 63 – 68% | 2.0% | 0.20% | 0.04% | 0.02% | Cost-effective deoxidation, foundry melting and alloy additions |
| FeSi 45 | 40 – 47% | 2.0% | 0.20% | 0.04% | 0.02% | Alloying where lower silicon per addition is preferred |
| FeSi 15 | 14 – 16% | — | — | — | — | Dense / heavy media separation (DMS / HMS) powder |
Typical export limits. "—" means the value is agreed per contract. Formal grade classes are defined in ISO 5445, ASTM A100 and GB/T 2272; final values are fixed in the sales contract and the lot's certificate of analysis.
Why Impurities Matter as Much as Silicon
Two lots of FeSi 75 can perform very differently in the melt shop. These are the elements experienced buyers check first.
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Aluminum
Forms hard alumina inclusions and can cause nozzle clogging. Low-Al ferrosilicon is specified for clean steel and electrical steel.
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Carbon
Must stay low for low-carbon and stainless grades, where every extra point of carbon affects the final chemistry.
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Calcium
Helps inoculation in foundries but can be unwanted in some steels. It is usually controlled by ladle refining.
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Phosphorus
Causes cold brittleness in steel. It is also the source of phosphine gas if damp material reacts with moisture.
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Sulfur
Promotes hot shortness and sulfide inclusions. Most contracts cap it at 0.02%.
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Titanium
Harmful to magnetic properties, so electrical steel producers often order ferrosilicon with very low titanium.
Sizes and Forms
Choosing the right size is as important as choosing the grade. It controls dissolution speed, recovery and dust losses.
Lumps
The standard form for ladle and furnace additions in steel mills. Sizes of 10–50 mm and 10–100 mm balance fast dissolution with low oxidation losses.
Granules
Used in foundries for in-stream and ladle inoculation, and in cored wire. Grades of 3–10 mm and 0–3 mm dissolve quickly in iron.
Powder
Milled or atomized FeSi 15 for dense media separation, plus fine FeSi for welding electrode coatings and powder metallurgy.
Custom Specifications on Request
Silicon windows, impurity caps and size ranges can be set to your process. Low-aluminum, low-carbon, low-calcium and low-titanium ferrosilicon are available for specialty steel and foundry work. Check our 2026 ferro silicon product overview for current availability.
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Key Applications of FerrosiliconSteelmaking, Cast Iron, Magnesium and Mineral Processing
Ferrosilicon earns its place in metallurgy through three properties: it removes oxygen, it adds silicon and it reduces other oxides. Each industry uses a different mix of those abilities, and each one favors different grades and sizes. For every use case in detail, read our ferrosilicon uses and applications guide.
In practice, FeSi 75 and FeSi 72 dominate steel shops, FeSi 75 and FeSi 65 serve foundries and magnesium plants, and FeSi 15 powder serves mining and recycling.
A. Steelmaking
Largest consumerSteel mills use ferrosilicon as a deoxidizer in the ladle and as an alloying addition. Silicon raises strength and elasticity in spring steels and raises electrical resistivity in electrical steels, which cuts energy losses in transformers and motors.
[Si] + 2[O] → (SiO₂)
B. Cast Iron Foundries
Inoculation & nodularizingMost foundry inoculants are ferrosilicon with controlled calcium, aluminum, barium, strontium or zirconium. Magnesium-bearing ferrosilicon (FeSiMg) is used to produce ductile iron.
- Promotes graphite formation instead of hard iron carbides.
- Reduces chill in thin sections.
- Improves machinability, ductility and consistency.
C. Magnesium Production
Pidgeon processIn the Pidgeon process, briquettes of calcined dolomite and FeSi 75 are heated under vacuum at about 1,150–1,200 °C. Silicon reduces magnesium oxide, and magnesium vapor condenses as crowns of pure metal.
2(MgO·CaO) + Si(Fe) → 2Mg↑ + Ca₂SiO₄ + Fe
D. Mineral Processing & Other Uses
Specialty markets- Dense media separation with FeSi 15 powder, which is magnetic and easy to recover.
- Diamond, iron ore and scrap metal recycling plants.
- Welding electrode coatings as a deoxidizer.
- Production of other ferroalloys and special alloys.
