Ferrosilicon 75 (FeSi75) and ferrosilicon 72 (FeSi72) are both iron-silicon alloys used in steelmaking, foundry operations and alloying. The numbers 75 and 72 refer to the nominal percentage of silicon in the alloy. Choosing between them is a routine decision for mills and foundries, balancing silicon efficiency against cost per tonne. This article compares their composition, performance and economics, and provides a practical selection guide.
Reference Price Snapshot
The table below shows indicative export reference levels published on the source page, in US dollars per metric tonne, FOB Tianjin port. These are point-in-time reference ranges and current quotations move frequently with raw-material costs and market demand; buyers should verify live levels with market sources before budgeting.
| Product | Grade | Quotation (USD/tonne) | Terms |
|---|---|---|---|
| Ferrosilicon | 72 | 1,020-1,040 | FOB Tianjin Port |
| Ferrosilicon | 75 | 1,100-1,120 | FOB Tianjin Port |
The premium of FeSi75 over FeSi72 reflects the higher silicon content and the additional processing cost required to reach it.
What Are FeSi75 and FeSi72?
| Grade | Silicon content (nominal) | Iron content (balance) | Common names |
|---|---|---|---|
| Ferrosilicon 75 (FeSi75) | 72-78% | 22-28% | FeSi75, silicon ferro 75 |
| Ferrosilicon 72 (FeSi72) | 68-72% | 28-32% | FeSi72, silicon ferro 72 |
The key difference is the silicon content: FeSi75 carries more active silicon per tonne than FeSi72. Both grades are produced by carbothermic reduction of quartz (SiO₂) with coke in submerged electric arc furnaces, with iron added as scrap or ore.
Key Differences in Performance
| Feature | Ferrosilicon 75 | Ferrosilicon 72 |
|---|---|---|
| Silicon content | 72-78% (higher) | 68-72% (slightly lower) |
| Iron content | 22-28% (lower) | 28-32% (higher) |
| Alloying efficiency per ton | More efficient (more Si) | Slightly less efficient |
| Deoxidation power | Stronger | Good, slightly weaker |
| Cost per ton | Usually higher | Usually lower |
| Cost per kg of silicon | Better value | Less value |
| Typical use | Premium steel, ductile iron, electrical steel | General steel, cost-sensitive casting |
Silicon is the active ingredient in ferrosilicon: it removes oxygen from the melt (deoxidation), raises strength, hardness and wear resistance, and controls graphite formation in cast iron. Higher silicon content therefore delivers more metallurgical effect per tonne of alloy added.
When to Choose Ferrosilicon 75
Choose FeSi75 when maximum deoxidation and alloying performance matters, such as in high-quality or specialty steels, electrical steel, spring steel, tool steel and stainless steel, where precise silicon control improves magnetic, mechanical or corrosion properties. It is also the standard choice for inoculation of gray iron and for producing spheroidal graphite in ductile iron, where the higher and more controlled silicon content leads to more predictable reactions in the furnace or ladle. Although the cost per tonne is higher, the cost per kilogram of silicon is usually better, making it the global standard for critical deoxidation, inoculation and alloying duties.
When to Choose Ferrosilicon 72
Choose FeSi72 when cost control is the priority and the application tolerates slightly lower silicon efficiency. It suits basic steelmaking, general cast iron and large-volume operations where the maximum deoxidation impact is not required, and it works well as a supplementary alloy alongside other silicon sources. For budget-conscious foundries and mills producing carbon or low-alloy steel, FeSi72 delivers dependable chemistry at a lower cost per tonne. Confirm the exact silicon range with the supplier, since 72% and 75% designations allow slight variations between batches.
Frequently Asked Questions
Is FeSi75 always better than FeSi72? Not in economic terms. FeSi75 is better per tonne of silicon efficiency, but FeSi72 can be the better choice when the specification does not demand maximum silicon effect and cost control dominates.
Can FeSi75 and FeSi72 be used together? Yes. FeSi72 can supplement FeSi75 or other silicon sources to meet a target chemistry at lower cost.
How do buyers verify the actual silicon content? Each batch should carry a certificate of analysis based on laboratory testing; spot checks by titration or X-ray fluorescence are common practice for incoming material.
What sizes are typically available? Both grades are commonly supplied as lumps (10-100 mm), granules, powder or briquettes; size selection depends on furnace type, charging method and dissolution rate requirements.
How should ferrosilicon be stored? Keep it dry and away from moisture and acids, since ferrosilicon can react with water or acid to release hydrogen gas. Ventilated storage and dry handling are standard precautions.
Which grade suits ductile iron production? FeSi75 is preferred for nodularizing and inoculation because its higher silicon content provides more consistent graphite control per tonne of addition.