1. What is Ferrosilicon?
Ferrosilicon is an alloy composed primarily of iron (Fe) and silicon (Si), widely used in metallurgy, foundry, chemical industries, and more. It serves not only as a critical deoxidizing agent but also as an alloying additive and reducing agent in various industrial processes.
The silicon content in ferrosilicon typically ranges from 15% to 90%. Common grades include FeSi45 (45% Si), FeSi65 (65% Si), FeSi72 (≥72% Si), and FeSi75 (≥75% Si). These alloys mainly consist of silicides such as FeSi and FeSi?, with FeSi being the most stable and commonly present phase.
Basic Properties of Ferrosilicon:
- Density: Approximately 3.0–4.5 g/cm3, depending on silicon content.
- Melting Point: Varies with silicon content, e.g.,
- FeSi45: ~1260°C
- FeSi75: ~1340°C
- Electrical Conductivity: Exhibits moderate conductivity, useful in electric furnace applications.
- Brittleness: Easily crushed, facilitating uniform dispersion during steelmaking.
2. Classification and Composition Differences
Based on silicon content, ferrosilicon can be categorized into several types:
| Type | Silicon Content | Common Uses |
|---|---|---|
| FeSi45 | 40%–50% | Foundry applications, low-silicon steels |
| FeSi65 | 60%–70% | Special alloy steels, cast iron inoculant |
| FeSi72 | ≥72% | Deoxidizer, alloying agent, nodular cast iron |
| FeSi75 | ≥75% | High-strength steel deoxidation, electrical steel |
Differences Between FeSi75 and FeSi72
1. Compositional Standards
FeSi75 (FeSiAl1.5-A)
- Minimum silicon: ≥75%
- Aluminum: ≥1.5%
- Impurity limits: Ca ≤0.06%, Mg ≤0.05%, P ≤0.04%, Mn ≤0.25%, Ti ≤0.10%, Al+Si ≤1.7%
- Known as "hard" ferrosilicon, ideal for high-strength steel production.
FeSi72 (FeSi75-B)
- Minimum silicon: ≥72%
- Carbon: ≤0.08%
- Stricter impurity control: P ≤0.05%, Cu ≤0.10%, Ti ≤0.10%, Mn ≤0.20%, Fe ≤1.00%, total impurities ≤1.00%
- Density ~4.2g/cm3, referred to as "soft" ferrosilicon, better suited for casting applications.
2. Application Scenarios
- FeSi75
- Used as a powerful deoxidizer in steelmaking to improve purity;
- Acts as an inoculant and spheroidizing agent in cast iron;
- Also used as a reducing agent in ferroalloy production.
- FeSi72
- Widely applied in low-alloy structural steels, spring steels, bearing steels, heat-resistant steels, and electrical steels;
- Inoculant for ductile and malleable cast iron;
- Also functions as a reducing agent in ferroalloy and chemical industries.
3. Production Process of Ferrosilicon
Ferrosilicon is typically produced using submerged arc furnaces (SAFs). The primary raw materials include:
- Silica (SiO?)
- Carbonaceous reductants (e.g., coke, charcoal)
- Iron scrap or pig iron
4. General Smelting Steps:
- Mix silica, reductant, and iron source in specific proportions
- Feed the mixture into the electric arc furnace and heat to temperatures between 1600–1800°C;
- Silicon is reduced from SiO? and reacts with iron to form ferrosilicon;
- Cool, crush, and screen the product into usable sizes.
5. Main Applications of Ferrosilicon
Steel Industry
- Deoxidizer: Removes oxygen from molten steel, improving its purity and quality;
- Alloying Agent: Enhances strength, hardness, and elasticity of steel;
- Improves Electromagnetic Performance: Reduces magnetic hysteresis loss and increases magnetic permeability in transformer steel.
Foundry Industry
- Inoculant: Promotes graphite precipitation, refines grain structure;
- Spheroidizing Agent: Used in ductile iron to encourage spherical graphite formation, enhancing toughness.
Ferroalloy Industry
- Intermediate alloy for producing low-carbon ferrochrome, ferromanganese, etc..
- Reductant in specialty alloy smelting (e.g., nickel iron, molybdenum iron).
Chemical Industry
- Raw material for producing organosilicon compounds, silanes, and silicates;
- Protective anode material in aluminum electrolysis.
Magnesium Metal Production
- In the Pidgeon process, ferrosilicon is the main reductant; approximately 1.2 tons of FeSi75 are required per ton of magnesium produced.
6. Factors Affecting Ferrosilicon Prices
Raw Material Cost Fluctuations
- Prices of silica, coke, and power significantly impact production cost.
Electricity Cost
- Electricity accounts for 60–75% of production cost, making it a key factor in profitability.
Steel Industry Demand
- Steel market conditions directly influence ferrosilicon demand.
Capacity Overload & Environmental Policies
- Excess capacity leads to intense market competition; environmental restrictions may cause temporary supply shortages.
Substitute Products
- Manganese-silicon alloys offer dual benefits of deoxidation and alloying, replacing ferrosilicon in some applications.
7. Leading Manufacturer of Ferrosilicon- LSFerroalloy
LSFerroalloy is a leading manufacturer in the field of ferrosilicon and other ferroalloys. With advanced production technology and a strict quality control system, we are committed to providing high-quality ferrosilicon products to global customers, supporting the development of various industries.