What is ferrochrome? High-carbon and low-carbon ferrochrome compared

What ferrochrome does

Chromium forms a dense, self-healing chromium oxide film a few nanometres thick on the surface of steel. This layer, known as the passive film, separates the metal from oxygen and moisture and so stops corrosion. For a steel to count as stainless it must contain at least 10.5% chromium by weight.

Chromium also increases hardenability, provides wear resistance through carbide formation, and raises oxidation resistance at high temperature. Ferrochrome is therefore used not only in stainless steel but in tool steels, spring steels, bearing steels and wear plate.

Adding chromium to a steel bath as the pure metal is impractical: chromium melts at 1907 °C while the bath generally sits at around 1600 °C. Alloyed with iron the melting point falls and the chromium dissolves quickly in the bath.

Grades by carbon level

Grade	Carbon	Typical use
High carbon (HC FeCr)	4–8%	Alloy steel, cast iron, wear parts; processes where carbon is not a problem or is removed later. The most economical grade.
Medium carbon (MC FeCr)	0.5–4%	Plants with limited decarburisation capacity, some alloy steels.
Low carbon (LC FeCr)	0.03–0.15%	Stainless steel, heat-resistant steel, welding wire and electrode production.

The price difference follows from this: high-carbon ferrochrome is produced by single-step carbothermic reduction and is cheap. The low-carbon grade requires additional decarburisation or metallothermic reduction and is therefore markedly more expensive.

Why carbon is so critical

In stainless steel, carbon combines with chromium between 450 and 850 °C to precipitate chromium carbide (Cr₂₃C₆) at the grain boundaries. The region around the carbide is depleted of chromium and the passive film weakens there. This phenomenon, called sensitisation, leaves the material open to intergranular corrosion; it is seen most often in the heat-affected zone after welding.

That is why carbon input is capped from the outset in stainless steel production. In L (low carbon) grades such as 304L and 316L the carbon ceiling is 0.03%; producing such a steel without low-carbon ferrochrome is not possible.

Do not write only "ferrochrome" in your specification. Always state the chromium range, the carbon ceiling and the silicon ceiling; those three numbers set both the grade and the price.

Other impurities

Silicon (Si): Naturally present in high-carbon grades. It affects slag basicity and is unwanted in some applications; a ceiling of 1.5% or 2% is usually given.
Sulphur (S) and phosphorus (P): Both carry through into the final steel. Sulphur causes hot shortness, phosphorus cold shortness. In critical applications a separate ceiling should be written for each.
Nitrogen (N): Deliberately present in some grades; it increases strength in nitrogen-bearing stainless steels but may be unwanted elsewhere.
Titanium, niobium, vanadium: Trace amounts from scrap, which can shift the composition of sensitive alloys.

Particle size and packaging

Ferrochrome is produced as lump and crushed to size against the order. The right size depends on the addition method:

Ladle addition: the 10–50 mm range gives fast and complete dissolution.
Furnace charging: coarser sizes such as 50–150 mm are preferred.
Wire feeding and injection: powder or granules are needed.
Fines: usually capped at 5–10%; more than that means loss, dust and lower furnace yield.

Packaging can be big bags, steel drums or bulk. For shipments that will stand in the open for a long time, closed packaging is safer against both moisture and loss of fines.

What sets the ferrochrome price

Chromium grade. The price is generally calculated on the chromium unit it contains; the difference between 60% and 65% chromium feeds straight into the price.
Carbon level. The low-carbon grade is the most expensive branch because of the extra process cost.
Energy cost. Carbothermic reduction consumes a great deal of electricity; the power price in the producer's region makes up most of the cost.
Particle size and packaging. Special sizing and closed packaging mean extra labour.
Delivery term and quantity. Freight, insurance and lot size change the unit price markedly.

Pre-order checklist

Is the chromium range written? (Cr 60–65%, for example)
Is the carbon ceiling stated? (C ≤ 0.10%, for example)
Are the ceilings for Si, S and P given?
Are the particle size range and the acceptable proportion of fines written?
Are the packaging and lot size settled?
Is a certificate of analysis (COA) for every lot, and EN 10204 3.1 where needed, requested?
Are the sampling method and the umpire laboratory for a dispute written into the contract?

Frequently asked questions

What is the difference between low-carbon and high-carbon ferrochrome?

The difference is the carbon content. High-carbon ferrochrome contains 4–8% carbon by weight, low-carbon ferrochrome generally 0.03–0.15%. Because carbon in stainless steel precipitates chromium carbide and leads to intergranular corrosion, the low-carbon grade is used there. The high-carbon grade is more economical and is preferred in alloy steel and cast iron production, where carbon is not a problem.

Which ferrochrome is used for stainless steel?

Low-carbon ferrochrome (LC FeCr) is used for stainless steel, and especially for low-carbon grades such as 304L and 316L. The carbon ceiling is usually written into the specification as 0.10% or 0.06%.

How is the ferrochrome price calculated?

The price is mostly set on the chromium unit contained: chromium grade, carbon level, particle size, packaging, lot size and the delivery term (Incoterms 2020) all affect the unit price directly. For a current price, sharing your specification and quantity is enough.

Which documents come with a ferrochrome order?

A certificate of analysis (COA) is supplied with every lot. On request, an EN 10204 3.1 inspection certificate, a safety data sheet (SDS) and a pre-shipment independent third-party inspection report are provided.

Items covered in this article

Open any of them in the catalogue, enter your own specification and request a quote.