Ferrosilicon - Properties, Applications

Topics Covered

Chemical Composition
Physical Properties


Ferrosilicon is a ferroalloy - an alloy of iron and silicon. Its CAS number is 8049-17-0. The average silicon content varies between 15 and 90 wt%. It contains a high proportion of iron silicides. Ferrosilicon is produced by reduction of silica or sand with coke in presence of iron.

Ferrosilicon is known to possess good resistance to abrasion, good resistance to corrosion, high specific gravity, and high magnetism, which allows easy magnetic recovery. The melting point and density of ferrosilicon depends on its silicon content and it is available at a low cost.

The following sections will discuss the various properties of ferrosilicon in detail.

Chemical Composition

The following table shows the chemical composition of Elkem FeSi low Al ferrosilicon.

Element Content (%)
Silicon, Si 74 - 78
Iron, Fe ≥ 21.32
Aluminum, Al ≤ 0.50
Carbon, C ≤ 0.050
Sulfur, S ≤ 0.0030
Phosphorous, P ≤ 0.020

Physical Properties

The following table discusses the physical properties of ferrosilicon.

Properties Metric Imperial
Density 3.20 g/cm3 0.116 lb/in3
Melting point 1200-1250°C 2192-2282°F
Boiling point 2355°C 4271°F


The following are the common application areas of ferrosilicon:

  • As a source of silicon to reduce metals from their oxides and to deoxidize steel and other ferrous alloys
  • Manufacture of other ferroalloys
  • Manufacture of silicon, corrosion-resistant and high-temperature resistant ferrous silicon alloys, and silicon steel for electromotors and transformer cores
  • Manufacture of cast iron, ferrosilicon is used for inoculation of the iron to accelerate graphitization
  • Manufacture of prealloys like magnesium ferrosilicon, used for modification of melted malleable iron.
  • As an additive to cast irons for controlling the initial content of silicon
  • In steel melting, casting, mineral processing and melting rod industry
  • Used in the Pidgeon process to make magnesium from dolomite
  • For heavy media separation and atomization
  • Used in casting, melting and related metallurgy industry
  • For production of semiconductor pure silicon in electric industry and silicon copper in chemistry industry

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