What are the grades of ferrosilicon? What is ferrosilicon used for? - Knowledge

What are the grades of ferrosilicon?

Ferrosilicon grades are mainly defined by silicon content. Commercial grades are expressed as FeSiXX, where "XX" is the approximate percentage of silicon.

Grade	Silicon Content (%)	Typical Uses
FeSi15	15%	Foundry inoculants, low-silicon steels
FeSi25	25%	Steel deoxidation, general foundry
FeSi45	45%	Welding electrodes, medium-grade steels
FeSi65	65%	Most common steelmaking grade
FeSi75	75%	High-quality steels, electrical steels
FeSi90	90%	Specialty alloys, chemical applications

Other classifications:

•By form: Lump, briquette, powder, granule

•By impurity limits: Low-Al, low-Ca grades for special steels

•By standards: Chinese GB, Indian IS, European EN, etc.

What Is Ferrosilicon Used For?

Ferrosilicon is an iron–silicon alloy mainly used in:

1.Steelmaking – Deoxidizer and alloying agent to improve strength, hardness, and corrosion resistance.

2.Foundry industry – Controls graphite formation in cast irons, improves machinability (used in malleable and ductile iron).

3.Manufacturing other ferroalloys – Feedstock for silicomanganese, etc.

4.Welding electrodes – Enhances fluidity and deoxidation.

5.Chemical & specialty uses – Source of silicon in certain reactions.

What Is the Composition of Ferrosilicon?

Ferrosilicon is primarily:

Iron (Fe) – Balance of composition (depends on Si %)

Silicon (Si) – Main alloying element (ranges from ~15% to 90%)

Minor elements – Aluminum (Al), calcium (Ca), carbon (C), phosphorus (P), sulfur (S) - contents depend on grade and production method.

Example (typical FeSi75):

Si: 72–78%

Fe: Balance (~20–25%)

Al: ≤0.5% (lower in special grades)

Ca: ≤1%

C: ≤0.2%

P, S: trace

What is the difference between silicon and ferrosilicon?

Difference Between Silicon and Ferrosilicon

Aspect	Silicon Metal	Ferrosilicon
Composition	>98–99% Si, small impurities	Iron + Silicon (15–90% Si)
Primary Use	Electronics, solar cells, silicones, aluminum alloy hardener	Steelmaking, foundry, welding, other ferroalloys
Production	Smelting quartz with carbon, high-purity refining	Smelting quartz + coke + iron ore/scrap
Cost	Higher (due to purity)	Lower (iron dilutes cost)
Form in Industry	Crystalline lumps/powder for chemicals	Lump/briquette/powder for metallurgy
Magnetic property	Non-magnetic	Magnetic (due to iron)

Key point:

•Silicon metal = high-purity Si for chemical/electronic uses.

•Ferrosilicon = metallurgical alloy of Fe + Si for steel/foundry industries.

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