How to Buy Ferrosilicon: A Buyer's ChecklistSix Points to Fix Before You Sign a Contract
Most disputes in ferro silicon trade come from specs that were left vague. Settle these points in writing and you remove almost all of the risk.
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Grade and Silicon Window
State the grade and a minimum silicon value, for example "FeSi 75, Si 75% min." Agree whether silicon below the minimum is rejected or priced down.
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Impurity Caps
List maximum Al, C, P and S — plus Ca or Ti if your process is sensitive. A generic "standard grade" leaves room for disagreement.
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Size Range and Tolerance
Specify the size, such as 10–50 mm, and the allowed undersize and oversize, typically up to 10% each.
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Packing and Moisture
Confirm 1 MT jumbo bags, inner liners and dry, ventilated stowage. Ferrosilicon must be kept dry from furnace to melt shop.
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Inspection and Sampling
Name an independent inspector such as SGS or Bureau Veritas, and agree whose analysis is final if results differ.
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Incoterms and Payment
Fix the trade term (FOB, CFR or CIF), the loading port, the laycan and the payment method before the price is locked.
Documents That Should Arrive With Every Export Shipment
- Commercial invoice
- Packing list
- Bill of lading
- Certificate of analysis
- Certificate of origin
- Inspection certificate
- Safety data sheet (SDS)
- IMSBC cargo declaration (bulk)
Ferrosilicon Export Markets WorldwideRegions We Supply, Ranked by Steel Output
Ferrosilicon demand follows crude steel production closely, because most FeSi is consumed in the ladle. The ranking below is approximate and is based on regional crude steel output reported by the World Steel Association. It shows where ferrosilicon is used most, from the largest steel hubs to smaller specialty markets.
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East Asia
China, Japan and South Korea produce well over half of the world's steel. That makes the region both the largest producer and the largest consumer of ferrosilicon.
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South & Southeast Asia
India's fast-growing steel sector, along with Vietnam and Indonesia, makes this the highest-growth ferrosilicon market, driven by infrastructure and construction.
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Europe & Türkiye
A large import market with demanding specifications. Buyers here favor low-aluminum and low-titanium FeSi for specialty and electrical steels.
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North America
Electric arc furnace mills and large foundries create steady demand for consistent, well-documented ferrosilicon lots.
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CIS & Central Asia
A traditional ferroalloy region that both produces and trades ferrosilicon, with flows depending on grade and power costs.
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Middle East
New DRI-EAF steel capacity has lifted regional import demand for FeSi 72 and FeSi 75 lumps.
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Latin America
Brazil and Mexico lead regional demand, with foundries and flat steel producers buying both domestic and imported ferrosilicon.
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Africa
Growing steel and mining sectors drive demand for ferrosilicon lumps and FeSi 15 dense media powder.
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Oceania
A smaller, quality-focused market where mineral processing is a major user of FeSi 15 powder.
We ship ferrosilicon to all of these regions. Contact our export desk for availability and lead times to your port.
Frequently Asked Questions About FerrosiliconUses, Grades, Safety, Trade and Pricing
What is ferrosilicon mainly used for?
Ferrosilicon is mainly used as a deoxidizer in steelmaking. It removes dissolved oxygen from liquid steel, which reduces inclusions and gas defects. It is also used to add silicon to steel, as the base of cast iron inoculants and as the reducing agent in magnesium production. See our ferrosilicon uses guide for the full list.
Is "ferro silicon" the same as ferrosilicon?
Yes. Ferro silicon, ferro-silicon and ferrosilicon all refer to the same iron-silicon alloy, usually shortened to FeSi. The one-word spelling is common in technical standards, while the two-word form often appears in trade offers and customs paperwork.
What is the difference between FeSi 75 and FeSi 45?
The difference is silicon content. FeSi 75 contains about 75% silicon, while FeSi 45 contains about 45%. FeSi 75 delivers more silicon per tonne, so smaller additions are needed and freight per unit of silicon is lower. That is why it is the standard grade in steelmaking. FeSi 45 is chosen when a lower, more gradual silicon addition is preferred. See the composition guide for impurity limits.
Which ferrosilicon grade should I choose?
