Ferro Silicon (FeSi) is an alloy composed of silicon and iron, widely recognized for its role as a powerful deoxidizing agent in the production of stainless steel. It is also crucial in the manufacturing of special steels and mild steel. Beyond steel production, FeSi is instrumental in creating silicon metal, corrosion-resistant, and high-temperature-resistant ferro silicon alloys, as well as silicon steel, which is essential for the cores of electromotors and transformers due to its magnetic properties.

Physical Properties:-

  Appearance:

• Colour: Dark grey or metallic grey with a silvery sheen.
• Form: Supplied in lumps, granules, or powder form depending on its application. The surface can be rough or slightly irregular due to the smelting process.

  Density:

• The density of ferro silicon depends on its silicon content. Typical density ranges:
  • FeSi 75%: Around 2.4 to 2.6 g/cm³.
  • FeSi 90%: Around 2.3 to 2.5 g/cm³.

  Melting Point:

• The melting point of ferro silicon varies with the silicon content:
  • FeSi 75%: Melting point ranges between 1,210 – 1,300°C (2,210 – 2,370°F).
  • FeSi 90%: Melting point is higher, around 1,350°C (2,460°F).

  Hardness:

• Ferro silicon is brittle and hard. It can fracture easily when subjected to mechanical force, and has moderate hardness.
• The hardness on the Mohs scale ranges from 5-6, making it relatively brittle and hard.

  Electrical Conductivity:

• Poor conductor of electricity, especially compared to pure iron. Silicon significantly reduces the electrical conductivity of the alloy.

  Magnetic Properties:

• Ferro silicon exhibits weak magnetic properties due to the presence of silicon, which diminishes the alloy’s magnetic permeability, especially in high-silicon grades.

  Carbon Content:

• The carbon content in ferro silicon is typically very low, usually less than 0.1%, making it a clean alloy for steelmaking applications where high purity is required.

  Solubility:

• Insoluble in water. Ferro silicon does not dissolve in water or organic solvents.

  Reactivity:

• Ferro silicon is highly reactive at high temperatures and acts as an effective deoxidizer in steelmaking.
• Reactivity with Oxygen: It reacts with oxygen to form silicon dioxide (SiO₂), helping to remove oxygen impurities from molten steel.
• In powder form, it can be pyrophoric (capable of igniting spontaneously) when exposed to air.

  Thermal Conductivity:

• Ferro silicon has low thermal conductivity compared to pure metals like iron. This is influenced by the presence of silicon.