Ferrosilicon is an alloy of iron and silicon with an average silicon content between 15 and 90 weight percent. It contains a high proportion of iron silicides.

Production and reactions

Ferrosilicon is produced by reduction of silica or sand with coke in the presence of iron. Typical sources of iron are scrap iron, millscale. Ferrosilicons with silicon content up to about 15% are made in blast furnaces lined with acid fire bricks. Ferrosilicons with higher silicon content are made in electric arc furnaces. The usual formulations on the market are ferrosilicons with 15%, 45%, 75%, and 90% silicon. The remainder is iron, with about 2% consisting of other elements like aluminium and calcium. An overabundance of silica is used to prevent formation of silicon carbide. Microsilica is a useful byproduct. A mineral perryite is similar to ferrosilicon, with its composition Fe5Si2. In contact with water, ferrosilicon may slowly produce hydrogen. The reaction, which is accelerated in the presence of base, is used for hydrogen production. The melting point and density of ferrosilicon depends on its silicon content.

Physical properties of ferrosilicon
Si content (wt. %) 0 20 35 50 60 80 100
Melting point (°C) 1538 1210 1210 1210 1230 1360 1414
Density (g/cm3) 7.87 6.76 5.65 5.1 4.27 3.44 2.33


Ferrosilicon is used as a source of silicon to reduce metals from their oxides and to deoxidize steel and other ferrous alloys. This prevents the loss of carbon from the molten steel (so called blocking the heat); ferromanganese, spiegeleisen, silicides of calcium, and many other materials are used for the same purpose.[3] It can be used to make other ferroalloys. Ferrosilicon is also used for manufacture of silicon, corrosion-resistant and high-temperature-resistant ferrous silicon alloys, and silicon steel for electromotors and transformer cores. In the manufacture of cast iron, ferrosilicon is used for inoculation of the iron to accelerate graphitization. In arc welding, ferrosilicon can be found in some electrode coatings.

Ferrosilicon is a basis for manufacture of prealloys like magnesium ferrosilicon (MgFeSi), used for production of ductile iron. MgFeSi contains 3–42% magnesium and small amounts of rare-earth metals. Ferrosilicon is also important as an additive to cast irons for controlling the initial content of silicon.

Magnesium ferrosilicon is instrumental in the formation of nodules, which give ductile iron its flexible property. Unlike gray cast iron, which forms graphite flakes, ductile iron contains graphite nodules, or pores, which make cracking more difficult.

Ferrosilicon is also used in the Pidgeon process to make magnesium from dolomite. Treatment of high-silicon ferrosilicon with hydrogen chloride is the basis of the industrial synthesis of trichlorosilane.

Hydrogen production

Ferrosilicon is used by the military to quickly produce hydrogen for balloons by the ferrosilicon method. The chemical reaction uses sodium hydroxide, ferrosilicon, and water. The generator is small enough to fit in a truck and requires only a small amount of electric power, the materials are stable and not combustible, and they do not generate hydrogen until mixed.[4] The method has been in use since World War I. A heavy steel pressure vessel is filled with sodium hydroxide and ferrosilicon, closed, and a controlled amount of water is added; the dissolving of the hydroxide heats the mixture to about 200 °F (93 °C) and starts the reaction; sodium silicate, hydrogen and steam are produced.[5]


Manganese alloy are the largest produced ferro-alloys in the wold with a share of about 41% of the global production of ferro alloys. Manganese is an essential requisite for iron & steel production due to its capability for sulphur fixing, de-oxidising and good alloying properties. For production of one ton of ferro manganese, about 2.6 tons of manganese ore , 0.5 ton of reductant and 3 MWh of electricity inputs are required. As per Indian Ferro Alloy Producers Association, the total installed capacity of manganese alloys including ferro manganese/silico manganese in the country was estimated to be around 2.75 million tons per annum.


The total production of various type of manganese alloys (high carbon ferro manganese, medium carbon ferro manganese and low carbon ferro manganese) was about 5.18 lakh tons in 2014-15 .


Silico Manganese is combination of 60-70% Mn, 10-20% silica and about 20% carbon. As per Monthly Statistics of Mineral Production, production of silico manganese was reported at 2.56 lakh tons in 2014-15.

The major factor driving the production of manganese alloys is high production growth of low nickel austenitic styai9nless steel. India is emerging as the largest producer of this steel where manganese is added substituting the expensive nickel.


Cost and technology militate substitution in major applications. However, for economic reasons there is only limited substitution in minor applications in chemical and battery industries. The steel industry has however made great strides in economising the use of manganese, largely through changes in steel-making techniques.


The deep-sea nodules can be a potential resource of manganese in the next decade to come. There is a trend towards using lower grade of ores in ferro-manganese production. New steel making practices and techniques are reducing the amount manganese consumed in the process. However, counter balancing this to some extent is a trend towards higher manganese specification for modern steels.


Imports of manganese ore and concentrates including ferruginous manganese ores and concentrates containing 20% or more manganese, agglomerated manganese ore sinters etc. are freely allowed. There is no change in policy for the period 2015-20.


The total world reserve of manganese ore is approximately 570 million tons of metal content which is unevenly distributed. Reserves are located in south Africa (26%), Ukraine 25%, Australia 17%. Brazil and India 9% each. Only a small fraction of global manganese reserve is clearly economic. This fact continues to support interest in deep-sea manganese nodules, which constitute an enormous untapped resource. Most nodule are found in areas of deep-sea floor at water depths of 5 to 7 km. The pacific Ocean alone is estimated to contain about 2.5 billion tons nodules containing about 25% Mn, making them similar in abundance to low-grade land based deposits. Most major steel making nations lack manganese resources. North America had less than 1% world reserves. Besides, United States have lean grade reserves and potentially high extraction cost. This situation has created an active global trade in manganese ore and manganese alloys.

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Production of crude steel is the single most important factor in the demand for manganese ore. Steel industry accounts for approximately 90% world demand for manganese. Carbon steel is the principal market accounting for 65 to 70% manganese consumption.

The production is estimated at 6.70 million tons and the apparent consumption is estimated at 7.31 million tons.