Choose FeSi 75 or FeSi 72 for steel deoxidation and alloying. Choose FeSi 65 as a cost-effective option for deoxidation and foundry melting. Use FeSi 45 for general alloying where less silicon per addition is needed, and FeSi 15 powder for dense media separation. For electrical or specialty steel, also specify low aluminum and low titanium.
Is ferrosilicon dangerous?
Solid, dry ferrosilicon is stable. The risks come from fine dust and moisture. When wet, it can release flammable hydrogen and, from phosphorus and arsenic impurities, toxic phosphine and arsine gases. Store it dry and well ventilated, and ventilate cargo holds before entry. For transport, ferrosilicon with 30% to below 90% silicon is classified as UN 1408, Class 4.3 (dangerous when wet) and carried under the IMSBC Code.
What is the HS code for ferrosilicon?
Ferrosilicon is classified under HS heading 7202. Grades with more than 55% silicon, such as FeSi 65, FeSi 72 and FeSi 75, use HS 7202.21. Lower-silicon grades such as FeSi 45 and FeSi 15 use HS 7202.29. National tariff schedules may add further digits.
What sizes and packing are available for export?
Standard export sizes are 10–50 mm and 10–100 mm lumps, 3–10 mm and 0–3 mm granules, and milled or atomized powder. Material is usually packed in 1 MT jumbo bags and shipped FOB or CIF by container or bulk. Custom sizing and packing are available on request.
How do I verify the quality of a ferrosilicon shipment?
Ask for a certificate of analysis for each lot, and appoint an independent inspector to sample at loading. Compare the results with your contract limits for silicon, aluminum, carbon, phosphorus, sulfur and size. Agree in advance which laboratory's result is final if the two analyses differ.
How is the ferrosilicon price determined?
The price mainly follows electricity costs, the cost of quartz and carbon reductants, steel production levels, and supply from the major producing countries. Trade policy and freight rates also move delivered prices. For current levels, see our ferrosilicon price today page or the price per ton trends.
Conclusion: The Quiet Backbone of Modern Metallurgy
Ferrosilicon rarely appears in the finished product, yet almost every tonne of steel and cast iron depends on it. From quartz and scrap smelted in a submerged arc furnace to a clean, sound casting, FeSi does the chemical work that makes quality metal possible.
As a deoxidizer, it protects steel integrity. As an inoculant base, it shapes the structure of cast iron. As a reducing agent, it makes magnesium production possible. For buyers, the key is simple: specify the grade, the impurities and the size clearly, and verify every lot.
Ferrosilicon Quick-Reference Summary
This table condenses the guide into one reference for buyers, engineers and procurement teams comparing ferrosilicon specifications and supply options.
| Aspect | Summary |
|---|---|
| Identity | Iron-silicon ferroalloy (FeSi), also written as ferro silicon. |
| Production | Carbothermic reduction of quartz in a submerged arc furnace, at about 8,000–9,000 kWh per tonne of FeSi 75. |
| Key Functions | Steel deoxidation, silicon alloying, cast iron inoculation and magnesium reduction. |
| Main Grades | FeSi 75, FeSi 72, FeSi 65 and FeSi 45; FeSi 15 powder for dense media separation. |
| Critical Impurities | Al, C, P, S, plus Ca and Ti for sensitive steels. |
| Trade & Shipping | HS 7202.21 / 7202.29; UN 1408, Class 4.3; 1 MT jumbo bags; FOB or CIF. |
| Market Drivers | Global steel output led by East Asia, power prices and raw material costs. |
| Outlook | Rising demand for low-impurity grades and lower-carbon, energy-efficient production. |
Standards & References
Specifications and trade data in this guide are based on these recognized standards and bodies:
- ISO 5445 — Ferrosilicon: specification and conditions of delivery
- ASTM A100 — Standard specification for ferrosilicon
- GB/T 2272 — Chinese national standard for ferrosilicon grades
- IMSBC Code / UN 1408 — maritime transport rules for ferrosilicon, published by the International Maritime Organization
- Harmonized System heading 7202 — customs classification of ferroalloys, maintained by the World Customs Organization
- Regional steel output — World Steel Association statistics
How this guide was prepared: the content combines published standards, metallurgical references and our export team's day-to-day experience with ferrosilicon specifications, inspection and shipping. Figures marked "typical" or "indicative" vary by producer and contract.
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