High-silicon ferrosilicon (typically referring to fesi alloys with a silicon content exceeding 70%) is a key additive and alloying material in modern metallurgical industry. It is not only a highly efficient deoxidizer and alloying agent in steelmaking, but also an indispensable inoculant and composition regulator in the foundry industry, and its quality directly affects the performance of downstream steel and castings.

High-silicon ferro silicon is mainly composed of silicon (Si) and iron (Fe), and its impurity elements are strictly controlled to meet the stringent requirements of different applications. Among them, FeSi75 (75# ferrosilicon) and FeSi72 (72# ferrosilicon) are the most commonly used and representative grades.

Ferrosilicon Si>70%

chemical composition

Grade	Si Content (%)	Al ≤ (%)	Ca ≤ (%)	C ≤ (%)	Key Features and Typical Applications
FeSi75-A	74.0 – 80.0	0.4	-	0.1	High purity, with extremely low levels of impurities such as aluminum and carbon. Primarily used in the smelting of special steels with extremely strict requirements for gas and impurity control, such as high-grade electrical steel and cold heading steel.
FeSi75-B	72.0 – 80.0	-	0.5	0.2	High versatility, it is the most widely circulated standard grade on the market. Widely used for deoxidation of ordinary carbon steel and as a casting inoculant, offering high cost-effectiveness.
FeSi75Al1.0-A	74.0 – 80.0	1.0	1.0	0.1	Moderate aluminum and calcium content. Calcium enhances deoxidation and desulfurization effects, while aluminum helps control grain size in steel. Suitable for high-quality steel smelting and spheroidizing treatment of ductile iron.
FeSi72	72.0 – 78.0	1.0 – 2.0	1.0	0.2	Slightly lower silicon content, typically slightly higher aluminum content. A mainstay in the foundry industry (especially for gray cast iron and ductile iron inoculation), and also used for steel deoxidation.

Physical Forms and Packaging

Form Specifications: We offer a full range of physical forms to meet different addition methods:

Lumps: Standard sizes of 10-50mm, 10-100mm, etc., suitable for addition in steelmaking furnaces, ladles, or hot metal ladles.

Granular: 3-8mm, 1-3mm, etc., suitable for precise addition processes such as wire feeding and in-flow inoculation.

Powder: 0-1mm, used for special alloying or as a welding material raw material.

Standard Packaging: 1-ton/bag (lined with moisture-proof film) to ensure safe transportation and moisture protection. Customized packaging solutions are available to meet specific customer needs.

ferrosilicon particles

Products Uses

1. Iron and Steel Smelting: The Core of Deoxidation and Alloying

As a powerful deoxidizer: Silicon has an extremely strong affinity for oxygen in molten steel, rapidly generating low-melting-point SiO₂ (silicon dioxide) which floats to the slag, significantly reducing the oxygen content in the steel, effectively eliminating bubbles and porosity defects, and improving the purity of the molten steel. FeSi75%, due to its higher silicon content, has even better deoxidation efficiency.

As an important alloying element: Silicon can dissolve in ferrite, producing a significant solid solution strengthening effect. It is indispensable in the following steel grades:

Spring steel: Improves elastic limit and fatigue resistance.

Heat-resistant steel: Enhances oxidation resistance and strength at high temperatures.

Electrical steel (silicon steel): A core alloying element that significantly reduces iron loss and increases magnetic permeability, key to manufacturing transformer and motor cores.

High-strength low-alloy steel: Improves strength and weather resistance.

2. Foundry Industry: Key to Improving Cast Iron Structure

Highly Efficient Inoculant: Adding ferrosilicon particles before pouring molten iron provides numerous nuclei, strongly promoting graphitization, preventing the formation of hard and brittle "white iron" structures, and ensuring the acquisition of fine, uniform type A graphite (gray cast iron) or rounded graphite spheres (ductile iron).

Precise Composition Adjuster: Used to flexibly adjust the final silicon content in molten iron to meet the chemical composition requirements of different grades of cast iron, ensuring the stability of casting performance.

3. Other High-End and Derivative Applications

Magnesium Smelting: In the Pidgeon Process for magnesium smelting, ferrosilicon (usually FeSi 75%) serves as the core reducing agent, reducing magnesium from calcined dolomite under high temperature and vacuum.

Welding Electrode Manufacturing: Ferrosilicon powder is a common alloying additive in welding electrode coatings, used to transition silicon to the weld metal, improving welding performance.

Iron-Based Powder Metallurgy: Used as an alloying additive in the manufacture of high-strength powder metallurgy parts.

Ferrosilicon Si>70%

FAQ

Q1: What are the main differences between FeSi75-A and FeSi75-B?

A1: The core difference lies in the level of impurity content control. FeSi75-A has stricter restrictions on impurities such as aluminum, calcium, carbon, and phosphorus, making it a "high-purity" ferrosilicon, and its price is usually higher. It is mainly used in applications where extremely high purity of steel is required. FeSi75-B is a general-purpose grade, suitable for most common deoxidation and casting scenarios, and offers better cost performance.

Q2: Why does ferrosilicon inoculant "decline" in casting? How can this be addressed?

A2: Inoculant decline refers to the phenomenon that the effect of ferrosilicon in promoting graphite nucleation weakens over time after being added to molten iron. The main reason is that the inoculum nuclei (such as SiO₂) dissolve or float to the surface in the high-temperature molten iron.

Countermeasures include:

① Using "in-flow inoculation" (adding simultaneously during casting) to shorten the reaction time;

② Selecting composite inoculants containing long-lasting elements such as barium (Ba) and strontium (Sr);

③ Strictly controlling the time window from inoculation to completion of casting.

Q3: When purchasing ferrosilicon, besides chemical composition, what other quality indicators should be considered?

A3: Key areas to focus on include:

Physical size: Whether it matches your additive process (e.g., silo, wire feeder).

Composition uniformity: Whether the composition of lumpy products is stable across different batches, and even within the same batch.

Appearance: Whether it is clean, without excessive powder or inclusions.

Supplier's quality assurance system: Whether it possesses standardized production capabilities and stable testing reports.

Q4: What value-added services can AON Metals provide?

A4: We not only provide products that meet standards, but also are committed to providing solutions:

Technical consultation: Recommending the most suitable grade and size based on your final product and process.

Customized processing: Production can be tailored to your specific chemical composition range and size distribution requirements.

Stable supply and logistics: Ensuring continuous operation of your production line.

Complete third-party testing reports: Provided with the goods, ensuring transparent and traceable quality.

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