What is Ferrosilicon?

Ferrosilicon is an alloy composed of iron and silicon, with the silicon content typically ranging from 15% to 90%. The most common commercial grades are those with 15%, 45%, 75%, and 90% silicon. The remaining portion of the alloy primarily consists of iron, with about 2% comprising other elements such as aluminum and calcium.

Ferrosilicon Primary Uses

Ferrosilicon is widely used as a silicon source in metallothermic reduction processes to extract metals from their oxides. Additionally, it plays a crucial role in deoxidizing steel and other ferrous alloys, which is essential in preventing carbon loss from molten steel, a process known as "blocking the heat." Ferrosilicon is also instrumental in the production of other ferroalloys and is a key component in manufacturing metallic silicon, which is used to produce corrosion-resistant and high-temperature-resistant ferrous silicon alloys, as well as silicon steel for electric motors and transformer cores.

In the foundry industry, ferrosilicon is used as an inoculant in cast iron production to accelerate graphitization. It also finds application in arc welding, where it is present in certain electrode coatings. Moreover, silicon metal, derived from ferrosilicon, is an essential alloying element in aluminum production and is crucial in manufacturing chemicals, especially silicones. Highly refined silicon metal can be used to produce solar-grade or even semiconductor-grade silicon for electronic applications.

Ferrosilicon Specialized Applications

Ferrosilicon serves as a foundation for producing alloys such as magnesium ferrosilicon (FeSiMg), which is used to modify molten malleable iron. FeSiMg typically contains 3% to 42% magnesium and small quantities of rare earth metals. This alloy is also used as a reductant in magnesium metal production from dolomite.

Ferrosilicon Production Process

Ferrosilicon is produced by reducing silica or sand with coke in the presence of scrap iron, mill scale, or other iron sources in submerged arc electric furnaces. An excess of silica beyond the stoichiometric requirement is necessary to prevent silicon carbide formation.

Ferrosilicon Additional Uses

Beyond its primary uses, ferrosilicon has other interesting applications. It is used for deoxidizing steel and ferrous alloys, blocking the heat to prevent carbon loss, and producing other ferroalloys. In cast iron production, ferrosilicon aids in inoculation to promote graphitization. In arc welding, it is found in some electrode coatings.

Ferrosilicon is also a critical component in producing pre-alloys like magnesium ferrosilicon (MgFeSi), which is used to produce ductile iron. MgFeSi contains 3% to 42% magnesium and trace amounts of rare earth metals. This alloy helps control the initial silicon content in cast irons and is instrumental in forming graphite nodules in ductile iron, providing it with its flexible properties. Unlike gray cast iron, which forms graphite flakes, ductile iron contains graphite nodules that make it more resistant to cracking.

Additionally, ferrosilicon is used in the Pidgeon process for magnesium production from dolomite and is also utilized in the manufacture of electrical transformer sheets, where it is used at a ratio of 3% to 3.5% to enhance the magnetic circuit of transformers.