Quick Answer: Ferrosilicon metal, also called ferro silicon or FeSi, is an iron-silicon alloy mainly used as a deoxidizer and silicon alloying material in steelmaking and as an inoculating material in foundry applications. Common commercial grades include FeSi75, FeSi72, FeSi70 and FeSi65. When selecting a grade, compare not only silicon content but also impurity limits, particle size, fines control and the actual batch COA.
What Is Ferrosilicon Metal?
Ferrosilicon is an alloy consisting mainly of silicon and iron. In steelmaking, silicon has a strong affinity for oxygen, which is why FeSi is widely used for deoxidation and silicon adjustment.
In foundry production, suitable ferrosilicon grades and particle sizes can also be used for silicon addition and inoculation.
The term ferrosilicon metal is commonly used in trade to refer to commercial FeSi products supplied as lump, granule or powder.
For available product forms and grades, see our ferrosilicon product range.
Ferrosilicon Grades and Chemical Composition
Ferrosilicon grades are mainly distinguished by silicon content, while Al, Ca, P, S, C and other elements may also be controlled according to the purchase specification.
The following values are reference specifications used for common commercial grades. Exact limits should be confirmed in the quotation, contract and batch COA.
| Grade | Si ≥ | Al ≤ | Ca ≤ | P ≤ | S ≤ | C ≤ | Fe |
|---|---|---|---|---|---|---|---|
| FeSi75 | 75% | 1.5% | 1.0% | 0.035% | 0.02% | 0.20% | Balance |
| FeSi72 | 72% | 1.5% | 1.0% | 0.040% | 0.02% | 0.20% | Balance |
| FeSi70 | 70% | 1.5% | 1.0% | 0.040% | 0.02% | 0.20% | Balance |
| FeSi65 | 65% | 2.0% | 1.0% | 0.040% | 0.02% | 0.20% | Balance |
The grade number should not be treated as the only purchasing criterion. Two batches sold under the same grade can still have different actual impurity values while remaining within the agreed limits.
If you are deciding between the main grades, see our guide to FeSi75, FeSi72 and FeSi65 specifications.
How FeSi75, FeSi72 and FeSi65 Differ in Use
The main practical difference between these grades is how much ferrosilicon is required to deliver the target silicon addition.
For example, before considering recovery:
- 10 kg of contained silicon requires about 13.3 kg of FeSi75 at a nominal 75% Si basis.
- 10 kg of contained silicon requires about 13.9 kg of FeSi72 at a nominal 72% Si basis.
- 10 kg of contained silicon requires about 15.4 kg of FeSi65 at a nominal 65% Si basis.
That does not mean FeSi75 is automatically the best or cheapest option. The correct comparison should also include actual silicon content, recovery, impurity limits and delivered price.
A lower-silicon grade may still be economical when the process accepts the higher addition quantity and its chemistry.
Ferrosilicon Particle Size and Product Form
Ferrosilicon is supplied in different physical forms according to the way it will be charged or added to the process.
| Form | Typical Size Example | Selection Consideration |
|---|---|---|
| Lump | 10–50 mm, 10–100 mm | Common for furnace or ladle addition where controlled lump sizing is required. |
| Granule | Application-specific | Used when a smaller and more uniform addition size is preferred. |
| Powder | Fine particle or mesh-based specifications | Selected for applications requiring fine FeSi rather than conventional lump addition. |
Particle size should be specified together with acceptable fines and oversize where these affect handling or process performance.
If you require fine material, see the available ferrosilicon powder specifications.
Main Applications of Ferrosilicon Metal
Ferrosilicon is used in several metallurgical processes, but the required grade and size depend on how the silicon is being introduced.
Steelmaking Deoxidation and Silicon Addition
FeSi is commonly added during steelmaking and refining to remove dissolved oxygen and adjust the final silicon content. The required grade depends on the silicon target, impurity allowance and addition practice.
Foundry Inoculation
Ferrosilicon-based inoculants are used in cast iron production to influence solidification and graphite formation. Ordinary ferrosilicon should be distinguished from FeSiMg nodularizer, which contains magnesium and performs a different metallurgical function.
Silicothermic Reduction and Alloy Production
High-silicon ferrosilicon can also be used as a silicon-bearing reducing material in selected metallurgical processes, including the production of some ferroalloys and magnesium.
What to Check Before Buying Ferrosilicon
Before comparing quotations, make sure the offers are based on the same specification.
| Item | What to Confirm |
|---|---|
| Grade | FeSi75, FeSi72, FeSi70, FeSi65 or another agreed specification |
| Chemistry | Si together with relevant Al, Ca, P, S, C or other impurity limits |
| Particle size | Required size range together with fines or oversize tolerance where necessary |
| Batch COA | Actual test values for the supplied production lot |
| Packing | Bag type and net weight required for transport and handling |
| Quotation basis | Quantity, trade term and destination port |
Need to Compare Ferrosilicon Grades or Get a Quote?
Send your required FeSi grade, Si and impurity limits, particle size, quantity and destination port. We can provide the available specification and recent batch COA for comparison before you confirm the order.
Ferrosilicon Product Appearance
The appearance of the material can help verify particle size, fines and obvious contamination, although chemical grade must still be confirmed by test results.
Ferrosilicon Storage and Handling
Keep ferrosilicon dry and protect bags from water ingress and contamination during storage. Dust should be minimized during crushing, transfer and handling, especially for fine ferrosilicon products.
For workplace handling, transport and emergency requirements, follow the SDS supplied for the specific product and the applicable local regulations.
FAQ About Ferrosilicon Metal
What is ferrosilicon metal made of?
Ferrosilicon is mainly composed of silicon and iron. Commercial grades also contain controlled amounts of Al, Ca, P, S, C and other elements depending on the specification.
What are the common ferrosilicon grades?
Common commercial grades include FeSi75, FeSi72, FeSi70 and FeSi65. Lower-silicon grades such as FeSi45 are also available for specific metallurgical requirements.
Is FeSi75 always better than FeSi65?
No. FeSi75 contains more silicon per tonne, but the better option depends on required silicon addition, impurity limits, recovery and delivered cost.
What size of ferrosilicon is commonly supplied?
Lump ferrosilicon is commonly supplied in ranges such as 10–50 mm or 10–100 mm, while granules and powders are supplied in smaller particle-size specifications according to the application.
Should I check the COA before buying ferrosilicon?
Yes. The COA shows the actual chemistry reported for a production batch and allows you to compare it with the agreed grade and impurity limits.
Is ferrosilicon powder a different grade?
Not necessarily. Powder describes the physical form. Ferrosilicon powder can still be produced with different silicon contents and chemical specifications.
