7202.21 - Containing by weight more than 55 percent of silicon:

This HTS category, 7202.21, specifically classifies ferrosilicon that contains by weight more than 55 percent silicon. Ferrosilicon is an alloy of iron and silicon, and this subcategory focuses on those with a significantly high silicon content, playing a crucial role in various metallurgical processes. Its primary uses include acting as a deoxidizer and alloying element in the production of steel and cast iron, improving their strength, hardness, and corrosion resistance.

Within the broader category of ferrosilicon (7202.2), this classification is distinct from its sibling, 7202.29, which covers "other" ferrosilicon not meeting the specified silicon percentage threshold. Therefore, any ferrosilicon with 55 percent or less silicon by weight would fall under the sibling category. The defining characteristic here is the quantitative measure of silicon content, ensuring accurate segregation for trade and statistical purposes.

Further subdivisions exist within this high-silicon ferrosilicon classification. These subcategories, such as 7202.21.75.00 and 7202.21.90.00, refine the classification based on even more precise silicon content ranges (more than 80% and more than 90% respectively). This granular breakdown allows for even greater specificity, reflecting nuances in the material's properties and intended applications in advanced industrial processes.