6 Surprising Ways Ferro Silicon Is Used in Modern Metallurgy

Ferro silicon (FeSi) has long been regarded as one of the most important ferroalloys in steelmaking and casting. But beyond its well-known role as a deoxidizer, this versatile alloy offers several unexpected benefits across different industries. Today, let’s explore what ferro silicon is, the different types available, and six surprising ferro silicon uses that many people overlook.

What Is Ferro Silicon?

Ferro silicon is an alloy consisting mainly of silicon and iron. It is produced by smelting coke, steel scrap, and quartz (silica) in an electric arc furnace.
Depending on customer requirements, the silicon content can range from 10% to 90%.

Common Forms of Ferro Silicon

• Ferro silicon lumps — widely used for steelmaking and casting

• Ferro silicon briquettes — suitable for ladle addition and high-efficiency deoxidation

• Atomized ferrosilicon powder — essential for mineral processing and welding industries

Each form is designed for different industrial needs based on its particle size and behavior in molten metal.

1. Ferro Silicon as a Deoxidizer in Steelmaking

The most common ferro silicon use is as an efficient deoxidizer during the final stage of steelmaking. Silicon has a strong affinity for oxygen, meaning it can quickly remove dissolved oxygen and improve steel purity.

FeSi 75 is the industry’s preferred grade because:

• It is stable, mature, and cost-effective in production

• Its higher density allows easy addition into molten steel

• It releases heat during reduction, helping raise furnace temperature

Because of its excellent performance, ferro silicon with 45–90% Si is widely used in steel plants, and FeSi 75 remains the most popular choice.

2. Ferro Silicon as an Alloying Agent

Silicon plays a key role in enhancing the properties of steel. When ferro silicon is added as an alloying element, it can significantly improve:

• Tensile strength

• Elasticity

• Hardness

• Magnetic performance

Therefore, ferro silicon is widely used for producing:

• Constructional steel (Si 2.8–4.8%)

• Tool steel (Si 0.3–1.8%)

• Spring steel (Si 0.4–2.8%)

• Transformer silicon steel (Si 2.8–4.8%)

Using ferro silicon as an alloying agent can also reduce steelmaking costs and save iron.

3. Ferro Silicon as an Inoculant and Nodulizer in Cast Iron

In the foundry industry, ferro silicon plays an essential role in improving cast iron microstructure.

Adding the appropriate amount of ferro silicon helps:

• Prevent carbide formation

• Promote graphite precipitation

• Improve the spheroidization effect in ductile iron

This makes ferro silicon an important inoculant and nodulizer for ductile cast iron, giving the casting better shock resistance and improved mechanical properties—often comparable to steel, but at a lower cost.

4. Ferro Silicon for Magnesium Smelting

A less-known but vital ferro silicon use is in Pidgeon-process magnesium production. During the chemical reduction stage, ferro silicon acts as a reducing agent that removes magnesium from dolomite (CaO·MgO).

On average, 1.2 tons of ferrosilicon are needed to produce 1 ton of magnesium metal.
Because of this, ferro silicon plays a strategic role in global magnesium production.

5. Low-Aluminum Ferro Silicon for High-Quality Steel

In many steel grades—especially high-carbon steel, stainless steel, and wire rod—aluminum content must be strictly controlled.

Low-aluminum ferrosilicon is preferred because it helps:

• Prevent nozzle blockage during continuous casting

• Reduce surface defects, especially on mirror-finish stainless steel

• Maintain consistent quality in tire cord steel, where composition control is critical

Low-Al FeSi has become an important material for modern steel mills pursuing higher quality standards.

6. Atomized Ferrosilicon Powder for Mineral Processing & Welding

Atomized ferrosilicon powder is a highly specialized product produced with about 45% silicon using a water-atomization technique. It is widely used in:

Heavy-media separation in ore processing

This powder offers:

• High hardness

• Strong magnetism

• Excellent oxidation resistance

• Reusability in dense-medium systems

For best separation performance, the ideal composition is 13–18% Si, balancing hardness and magnetic recovery.

Welding electrode coating

Atomized ferrosilicon powder is also used in welding as a deoxidizer, helping:

• Improve arc stability

• Reduce oxygen disturbance

• Enhance weld seam quality

These features make it a reliable additive for coated welding rods.

Ferro Silicon’s Role Continues to Expand

From steelmaking and casting to welding, magnesium smelting, and mineral processing, ferro silicon has become indispensable in modern industrial applications. As technology advances, new forms and new uses of ferro silicon will continue to emerge—offering improved efficiency, cleaner steel, and more precise metallurgical control.

For manufacturers, traders, and steel plants, understanding these ferro silicon uses helps in selecting the right grade and optimizing production.