Rare earth ferrosilicon (also written RE ferrosilicon, RE-FeSi or FeSiRe) is a ferrosilicon-based alloy containing rare earth elements, produced by melting ferrosilicon together with rare earth and other charge components.
What Is Rare Earth Ferrosilicon?
One supplier describes its alloy as made from ferrosilicon, rare earth, calcium, pig iron or scrap steel, proportioned and melted at high temperature.
According to a Chinese national standard planning record for its analysis methods, the alloy is mainly used in the iron and steel industry to remove harmful elements such as oxygen, sulfur, nitrogen and arsenic from molten steel. The same record describes it as a base material for nodularizers, vermiculizers and inoculants, and as an additive or alloying agent in steel and iron production.
In practice, results depend on the grade, addition method, melt condition and base metal chemistry, so treat the alloy as a process input to be specified, not a guaranteed fix.
Rare Earth Ferrosilicon vs. Ferrosilicon vs. FeSiMg
Buyers often confuse three related products. The differences below are about what each product is for, not about exact composition, which varies by grade.
| Product | What it is | Typical role |
| Ferrosilicon (FeSi) | Iron-silicon alloy; in China, ferrosilicon is covered by GB/T 2272 | Deoxidizer and silicon source in steelmaking and foundry work |
| Rare earth ferrosilicon (FeSiRe) | Ferrosilicon-based alloy with a specified rare earth content | Deoxidation and desulfurization; base material for nodularizer, vermiculizer and inoculant production |
| RE-bearing magnesium ferrosilicon (RE-MgFeSi, FeSiMg) | Magnesium-containing ferrosilicon treatment alloy with rare earth as a supporting element | Used for ductile iron nodularizing treatment; the grade code (for example FeSiMg8RE3) indicates nominal Mg and RE levels |
Chemical Composition and Grade Specifications
A rare earth ferrosilicon specification is read mainly through its rare earth (RE) content, silicon content, and the limits on other agreed elements. Use the producer's full grade sheet rather than assuming identical composition across grades.
An article on the LSFerroalloy website describes rare earth ferrosilicon (RE-FeSi) as an alloy with silicon content of 40–70% plus rare earths such as cerium (Ce) and lanthanum (La) . The table below only summarizes that article's description and is not a guaranteed specification for any specific grade:
| Item | What the verified passage states |
| Silicon content | Si 40–70% |
| Rare earth elements | Cerium (Ce) and lanthanum (La) listed; individual contents not given |
| Total RE and specific grades | Not listed in that RE-FeSi passage |
Light vs. heavy rare earth
The SAMR standard record notes that products are mainly of two types: light rare earth cerium-group alloys and heavy rare earth yttrium-group alloys. It also notes that alloys with specific distributions, such as lanthanum-cerium ferrosilicon, have been developed, and that different rare earth compositions lead to different production processes and product performance
That is why a total RE number alone is not enough for a technical specification. If your process is sensitive to the rare earth distribution, ask the supplier for the Ce, La and Y breakdown, not only total RE.
Applications in Steelmaking and Foundry Production
Based on the sources above, the main uses fall into three groups:
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Steel and cast iron treatment. Deoxidation and desulfurization in cast steel and cast iron.
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Additive and alloying agent. Used as an additive or alloying agent in steel and iron production.
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Base material for treatment alloys. Used to produce nodularizers, vermiculizers and inoculants.
Keep these separate when you write a purchase specification. The function of the base alloy is not the same thing as the performance of a finished nodularizer or inoculant, which also depends on how that product is formulated and used.
How to Select Rare Earth Ferrosilicon
Work through these points before you compare offers:
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Define the purpose. Direct addition to steel or iron, or use as raw material for making treatment alloys. The answer drives grade choice.
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Set the target composition. State required total RE, minimum and maximum Si, and limits on Ca, Mn, Ti and any element your process cannot tolerate. Do not assume the same limit applies to every supplier's grade.
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Specify the rare earth distribution if it matters. Cerium-group, lanthanum-cerium and yttrium-group alloys are different products.
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Agree on the test method. Define how RE content will be measured and which laboratory result governs in a dispute.
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Ask about batch consistency. Request analysis per lot, not a one-time sample result.
How rare earth content is tested
The national standards platform lists GB/T 16477.1-2024 as a published chemical-analysis standard for determining total rare earth and fifteen individual rare earth element contents in these alloys—not as a product-grade specification.
Agree on the applicable test method, standard edition and acceptance criteria with your supplier and laboratory before ordering.
What to Include in an RFQ
A complete inquiry saves time and avoids mismatched quotations. Include:
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Intended use (direct addition, or raw material for nodularizer, vermiculizer or inoculant production)
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Target grade or composition: total RE, Si, and limits on other elements
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Required rare earth distribution (Ce, La, Y) if relevant
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Particle size range and tolerance for fines
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Quantity per shipment and annual forecast
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Packaging preference and labeling requirements
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Destination port and Incoterms
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Required documents: certificate of analysis per lot, safety data sheet and any third-party inspection
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Analysis method and arbitration laboratory
Frequently Asked Questions
Is rare earth ferrosilicon the same as FeSiMg nodularizer?
No. RE-bearing FeSiMg is a magnesium-containing ferrosilicon treatment alloy used for ductile iron . Rare earth ferrosilicon is a different product, and the SAMR record describes it as a base material for producing nodularizers, vermiculizers and inoculants . Confirm the grade name on every quotation.
How do I confirm the specific grade and composition?
Request the full grade table from your supplier and confirm total RE, silicon content, limits on other elements and particle size requirement item by item. Do not set acceptance criteria based on the grade code alone.
Can the specification be customized?
The LSFerroalloy website states that customized specifications and third-party inspection are available on request . For non-standard grades, confirm minimum order quantity and lead time.
How should I check rare earth content on arrival?
Agree on the analysis method with the supplier before shipment. GB/T 16477.1-2024 is listed as a published chemical-analysis standard for these alloys on the SAMR platform, but the specific method must be agreed and checked in the final published text.
Request a Specification-Based Quotation
When requesting a quotation, include your target composition, particle size, quantity and destination so suppliers can assess your requirements.