7307.91.50.30 - Of alloy steel (except stainless steel)

This HTS category specifically covers flanges made of iron or steel that are not constructed from stainless steel alloys. These are fittings designed to connect pipes, valves, pumps, and other equipment to form a piping system. The critical defining characteristic of this subcategory is the material composition: it includes flanges made from carbon steel, alloy steel (excluding stainless varieties), and other ferrous metals, provided they do not meet the criteria for stainless steel under Note 1(f) to Section XV.

This classification distinguishes itself from its sibling category, 7307.91.50.10, which exclusively covers flanges made of iron or nonalloy steel. Therefore, while both are "Other" flanges with an inside diameter of less than 360 mm, this category encompasses a broader range of ferrous alloys beyond simple iron or nonalloy steel. The inclusion of "alloy steel (except stainless steel)" here signifies that the material has elements added to enhance its properties, but it does not possess the minimum chromium content (typically 10.5% or more) that would classify it as stainless steel.

As this is a leaf node, there are no further subcategories. Classification within this specific HTS code hinges on confirming the material is indeed alloy steel but not stainless steel, and that the flange fits the criteria of having an inside diameter less than 360 mm, within the broader context of "Other" flanges not elsewhere specified or included. Careful examination of the material composition and dimensional specifications is paramount for accurate classification.