7202.21.10.00 - Containing by weight more than 3 percent of calcium

This HTS classification, 7202.21.10.00, specifically identifies ferrosilicon containing by weight more than 3 percent of calcium. Ferrosilicon, in general, is an alloy of iron and silicon used primarily as a deoxidizer and alloying element in the production of steel and cast iron. The defining characteristic of this subcategory is the elevated presence of calcium, which can influence the metallurgical properties of the alloy, impacting its application in specific steelmaking processes.

Distinguishing this category from its sibling, 7202.21.50.00 "Other," is crucial. While the sibling category encompasses ferrosilicon meeting the broader criteria of containing more than 55% silicon but not more than 80% silicon, but *without* the specific calcium content stipulated here, this category is precisely for those instances where the calcium threshold is met. This differentiation allows for more granular tracking and potential duty rate application based on the specific composition of the ferrosilicon.

As this is a leaf node within the HTS structure, there are no further subcategories for this specific classification. Therefore, the focus for classification under 7202.21.10.00 rests solely on confirming the alloy's composition: it must contain by weight more than 55 percent but not more than 80 percent of silicon, and critically, more than 3 percent of calcium. Variations in either the silicon or calcium content would necessitate classification under a different HTS code.