Alloys of iron with a high proportion of manganese, silicon, chromium, molybdenum, vanadium, niobium or another element, used to add that element to steel and to remove oxygen from it. Every tonne of steel needs ferro-alloys; manganese alloys alone account for roughly 1% of a carbon steel's weight.
Also called
Ferroalloys
Ferromanganese
FeMn
Silicomanganese
SiMn
Ferrosilicon
FeSi
Ferrochrome
FeCr
Charge chrome
Ferromolybdenum
Ferrovanadium
Ferroniobium
Noble alloys
AR
السبائك الحديدية (الفيروسبائك)
ZH
铁合金
DE
Ferrolegierungen
FR
Ferro-alliages
ES
Ferroaleaciones
IT
Ferroleghe
TR
Ferro alaşımlar
RU
Ферросплавы
Main formsCrushed and screened lumps, small-size grades, fines; cored wire and briquettes for some alloys
Typical sizesTypically 10–50 mm or 10–100 mm lumps; 3–10 mm and below for ladle and cored-wire use
Main standardsISO 5445 (FeSi), ISO 5446 (FeMn), ISO 5447 (SiMn), ISO 5448 (FeCr), ISO 5451 (FeV), ISO 5452 (FeMo), ISO 5453 (FeNb)
Key gradesHC/MC/LC FeMn, SiMn 65/17, FeSi 75, HC FeCr and charge chrome, LC FeCr, FeMo 65–70, FeV 80, FeNb 65
Typical usesDeoxidation and alloying in EAF, BOF and ladle; stainless steel (FeCr, FeNi); cast iron (FeSi, inoculants)
Overview
Ferro-alloys are the practical way to put an element into molten steel. Pure manganese, chromium or vanadium are expensive or awkward to make; an alloy with iron melts and dissolves readily in steel, is denser than slag so it sinks into the bath, and can be produced directly by smelting the ore with carbon or silicon. They do two jobs: deoxidising the steel (silicon and manganese, aluminium beside them) so that it casts sound, and alloying it to the specified grade.
The bulk alloys — ferromanganese, silicomanganese, ferrosilicon and ferrochrome — are made by smelting ore with coke or coal in submerged-arc electric furnaces, which takes a great deal of electricity; refined low-carbon grades are made by further silicothermic or oxygen refining. The noble alloys — ferromolybdenum, ferrovanadium, ferroniobium, ferrotitanium, ferrotungsten — are made in smaller quantities, often by aluminothermic reduction, and are priced on their contained element.
Silicomanganese is the most used alloy in long-product and rebar steelmaking, because it deoxidises and adds manganese in one; flat-product and special-steel plants use more refined ferromanganese and aluminium. Ferrochrome goes overwhelmingly into stainless steel. Vanadium and niobium, added at a few hundredths of a percent, strengthen rebar and high-strength structural steel by grain refinement and precipitation.
The GCC's steel plants, almost all of them EAF mills making rebar, wire rod, billets and sections, are large consumers of silicomanganese and ferrosilicon and of ferrovanadium for high-strength rebar. There is regional production: Gulf Ferro Alloys Company (Sabayek) at Jubail in Saudi Arabia, and ferrochrome smelters in the Sohar Freezone in Oman, which use Omani chromite. Most supply is imported from India, China, South Africa, Kazakhstan, Ukraine, Brazil and Malaysia.
Forms & sizes
The typical contents and the ISO delivery standard for each alloy are in the table Common ferro-alloys.
Lumps
Crushed and screened, commonly 10–50 mm, 10–100 mm or 50–150 mm
Small sizes
3–10 mm and 0–3 mm for ladle additions and cored wire
Cored wire
Powdered FeSi, FeTi, CaSi, FeB and others in a steel sheath, fed into the ladle
Packing
1 t jumbo bags, steel drums for noble alloys, or bulk for SiMn and FeSi
Pricing
Bulk alloys by tonne of alloy; noble alloys by kg of contained Mo, V or Nb
Each ISO delivery standard defines the grades of one alloy, their chemistry limits, sizes and sampling. Many buyers use the national equivalents or a producer's typical analysis instead.
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