HS Code for Carbon steel flanges

Carbon steel flanges are classified under HS code 7307.91. This classification is determined by the product's specific function as a flange and its material composition. Under the Harmonized System, heading 7307 covers tube or pipe fittings of iron or steel. The subheadings are organized to distinguish between cast and non-cast products, and then by material type. Flanges made of iron or non-alloy steel (carbon steel) are explicitly provided for in subheading 7307.91. A flange is defined as a projecting rim, collar, or ring used to connect pipe sections or to attach a pipe to a valve, pump, or other equipment. These are typically bolted together with a gasket in between to create a sealed, yet detachable, joint. The material must meet the definition of non-alloy steel found in Chapter 72, Note 1(f), ensuring it does not contain alloying elements above specified weight percentages. These flanges are commonly manufactured to standards such as ASME B16.5 or EN 1092-1 and are used extensively in high-pressure piping systems across the energy and manufacturing sectors.

Products Included

• Carbon steel slip-on flanges
• Weld neck flanges (non-stainless)
• Blind flanges for pipe termination
• Socket weld and lap joint flanges
• Threaded carbon steel flanges

Common Misclassification

Carbon steel flanges are often misclassified under 7307.21, which is the specific code for stainless steel flanges. Importers must verify the chemical mill test report (MTR) to ensure the chromium content is below 10.5%. Another error involves 7307.11 or 7307.19, which are for cast iron or cast steel fittings. While many flanges start as castings, if they are subsequently forged or heavily machined, they are generally classified under 7307.91. Finally, some users confuse these with structural plates under 7208, but once a plate is worked into a flange shape, it must be classified under 7307.

FAQ

What is the HS code for Carbon steel flanges?

The HS code for flanges made of iron or non-alloy steel (carbon steel) is 7307.91.

Are galvanized carbon steel flanges classified differently?

No, the application of a zinc coating (galvanization) does not change the HS code; they remain under 7307.91 as long as the base material is carbon steel.