The distinction is primarily one of particle size and production method. Granules are coarser particles typically produced by atomization or crushing and used in shot blasting or welding. Powders are finer particles produced by atomization, reduction, or electrolysis and used in powder metallurgy or additive manufacturing. The heading notes and relevant chapter notes provide guidance on the boundary.

Granules and powders of iron and steel fall within the broad scope of Section 232 measures on steel and iron products. Whether a specific line is covered and whether any country-specific exemptions apply depends on the tariff line and origin. Importers should verify current proclamation language and any applicable exclusions with CBP or a licensed customs broker.