Grades of ferrosilicon are classified depending on the silicon content, the maximum content of impurities and the purpose. Brand names vary slightly from country to country and from system to standard.
The following is a detailed description of ferrosilicon grades in major standards systems (e.g., China, ISO, ASTM, EN, etc.):
1. Chinese Standard (GB/T 2272)
Chinese brands of ferrosilicon are expressed as "FeSi + number", with the number meaning the average silicon content (e.g., FeSi75 means a silicon content of about 75%). Specific grades and formulations are given below:
Grade Silicon content (Si)/% Aluminum (Al)/% Carbon (C)/% Phosphorus (P)/% Sulfur (S)/% Main uses
FeSi90 87.0~95.0 ≤1.5 ≤0.2 ≤0.04 ≤0.02 High-purity special steel, reduction of metallic magnesium (Pidgeon method)
FeSi75 72.0~80.0 ≤1.5 ≤0.2 ≤0.04 ≤0.02 Deoxidation, alloying, casting in steelmaking
FeSi65 65.0~72.0 ≤2.0 ≤0.2 ≤0.04 ≤0.02 General steelmaking, priming for cast iron
FeSi45 40.0~47.0 ≤2.0 ≤0.3 ≤0.04 ≤0.02 Low-tech steel smelting, casting
2. International Standard (ISO 5445)
International standards are expressed as a "FeSi+silicon content range", for example, FeSi75 corresponds to a silicon content of 72% to 80%.
Grade Silicon (Si) /% Aluminum (Al) /% Carbon (C) /% Typical Use
FeSi90 87~95 ≤1.5 ≤0.1 High Purity
Application FeSi75 72~80 ≤1.5 ≤0.2 Steelmaking, Magnesium Metal
FeSi65 65~72 ≤2.0 ≤0.2 General Metallurgy,
Foundry FeSi45 40~47 ≤2.0 ≤0.3 Low Tech Applications
3. American Standard (ASTM A100)
The American standard uses a similar naming method, but the requirements for impurities are more stringent:
Silicon (Si)/% Aluminum (Al)/% Carbon (C)/% Typical Application
FeSi75 74~80 ≤1.0 ≤0.15 High-tech metallurgy, alloy steel
FeSi65 63~68 ≤2.0 ≤0.2 Total deoxidation,
cast iron FeSi50 47~52 ≤2.0 ≤0.3 Foundry, low-cost applications
4. European Standard (EN 13835)
The European standard focuses on silicon content as a key indicator and emphasizes environmental requirements:
Grade Silicon (Si)/% Aluminum (Al)/% Carbon (C)/% Environmental Rating
FeSi75 72~80 ≤1.5 ≤0.2 General Purpose (Low Emission)
FeSi65 65~72 ≤2.0 ≤0.2 Industrial Grade
FeSi45 40~47 ≤2.5 ≤0.3 Economical
5. Special Stamps
There are special stamps for special needs:
Low-Al FeSi75: Aluminum content ≤0.5%, used to reduce magnesium metal (Pidgeon method) to avoid aluminum affecting magnesium purity.
High-purity ferrosilicon (FeSi90): 87% silicon content ≥, very low impurity content, used in the production of electrical steel, stainless steel and other special steels.
Ferrosilicon for foundry: 1%-3% aluminum, contributes to the graphitization of cast iron (e.g., ductile iron).
6. Key points when choosing a brand
Silicon content:
High silicon (FeSi75-90): steel deoxidation, alloying, magnesium production.
Medium-low silicon (FeSi 45-65): foundry, general types of steel.
Impurity Control:
Steelmaking requires low aluminum and carbon content, while foundry can reduce aluminum content.
Cost factors:
High-silicon grades are more expensive, and the cost-effectiveness must be weighed depending on the application.