Ferrosilicon Blocks Of Various Sizes

Ferrosilicon, commonly abbreviated FeSi, is an iron–silicon alloy that also contains smaller proportions of other elements. The most popular grade of ferrosilicon contains 75 wt% silicon ('FeSi75'), but the amount can range from 15–90 wt% depending on the application.

The highest-quality ferrosilicon is made in an electric arc furnace by reducing silica with coke in the presence of iron (usually derived steel scrap or iron ore). The ferrosilicon usually takes the form of shiny, metallic-grey lumps, but is also available as pre-formed briquettes.

The role of ferrosilicon in steelmaking

In steelmaking, ferrosilicon is used for:

Product performance – Ferrosilicon is a convenient way of adding silicon as an alloying element, to improve various properties of the final steel.

Slag reduction – In the manufacture of stainless steels, the presence of silicon reduces chromium oxides in the melt, improving recovery of metallic chromium.

Deoxidation – Ferrosilicon provides quick-acting removal of oxygen from the melt, so avoiding the presence of inclusion-forming oxides and avoiding loss of desirable elements.

Fuel – Some steel mills add ferrosilicon to the melt so that it can be burnt off to get heat into the furnace, and so reduce energy costs.