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Ferrosilicon

All ferrosilicon produced by Finnfjord is sold through our distributor Nizi S.A.

The FeSi-alloy is composed of 75% silicon and 20-23% iron. The purity may be specified according to the customer's demand. Some typical analyses are shown under 'chemical properties' below. The annual production is 100 000 metric tonns. The company is certified in accordance with ISO 9001-2008 and ISO 14001-2004.

What is Ferrosilicon?

FeSi is an alloy of iron and silicon, based on quartz (SiO2), iron ore (Fe2O3), coal and coke (C). The carbon in the coal and coke is needed for extracting oxygen so that pure silicon and iron can be formed. The FeSi alloy is used to give steel and cast iron the desired qualities, such as strength, hardness, temperateness and corrosion resistance. One metric ton of steel contains approximately 3-4 kilograms of FeSi, whereas one metric ton ot stainless steel contains approximately 20 kilograms of FeSi. Hence, we are always surrounded by products containing ferrosilicon.

Production of ferrosilicon

Prosessen - slik lages ferrosilisium.

In short terms, the process may be described as follows: Fe3O2 (iron ore), SiO2 (quartz) and carbon in the form of coal and coke is added at the top of the furnace. Three electrodes is lowered into the furnace, heating the material while moving downwards. After a while the material melts, and a chemical reaction begins. At approximately 2000˚C the carbon reacts with the oxygen in the quartz and we are left with liquid silicon metal. The iron oxide in the iron pellets reacts with the carbon through a similar reaction and forms pure iron. Melted iron and silicon mix and is then tapped in bailers. The metal is cooled and crushed into pieces of variable size, to meet the customer's demand.

The reaction forming pure silicon metal:

SiO2(s) + 2C(s)  → Si(s) + 2CO(g)

The reaction forming iron:

Fe2O3(s) + 3C(s) → 2Fe(s) + 3CO(g)

In the core of the furnace it is too hot for CO2(g) to form. However, the following reaction occurs when the CO-gas  climbs higher in the furnace and mixes with air:

CO(g) + ½02(g) → CO2(g)

Chemical properties of ferrosilicon manufactured by Finnfjord

Element Typical values
Si >75%
Fe ~23%
Al 0,8-1,25%
C 0,05-0,1%
Ti 0,07-0,10%
Ca 0,2-0,4%
AttachmentSize
prosessen.pdf116.03 KB
ISO-9001-2000.pdf180.54 KB