7307.91.50.50 - Of iron or nonalloy steel

This HTS category, 7307.91.50.50, specifically covers flanges made from iron or nonalloy steel. These fittings are designed to connect pipes, valves, pumps, and other equipment to form a piping system. The key defining characteristic for this classification is the material composition, which must be iron or nonalloy steel, and that the flange has an inside diameter of 360 millimeters or more. This size threshold distinguishes it from smaller diameter flanges that would fall under different subheadings.

The primary distinction between this category and its sibling, 7307.91.50.70, lies in the material. While both cover flanges with an inside diameter of 360 mm or more, this classification is for those made of "iron or nonalloy steel." The sibling category, conversely, is reserved for flanges made of "alloy steel (except stainless steel)," indicating a difference in the specific metallurgical composition and the presence of alloying elements beyond what is considered nonalloy.

As this is a leaf node in the HTS classification, there are no further subcategories within 7307.91.50.50. Therefore, all iron or nonalloy steel flanges with an inside diameter of 360 mm or more are classified directly under this heading. Classification will rely on confirming the material is indeed iron or nonalloy steel, as opposed to alloy steel, and verifying the specified inside diameter to ensure it meets the 360 mm or greater threshold.