Commercial ferrosilicon grades range from roughly 15% to 90%+ silicon. Lower-silicon grades (15–45% Si) are primarily used as deoxidizers and inoculants in steelmaking and foundry applications. Higher-silicon grades (above 55–75% Si) are used in electrical steel production and as a precursor to metallurgical-grade silicon. The silicon percentage is declared on the commercial invoice and mill certificate and is the key variable customs authorities use to verify classification.

Antidumping duty orders on ferrosilicon from certain countries have been in place at various times, and Section 232 tariffs also apply to ferrosilicon as a steel-related product. Importers should consult the Commerce Department's current order list and confirm the country of origin and silicon grade fall outside any active scope before finalizing supplier contracts.